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1981
Experimental colonization of crude oil contaminated sediments by benthos on the Middle Atlantic continental shelf
Donald Boesch Virginia Institute of Marine Science
Eugene Burreson Virginia Institute of Marine Science et al
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Recommended Citation Boesch, D., Burreson, E., & et al. (1981) Experimental colonization of crude oil contaminated sediments by benthos on the Middle Atlantic continental shelf. Virginia Institute of Marine Science, William & Mary. https://scholarworks.wm.edu/reports/2413
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l EXPERIMENT AL COLONIZ CONTAMINATED SEDIMENTS BY BENTHOS ON THE MIDDLE ATLANTIC CONTINENTAL SHELF ...
- DONALD F. BOESCH Chief Scientist
EUGENE M. BURRESON Program Manager
Conducted Under Contract No. AA551-CT8-32 With the Bureau of Land Management United States Department of Interior
VIRGINIA INSTITUTE OF MARINE SCIENCE SCHOOL OF MARINE SCIENCE COLLEGE OF WILLIAM AND MARY Gloucester Point, Virginia 23062
William J. Hargis, Jr., Director ,0272 •101 REP~~T DOCUMENTATION 1-l~REPORT NO. 3. Recipient's Accession No. PAGE . 12. •------~------. 7------..... 4. Tlllo ,nd Subtitle 5. Report Date ~xperimental Colonization of Crude Oil Contaminated Sediments April t----"------1981 by Benthos on the Middle Atlantic Continental Shelf 6. 1----~------· ------·- 7. Auttlor($) D. F. Boesch, E. M. Burreson, L. C. Schaffner, H. I. Ka tor, 8. Performing Orsanlzatlon Rept. No. C.L. Smith, D.M. Alongi, M.A. Bowen, P.O. deFur 9. P,i-formlng Organization Name and Address 10. Project/Task/Work Unit No. College of William and Mary ------1 Virginia Institute of Marine Science 11. Co1"1tract(C) or Grant(G) No.
School of Marine Science (C) AA551-CT8-32 GlQuceater Point, Virginia 23062 CG)
12. Spo"'sorlng Organization Name and Address 13. Type of Report & Period Covered Branch of Environmental Studies (733) Final Report Bureau of Land Management, U.S. Department of Interior - ______. __ . _,_ __ 18th & C Streets, NW 14. t------==~--";__Washington, D.C.______20240 .J_ ------1 1$. ~upplc,mentary Notes
------··-·-•···------~ ---~--- ·-~-----·--·--~---.. · US •. Ab~tract (Limit: 200 words) In August 1979 six arrays of defaunated sediment were deployed at each of three sites in the Middle Atlantic Outer Continental Shelf. Three arrays at each site had -Prqdhoe Bay crude oil mixed with the sediment. Because of technical difficulties r~covery was limited to one control and one oiled array from two sites--one near the shelf break and one in a mid-shelf swale--after 10 months in situ. Moderate to severe sediment e~osion occurred in boxes recovered from the mid-shelf. Chemical analyses indicated that between 50 and 90 percent of the added oil remained in the $ediments after 10 months and also that the oil was qualitatively similar to th~ added oil. R~latively more oil was retained in the muddy sands near the ~he~f break than in the mid-shelf fine sands. Generally, there was no demonstrable effect of Prudhoe Bay crude oil contamination on colonization by either macrobenthos or me!obenthos, although at the shelf break certain species were less successful colonizers of oiled boxes. Results are consistent with the hypothesis that less frequently disturbed finer grained habitats are more susceptible and sensitive to oil contamination.
17. Document Analysis a. Descriptors Etperimental Studies Grain Size O~ter Continental Shelf Species Abundance Recolonization Connnunity Response Gias Chromatography Petroleum Degrading Bacteria
b. ldentlflers/Ope11-Ended Terms ·Biological Oceanography Meiobenthos ~hemical Oceanography Microbiology Oil :Pollution Hydrocarbon Chemistry Macrobenthos Sedimentology
c, COSATI Field/Group i9r· Avallablllty ~atement 19. Security Class (This Report) 21. No. of Po1es Unclassified approx. 231 Release Unlimited 20. Security Class (This Page) 22. Price Unclassified '(Sea ANSI-Z39.18) See Instructions on Reverse OPTIONAL FOAt.1 272 (4-77) (Formerly Nl'IS--35) Department of Commerce EXPERIMENTAL COLONIZATION OF CRUDE OIL CONTAMINATED SEDIMENTS BY BENTHOS ON THE MIDDLE ATLANTIC CONTINENTAL SHELF
conducted by the
Virginia Institute of Marine Science under Contract No. AA551-CT8-32
with the
Bureau of Land Management United States Department of Interior
Donald F. Boesch Chief Scientist
Eugene M. Burreson Program Manager
Virginia Institute of Marine Science School of Marine Science College of William and Mary Gloucester Point, Virginia 23062
William J. Hargis, Jr., Director
- (' '? "j:J I .:.):,YU~ {'. 3
I I This report has been reviewed by the Bureau of Land Management and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Bureau of Land Management or the Virginia Institute of Marine Science nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
·(le< ACKNOWLEDGMENTS
This study could not have been completed without the assistance of the following people. Marcia Bowen was responsible for most details of cruise logistics as well as for assuring that all samples were properly taken at sea. She also assumed responsibility for benthos sample analyses after Dr. Boesch's departure. Ms. Bowen performed all these duties with patience and competence. Linda Schaffner assumed responsibility for analyzing and discussing the macrobenthos data after the departure of Dr. Boesch and Ms. Bowen. She provided an insightful, well-written chapter, on time, amidst myriad other responsibilities. Dan Alongi provided equally professional assistance with meiobenthos data. The following people assisted at sea: Dan Alongi, Andy Applegate, Rod Bertelsen, Joe Boyer, Gary Gaston, Bill MacIntyre, Cindy Miekley, Karl Nilsen, Linda Schaffner, Cliff Ryer, and Don Weston. This report was typed by the VIMS Report Center and special thanks are due Ruth Edwards, Annette Stubbs, and especially Cheryl Ripley for typing and report organization expertise.
E. M. Burreson SUMMARY TABLE OF CONTENTS 1
EXECUTIVE SUMMARY by Eugene M. Burreson
CHAPTER 1. INTRODUCTION by Donald F. Boesch
CHAPTER 2. FIELD METHODS AND PRELIMINARY EXPERIMENTATION by Eugene M. Burreson and Marcia A. Bowen
CHAPTER 3. SEDIMENT TEXTURE AND ORGANIC CARBON by Linda C. Schaffner and Donald F. Boesch
CHAPTER 4. CHANGES IN PETROLEUM HYDROCARBONS IN EXPERIMENTALLY OILED SEDIMENTS by Craig L. Smith and Paul O. deFur
CHAPTER 5. MICROBIAL RESPONSES by Howard I. Kator
CHAPTER 6. MACROBENTHOS COLONIZATION by Linda C. Schaffner, Donald F. Boesch and Marcia A. Bowen
CHAPTER 7. MEIOBENTHOS COLONIZATION by Daniel M. Alongi and Donald F. Boesch
CHAPTER 8. SYNTHESIS AND CONCLUSIONS by Donald F. Boesch and Eugene M. Burreson APPENDIX A. PHASE I FINAL REPORT - DEVELOPMENT AND FINAL DESIGN OF THE SURFACE ACTIVATED DEPLOYMENT AND RECOVERY SYSTEM
APPENDIX B. RECOLONIZATION BOX OBSERVATIONS AND PHOTOGRAPHS
APPENDIX C. CHARACTERIZATION OF PRUDHOE BAY CRUDE OIL by C. L. Smith
APPENDIX D. MACROBENTHOS AND MEIOBENTHOS RAW DATA (on microfiche)
lDetailed Tables of Contents are provided with each chapter. EXECUTIVE SUMMARY
Eugene M. Burreson EXECUTIVE SUMMARY
TABLE OF CONTENTS
INTRODUCTION . • • . • • • • . . 1 Basic Program • • . • • . • I Role of Key Participants 2 Geographical Area of Study •••. 2 Other Pertinent Studies in the Same Geographical Area 3 Summary of Cruise Information •.• 3 Surface Activated Deployment and Recovery System (SADRS) •• 4 Experimental Design ~nd Sampling Scheme. 4 Summary of Samples Collected ..••.••••. 5 Sediment Collection and Initial Experimentation ...••• 6 Sediment Preparation 6 Deployment •...•• 6 Laboratory Methods 7 Sediment Grain Size 7 Total Organic Carbon. 7 Hydrocarbons .••• 7 Bacteria. • .•• 8 Meiofauna 8 Macro fauna 8 Data Analysis. 8 Meiofauna 8 Macrofauna 8
SIGNIFICANT FINDINGS. 9 Experimental Techniques ...• . . . . . 9 Macrobenthos and Meiobenthos Colonization. 9 Petroleum Hydrocarbon Weathering and Microbial Response. • IO
CONCLUSIONS • • • 10
LITERATURE CITED. • 11 EXECUTIVE SUMMARY
Eugene M. Burreson
INTRODUCTION
Understanding of the potential effects of petroleum exploration and production activities on living resources of the outer continental shelf needs to be improved to allow more competent decision-making. Because of the affinity of hydrocarbons for particulate surfaces, concentrations in bottom sediments may be much higher than in the surrounding water column following an oil spill or chronic emission, and frequently the only demonstrable effects of oil pollution are found in sediment-inhabiting benthos. However, the difficulty of maintaining outer shelf infauna! organisms or environmental conditions precludes realistic laboratory experimentation on fate and effects of petroleum hydrocarbons on outer shelf benthos. In situ field experiments provide a solution to these problems-;-although they also have significant limitations.
The studies described in this report are an attempt to enhance understanding of the fate and effect of petroleum hydrocarbon constituents of crude oil in the benthic environment of the Middle Atlantic outer continental shelf under relatively realistic environmental conditions. The specific objectives of this study were: a) to develop and refine techniques for conducting in situ experiments involving exposure of oil-contaminated sediments under continental shelf conditions, b) to assess the colonization of macrobenthos and meiobenthos following catastrophic disturbance in different Middle Atlantic outer shelf habitats, and to determine the effects of petroleum hydrocarbon contamination on colonization, and c) to determine the quantitative and qualitative changes in petroleum hydrocarbons incorporated in natural sediments under in situ conditions, and to assess the response of microbes capable of degrading petroleum hydrocarbons.
Basic Program
The Virginia Institute of Marine Science was contracted (AA551-CT8-32) to conduct an in situ recolonization experiment utilizing defaunated sedimentfroiii"v"arious physiographic provinces on the Middle Atlantic Shelf and housed in arrays deployable and recoverable from the surface. The program consisted of two phases. Phase I entailed the design, construction, and testing of a surface-activated deployment and recovery system (SADRS). The resul~s of Phase I, including the initial design of .the SADRS, the testing program conducted, modifications to the initial design, the final design, and the method of deployment are given in the Phase I Final ieport, submitted to BLM, May 1979 (Appendix A). The prototype SADRS
1 was designed and constructed by Advex Corporation, Hampton, Virginia. Phase II, dependent upon the satisfactory completion of Phase I, entailed a series of recolonization experiments and subs~diary studies that are described in this report.
Role of Key Participants
The major program elements for the Benthic Recolonization Study, and the responsible principal investigators are listed in below.
Program Elements Principal Investigators ($!}. Associate Investigators
I. Chief Scientist Donald F. Boesch
II. Principal Elements lb-- Meiobenthos Donald F. Boesch Daniel M. Alongi Macrobenthos Donald F. Boesch Marcia A. Bowen Linda c. Schaffner Gary R. Gaston Bacteriology Howard I. Kator Joseph N. Boyer Hydrocarbon Chemistry Craig L. Smith William G. MacIntyre Paulo. deFur Rudolph N. Bieri (GC-MS) ~
III. Supporting Elements Organic Carbon Michael A. Champ (American University) Program Management Eugene M. Burreson /1!!,..
Geographical Area of Study
Recolonization arrays were deployed at three sites on the Middle ., Atlantic Outer Continental Shelf off the coast of New Jersey. Station AS (39°21.S'N, 72°37.O'W, 118 m) was established on the shelf-br~ak in the same environmental regime as the lease tracts which yielded the only significant reports of oil or natural gas, but far enough removed to minimize interference by exploratory activities. Two sites were chosen from the outer shelf which reflect the extremes in sedimentary regime for that region. Station B3 (39°21.O'N, 73°O2.l'W, 72 m) is in a topographical depression (swale) and was sampled during the
2 Environmental Studies Program. Station B6 (39°22,S'N, 73°02.0'W, 54 m) was selected to represent the outer shelf ridge habitat.
Other Pertinent Studies in the Same Geographical Area
Most of the studies on Middle Atlantic Bight outer continental shelf benthos have been basically monitoring or descriptive studies. These include the Bureau of Land Management Middle Atlantic Environmental Studies Program conducted by the Virginia Institute of Marine Science, which terminated in August 1977 (VIMS 1979); the Environmental Protection Agency Philadelphia Dumpsite Studies which are being continued by the Office of Marine Pollution Assessment of NOAA; the ongoing BLM funded continental slope and canyon study conducted by Lamont-Doherty Geological Observatory; and the ongoing NMFS, N~rtheast Fisheries Center, Ocean Pulse Program which is monitoring the marine benthos of representative continental shelf habitats including VIMS Station B3, one of the sites for the present Recolonization Study. The BLM Middle Atlantic Environmental Studies Program also included a preliminary recolonization study that was the impetus for the present investigation. The tripod studies conducted by the U.S. Geological Survey provided valuable data on bottom currents and sediment mobility in the area, as well as information on problems of long-term deployment of instrument systems (USGS 1979). A recent study by Menzie et al. (1980) on the effects of exploratory drilling at a site similar to recolonization Station AS demonstrated some local disruption of the benthic community.
Summary of Cruise Information
Five cruises were conducted during this study. Vessel utilized, cruise dates and purpose of each cruise are listed in below.
Cruise No. Vessel Date Purpose
lOR R/V Cape Henlopen 23-24 January 1979 Field test of 2-5 March 1979 SADRS prototype
llR R/V Cape Henlopen 19-22 June 1979 Sediment collection
-- . 12R R/V Retriever 7-16 August 1979 SADRS deployment
13R R/V Virginian Sea 5-9 November 1979 First recovery attempt
14R R/V Aloha 17-25 April 1980 Second recovery 1-14 June 1980 attempt
3 Surface Activated Deployment and Recovery System (SADRS)
Each SADRS array consisted of a 1.53 m square by 20.3 cm high stainless steel base. This base held four fiberglass boxes that were 15 cm deep by 47.5 cm square. A 1.5 m high tubular stainless steel quadripod above the base supported a lifting eye and an acoustic release-buoy system. Each array was lowered to the sea floor with an acoustic release-load bar system. At the appropriate signal the release detached from the array and was hauled back to the surface with the vessel's winch. Four dacron covers that had been securely fastened to the fiberglass boxes with velcro were attached to the deployment release and were pulled off the boxes as the release was recovered. A separate acoustic release-buoy system was attached to each array and connected to 1.3 cm (1/2 inch) retrieval line packed into an attached rope cannister. At the appropriate acoustic signal the recovery release detached from the array and was carried, along with the retrieval line, to the surface by the buoy. The retrieval line was attached to each array via a twin stainless ste~l cable-cover closing system. Lifting tension on the retrieval line add thus to the closing cables pulled two sets of dacron covers across the fiberglass boxes to assure that no sediment was lost during recovery. The arrays were then hauled to the surface.
Experimental Design and Sampling Scheme
Three control (unoiled) arrays and three oiled arrays were deployed at each of the three stations in August, 1979. Each control array contained four boxes filled with sediment (collected on an earlier cruise) from the appropriate station which had been repeatedly frozen to kill all organisms. Each oiled array contained four boxes of similarly treated sediment but mixed with Prudhoe Bay crude oil. Three boxes contained 250 mg oil/kg sediment. The fourth box was subdivided by a fiberglass partition; one side contained 50 mg/kg and the other contained 2500 mg/kg.
The experimental design called for surface vessel recovery of a control and oiled array from each station at three month intervals after deployment. Thus the first recovery was scheduled for November, 1979, the second for February, 1980. However, because of corrosive failure of the closing cable no arrays were recovered on the first recovery cruise and it was apparent that arrays could not be recovered as originally planned. Therefore a manned submersible (Mermaid II, IUC International) was employed to locate and recover the arrays-.- The added expense of the submersible forced a reduction in the scope of work to one recovery of a control and oiled array at Stations AS.and B3. This recovery was successfully completed in June 1980.
4 Summary of Samples Collected
Prior to deployment of arrays at each station nine Smith-McIntyre grabs were taken, six for biological analyses and three for chemical analyses. Three small cores were removed from the first grab for bacterial analyses and two cores each from the fourth, fifth and sixth grab for meiofauna analyses. Cores for grain size and total organic carbon were removed from all six biological grabs. The remaining sample was processed for macrofauna. Cores for grain size, TOC, and hydrocarbon chemistry were removed from the three chemical grabs and pooled. Also prior to deployment one grain size core was taken from each control array box and two bacteria cores were taken from one box in each array. One core each for grain size, TOC, and. hydrocarbon analysis was also taken from each oiled array box. The samples from each of the three oil concentrations at each station were pooled. Six grabs were taken at each station during recovery operations and processed similarly to the deployment biological grabs. Upon recovery of a control array each box was photographed, three cores were taken from one box for bacteria, one core from each of the four boxes for hydrocarbon, TOC and grain size analyses, and five cores from three boxes for meiofauna analyses. The remaining sediment was processed for macro~auna. For oiled arrays, each box was photographed and, for bacteriology, five cores were taken from the three boxes with the medium oil concentration and two cores each from the low and the high concentrations. One core was taken from each of the five boxes for hydrocarbon, TOC, and grain size analyses. For meiofauna, one core each was taken from the low and high oil concentrations and from two of the medium concentration boxes. Three cores were taken from the third medium concentration box. The remaining sediment was processed for macrofauna. Total number of samples collected is listed in Table 1.
Table 1. Total number of samples collected by sample type.
Boxes Deployment Recovery Type Grabs control oiled control oiled
Bacteriology 15 18 18 6 18 Total organic carbon 33 0 15 8 10 Grain size 33 36 45 8 10 Hydrocarbons 3 0 15 8 10 Meiofauna 30 ,;, ,;, 10 14 Macrofauna 30 0 0 8 10
5 Sediment Collection and Initial Experimentation
Approximately 225 gallons of sediment was collected at each of the three sites from 19-22 June 1979, using an anchor dredge. The sediment was stored in acetone-cleaned 55 ·gallon drums. The oil-sedim~nt mixtures were prepared in a nine cubic foot cement mixer. Preliminary experiments were conducted to assure that one hour of mixing provided an homogeneous mixture of all three oil concentrations and also that the extraction technique recovered all the oil. Small scale experiments were also conducted to determine the extent to which an homogeneous sediment-oil mixture loses oil when exposed to flowing sea water, so that this loss could be compensated for during sediment preparation. Results suggested that little oil was lost so the target concentration was increased by 10%. Prudhoe Bay crude oil was chosen by the Bureau of Land Management for use in this study because of its expected similarity to oil recovered from Baltimore Canyon trough structures.
Sediment Preparation
The unoiled or control samples were prepared first by filling an acetone-washed cement mixer with 50 gallons of sediment from the appropria.te station, and mixing for one hour. The sediment was then poured into the fiberglass recolonization boxes, dacron covers were attached along all four sides with velcro, and the boxes were placed in large wooden racks. For oiled sediments equal amounts of sediment were taken from each barrel from the appropriate station, weighed, placed in the acetone-washed mixer and mixed for ten minutes. The appropriate amount of oil for each concentration was dissolved in heptane, added to the sediment, mixed for 1.5 hours, and transferred to the fiberglass boxes. Each box was immersed in running sea water for eight hours to remove leachable oil and then covered and transferred to wooden racks. All boxes were frozen for four days at -35°F, then thawed for 12 hours, refrozen for 36 hours, thawed for 12 hours, and finally frozen for five days. This freezing-thawing regime was an attempt to assure that all organisms in the boxes, including bacteria, were killed.
Deployment
The racks of boxes were transferred from the freezer to the ship immediately prior to departure and covered with sheets of one inch styrofoam to prevent excessive warming during transit. Boxes were installed in each array immediately prior to deployment. Arrays -were deployed on 8-14 August 1979, as previously described.
6 Laboratory Methods
Sediment Grain Size
Because of the varied composition of bottom sediments at the three stations, a combined analysis was performed using sieve separation, pipette analysis, rapid sand analyzer, and coulter electronic particle counter. The various subanalyses were then recombined to obtain total sample weight and a cumulative frequency curve was constructed. The percentile levels were read from the curve and desired graphic moments were calculated.
Total Organic Carbon
Sediment samples were oven dried, sieved through a 1 mm seive to remove shell and pebbles, powdered, weighed, and placed in an ampule. The ampule was purged of inorganic carbon constituents, sealed, and heated to oxidize the organic carbon to carbon dioxide. The carbon dioxide of each ampule was flushed with a nitrogen stream and measured by an infrared analyzer.
Hydrocarbons
Frozen samples were thawed and freeze-dried. A 20 g portion was soxhlet-extracted in methylene chloride for 48 hours and reduced in volume on a rotary evaporator. One ml aliquots were fractionated on silica gel columns topped with a 1.5 cm layer of activated copper powder. Samples of approximately 1.0 µ1 were injected using a hot-needle splitless injection technique into gas chromatographs with Grob-type injection ports and 20 m glass capillary columns coated with SE-52. Peak integration was done electronically and quantitation was accomplished by comparison of peak areas with those of known standards. Amount of oil in extracted sediment samples was calculated by dividing the sum of the measured concentrations of the C18, C20, and C22 n-paraffins in the sediment by the measured concentration of the three compounds in fresh Prudhoe Bay crude oil.
Gas chromatography-mass spectrometry was performed with a 21-492-B DuPont mass spectrometer with a 21-492-B data system, interfaced to a Varian 2740 gas chromatograph modified for wall coated glass capillaries. The instrument was operated in continuous scan mode, covering the mass range from m/e=30 to m/e)550 at 1 sec/decade. All data were stored on magnetic disk until analysis and then transferred to tape. For compound analysis the mass spectrum of each peak in the reconstructed chromatogram was generated if the number of ions was sufficient.
7 Bacteria
Sediment samples were enumerated immediately after collection by homogenizing in a blender and serially diluting appropriate volumes of homogenate in sterile sea water blanks. Using. a three tube most probable number technique, selected dilutions were planted in tubes containing a heterotrophic medium and tubes containing an inorganic salts enriched medium with sterile Prudhoe Bay crude oil as the sole carbon source. Tubes were incubated at 20-22°C for one month and read at weekly intevals.
Meiofauna
Sediment cores were agitated three times with an isotonic solution of magnesium chloride, the supernatant decanted through 0.5 nnn and 0.063 mm sieves, and preserved in 5% buffered formalin. Samples were stained with Rose Bengal and sorted into major taxa.
Macrofauna
The elutriated "light" fractions were sorted into major taxa by examination with a binocular dissecting microscope. The "heavy" fractions were processed by placing a small amount of sediment in a metal pan and elutriating and decanting repeatedly through a 0.5 mm Nitex screen. This material was examined as with the light reaction, while the remaining sediment was spread out in a white pan and examined with the naked eye for the Rose Bengal stained organisms. All organisms were sorted into major taxonomic groups. Wet weight biomass was determined for each major group following blotting on paper towels.
Data Analysis
Meiofauna1
Relative abundance and frequency of occurrence values were calculated for nematodes and harpacticoid copepods. In addition, the community structure indices of species diversity (.Shannon), evenness, and species richness were calculated. Reciprocal averaging ordination was employed for the harpacticoid copepods.
Macro fauna
Abundance and biomass data were entered on specially designed coding forms using the 10-digit NODC taxonomic code. Species diversity, evenness, and species richness were calculated for each grab or box sample. Comparisons among grabs and boxes was accomplished by reciprocal averaging ordination.
8 SIGNIFICANT FINDINGS
Despite the problems encountered during the course of these studies it is clear that long-term in situ experiments on the outer continental shelf, although confronted--i;y-formidable obstacles, provide important information that cannot be obtained in any other manner. Significant findings will be discussed in the order of the three objectives listed in the Introduction.
Experimental Techniques
Failure of the array retrieval system because of corrosion limited the experimental design to one recovery after about ten months rather than three recoveries as planned. Although intermediate recoveries may have demonstrated some short-term effects, it can be concluded that the overall findings would not have changed because even after 10 months in situ little degradation of the added oil had occurred. Interim samples would have been critical if most of the oil had been degraded.
Results of sample analyses indicate that the SADRS design is sound from a biological point of view even though two important artificial effects are introduced. Because sediment in the recolonization boxes is contained above the natural seafloor, it tends to erode from the boxes during periods of storm-induced currents. The only practical solution may be to limit experimental studies on the mid shelf to more quiescent periods by avoiding winter months. Wave induced erosion is not a problem near the shelf break. The second artificial effect is the refugium attraction for nestling organisms (primarily hakes, Urophycis sp., and cancroid and galatheid crabs). Other than possible caging, no acceptable solution exists. The cover-closing mechanism design is also satisfactory, only the materials used in its construction need improvement. Portions of the arr~y which move or must bear critical weight must be non-corroding or well isolated and protected by anodes. Because of the diversity of materials (sheets, tubes, bolts, bars) it is virtually impossible to build experimental arrays from completely galvanically compatible metals.
Macrobenthos and Meiobenthos Colonization
Erosion of sediment from the recolonization boxes at Station B3 because .of storm-generated currents obviously affected recolonization by both macrofauna and meiofauna and many potential effects of oil on recolonization may have been obscured. However, species abundance differences between oiled and unoiled boxes can be interpreted as oil effects.
The rate of colonization of unoiled sediments by macrobenthos was intermediate between that observed in shallow-water habitats and that
9
,,1 observed in the deep-sea. Colonization rate appeared somewhat slower at the shelf break Station A5 than at the more frequently disturbed mid shelf Station B3, and long-lived species relying on planktonic larval dispersal were $lower to recolonize than short-lived species with effective short range dispersal. The colonization of unoiled sediment by meiobenthos was apparently much slower than previously reported, but may have been the result, at least partially, of selective erosion of meiobenthos with the sediment, especially at Station B3.
Generally, based upon comparison of oiled and unoiled sediment, there was no demonstrable effect of Prudhoe Bay crude oil contamination on the colonization by either macrobenthos or meiobenthos. At the swale Station B3 there was no effect of oil contamination on the colonization success of any dominant macrobenthic or meiobenthic species, although trends may have been obscured by erosion induced, altered sediment parameters in the recolonization boxes. At the shelf break (Station AS) the amphipod, Leptocheirus pinguis, and the polychaete, Lumbrineris latreilli, seemed to be less successful colonizers of oiled sediment, but the opportunistic polychaete, Capitella capitata, was more abundant in oiled sediment. Other benthic amphipods, a group with documented sensitivity to petroleum hydrocarbons, were equally abundant in oiled sediment and control 'sediment.
Petroleum Hydrocarbon Weathering and Microbial Response
The persistence of the oil in sediments in the recolonization boxes, both total amount and qualitative composition, is probably the most surprising result of this study. Except for one treatment between 45% and 91% of the total added oil remained in· the sediments. In addition, although the potentially toxic naphthalenes and phenanthrenes were selectively lost from the sediments, concentrations of these compounds remained approximately one-third to one-half those originally added. The muddy sands at the shelf break (Station AS) generally retained about twice as much oil as the fine sands at the swale Station B3.
CONCLUSIONS
Since the experiment described in this report tested the effects of oil contamination on colonization of azoic sediment and not the effects on indigenous connnunities, since colonization of uncontaminated sediment was slow and generally incomplete, and since Prudhoe Bay crude oil is of relatively low toxicity, it is unwise to conclude that contamination of the Middle Atlantic outer continental shelf sea-bed by crude oil will not harm the benthos. A cautious conclusion appears to be that if crude oil from formations in the Middle Atlantic Bight is similar to Prudhoe Bay crude in toxicity, contamination of the seafloor on the outer continental shelf would
10 pose a less serious biological threat than it may in other OCS areas, and probably would not result in effects as severe as those reported from spills of more toxic refined products.
Results of this study are consistent with the hypothesis that habitats consisting of finer grained sediments which are less frequently disturbed (e.g. the shelf break versus the outer shelf, swales versus ridges) are more susceptible and sensitive to oil contamination.
LITERATURE CITED Menzie, c. A., D. A. Maurer and w. A. Leathem. 1980. An environ mental monitoring study to assess the impact of drilling discharges in the mid-Atlantic. IV. The effects of drilling discharges on the benthic community. In: Research on Environmental Fate and Effects of Drilling Fluids and Cuttings. Proceedings: Volume I, pp. 499-540. Washington, n.c. u.s.G.S. 1979. Middle Atlantic Outer Continental Shelf Environmental Studies. Volume III. Geologic Studies. U.S. Geological Survey, Woods Hole, MA (for the Bureau of Land Management under Memorandum of Understanding No. AA550-MU7-31).
V.I.M.S. 1979. Middle Atlantic Outer Continental Shelf Environmental Studies. Volume II. Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (Bureau of Land Management Contract Report No. AA550-CT6-6), 2420 P•
11 -
CHAPTER 1
INTRODUCTION
Donald F. Boesch - CHAPTER 1 TABLE OF CONTENTS
Rationale • .,.., Background 1-2
Objectives 1-4
LITERATURE CITED • 1-5 CHAPTER 1
INTRODUCTION
Donald F. Boesch
Rationale
The opening of the so-called frontier areas of the United States outer continental shelf (OCS) to petroleum exploration and production poses some new and significant environmental management questions for which technical information is urgently required. Understanding of the potential effects of development activities on ecosystem productivity and living resources needs to be improved to allow confident decision-making. Such effects are obviously difficult to predict for a number of reasons. Firstly, knowledge of environmental effects in areas of historic OCS petroleum development is generally quantitatively deficient and, furthermore, suffers from limitations of extrapolatability from one geographic area to another. Secondly, studies which could contribute to the prediction of effects have often severe limitations in their pertinence to the actual activities and environments. For example, laboratory bioassays of the lethal concentration of crude oil generally do not well simulate actual conditions of exposure. As a consequence, studies conducted to improve the basis of environmental decision-making are predominantly oriented toward description of environmental features or processes, which only indirectly relates to a definition of the susceptability and sensitivity of the ecosystem.
The studies described in this report are an attempt to enhance understanding of the fate and effect of petroleum hydrocarbon constituents of crude oil in the benthic environment of the outer continental shelf of the Middle Atlantic Bight under relatively environmentally realistic field conditions. Petroleum hydrocarbon contamination poses perhaps the most serious threat of oil and gas development to the outer shelf ecosystem. Petroleum pollution may result from catastrophic or small accidental discharges and from routine, low-level emissions. Because of the generally low solubility of petroleum hydrocarbons and the rapid dilution characteristic of outer shelf waters, toxic components of oil pose little threat to organisms resident in the water column, although life forms concentrated at the air-sea interface may·be susceptible. However, due to the affinity of hydrocarbons for particulate surfaces, concentrations of petroleum hydrocarbons in bottom sediments may be several orders of magnitude higher than in the water column following ~n oil spill or chronic emission. The most significant and frequently the only demonstrable effects of oil pollution are evidenced in the benthos of sediment habitats.
1-1 On the outer shelf, petroleum hydrocarbons might reach the seabed by direct introduction via a well or pipeline leak or by sedimentation of floating, dissolved or suspended oil by association with particles or aggregates of particles (e.g. zooplankton fecal pellets). The benthos of the outer shelf of the Middle Atlantic Bight comprises a significant portion of the food of demersal fishes (Sedberry and Musick 1979) and, in fact, contains several species of resource importance, e.g. the deep-sea scallop Placopecten magellanicus and the mahogan~ clam Arctica islandica.
Experimental determination of the effects of oil on the benthos is made difficult by problems associated with long-term maintenance of infauna! communities in the laboratory. This problem is only worsened by difficulties in maintaining outer shelf biota and outer shelf environmental conditions in the laboratory. Differences between experimental and natural conditions affect not only the organisms but the processes of loss and weathering of the petroleum hydrocarbons. Furthermore, it may be the young, post-larval stages of benthic organisms at the time of their recruitment which are most susceptible. These forms are difficult to work with experimentally.
It was reasoned that in situ field experiments provided a solution to some of these problems. On the other hand, there are some significant practical limitations for such experiments. In addition to technical obstacles concerning treatment and recovery of contaminated sediments, such experimental incorporation of oil could not be accomplished without severe disturbance to the natural community. Consequently, the experiments must have a somewhat artificial starting point following elimination of all animal. life, i.e. they must test the effects of subsequent colonization by benthos between azoic sediment and similarly treated but oil-contaminated sediment.
Background
Field experiments designed to elucidate the patterns of colonization of sediments by benthic organisms have been conducted in a variety of habitats and for a variety of purposes. Most studies have, oi course, been conducted in shallow water habitats where manipulation, deployment and retrieval of sediments is facilitated; however, studies have recently been extended to continental shelf (Boesch 1979) and deep sea (Grassle 1977, Desbruyeres et al. 1980). Although most of these studies have been conducted for the purpose of .elucidating rates and processes of connnunity recovery following disturbance, Brunswig et al. (1976) designed their study to assess growth rates and production by macrobenthos and many studies have heuristically produced understanding about population dynamics, dispersal mechanisms and species interactions.
1-2 Most studies of the colonization of azoic sediments by macrobenthos were reviewed by Boesch and Rosenberg (in press). Other ~9re recent publications not included in their review are by Fredette (1~80), Santos and Simon (1980) and Desbruyeres et al. (1980). These studies have basically shown that in inconstant and frequently ·perturbed habitats, colonization by macrobenthos may proceed very ~apidly, within a few weeks, and the initial colonists are generally ao~inants in the antecedent, natural community. On the other hand, in ~nvironmentally constant, infrequently disturbed, and cold water habitats, colonization proceeds much more slowly (Boesch and Rqsenberg, in press). A recently demonstrated exception to this pattern w~s the s~rprisingly rapid colonization of sediments exposed .in ·the deep sea for 6 months by Desbruyeres et al. (19.80).
Preliminary colonization experiments on the outer continental shelf of the Middle Atlantic Bight suggested an intermediate rate of colonization and community resilience, wherein important components of the natural community were lacking after 9 months of exposure (Boesch 1979, Boesch and Rosenberg, in press). Species which were relatively mo~ile as adults, such as amphipod crustaceans, were successful early col~nizers, while those which rely on periodic production of . ·planlctonic . larval stages for dispersal were slow to re-establish. fhis study was conducted at Station BS, in an eroded flank habitat near the pres~nt stations B3 and B6.
Fewer studies have been conducted on the colonization of azoic sediments by meiobenthos (Conrad 1976, Sherman and Coull 1980, De~bruyere$ et al. 1980). These results have shown very rapid colonization, within hours or days, of the community as a wesult of "passive" tr~nsport of resuspended meiofauna (Bell and Sherman 1980)~
'1'1!\ Although th~re is substantial literature on the effects of oil on benthic coDllllunities (reviewed by Sanders et al. 1980), most of the e~isting knowledge of these effects results from observations following spills or chronic discharges in which the conceµtration or mpde of exposure of the organisms to petroleum hydrocarbons are frequently not known and is uncontrolled. The most thoroughly documented episode of substantial lasting effects of petroleum on benthos resulted from studies following the spill of the barge Florida off We$t Falmouth, Massachusetts (Michael et al. 1975, Sanders et ~1, 1980). Effects were demonstrated at least 7 years after the spill. Ano~her particularly deleterious episode resulted from the large spill of the Amoco Cadiz off Brittany (Cabioch et al. 1978). In both the Wr~t Fal~outh and Brittany incidents benthic am.phipod crustac~ans were among the most. seriously affected biota. Because benthic amphipods comprise such an important component of the benthos of ·the Middle Atlantic outer continental shelf and are successful colonizers of ~isturbed sediment (Boesch 1979) it was reasoned that they would b~ useful indicators of the toxic effects of petroleum hydroacarbon~ ex_perimentally incorporated· into sediments.
1-3 Although there have been extensive laboratory testing of the toxicity of petroleum and its components on a variety of marine organisms and there have been studies of the degradation and weathering of oil in the laboratory and in surface slicks, few studies have attempted in situ experiments on the ef~ects of sediment-accommodated oil and the weathering of that oil. The most notable and relevant example is the study by Anderson et al. (1978). Their experiments included placing oil atop and mixing oil into azoic sediments and placing them in an intertidal habitat off the Strait of Juan de Fuca, Washington. They found significant, but not major, effects on the colonizing macrobenthos, particularly bivalves, and slower weathering of petroleum hydrocarbons mixed into sediments compared to oil introduce4 on the surface. The concentration of total petroleum hydrocarbons incorporated into the sediments was reduced by a factor of two after an exposure period of 100 days. Microbial decomposition of the oil homogenized into the sediment was thought to be limited by lack of oxygen penetrating below uppermost sediment layers.
Objectives
1. Develop and refine techniques for conducting in situ experiments involving exposure and recovery of pollutant-contaminated sediments at continental shelf sites.
2. Assess the colonization of macrobenthos and meiobenthos following catastrophic disturbance (complete mortality of fauna) in different outer continental shelf habitats of the Middle Atlantic Bight.
3. Determine the effects of petroleum hydrocarbon contamination on the rate of colonization and recovery of these communities.
4. Determine the response of the microbial community to disturbance and contamination of sediments with crude oil under in situ conditions and, in particular, assess the response of microbes capable of degrading petroleum hydrocarbons.
5. Determine the quantitative and qualitative changes in petroleum hydrocarbons incorporated in natural sediments under in situ conditions on the outer continental shelf.
6. Synthesize these and other results to assess the magnitude and duration of effects of crude oil contamination of sediments in the benthic ecosystem and identify sensitive and susceptible habitats.·
1-4 LITERATURE CITED Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydrocarbon concentrations in the sediment. J. Fish. Res. Bd. Canada 35 (5): 776-790.
Bell, S. S. and K. M. Sherman. 1980. A field investigation of meiofaunal dispersal: tidal resuspension and implications. Mar • .Ecol. Prog. Ser. 3:245-249.
Boesch, D. F. 1979. Benthic ecological studies: macrobenthos. In: Middle Atlantic Outer Continental Shelf Environmental Studies, Volume IIB, Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62), Chap. 6, 301 P•
Boesch, D. F. and R. Rosenberg. In press. Response to stress in marine benthic communities. In: G. M. Barrett and R. Rosenberg (eds.), Stress Effects on Natural Ecosystems. John Wiley, New York.
Brunswig, D., w. E. Arntz and H. Rumohr. 1976. A tentative field experiment on population dynamics of macrobenthos in the western Baltic. Kieler Meeresforsch., Sonderb. 32:49-59.
Cabioch, L. J., c. Dauvin, and F. Gentil. 1978. Preliminary obser vations on pollution of the sea bed and disturbance of sub-littoral connnunities in Northern Brittany by oil from the AMOCO CADIZ. Mar. Pollut. Bull. 9:303-307.
Conrad, J.E. 1976. Sand grain angularity as a factor affecting colonization by marine meiofauna. Vie et Milieu, Ser B, 26:181-198.
Pesbruyeres, D., J. Y. Bervas, and A. Khripounoff. 1980. Un cas de colonisation 'rapide d'un sediment profond. Ocean. Acta 3(3):285-291.
Fredette, T. J. 1980. Macrobenthic colonization of muddy and sandy substrates in the York River, Virginia. A thesis presented to the School of Marine Science, College of William and Mary, Gloucester Point, Virginia. 62 P•
Grassle, J. F. 1977. Slow recolonization of deep-sea sediment. Nature 265:618-619.
1-5 Michael, A. D., c. R. Van Raalte and L. s. Brown. 1975. Long-term effects of an oil spill at West Falmouth, Massachusetts. In: 1975 Conference on Prevention and Control of Oil Pollution-, Proceedings, March 25-27, San Francisco. American Petroleum Institute, Washington, D.C., pp. 573-582. Sanders, H. L., J. F. Grassle, G. R. Hampson, L. s. Morse, s. Garner-Prince, and C. C. Jones. 1980. Anatomy of an oil spill: long-term effects from the grounding of the barge Florida off West Falmouth, Massachusetts. J. Mar. Res. 38:265-380. Santos, s. L. and J. L. Simon. 1980. Marine soft-bottom community establishment following annual defaunation: larval or adult recruitment. Mar. Ecol. Prog. Ser. 2:235-241.
Sedberry, G. R. and J. A. Musick. 1979. Food habits of fishes. In: Middle Atlantic Outer Continental Shelf Environmental Studies, Volume IIC, Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62), Chap. 9, 159 p. Sherman, K. M. and B. C. Coull. 1980. The response of meiofauna to sediment disturbance. J. Exp. Mar. Biol. Ecol. 46:59-71.
1-6
\ CHAPTER 2
FIELD METHODS AND PRELIMINARY EXPERIMENTATION
Eugene M. Burreson and Marcia A. Bowen
-
- CHAPTER 2
TABLE OF CONTENTS
Rationale for Station Locations •.••• . • 2-1
Surface Activated Deployment and Recovery System • 2-1
Oil Characterization • . 2-1
Target Oil Concentration, Replication and Recovery Schedule ••• 2-3
Sediment Collection and Initial Experimentation. •• 2-3
Sediment Preparation 2-5
Deployment • • 2-7
Recovery 2-7
Recolonization Box Sampling. •• 2-9
LITERATURE CITED . . 2-11 CHAPTER 2
FIELD METHODS AND PRELIMINARY EXPERIMENTATION*
Eugene M. Burreson and Marcia A. Bowen
Rationale for Station Locations
Three sampling sites were chosen on the Middle Atlantic Outer Continental Shelf. Station AS (39°21.S'N, 72°37.0'W, 118 m depth) was established on the shelf break at a location four nautical miles WNW of Station A2, a station sampled during the two-year BLM Environmental Studies Program (Figure 2-1). This location was chosen on the basis of its similar muddy-sand sediments and depth as previously sampled Station A2, but its greater distance from the two exploratory drilling rigs that were working very close to A2. Alternate locations along the same isobath as A2 are preempted by active exploratory drilling on leased tracts. Thus AS is in the same environmental regime as the lease tracts which yielded the only significant shows of oil or gas reported, but far enough removed so that there should be no significant interference by exploratory activities (Menzie et al. 1980). Two sites were chosen from the outer shelf zone (Boesch 1979) which reflect the extremes in sedimentary regime for that region. Station B3 (39°21.0'N, 73°02.l'W, 72 m depth) is in a topographical depression (swale) and was sampled during the Environmental Studies Program. Topographical depressions generally have finer sands with higher silt-clay content and lower rates of hydrodynamic disturbance than surrounding habitats and may serve as depositional sinks for pollutants. Station B6 (39°22.5'N, 73°02.0'W, 54 ~ depth) was selected to represent the outer shelf ridge habitat, areas of medium-coarse sand and moderate disturbance which would theoretically be least likely to retain pollutants. Station B6 is 2.5 nautical miles SW of previously sampled Station B2.
Surface Activated Deployment and Recovery System (SADRS)
Biological considerations, development, testing and final design of the SADRS array used in these experiments have been described in the Phase I Final Report which is included here as Appendix A.
Oil Characterization
Prudhoe Bay crude oil, provided by Battelle Northwest, was utilized in these experiments. This oil was chosen by the Bureau of
* Laboratory methods are given in subsequent chapters.
2-1 i / l ~--,~-- { " ,~------... ,-..._ •.J .... (~·-...... ------.___, ___ __ -· ---, \•." \ ··-- ..., ! ··-··-··, ...,, I ' \ ii i' \ ; : i • A5 / i / '\ I / ) 'l ;/ ,. ./at ,,/ I "-j ( I j '"',•\ ( I I I' I I I ,-"I I I i \ I I .i ,' V J I . I i .I / i l ,_I . \ I : I i I ' i .. l / J<' 1:..,· I I . " .. I // \.j ' I ~If i ~
Figure 2-L Station locations for the Benthic Recolonization Study.
2-2 Land Management as being potentially most like the oil expected from Baltimore Canyon Trough structures. Characterization was provided by Battelle and analysis using VIMS methodology and equipm~nt was also coµducted (Appendix C).
Target Oil Concentrations, Replication and Recovery Schedule
Three oil concentrations were used in these experiments-- SO mg/kg, 250 mg/kg and 2500 mg/kg. These concentrations were chosen based on their correspondence to the range of concentrations of . petroleum hydrocarbons in sediments contaminated by oil spills or chronic discharges, and concentrations shown to produce deleterious effects in other experimental ·studies (Anderson et al. 1978).
Each oil array contained three fiberglass boxes with the middle oil concentration (250 mg/kg). The fourth box was divided in half by a fiberglass partition. One half contained sediment with the low oil concentration and the other half sediment with the high oil concen tration. Thus there were three replicates of the middle oil concentration, but no replication of the high or low concentrations. Each control (unoiled) array contained four undivided boxes with unoiled sediment from the appropriate station.
The experimental design called for deployment of three control and three oiled arrays at each station. Subsequently, at 3 month intervals, one control and one oiled array would be recovered from each station.
Each recolonization box was labeled with a 5-digit alpha-numeric sequence as follows:
First two digits - Station Number Third digit - Array type, 0 = oiled, C = control Fourth digit - Recovery.period= 1, 2, or 3 Fifth digit - Box number. For oiled arrays 1, 2 and 3 are · middle concentrations, 4 is low concentration and 5 is high concentration. For control arrays 1-4 are the four unoiled control boxes.
For example, AS-02-4 is the low oil concentration box in the oil array from the second (6-month) recovery at Station AS.
Sediment Collection and Initial Experimentation
Approximately 225 gallons of sediment were collected at each of the three sites during 19-22 June 1979 using an anchor dredge with an attached impervious reinforced plastic bag. The sediment was stored in acetone-cleaned 55 gallon drums.
2-3 In order to assess the degree of homogenization of a 9 cubic foot cement mixer and the percent recovery of the hydrocarbon extraction method, a short experiment was conducted using three different oil concentrations. Ten kilograms of sediment from Station BJ were mixed for one hour in the cement mixer and three 20 gram control samples were removed. A 2.58 ml sample of Prudhoe Bay crude oil dissolved in . hexane was added to the remaining sediment in the cement mixer and mixed for one hour. Three 20 gram samples were selected from different areas in the mixer. This procedure was repeated, adding 25.37 ml of oil and then 27.62 ml of oil. After each addition the sediment was mixed for one hour and then three 20 gm samples were removed. All samples were immediately extracted in CH3-0H-hexane by a method used by Anderson (pers. comm.) which is a slight modification of his published method (Anderson 1978). The sample extra.ct was concentrated by evaporation and separate aliphatic and aromatic fractions were eluted on a silica-gel column., Chromatograms resulting from capillary column chromatography were used to'measure total oil in each sample. Concentrations of the n-alkanes C18, C20, and C22 in the sediment were derived based on known concentrations of these components in the oil, based on the assumption that these components are not lost by volatility and are completely dissolved in the hexane. In the two lower oil concentrations (Table 2-1) n-alkaline concentrations were variable. However, for the highest concentration, new glassware and a more precise injection technique was used. These results show good replicability, indicating a homogeneous mixture, and a concentration close to the target concentration, showing that the methodology employed accurately extracts and measures all the oil in the sediment.
Table 2-1. Concentration of three n-alkanes recovered from oil dosing experiment. Values are ml/kg sediment.
Sample No. C18 C20 C22 ~ Target Concentration 0.29 ml oil/kg sed (dry weight) I 1 0.70 2 0.38 0.53 0.42 3 0.15 0.19 0.18 $,
Target concentration 2.94 ml oil/kg sed (dry weight)
1 0.95 .78 2 3.64 5.19 4.46 3 2.75 3.14 2.38 ~
Target concentration 5.88 ml oil/kg sed ('dry weight)
1 5.32 6.33 5.73 2 6.10 6.06 5.62 3 8.25 7.59 5.45 t3!I
2-4 The target oil concentrations should be those concentrations remaining in the sediment after deployment on the sea floor. Thus it was necessary to ascertain the extent to which a homogeneous oil-sediment mixture lose$ oil when exposed to flowing sea water, so that this loss could be compensated for during sediment preparation. To assess this loss, five kilograms of sediment from each station were ~ixed by hand for about 10 minutes with 5 ml of Prudhoe Ray crude oil. A 20 gram sample was removed from each 5 kilogram portion and the re~aining sediment was placed in two one-quart polyethylene containers (232 cm2 surface area) filled to within 1 cm of the top. The cont"ainers were then immersed for 19 hours to a depth of 5 cm in freshwater flowing at a rate of 500 ml/min. Containers were removed and .a 20 gram sediment sample was taken and analyzed as previously described. While this experiment does not exactly duplicate oceanic deployment, it gives a relative approximation of oil lost. Although results (Table 2-2) suggest that hand mixing does not yield a homog~neous oil-sediment mixture, they also indicate that most of the oil remains in the sediment. Thus a decision was made to increase the target concentration by 10% to compensate for any possible loss during deployment.
Table 2~2. Results of immersion test (mg oil/20 gm sediment)
Station AS B3 B6
Before Immersion 11.0 29.6 25.9
After Immersion 8.7 19 .o 26.3
Sediment Preparation
The control or unoiled samples were prepared first, A 9 cubic foot cement mixer was washed first with water, then with acetone and filled with 50 gallons of sediment--10 gallons from each of the 5 barrels for that station. The mixer opening was covered with aluminum foil to prevent contamination from diesel fumes and mixed for one hour. The sediment was then poured into the fiberglass recolonization boxes. In one control box in each array three thin layers of colored sand {blue, red and yellow) were placed every 3.8 cm throughout the box to ~llow assessment of sediment disturbance. Dacron covers we.re attached along all four sides of each box with velcro, and the boxes were placed in large wooden racks. The racks were transferred to a walk-in freezer and the boxes frozen at -35°F. For oiled sediments, equal amounts of sediment were taken from ~ach barrel from the appropriate station, weighed, placed in the acetone-washed mixer and mixed for approximately 10 minutes. The appropriate amount of oil for each concentration (Table 2-3) was dissolved in 500 ml of heptane and added to the sediment. The mixer opening was covered, the sediment mixed for 1.5 hours, and then transferred to the fiberglass boxes. No colored sand layers were placed in oiled boxes. Each ~ox of
2-5 fa.,
Table 2-3. Amounts of oil and sediment used in mixing the three target concentrations.
~
~ I. 50 mg/kg Sed. Wts. Oilin~
AS - 0.0491 ml oil/kg sed. X 85.5 kg C 4.2 ml oil
B3 - 0.054 ml oil/kg sed. X 86.8 kg = 4.7 ml oil r-,.
B6 - 0.053 ml oil/kg sed. X 99.1 kg = 5.3 ml oil
II. 250 mg/kg
{!et. AS - 0.243 ml oil/kg sed. X 282. 7 kg = 68.7 ml oil
AS' 2 - 0.243 ml oil/kg sed. X 208.0 kg = 50.6 ml oil
B3 - 0.269 ml oil/kg sed. X 279.0 kg = 75.1 ml oil
B3' - 0.269 ml oil/kg sed. X 298.2 kg = 80.2 ml oil
B6 - 0.264 ml oil/kg sed. X 268.6 kg = 70.0 ml oil
B6' - 0.264 ml oil/kg sed. X 314.1 kg = 82.9 ml oil
pt,
III. 2500 mg/kg
AS 2.4 ml oil/kg sed. X 106.3 kg = 225.3 ml oil
B3 2.7 ml oil/kg sed. X 101.0 kg = 272.0 ml oil A
B6 2.6 ml oil/kg sed. X 104.1 kg = 270.6 ml oil
1 Example calculation.
50 mg/kg+ 10% (to allow for washing)= 55 mg/kg dry sediment 0.055 gm/kg dry x 0.78 gm dry/gm wet= 0.043 gm oil/kg wet sed. 0.043 gm oil/kg ~et sed. x 1 ml oil/0.884 gm oil= 0.049 ml oil/kg wet sed.
2 The primary oil concentration was mixed in two separate batches because of the large amount of sediment required.
2-6 oiled sediment was immersed in a running seawater bath for 8 hours to remove the readily leachable oil. The boxes were then covered and placed in racks at -35°F. All boxes were frozen for at least 4 days, then thawed for 12 hours, frozen for 36 hours, thawed for 12 hours, and finally frozen for 5 days. This freezing-thawing regimen was an attempt to assure that all organisms in the boxes, including the bacteria, were killed.
Deployment
The racks of boxes were transferred from ~he freezer to the ship i~ediately prior to departure and covered with sheets of 1 inch styrofoam to avoid excessive warming during transit to the first station. Upon arrival at each station nine Smith-McIntyre grabs were taken and samples were removed from each as follows:
Grab No. 1 2 3 4 5 6 7 8 9
Meiobenthos 2 2 2 Bacteria 3 Grain Size 1 1 1 1 1 1 (1 - 1 - 1) pooled TOC 1 1 1 1 1 1 (1 - l - 1) pooled Hydrocarbons (1 - 1 - 1) pooled
The remaining sediment was elutriated onto a 0.5 mm mesh screen to remove soft-bodied organisms and then washed through a second 0.5 mm scr~en. These two portions from each grab were placed into a 6.5% magnesium chloride solution for 30 minutes and then preserved in 10% formalin.
The arrays were rigged and deployed as shown in Appendix A. The sediment filled boxes were installed in each array and, immediately prior to deployment, one grain size core was taken from each control box and two bacteria cores were taken from one box in each control array. One core each for grain size, TOC, and hydrocarbon analysis was also taken from each oiled array box. Six arrays, three oiled and three control, were deployed at each station (Figure 2-2, Table 2-4).
Recovery
The first recovery cruise was conducted 5-9 November 1979, approximately three months after deployment. Because of problems discussed in Appendix A no arrays were recovered, and it was apparent that they could not be recovered from the surface as origin~lly planned. After considering many options it was determined that a manned submersible offered the best chance for a successful recovery. The second re~overy cruise was conducted on 17-25 April 1980 using the submersible MERMAID II. One control array was recovered at Station B3. The third recovery cruise was conducted from 1-14 June 1980. An oiled and cont~ol array were recovered from Station AS and an oiled array was
2-7 A5 B3 B6 y 43025 y 43010 , I I I I ' j C3 .. • i> 03 ~ N co coN N X I .01 N
02 X X • l C2 • • Jc1 l
j j j I J - y 43020 y 43005 y 43020
0 0.1 0.2 0.3 0.4 0.5
Nautical Miles
Figure 2-2. Relative positions of arrays on deployment at each station. Coordinates are 9960 series Loran C Signals in microseconds. X marks the position of grab sampling.
}) , 1) ' 13 Table 2-4. Loran C coordinates (microseconds) and deployment date for arrays deployed.
9960 Loran C
Station X y Array Date/Time
AS 26280.1 43022.9 C3 9 Aug/2108 26278.3 43022.9 03 "/2158 26277.8 43022.0 01 9 "/2238 26278.1 43021.3 Cl "/2334 26278.9 43021.3 C2 10 "/0015 26279.5 43021.5 02 10 "/0045
B3 26437.3 43008.2 03 10 Aug/1145 26436.8 43007.2 C3 "/1222 26437.5 43008.4 01 "/1330 26437.6 43008.6 02 11 "/0640 26436.5 43007.5 C2 11 " /1030 26436.2 43008.1 Cl 14 " /1130
B6 26457. 7 43021.8 03 14 Aug/0805 26456.5 43022.1 C3 "/0850 26457.0 43021.9 02 "/0924 26456.7 43021.7 Cl "/0948 26456.4 43021.4 C2 "/1010 26456.2 43021.9 01 "/1030 recovered from B3 (Table 2-5). Arrays were located with the submersible's sonar after the sub was directed to the appropriate Loran C coordinates by the support vessel. The submersible then placed a cover into each box of the array. Each cover consisted of a large square of 3/8 inch neoprene glued to the bottom of a heavy circular steel plate. After deploying all the covers the submersible attached one end of a heavy line to the array and released a buoy attached to the other end of the line. When the buoy surfaced the line and array were hauled to the surface from the support vessel. Six grab samples were also collected at each station and sampled similarly to the first six deployment grabs.
Recolonization Box Sampling
Immediately after recovery each box in each array was photographed and the sediment depth recorded for each box. For control arrays three cores were taken from one box for hydrocarbon, TOC, and grain size analyses, and five cores from three boxes for meiofauna analysis. The remaining sediment was processed for macrofauna as described for grabs.
2-9 Table 2-5. Fate of all arrays deployed for the Benthic Recolonization Study. See appropriate cruise reports for details.
Cruise 14R Array Cruise 12R Cruise 13R Leg 1 Leg 2
AS Cl Deployed 8/9/80 Signal-No Response C2 ti Signal-N.R. Recovered C3 ti Signal-N.R. 01 ti Signal-N.R. Recovered 02 " Signal-N.R. Located not recovered 03 ti Signal-N.R.
B3 Cl Redeployed 8/14/80 Cable parted C2 Lost* Recovered empty C3 Deployed 8/11/80 Signal-N.R. Recovered 01 II Signal-N.R. 02 Lost* Recovered 03 Deployed 8/11/80 Signal-N.R.
B6 Cl Deployed 8/14/80 Cable parted C2 II C3 ti 01 ti Cable parted 02 II 03 ti
* Array B3C2 broke from release and free-fell to the sea floor. Array B302 was deployed with the release safety pin in place.
2-10 IA. For oiled arrays, five bacteria cores were taken from the three boxes with the medium oil concentration and two cores each from the low and high concentrations. One core was taken from each of the five boxes and frozen for hydrocarbon, TOC, and grain size analyses. For meiofauna, one core each was taken from the low and high oil concentrations and from two of the medium concentrations boxes. Three cores were taken from the third medium concentration box. The - remaining sediment was processed for macrofauna. LITERATURE CITED
Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydrocarbon concentrations in the sediment. J. Fish Res. Bd. Canada 35(5):776-790.
Boesch, D. F. 1979. Benthic ecological studies: macrobenthos. In: Middle Atlantic Outer Continental Shelf Environmental Studies. Volume IIB. Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62). Chap. 6, 301 P• Menzie, c. A., D. Maurer and w. A. Leathern. 1980. An environmental monitoring study to assess the impact of drilling discharges in the Mid-Atlantic. IV. The effects of drilling discharges on the benthic community. In: Research on Environmental Fates and Effects of Drilling Fluids and Cuttings. Proceedings: Volume I, pp. 499-540. Washington, D.C.
2-11 CHAPTER 3
SEDIMENT TEXTURE AND ORGANIC CARBON
Linda C. Schaffner and Donald F. Boesch
- CHAPTER 3
TABLE OF CONTENTS
INTRODUCTION . . . . ~ . . . 3-1
METHODS ...... ~ . . . 3-1 RESULTS AND DISCUSSION 3-1 Grain Size ••• 3-1 Organic Carbon •••• 3-4
LITERATURE CITED .•. . 3-8 CHAPTER 3
SEDIMENT TEXTURE AND ORGANIC CARBON
Linda c. Schaffner and Donald F. Boesch
INTRODUCTION
It has been shown that subtle differences in bottom sediment texture on the Middle Atlantic continental shelf may strongly influence biotic and geochemical variables (Boesch 1979; Boesch and Gaston, in press). Therefore, it is essential that bottom sediments be carefully characterized in any study designed to evaluate geochemical alterations on biotic response during the colonization experiments. Analyses of sediments during this experiment were designed to: a) determine if sediment characteristics in experimental boxes were altered by biological and physical processes during the duration of the experiment; b) evaluate the possibility that faunal patterns in the boxes could be attributed to sediment varability rather than experimental treatment; and c) consider th~ effects of experimental treatments on chemical constituents.
METHODS
Samples for grain size and total organic carbon analyses were collected from. grab samples or experimental boxes and analyzed in the laboratory using procedures identical to those described by Boesch (1979). Grain-size samples were collected in 3.5 cm diameter clear acDylic core tubes and total organic carbon samples were collected in similar 2.2 cm diameter tubes. Those cores pooled (Chapter 2) were thoroughly mixed in the laboratory before subsampling. Grain size distribution was determined using sieve separation, a rapid sand analyzer outfitted with a gravimetric sensor, and a Coulter electronic particle counter for the 263 µm fraction. Statistics of the distribution were determined using Folk's (1968) graphic measures.
RESULTS AND DISCUSSION
Grain Size
Sediment placed in experimental boxes at AS changed little over the 45 weeks of exposure (Figures 3-1 and 3-2). Nearly all variation in experimental treatments fell within the ranges exemplified by the natural community. Visual observations of the boxes when retrieved indicated that, except for some winnowing in the corners, most boxes
3-1 MEDIAN DIAMETER ( (1) SORTING COEFFICIENT ( £)) 3.0 2.5
2.0
2.5 1.5 1.0 I 2.0 0.5
0 R D R 0 R D R D R D R D R D R D R D R NATURAL CONTROL OIL-- NATURAL CONTROL ---OIL -- MIO LOW HIIH MID LOW HIGH
0.6 SKEWNESS 12.0 GRAVEL (%)
0.4 o---e 10.0
0.2 ~ o-A 8.0
0 6.0
-0.2 4.0
-0.4 2.0
D R 0 R D R 0 R 0 R DR OR DRORDR NATURAL CONTROL OIL-- NATURAL CONTROL ---OIL-- MIO LOW HIGH MID LOW Hl8H
FINE SAND (%) SILT and CLAY (%)
80.0
70.0 20.0
60.0 h ~ 0-... 50.0 -r 10.0
40.0
D R D R D R D R D R D R D R D R D R D R NATURAL CONTROL OIL-- NATURAL CONTROL--- OIL-- ,.. MID LOW Hl8H MID LOW HIGH
Figure 3-1. Comparison of sediment grain size parameters from deployment (D) to recovery (R) at Station AS. Lines connect medians or single values and vertical lines represent ranges. 3-2 j , j
A NATURAL COMMUNITY 6 CONTROL 0 LOW OIL
t> MIO OIL
• HIGH OIL
w I w
R
R~DR R D D D
40 30 20 10 ----- PERCENT COARSE SANO ANO GRAVEL---- Figure 3-2. Changes of grain size distribution in grab samples and recolonization boxes recovered from -Station AS. D, deployment; R, recovery •. had 10 to 12 cm of sediment remaining. The exception to this was the low concentration oiled box which had fairly severe erosion in box corners. Three complete dyed sand layers were noted in an AS control box indicating that there was lit•t1e mixing of sediments in this box by either physical or biological processes.
The sediment in boxes at Station BJ changed markedly during the experimental period (Figures 3-3 and 3-4). The relative percentage increase in coarse components and the lack of change in the silt-clay fraction from deployment to recovery suggest that fine sands were the primary constituent removed from the boxes. Sanders (1958) noted that particles of this size are the most easily resuspended in ~he grain size spectrum. Boxes with sediments oiled at the mid and high concentrations were apparently the most severely eroded, exhibiting depressed concentrations of medium as well as fine sands with a concomitant increase in the coarse sand and gravel components. Recorded sediment depths in control boxes ranged from O cm in corners to between 3 and 7.5 cm in box centers. Only the lowermost layer of dyed particles were observed in control boxes. Oiled boxes from BJ had less than 4 cm of sediment in all boxes.
Organic Carbon
Total organic carbon concentrations in natural sediments and in experimental sediments prior to deployment (Figure 3-5) were similar to those previously determined at Station A2 and Station B3, respectively (Boesch 1979). Addition of crude oil to the sediments resulted in no obvious increase in total organic carbon in pre-deployment sediments at AS. Given the concentrations of oil added, increase in organic carbon content of the sediments should be within the natural variability at the low and middle oil concentrations, but nearly 2 mg/g at the high oil concentration. Major changes in organic carbon concentration on recovery were not noted at AS except for a substantial reduction in the box treated with high concentration of oil. We have no explanation for this apparant reduction.
Organic carbon concentrations in the high oiled treatment at B3 did reflect the addition of crude oil. Total organic carbon concentration increased about 1 mg/g above natural concentrations. All experimental treatments showed marked decreases in the organic carbon concentrations on recovery. This parallels and is probably caused by the selective erosion of fine sediment from the boxes.
3-4 2.5 MEDIAN DIAMETER ( 0) SORTING COEFFICIENT ( ~)
2.0 +-+ 2.0
\ \ '~ 1.5
1.5 1.0
0.5
D R D R D R D R D R D R D R D R O R O R NATURAL CONTROL OIL --- NATURAL CONTROL OIL--- MID LOW HIGH MID LOW HIGH
SKEWNESS 30 GRAVEL {%)
0
-0.2 20
-0.4
-0.6 10 -0.8 I D R D R DRDRDR 0 R D R D R D R O R NATURAL CONTROL OIL -- NATURAL CONTROL OIL -- MID LOW HIGH MID LOW Hl8H
FINE SANO (%) SILT and CLAY (%) 9.0 80 8.0 7 0 L 7.0 60 Ti 6.0 50 5.0 40 4.0
D R 0 R D R D R O R 0 R 0 R D R O R D R NATURAL CONTROL OIL- NATURAL CONTROL OIL -- MID LOW HIGH MID LOW HIGH Figure 3-3. Comparison of sediment grain size parameters from deployment (D) to recovery (R) at Station B3. Lines connect medians or single values and vertical lines represent ranges. 3-5 • NATURAL COMMUNITY 6 CONTROL
0 LOW OIL
t> MIO OIL
• HIGH OIL
w I 0\
•R
40 30 20 10 ----PERCENT COARSE SANO ANO GRAVEL---- Figure 3-4. Changes of grain size distribution in grab samples and recolonization boxes recovered from Station B3. D, deployment; R, recovery •
. l ,,\ .l ,l l _) ,l ) ,) 5 A5 83
4 .... z IJJ :E 3 0 ,,i IJJ (/)
2 ~ ~ C' E •t+
o_....--,--r---r--.-r----r----- D R R D R R R D R D R R D R D R D R NATURAL CONTROL ---OIL-- NATURAL CONTROL ---OIL--- MID LOW HIGH MID LOW HIGH
-~
Figure 3-5. Comparison of sediment total organic carbon values at Stations AS and B3 from deployment (D) to recovery (R). Lines connect means or single values and vertical lines represent ranges.
3-7 LITERATURE CITED
Boesch, D. F. 1979. Benthic ·ecological studies: macrobenthos. In: Middle Atlantic Outer Continental Shelf Environmental Studies, Volume II B, Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62), Chap. 6, 301 p.
Boesch, D. F. and G. R. Gaston. In press. The macrobenthos of the New York Bight: medium and small scale patterns. In: The macrobenthos of the New York Bight region. N0AA/0MPA Tech. Rept., Rockville, Md.
Folk, R. L. 1968. Petrology of sedimentary rocks. Hemphill's, Austin, Texas. 170 P• Sanders, H. L. 1958. Benthic studies in Buzzards Bay. I. Animal-sediment relationships. Limnol. 0ceanogr. 3:245-258.
3-8 CHANGES IN PETROLEUM HYDROCARBONS IN - EXPBRIMENTALLY OILED SEDIMENTS
Craig L. Smith and Paul O. deFur
- CHAPTER 4
TABLE OF CONTENTS
INTRODUCTION. 4-1
METHODS • 4-1 Extraction • 4-1 Fractionation. . .. . 4-2 Gas Chromatography . 4-2 GC-MS . . 4-2 Calculations 4-3
RESULTS . 4-3
DISCUSSION. . 4-8
LITERATURE.CITED. • 4-13
A CHAPTER 4
CHANGES IN PETROLEUM HYDROCARBONS IN EXPERIMENTALLY OILED SEDIMENTS
Craig L. Smith and Paul O. deFur
INTRODUCTION
_The purpose of these studies is to provide a detailed description of the nature of the Prudhoe Bay crude oil which was mixed with the experimentally treated sediments.
Sediments nominally containing O (control), 50 (low-oil), 250 (mid-oil), and 2500 (high-oil) mg/kg of Prudhoe Bay crude oil were analyzed prior to deployment and after about nine months of in situ exposure at Stations AS and B3. --
The measurement of oil is not a straight-forward procedure because oil is a complex mixture of compounds with widely differing physical properties. Thus, determination of bulk oil by gravimetric or spectroscopic procedures readily shows how much oil is present, but gives no indication of relative concentrations of the various compounds which constitute the total oil sample. The gas chromatographic methods used in this study serve to measure not only total amount of oil, but to determine actual concentrations of certain aromatic compounds and compound classes which are expected to have measurable toxicity to marine organisms.
METHODS
All solvents used in this study were Burdick & Jackson high purity grade. Periodic gas chromatographic checks on the solvent were made to confirm purity. Silica gel was from Bio-Rad (Bio-Sil A, 100-200), and was oven dried to Activity I and solvent washed before use. All glassware was detergent washed, rinsed in distilled water and acetone, and oven-dried before use. Procedural blanks, employing the entire analytical process, were run to ensure the absence of artifacts.
Extraction Sediment core samples from the recolonization trays were extruded into pre-cleaned glass jars, which were immediately sealed with teflon-lined screw caps and frozen. After return to the laboratory, the samples were thawed and dried. Pre-deployment samples were oven-dried at 60°C; this procedure proved to yield unreliable results,
4-1 and was replaced by freeze-drying. A 20 g portion of well mixed dry sediment was Soxhlet-extracted for 48 hr with methylene chloride. The extract was reduced in volume on a rotary evaporator, and the methylene chloride replaced with hexane. Final stages of evaporation were effected by a stream of dry nitrogen. The extracts from the control, low-, and mid-oil sediments were adjusted to 1 ml, and the high-oil sediment extract to 25 ml.
Fractionation
A 1 ml aliquot of sediment extract in hexane was placed on a 1 x 20 cm column of silica gel topped with a 1.5 cm layer of activated Cu powder. Elution with 25 ml of hexane yielded an aliphatic fraction. The aromatic fraction was eluted with 40 ml of 80/20 (v/v). hexane/methylene chloride. The fractions were reduced in volume under a stream of dry nitrogen, and the solvent replaced with toluene. Final volume was adjusted to 0.2 ml.
Gas Chromatography
Gas chromatograms were obtained using a Varian 2740 instrument fitted with a flame ionization detector, Grob-type injection port, and a 0.3 mm x 20 m glass capillary column coated with SE-52. Samples of approximately 1 µl were injected with a toluene solvent plug using a hot-needle splitless injection technique. The GC oven was temperature programmed from 70-280C at 6C/mn, and held at 280C until sample elution was complete. Peak integration was done electronically using an HP-3354B Laboratory Data System. Quantification was accomplished by comparison of peak areas with those of known standard mixtures of n-paraffins and aromatic hydrocarbons chromatographed under identical conditions on the same day as the sample. GC peaks in the aliphatic fractions were mostly n-paraffins, and were easily recognizable by retention time and peak patterns. Aromatic fraction peaks were identified, using a GC-MS analysis of a Prudhoe Bay crude oil sample as a reference, by retention time and characteristic patterns of abundance. Although the various isomers of most aromatic compound groups were not separately identified because of overlapping peaks and the difficulty of distinguishing isomers by mass spectrum alone, the group identification is adequate for most purposes.
GC-MS Aromatic fractions A501-3 and A501-5 were analyzed by GC-MS. The samples were separated on a 30 m, 0.3 mm i.d. wall coated glass capillary containing SE-52 on silanized pyrex. The effluent was fed via an open, helium flushed coupling into a silanized pyrex, 350°C interface connecting directly to the mass spectrometer source. Operating parameters, of the mass spectrometer were as follows:
4-2 The estimations of total oil (as fresh crude oil equivalents) given in Table 4-1 rely on the assumption that the amount of the three n-paraffins in the oil is constant when compared to the bulk of the oil. The major processes which might alter this are microbial degradation and evaporation/dissolution. Since microbial degradation consumes n-paraffins at a far greater rate than isoprenoid hydrocarbons, this process would be detectable by changes in Cl7/pristane and Cl8/phytane ratios. Table 4-2 shows that these ratios determined from the recovered sediments are close to those in the fresh crude oil. Thus, microbial degradation has not been an important modifier of the nature of the oil, at least when considering the entire core depth. Evaporation or dissolution seem likewise not to have affected the amounts of n-paraffins of 16 or more carbons. The relative n-paraffin peak heights for Cl8, C20, and C22 compared with far less-volatile and soluble compounds are unchanged (see Figures 1 through 13).
Since the oil concentrations reported in Table 4-1 are in fresh crude oil equivalents, and the methods used in calculation were chosen to be insensitive to normal weathering changes in oil composition, these figures actually represent the oil not lost by physical processes such as oil flotation or winnowing away of oil-coated fine-grained sediments. This latter process is probably responsible for the low oil content of tray B302-l, which was extensively scoured by currents, leaving only a coarse residue of shell hash.
Because certain procedures employed in the analysis such as sediment drying and solvent evaporation incur evaporative losses of the most volatile crude oil components (alkylbenzenes, naphthalene, and n-paraffins smaller than Cl2), it is not possible to distinguish losses of these components during the environmental exposure from those during analysis. It may be noted, however, that conditions of relatively warm temperature and exposure to air prevailed during the mixing of oil and sediment, and other pre-deployment activities. It is therefore highly probable that much of this very volatile crude oil fraction was lost prior to deployment.
The aromatic fraction of the oil is less easily separated into identifiable compounds than the aliphatic fraction, because many different isomers of most compounds exist in abundance. A group of six compound types identified by GC-MS, selected because they are easily recognizable, exhibit bioligical effects, and are not lost by the normal analytical workup, are featured in Table 4-3. Only the results for the recovered sediments are given, as the results for ehe pre-deployment samples were invalidated by excessive evaporative losses in drying. Since the compounds in these six types represent a substantial fraction of the potentially toxic components of the oil, these data are probably the most important with respect to the interpretation of the biological data.
li-5
:· J. Table 4-2. N-alkane/isoprenoid hydrocarbon ratios for extracts of recovered recolonization tray sediments.
Source n-Cl7/Pristane n-Cl8/Phytane
PB Crude Oil 1.7 2.2
A501-1M 2.2 2.7
A501-2M 2.1 2.7
A501-3M 2.0 2.0
A501-4L 2.3 1.9
A501-5H 1.9 2.4
B302-1M 1.3 1.7
B302-2M 1.9 2.0
B302-3M 2.0 3.0
B302-4L 1.7 2.0
B302-5H 2.0 2.3
4-6 Table 4-3. Concentrations of selected aromatic hydrocarbons (µg/kg dry sediment= ppb) and (in parentheses) the percent of the original concentrations in the crude oil remaining in recovered recolonization box sediments.
Sam2le Cl-NaEh•* C2-NaEh•* C3-NaEh•* Phen. Cl-Phen. C2-Phen.* A501-1M 135(42) 332(41) 374(24) 32(52) 105(29) 103(40)
A501-2M 86(27) 263(32) 321(21) 26(42) 69(19) 70(27)
A501-3M 97(30) 272 (33) 406(26) 34(55) 104(29) 104(40)
A501-4L 30(47) 52(32) 37(12) 5(41) 13(18) 15(29)
A501-5H 715(22) 3434(42) 5633(36) 608(99) 2104(58) 2018(78)
AS Control <1 <1 <1 <1 <1 <1
B30i-1M 103(32) 160(20) 93(6) 8(13) 21(6) 23(9)
B302-2M 83(26) 248(30) 310(2) 38(62) 122(34) 137(53)
B302-3M 131(41) 339(42) 476(31) 38(62) 125(35) 142(55)
B302-4L 57(89) 82(50) 66(21) 8(65) 15(21) 14(27)
B30 2-SH 103(3) 494(6) 1613(10) 256(42) 864(24) 615(24)
B3 Control <1 <1 <1 <1 <1 <1
*Cl-Naphthalenes arethe 1- and 2-methyl isomers. *CZ-Naphthalenes include the ethyl and dimethyl substituted naphthalenes and .. -- .•. biphenyl. *C3-Naphthalenes include propyl-, methylethyl-, trimethyl- substituted naphthalenes and methyl-biphenyls and fluorene. *C2-Phenanthrenes include dimethyl- and ethyl isomers.
4-7 After approximately 295 days exposure at Station AS about 30% of the total methylnaphthalenes remained in the sediment at all three oil concentrations (Table 4-3). After similar exposure times at Station B3 about 20% of the methylnaphthalenes remained in the sediment in boxes treated with the medi\Dll oil concentration. About 40% of the total methylnaphthalenes remained in the sediment in the low oil concentration box, but the high oil concentration box retained only about 8% of these components. Oddly, analyses indicate that some sediment boxes (B302-1, B302-4 and ASOl-4) retained relatively greater amounts of lower boiling aromatic hydrocarbons than higher boiling compounds.
Analysis of procedural blanks and control sediments (unoiled) using the same methods as the other samples confirmed that there were no artifacts or naturally occurring materials which interf~red with the reported determinations. In some chromatograms, a peak derived from the GC septum is observed. The aromatic fractions of the control sediments, see Figure 4-16 for example, are essentially free of aromatic hydrocarbons. The aliphatic fractions of the control sediments, Figures 4-3 and 4-9, show the presence of a suite of high-boiling n-paraffins with a modest unresolved envelope centered near n-C28. The chromatograms displayed in this report are of variable magnification to expose details, and peak heights should not be compared from one to another. The size of the paraffins and their strong odd/even predominance suggests that they are a natural hydrocarbon assemblage, probably deriving from terrestrial plant waxes. These naturally-occurring n-paraffins are observable in the sediment samples treated with the low-oil concentration (Figures 4-7 and 4-13) as a break in the smooth curve formed by then-paraffin peaks at C27, C29, and C31. -
Results of GC-MS analyses are presented in Tables 4-4 and 4-5 and Figures 4-20 and 4-21. It should be noted that the independent assignment of ARI's in GC and GC-MS data eliminates the problems of correlating the GC and GC-MS outputs that were encountered in previous analyses.
DISCUSSION
After approximately 295 days (9 months) of exposure to the continental shelf environment only minimal weathering or alteration of the oil had occurred in the sediment boxes. At Station AS, a region of relatively fine-grained sediments, about 75% of the total oil remained in the sediments of the low and medium oil concentration and 91% remained in the high oil concentration box. These results closely parallel those of Anderson et al. (1978) who found that 73% of similar concentrations of Prudhoe Bay crude oil mixed into intertidal sediments remained after a similar time period. Generally, less oil was retained in sediment boxes at Station B3 than at AS, although retention still averaged near 50%, except for a severely eroded box
4-8 Table 4-4. Aromatic compound identifications from array A502 meditnn oil concentration box 3.
~ Scan ARI Compound
30. 40.7 Not Identified 42. 54. 7 ME-Naphthalene 50. 64.0 ME-Naphthalene 71. 88.4 N.I. 81. 100.0 Biphenyl 87. 103.5 C2-Naphthalene + ••• 92. 106.4 C2-Naphthalene 100. 111.0 C2-Naphthalene 107. 115.0 C2-Naph-thalene 109. 116.2 C2-Naphthalene 114. 119.1 C2-Naphthalene 116. 120.2 CJ-Naphthalene+ ••• 123. 124.3 N.I. 129. 127.7 ME-Bi phenyl 134. 130.6 CJ-Naphthalene+ ••• 137. 132.4 CJ-Naphthalene 142. 135.3 CJ-Naphthalene+ ME-Biphenyl 145. 137.0 CJ-Naphthalene+ ••• 147. 138.2 CJ-Naphthalene 149. 139.3 CJ-Naphthalene 156. 143.4 CJ-Naphthalene 163. 147.4 CJ-Naphthalene 171. 152.0 Fluorene + CJ-Naphthalene 174. 153.8 CJ-Naphthalene 179. 156.6 C4-Naphthalene + ••• 181. 157.8 C2-Biphenyl + ••• 187. 161.3 C4-Naphthalene + ••• 189. 162.4 C4-Naphthalene + ••• 198. 167.6 C4-Naphthalene + ••• 201. 169.4 C4-Naphthalene + ••• 210. 174.6 C4-Naphthalene + ••• 215. 177 .5 N.I. 217. 178.6 C4-Naphthalene ••• 224. 182.7 ME-Fluorene 229. 185.5 ME-Fluorene 242. 193.1 C3-Biphenyl + ••• 254. 200.0 Phenanthrene 269. 212.0 C2-Fluorene + ••• 274. 216.0 C2-Fluorene + ••• 279. 220.0 C2-Fluorene + ••• 287. 226.4 MW 210 300. 236.8 ME-Phenanthrene 302. 238.4 ME-Phenanthrene
Al\ 4-9 .. Table 4-4 (continued)
Scan ARI Compound ~
309. 244.0 ME-Phenan threne 311. 245.6 ME-Phenanthrene 317. 250.4 C3-Fluorene + ••• 330. 260.8 N.I. 339. 268.0 C3-Fluorene + ••• 348. 275.2 N.I. 352. 278.4 C2-Phenanthrene 354. 280.0 C2-Phenanthrene 356. 281.6 C2-Phenanthrene 360. 284.8 C2-Phenanthrene 361. 285.6 Fluoranthene fl!!,.-- 365. 288.8 C2-Phenanthrene 371. 293.6 N.I. 377. 298.4 N.I. 379. 300.0 Pyrene 385. 305.2 C3-Phenanthrene 392. 311.3 C3-Phenanthrene 395. 313.9 C3-Phenanthrene 399. 317.4 C3-Phenanthrene 401. 319.1 C3-Phenanthrene 404. 321.7 N.I. 413. 329.6 N.I. 422. 337.4 C3-Phenanthrene 432. 346.1 ME-Pyrene + ••• 486. 393.0 N.I. 456. 367.0 C2-Pyrene + ••• 494. 400.0 Chrysene/Triphenylene 531. 430.3 ME-Chrysene/Triphenylene (!'b. 586. 475.4 Benzo (k) Fluoranthene + ••• ; 606. 491.8 Benzo (e) Pyrene 622. 505.8 N.I. 645. 527.9 N.I. 670. 551.9 N.I.
~-
4-10 Table 4-5. Aromatic compound identifications from array A502 high oil concentration.
Scan ARI Compound
19. o.o Naphthalene 25. 7.0 Not identified 66. 54.7 ME-Naphthalene 74. 64.0 ME-Naphthalene 105 •. 100.0 Biphenyl 112. 104.0 C2-Naphthalene + ••• 117. 106.8 C2-Naphthalene 125. 111.4 C2-Naphthalene 132. 115.3 C2-Naphthalene + ••• 134. 116. 5 C2-Naphthalene 141. 120.s CJ-Naphthalene+ ••• 146. 123.3 N.I. 154. 127.8 ME-Biphenyl + 163. 133.0 CJ-Naphthalene 165. 134.1 CJ-Naphthalene 175. 139.8 CJ-Naphthalene 182. 143.8 CJ-Naphthalene 189. 147.7 CJ-Naphthalene 197. 152.3 Fluorene + ••• 200. 154.0 CJ-Naphthalene 207. 158.ol ME-Fluorene + C2-Biphenyl + ••• 213. 161.4 C4-Naphthalene + ••• 215. 162.5 C2-Biphenyl + ••• 227. 169.3 C4-Naphthalene + ••• 233. 172.7 N.I. 237. 175.0 C4-Naphthalene + ••• 241. 177 .3 N.I. 244. 179.0 C4-Naphthalene + ••• 251. 183.0 ME-Fluorene + ••• 253. 184.1 C3-Biphenyl + ••• 255. 185.2 C2-Fluorene + ••• 263. 189.8 C4-Naphthalene + C3-Biphenyl 269. 193.2 Dibenzothiophene 281. 200.0 Phenanthrene 285. 203.2 C2-Fluorene + ••• 296. 211.9 C2-Fluorene + ••• 299. 214.3 C2-Fluorene + ••• 301. 215.9 C2-Fluorene + C3-Biphenyl + ••• 306. 219.8 ME-Dibenzothiophene 316. 227.8 N.I. 319. 230.2 ME-Dibenzothiophene 327. 236.5 ME-Phenanthrene 329. 238.1 ME-Phenanthrene 337. 244.4 ME-Phenanthrene --
4-11 Table 4-5 (continued)
Scan ARI Compound tfll!:l
347. 252.4 N.I. 350. 254.8 C2-Dibenzothiopene 358. 261.1 C2-Dibenzothiophene 366. 267.5 N.I. 373. 273.0 N.I. ,e.. 380. 278.6 C2-Phenanthrene 382. 280.2 C2-Phenanthrene 384. 281.7 C2-Phenanthrene + C3-Dibenzothiophene + ••• 388. 284.9 C2-Phenanthrene + 393. 288.9 C2-Phenanthrene + C3-Dibenzothiophene 404. 297.6 N.I. ·,el. 407. 300.0 Pyrene 420. 311.2 C3-Phenanthrene + 423. 313.8 C3-Phenanthrene 429. 319.0 C3-Phenanthrene + ••• 433. 322.4 N.I. 450. 337.7 C3-Phenanthrene + ••• 458. 344.0 ME-Pyrene + ••• 498. 378.4 C4-Phenanthrene + ••• 523. 400.0 Chrysene/Triphenylene 552. 423.8 N.I. 560. 430.3 ME-Chrysene/ME-Triphenylene 674. 527.9 N.I. 727. 578.8 N.I.
4-12 with only 6% of the added oil remaining. Since sediments at Station B3 are not as fine-grained as those at AS.they should retain less oil; however, the loss at B3 during this experiment is probably primarily a result of strong currents removing fine-grained sediments and associated oil from the boxes.
No evidence of significant microbial degradation was found in any oil-treated sediment boxes, and evaporative or dissolution losses of low-boiling materials was obscured by the analytical work up, which itself caused some losses •
. The methylnaphthalenes and methyl phenanthrenes, which have been shown to be among the most toxic components of oil (Neff et al. 1976), were still present in moderate concentrations in most oil-treated sediment boxes after ~he 295 day exposure period. For example, at Station AS concentrations of methylnaphthalenes averaged about 0.7 ppm in the three medtum oil concentration boxes and about 9 ppm in the high oil concentration box. These values represent a loss of about 70% from the original concentrations present in the added oil. As previously noted, these losses may have occurred prior to deployment, although the most extensive losses are associated with severely eroded boxes. Percent loss of these toxic compounds is slightly greater than those reported by Anderson et al. (1978) after a similar exposure period.
LITERATURE CITED
Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydrocarbon concentrations in the sediment. J. Fish. Res. Bd. Canada 35:776-790.
Neff, J.M., J. w. Anderson, B. A. Cox, R. B. Laughlin, Jr., s. s. Rossi, and H. E. Tatem. 1976. Effects of petroleum on survival, respiration and growth of marine animals. In: Sources, Effects and Sinks of Hydrocarbons in the Aquatic Environment. American Institute Biological Science, Washington, D.C. pp. 515-539.
4-13 Cl2
Cl3
C20 Cl4 Cl9 C15 Cl6 Cl7 Cl8 C21 CZ 2 C23 C24
C25 C26
C27 C28 C29 ego C11
0 5 10 15 20 25 30 35 40 45 50
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4-36 (!,A CHAPTER 5
- MICROBIAL RESPONSES
Howard I. Kater
- -
- CHAPTER 5
TABLE OF CONTENTS
INTRODUCTION 5-1 !~ METHODS 5-1 RESULTS ...... 5-2 Deployment at Station AS • . . 5-2 Deployment at Station B3 " . . . . 5-2 ~ Deployment at Station B6 . . . . 5-9 Recovery at Station AS . 5-9 Recovery at Station B3 ...... 5-9 DISCUSSION 5-10 LITERATURE CITED ...... 5-11 CHAPTER 5
MICROBIAL RESPONSES
Howard I. Kator
INTRODUCTION
Fate and biological effects of oil weathering in continental shelf sediments are not well understood. The objectives of this study were to assess time dependent responses of marine bacteria in petroleum-treated sediments placed in situ on the Middle Atlantic continental shelf and to relate bacterial data to relevant sediment parameters. Unfortunately, the experimental design, which required recovery of treated sediment at intervals could not be consummated and resulted in a deployment phase and (after an extended interval) one recovery. Bacterial data from these two events are discussed in· this report.
METHODS
Two samples were obtained for each sediment type sampled, i.e., grab or sediment box, for determination of aerobic heterotrophic and _petroleum-degrading marine bacterial populations. Sterile plastic syringes or mini-corers, fabricated by removal of the luer end, wer·e pushed into undisturbed portions of the sediments to a maximwn penetration of about 8-10 cm. In addition, for each sediment sample removed for bacteriological analysis, a replicate sample was obtained for sediment dry weight determination. Sediment samples for dry weight determinations were immediately frozen for processing at ·a· later date.
Sediment samples were enumerated immediately after collection ·by extrusion into a sterile blender containing 90 ml sterile chilled seawater and blending for one minute (Stevenson et al. 1974). In most instances the entire core (composite) was homogenized. However, some samples were collected in large diameter syringes in order that the core could be divided into three 10 ml portions, corresponding to upper, mid- and bottom, and blended independently.
Immediately after homogenization, appropriate volumes of homogenate were serially diluted in sterile seawater blanks (1 ml in 9 ml of sterile seawater). Using a three tube most probable number technique (Lewin 1974), selected dilutions were planted in tubes containing a heterotrophic medium and tubes containing an inorganic salts enriched medium (Miget et al. 1969) with sterile Prudhoe Bay crude oil as the sole added carbon source. The heterotrophic medium consisted of 1 g/1 peptone, 0.5 g/1 yeast extract, 0.01 g/1 ferric
5-1 citrate, 0.1 g/1 sodium glycerol phosphate and 1000 ml aged seawater. Petroleum-degrading bacteria were enumerated in a medium containing 1 g/1 NH42S04 and 0.1 g/1 K2HP04 in 1000 ml aged seawater. Membrane sterilized Prudhoe Bay crude oil was added at a concentration of approximately 1% after inoculation. Heterotroph enumeration tubes were incubated at 20-22°C to two weeks and read at weekly intervals. Petrole1.DI1-degrading bacteria enumeration tubes were incubated at the same temperature on a rotary shaker (140 rpm) for one month and read at bi-weekly intervals. Heterotroph tubes were scored positive when turbid; petroleum-degrading tubes were scored positive when turbid; if the oil showed obvious signs of degradation with associated cellular debris; or a combination of both. MPN values were calculated using standard tables (APHA 1975) for three tube MPN distributions. Counts were expressed as b_acterial units/ g dry sediment.
RESULTS
Bacterial biomass data, types and numbers of samples obtained are listed in Tables 5-1 and 5-2. These data are graphically depicted in Figures 5-1 and 5-2.
Deployment at Station A5
Control box sediment contained similar levels of heterotrophic and petroleum-degrading bacteria compared with grab samples from the natural community. A decrease with depth in the sediment was noted for heterotrophic bacteria and petroleum-degrading bacteria in grab sediment. Control sediment manifested uniform heterotroph counts with depth but the lower third exhibited larger counts of petroleum-degrading bacteria than the upper two thirds. Bacterial levels in sediment treated with the intermediate oil concentration exhibited greater counts of petroleum-degrading and heterotrophic bacteria than control and grab sediment. In addition, ratios of pe:troleum-degrading to heterotrophic bacteria were largest for oil-treated samples. Comparison of counts within vertical segments of the sediment profile indicated petroleum-degrading bacteria were uniformly distributed and that heterotrophic bacteria were somewhat more abundant in the upper layer.
Deployment at Station B3 A Petroleum-degrading bacteria in grab sediments from B3 were less abundant than at AS. Total heterotrophs and to a lesser extent,· petroleum-degrading bacteria, were approximately ten times more abundant in control sediment and were uniformly distributed within the core. Counts of total heterotrophs and petroleum-degrading bacteria in oil-treated sediment (intermediate concentration) were significantly larger than in grab or control sediment. Values of the
5-2 J ) ) ) '
Table 5-1. Viable counts of petroleum-degrading and heterotrophic marine bacteria in sediment samples from grabs, control and oiled arrays at deployment.
MPN Values*/gm Dry Sediment HC Sample Sediment Heterotrop}:ls Petroleum Log BET Date oc (HET) .Station Type Temp I Degraders (HC) AS 8-9-79 Gl 18 2 .1E06 (6.3) 6.7E02 (2.8) -3.5 AS 8-9-79 G2 18 4.8E06 (6.3) l.2E03 (3.1) -3.6 AS 8-9-79 G3A 18 2.0E06 (6.3) 2.0E03 (3.3) -3.0 AS 8-9-79 G3B 18 l.3E05 (5.1) 8.6E01 (1.9) -3.2 AS 8-9-79 G3C 18 1.2E05 (5.1) l.2E02 (2.1) -3.0
AS 8-9-79 Bl Amb. >l.5E06 (6.2) >1.5E03 (3 .2) -3.0 AS 8-9-79 B2A Amb. >7. 7EOS (5.9) )7. 7E02 (2.9) -3.0 AS B2B Amb. )8.1E05 U1 8-9-79 (5.9) )8.1E02 (2.9) -3.0 I 8-9-79. B2C Amb. (6.0) vJ AS >9 .5E05 >9.5E02 (3.0) -3.0 AS 8-9-79 Ol(M} Amb. >L 7E07 (7.0) >7.4E05 (5.9) -1.4 AS 8-9-79 02A(M) Amb. -5.8E06 (6.8) -4. 9E04 (4.9) -2 .1 AS 8-9-79 02B(M) Amb. 4.2E05 (5.6) 3.7E04 (4.6) -1.1 AS 8-9-79 02C(M) Amb. >3.8E05 (5.6) )3.0E04 (4.5) -1.1
B3 8-10-79 Gl Amb. 2.9E06 (6.5) 5.8E01 (1.8) -4.7 B3 8-10-79 G2 Amb. l .4E06 (6.1) 6.2E01 (1.8) -4.4 B3 8-10-79 G3A Amb. 2.1E06 (6.3) 9.0EOl (2.0) -4.4 B3 8-10-79 G3B Amb. 2.2E05 (5.3) l.1E02 (2.0) -3.3 B3 8-10-79 G3C Amb. l.3E04 (4.1) 4.7E01 (1. 7) -2.4 .,., B3 8-10-79 Bl Amb. >I. 7E06 (6.2) )1. 7E03 (3.2) -3.0 B3 8-10-79 B2A Amb. )8.2E05 (5.9) )8.2E02 (2.9) -3.0 B3 8-10-79 B2B Amb. >B. 7E05 (5.9) -4.0E02 (2.6) -3.3 B3 8-10-79 B2C Amb. )l .1E06 (6.0) )l.1E03 (3.0) -3.0 Table 5-1. (concluded)
MPN Values*/gm Dry Sediment HC Sample Sediment Heterotrophs Petroleum Log BET Station Date Type Temp oc (HET) Degraders (HC)
B3 8-10-79 Ol(M) Amb. )l.9E07 (7 .3) )l.9E06 (6.3) -1.0 B3 8-10-79 02A(M) Amb. )l.4E07 (7.1) )l .4E06 (6.1) -1.0 B3 8-10-79 02B(M) Amb. )l .4E07 (7 .1) >l .4E06 (6.1) -1.0 B3 8-10-79 02C(M) Amb. >l.8E07 (7 .3) ~l.8E06 (6.3) -1.0 B6 8-14-79 Gl 13 2.8E05 (5.4) 2.2EOO (0.3) -5.1 B6 8-14-79 G2 13 1.4E05 (5.1) l.1E02 (2.0) -3.1 B6 8-14-79 G3A 13 2.9E04 (4.5) >l.4EOO (0.1) -4.3 B6 8-14-79 G3B 13 4.2E03 (3.6) >l .3EOO (0.1) -3.5 VI B6 8-14-79 G3C 13 5.3E03 (3.7) )l.lEOO (0.1) -3. 7 I ~ B6 8-14-79 Bl Amb. )l.6E06 (6.2) )l.6E03 (3.2) -3.0 B6 8-14-79 B2A Amb. )1. 1E06 (6.0) )l .1E03 (3.0) -3.0 B6 8-14-79 B2B Amb. )l .1E06 (6.0) )l.1E03 (3.0) -3.0 B6 8-14-79 B2C Amb. >8.7E05 (5.9) )8.7E02 (2.9) -3.0
B6 8-14-79 Ol(M) Amb. )l.5E07 (7 .2) )l.5E06 (6.2) -1.0 B6 8-14-79 02A(M) Amb. )9.0E06 (7.0) )8.9E05 (5.9) -1.0 B6 8-14-79 02B(M) Amb. )9. 7E06 (7 .O) )9. 7E05 (6.0) -1.0 B6 8-14-79 02C(M) Amb. >l .OE07 (7.0) >l.OE06 (6.0) -1.0 ) ) ) ) j j
Table 5-2. Viable counts of petroleum-degrading and heterotrophic marine bacteria in sediments sampled from grabs, control and oiled arrays after recovery.
MPN Values*/gm Dry Sediment HC Sample Sediment Heterotrophs Petroleum Log HET Station Date Type Temp oc (HET) Degraders (HC)
AS 6-6-80 Gl 11 l.1E06 (6.0) 2.2E03 (3.3) -2.7 A5 6-6-80 G2 11 l.3E06 (6.1) l.3E03 (3.1) -3.0 AS 6-6-80 G3 11 l.2E06 (6.1) 3.4E03 (3.5) -2.5
A5 6-6-80 Bl 11 2.8E06 (6.4) 7.7E03 (3.9) -2.6 AS 6-6-80 B2 11 l.8E06 (6.3) 6.6E04 (4.8) -1.4 A5 6-6-80 B3A 11 5.9E06 (6.8) l.3E05 (5.1) -1.7 AS 6-6-80 B3B 11 5.0E06 (6. 7) 2.0E04 (4.3) -2.4 V1 I A5 6-6-80 B3C 11 2.5E06 (6.4) 2 .1E04 (4.3) -2.1 V1 AS 6-12-80 01 (M) 12 l.8E05 (5.3) l.8E05 (5.3) o.o AS 6-12-80 02{M) 12 7.7E06 (6.9) l.2E05 (5.1) -1.8 AS 6-12-80 03(M) 12 3.6E05 (5.6) 3.8E04 (4.6) -1.0 A5 6-12-80 04(M) 12 l.8E06 (6.3) l.8EOS (5.3) -0.1 AS 6-12-80 . OSA(M) 12 2.2E05 (5.3) 9.3E04 (5.0) -0.4 A5 6-12-80 05B(M) 12 8.4E03 (3.9) 2.6E03 (3.4) -0.5 AS 6-12-80 OSC(M) 12 1.3E04 (4.1) 1.5E02 (2.2) -1.9 AS 6-12-80 06(1) 12 6.5E03 (3.8) l.5E03 (3 •. 2) -0.6 AS 6-12-80 07(1) 12 2.3E04 (4.4) 1. 3E03 ( 3. 1) -1.3 A5 6-12-80 08(H) 12 5.7E05 (5.8) . 7. 9E05 ( 5. 9) -0.1 AS 6-12-80 09(H) 12 2.1E06 (6.3) 1.1E06 (6.0) -0.3
B3 6-12-80 Gl 11 2.8E06 (6.4) 1.7E03 (3.2) -3.2 B3 6-12-80 G2 11 1.3E05 (5.1) 8.7E03 (4.0) -1.2 B3 6-12-80 G3 11 2.6E05 (5.4) l.9E04 (4.3) -1.1 Table 5-2. (concluded)
MPN Values*fgm Dry Sediment HC .Sample Sediment Heterotrophs Petroleum Log HET Station Date Type Temp oc (HET) Degraders (HC) B3 4-21-80 Bl 7 l.6E06 (6.2) 4.8E03 (3.7) -2.5 B3 4-21-80 B2 7 5.4E05 (5.7) 5.4E02 (2.7) -3.0 B3 4-21-80 B3 7 7.8E05 (5.9) l.OE03 (3.0) -2.9
B3 6-13-80 Ol(M) 8 2.9E06 (6.5) 2.9E06 (6.5) -0.01 B3 6-13-80 02(M) 8 l.3E07 (7.1) 6.1E05 (5.8) -1.3 B3 6-13-80 03(H) 8 2.8E07 (7.4) 2.8E06 (6.5) -1.0 B3 6-13-80 04(L) 8 3.7E03 (3.6) 2.2E03 (3.3) -0.2 V1 B3 6-13-80 05(L) 8 6.9E06 (6.8) 4.7E05 (5.7) -1.2 I O"I B3 6-13-80 06(M) 8 3.8E06 (6.6) l.6E05 (5.2) -1.4
* values in parentheses are log viable counts
G = grab sample A= top 1/3 of sediment sample core, (approx. 2 cm) B = control box B = middle 1/3 of sediment sample core, (approx. 2 cm) 0 = oiled box C = bottom 1/3 of sediment sample core, (approx. 2 cm)
(L) = low oil concentration (M) = medium oil concentration (H) = high oil concentration
0 Q Q \ .. } · i l / ~ _T_a_b-le_5_-_2_. __(_co_n_c_l_u_d_e_d_) ______~---:--.,------~~:------\ MPN Values*/gm Dry Sediment HC Sample Sediment Heterotrophs Petroleum Log BET Station Date Type Temp oc (HET) Degraders (HC) \
B3 4-21-80 Bl 7 l.6E06 (6.2) 4.8E03 (3.7) -2.5 B3 4-21-80 B2 7 5.4E05 (5.7) 5.4E02 (2.7) -3.0 B3 4-21-80 B3 7 7.8E05 (5.9) l.OE03 (3.0) -2.9
B3 6-13-80 Ol(M) 8 2.9E06 (6.5) 2.9E06 (6.5) -0.01 B3 6-13-80 02(M) 8 l.3E07 (7 .1) 6.1E05 (5.8) -1.3 B3 6-13-80 03(H) 8 2.8E07 (7 .4) 2.8E06 (6.5) -1.0 B3 6-13-80 04(L) 8 3.7E03 (3.6) 2.2E03 (3.3) -0.2 V1 B3 6-13-80 OS(L) 8 6.9E06 (6.8) 4.7E05 (5.7) -1.2 I B3 6-13-80 06(M) (6.6) °' 8 3.8E06 l.6E05 (5.2) -1.4
* values in parentheses are log viable counts
G = grab sample A= top 1/3 of sediment sample core, (approx. 2 cm) B = control box B = middle 1/3 of sediment sample core, (approx. 2 cm) 0 = oiled box C = bottom 1/3 of sediment sample core, (approx. 2 cm)
(L) = low oil concentration (M) = medium oil concentration (H) = high oil concentration
·,} I }) ,) '. T) JJ J j }
GRAB CONTROL ARRAY OIL-TREATED ARRAY INTERMEDIATE 7 OIL 6
TOTAL HETEROTROPHIC 5 • BACTERIA.
I- 4 ~ PETROLEUM-DEGRADING z BACTERIA. w 3 :E 0w 2 (/) > U1 0:: I 0 ...... 0 O> I ...... I I LOW HIGH I- I z 7 I I OIL OIL ::> I 0 6 I (.) {!) 5 0 -' 4 3 2
0 ~ ~ ~ \' ~ S~-S' 1-...' Figure· 5-1. Bacterial counts in grab, control and oil-treated array sediments at deployment (lower) and recovery (upper) for Station AS. GRAB CONTROL ARRAY 01 L - TREATED ARRAY 7 INTERMEDIATE OIL 6 5 TOTAL HETEROTROPH IC • BACTERIA 4 zt- w D') PETROLEUM-DEGRADING :i: 3 IZd BACTERIA 0 w 2 (I) a::>- 0 u, 0 I Cl I I I LOW HIGH co I I I t- I I I OIL OIL ' 7 I I z I :J 0 u 6 2 0 ~ S' S's ~ \' \' ~ J....w ~ \' .....\' ' ~ ' ' ..... ~ ..... ' 8' ~ ~ ~ q_o ,:-~~ 0 ~ ~ ~w q_ ~ ~ ~~~ t .§ 0 I ~q_ ~ ~ c.,o c.,ct .:::,q_ ~ ..::, 0 " ~ " Figure 5-2. Bacterial counts in grab, control, and oil-treated array sediments at deployment (lower) and recovery (upper) for Station B3. .} ,) ratio of petroleum-degrading to heterotrophic bacteria were correspondingly larger and uniform with depth in oil-treated sediments. Deployment at Station B6 B~cterial counts, especially petroleum-degrading bacteria, were much.lower compared with counts from grabs at AS or B3. Heterotroph counts were larger in the upper third of the grab core. Counts in control sediment were significantly larger than in grab sediment and similar to those measured for AS and B3 controls. As previously observed, levels of both heterotrophic and petroleum-degrading .~acteria were significantly larger in oil-treated seqiment compared with grab or control sediment. Recovery at Station A5 Grab sediment at AS exhibited similar counts to those measured at deployment. Heterotrophic and petroleum-degrading bacterial c~unts in control sediment were elevated with respect to deployment counts. Heterotroph ¢.ounts in control sediment were larger than in oil-treated sediment. Counts in oil-treated sediments exhibited ·a vertical. gradient with both heterotrophic and petroleum-degrading bacterial counts decreasing with depth. Petroleum-degrading bacterial levels were similar for both oil-treated (intermediate concentration) and control sediment. Counts in the low oil concentration sediment were lower than counts from the intermediate oil concentration sediment and the control sediment. Heterotroph counts in the high oil concentration sediment were similar to those in the intermediate oil concentration sediment but petroleum-degrading bacterial levels were larger in the high oil concentration sediment with the value of the ratio of petroleum-degrading to heterotrophic bacteria approaching the theoretical maximum. Recovery at Station B3 Grab sediment at B3 exhibited heterotroph counts slightly lower than measured at deployment although petroleum-degrading bacterial levels were significantly larger. Heterotroph levels in grab sediment were similar ·to control sediment although the levels of petroleum-degrading bacteria were lower. In oil-treated sediment (intermediate oil concentration), the largest counts were measured for the high oil sediment and these were similar to ·counts obtained for the intermediate oil sediment at deployment. Lower counts were detected in the low oil sediment and those in the intermediate oil sediment were slightly lower than measured at deployment. Vertical 5-9 sampling within the core was not possible at this station owing to the minimal amount recovered in the array boxes. DISCUSSION This discussion of the responses of bacterial populations in oil-treated and other sediments is limited by the lack of a complete time series of samples, however the following observations have been made. Relative differences in bacterial densities from grab sediments at AS, B3 and B6 followed a general pattern previously discussed (Kator 1979), that is, bacterial counts tended to be greater in sediments containing higher proportions of fine particles and organic carbon. Preparation of control and oil treated sediments by freeze-thawing did not reduce bacterial levels. On the contrary, this method resulted in more-or-less uniform increases of petroleum-degrading bacteria regardless of sediment grain size distribution. Such responses must have been related to the release of and/or possible alteration of both living and non-living organic carbon (which includes hydrocarbon-like lipoidal material) and inorganic nutrients. Organics would be expectedly derived from the deaths of allochthonous microbiota and meiofauna. Addition of petroleum to these sediments added another complex source of organic carbon which produced an anticipated increase in the relative biomass of heterotrophic and petroleum-degrading bacteria and a corresponding increase in the value of the ratio of petroleum-degrading to heterotrophic bacteria. This latter phenomenon has been demonstrated in vivo (Kator 1979). Vertical sampling within array sediment cores illustrated the relatively well mixed nature of the prepared sediments expressed in terms of bacterial densities for both control and oil-treated sediments. IS'!< -✓ Recovered control sediments exhibited increases in levels of petroleum-degrading bacteria relative to deployment. This was probably a reflection of in situ degradation of the organic carbon "set free" by the freeze-thaw preparation method. Changes in the relative recalcitrance of the organic carbon originally present in the sediments was not measurable by the TOC analytical technique employed and TOC data were not available for control sediments. Therefore, it is not possible to comment on the extent of in situ degradation or conversion of this organic matter by bacteria. Petroleum-degrading bacteria recovered from oil-treated sediment exhibited a vertical gradient of biomass with core depth. Such a 5-10 distribution was not totally unexpected because petroleum degradation is an obligately oxygen requiring process. Therefore, hydrocarbon oxidation would be expected to occur in the uppermost surface sediments and to diminish with depth in reduced sediments. This change in extent of degradation was reflected as a decrease in biomass of petroleum-degrading bacteria with core depth. The significance of this observation may extend to interpretation of other measurements obtained using composite rather than vertical portions of the sediment profile. Thus, composite samples would not provide evidence of diminished activity in reduced subsurface sediment and conversely, evidence for degradation in surface or oxidized sediments would be "diluted out" by non-degraded oil in sediments from the lower or reduced protion of the profile. This hypothesis must be considered with respect to interpretation of hydrocarbon data since a composite sample would be less likely to reflect the extent of degradation than a surface sample. The effect of petroleum concentration on bacterial populations was evident in the comparative levels of petroleum-degrading bacteria at each concentration level. Based on the relative changes in numbers of petroleum~degrading bacteria present at deployment and recovery, the combined observations of still elevated levels and the vertical gradient found at AS provide indirect evidence for active bacterial populations in oil treated sediments. In conclusion, bacterial data from sediments sampled indicated addition of petroleum produced an increase in populations of petroleum-degrading bacteria. At the time of recovery, bacterial levels in oil treated sediments were elevated with respect to grab sediments at the intermediate and high oil concentrations. Apparently, the low concentration did not produce a detectable increase above ambient population levels. Limited vertical sampling within a sediment core recovered from AS implied that degradation was occurring in surface sediments and highlighted the need to carefully interpret chemical and biological data from composite samples. LITERATURE CITED American Public Health Association. 1975. Standard methods for the examination of water and wastewater. APHA, Washington, D.C. Kator, H. I. 1979. Bacteriology. In: Middle Atlantic Outer Continental Shelf Environmental Studies, Volume IIC, Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62), Chap. 11, 283 p. Lewin, R. A. 1974. Enumeration of bacteria in seawater. Int. Rev. Hydrobiol. 59:611-619. 5-11 Mi.get, R. J., C.H. Oppenheimer, H. I. Kator, and P.A. LaRock. 1969. Microbial degradation of normal paraffin hydrocarbons in crude oil. In: Joint Conference on Prevention and Control of Oil Spills-,-Proceedings API-FWPCA, New York, PP• 327-331. Stevenson, L., c. Millwood, and B. Hebler. 1974. Aerobic, heterotrophic bacterial populations in estuarine waters and sediments. In: The Effect of the Ocean Environment on Microbial Activities, R. Colwell and R. Morita, eds., University Park Press, Baltimore, Maryland, PP• 268-285. 5-12 CHAPTER 6 MACROBENTHOS COLONIZATION Linda C. Schaffner Donald F. Boesch Marcia A. Bowen I~ CHAPTER 6 TABLE OF CONTENTS INTRODUCTION. . 6-1 METHODS • 6-2 Laboratory Procedures 6-2 D{lta Analysis. .. 6-3 Data Processing •• 6-3 Data Reduction. • •••••• 6-3 Ordination . • • • • • • • 6-3 Species Diversity •••• • 6-3 RESULTS . . • 6-4 Abundance of Colonizing Macrobenthos. • • 6-5 ~- Biomass •••.•••• • 6-5 Assemblage Composition •• •• 6-8 Dominant Species •• • 6-21 Individual Species Patterns 6-27 Species Diversity •• 6-34 DISqUSSION. •.• 6-40 ACKNOWLEDGEMENTS . . . . ' . . . . . 6-44 LITERATURE CITED...... 6-45 -~ CHAPTER 6 MACROBENTHOS COLONIZATION Linda c. Schaffner, Donald F. Boesch, Marcia A. Bowen INTRODUCTION · The colonization of azoic sediment by marine macrobenthos has been experimentally studied by several investigators in a wide enough variety of habitats to permit general conclusions about the environmental factors controlling the rate of colonization (Boesch and _411:\ Rosenberg in press). In frequently perturbed habitats, colonization of defaunated sediments may proceed very rapidly, within a few weeks, and the initial colonists are generally dominants in the antecedent, natural community. Colonization is particularly rapid during periods of active reproduction or recruitment of planktonic larvae (McCall 1977, Santos and Simon 1980), which in cold temperate environments corresponds with the warmer portion of the year. In infrequently disturbed, cold water habitats, colonization of perturbed sediments proceeds much more slowly and initially colonizing species are typicaliy not dominant in the natural community. For example, in the deep sea several years appear to be required for the community in defaunated sediment to return to ambient density and diversity (Grassle 1977). In initial studies of the colonization of azoic sediments by· macrobenthos in an eroded flank habitat in Area B of the Middle Atlantic outer continental shelf, Boesch (1979) found relatively slow recovery after 9 months of exposure. Although most of the dominant ·-ti'.!!\ amphipod species had quickly colonized the sediment in two months (the minimum time of exposure), their densities were lower than those in the natural community. Boesch concluded that because of their motility as adults and brooding behavior they were adapted for recovery from such local disturbance, thus allowing their success in outer shelf habitats. Also, some species characteristic of the natural community were rare or absent in the experimental sediment, while the polychaete Capitella capitata and juvenile Nephthyidae were abundant only in the experimental sediment. Although the parallel investigation of the colonization of azoic sediments contaminated with a pollutant allow the testing of effects under conditions of exposure more relevant to the benthos than experimental aqueous-phase exposure, few have used such tec~niques. Anderson (Anderson et al. 1978, and personal communication) has conducted similar experiments wherein sediments were contaminated with Prudhoe Bay crude oil in the intertidal zone of Puget Sound, Washington. Although some effects on colonization were demonstrated, 6-1 particularly on some bivalve mollusc species, the overall effects were not substantial in comparison to effects noted after some oil spills. J. F. Grassle (personal communication) has conducted similar experiments in which sediments were contaminated with number two fuel oil and exposed in shallow water (Buzzards Bay, Massachusetts) and deep-sea habitats. His re~-~~t's-· are·. as yet incomplete. The hypotheses to be tested in this study may be stated as follows: 1) The rate of colonization by macrobenthos is more rapid and the colonizing fauna •is more like that of the natural community in - more frequently disturbed outer shelf habitats than in shelf-break habitats. 2) Colonization is more complete in uncontaminated than in oil-contaminated sediments because colonization of more sensi- tive forms, such as crustaceans is delayed (Sanders et al. 1980, Cabioch et al. 1978). 3) The effect of crude-oil contamination on colonization is proportional to the concentrations of oil in the sediment. 4) Because sediments with high silt and clay content better accommodate the oil and reduce its rate of weathering due both to dissolution and biodegradation, the effect of contamination on colonization is greater at station AS than at station B3. METHODS Laboratory Procedures Samples were first soaked for several hours in fresh water. The "light" fractions were sorted into major taxa by examination with a binocular dissecting microscope. The heavy fractions were processed by placing a small amount of sediment in a metal pan~ and elutriating and decanting repeatedly through a 0.5 mm Nitex screen. This material was.examined as with the "light" fraction, while the remaining sediment was spread out in a white enamel pan and examined for the stained organisms with the naked eye. All organisms were sorted into major taxonomic groups, at a minimum, Annelida, Mollusca, Crustacea, Echinodermata, and other taxa, and stored in 70% ethanol. Wet weight biomass was determined for each major group in each replicate grab sample following removal of external fluid by blotting on paper towels. The weights include skeletal material such as shells and tests and in some cases tube and protective encrustations not easily removable. Organisms were identified and counted for each sample. Determinations were possible to species with most individuals; however, only genus, family, or higher taxon identifications were possible in some cases. 6:-2 Data Analysis Data Processing Abundance and biomass data for macrobenthos were entered on specially designed coding forms. Taxa were encoded using the 1O-digit NODC taxonomic code. Once the data were machine readable, listings were carefully edited by the responsible technical· staff and corrected. Subsequent analyses were performed using these corrected data'! Data Reduction Because the total number of species collected was too large for practical computation involved in ordination, it was necessary to reduce the data to a subset of species. Several criteria were used to accomplish this data reduction. Colonial species which were not enumerated were eliminated as were taxa not separated to species. Secondly, species not meeting one of the criteria below were also eliminated : ; a)> IO.individuals in an unreplicated box treatment. b) occurrence in two replicated box treatments, c) occurrence in three replicated grabs. Ordination Reciprocal averaging ordination (Hill 1973) was employed on reduced sets of square root transformed data. This technique, also known as correspondence analysis (Chardy et al. 1976), is an eigenvector method which seeks to maximize the amount of variation explained by initial axes derived from the complex species x collections space. Reciprocal averaging is particularly appealing because it is less prone to distortion (nonlinearity of linear factors) characteristic of most ordinations of ecological data {Gauch et al. 1977) and because it produces both normal and inverse ordinations in the same space. Thus, it is possible to explain the pattern of similarity among collections directly in terms of the species responsible for those patterns. Computations involve extraction of eigenvectors and determination of collection and species scores on successive axes of variation. The program ORDIFLEX of the Cornell Ecology Program Series (Gauch 1977) was used to execute reciprocal averaging ordination. Species Diversity Species diversity was measured by the commonly used index of Shannon (Pielou 1975), which expressed the information content per 6-3 individual. The index denotes the uncertainty in predicting the specific identity of a randomly chosen individual from a multispecies assemblage. The index H' is given by: s ff' •-t pl i•l i o12Pi wheres= number of species in the sample and Pi= proportion of the i-th species in the sample·. As considered above, species diversity is a composite of two components: species richness (the number of species in a community) and evenness (how evenly the individuals are distributed among the species). Species richness was measured in terms of area (areal richness) simply by the number of species in collections of standard area (0,6 m2 or 0.4 m2) and also as standardized in terms of numbers of individuals (numerical richness). Numerical richness was expressed using Hurlburt's (1971) modification of· Sanders' (1968) rarefaction technique, by which the number of species in a rarefied sample of given size in terms of number of individuals is computed based on known abundance relationships. For a given sample size n, the expected number of species is: s BS(n) • t ial where N is the number of individuals, sis the number of species in the collection, and Ni is the number of individuals of the i-th species. In this case a sample size of 500 individuals was used since the number of specimens collected exceeded this at almost all of the stations. Evenness was reflected by the ratio of Pielou (1975) expressed as J = H' /log2s RESULTS Because of the very limited success in recovering experimental arrays (Chapter 2), the experimental design was significantly · compromised. Only one pair of arrays, one containing oiled sediments and the other azoic control sediments, was recovered from each of station AS and B3 between 8 and 10 months after deployment. 6-4 Abundance of Colonizing Macrobenthos Faunal abundances in all experimental boxes were depressed relative to the surrounding natural communities (Figure 6-1). At Station AS echinoderms comprised a major numerical component of the natural community throughout the experimental period yet were absent or rare in experimental boxes. Annelids comprised the most abundant taxon in the experimental boxes at this station where their densities in control boxes approached that of the natural community; abundances in oiled boxes were generally lower. Crustacean densities, variable in both the natural community at A5 and in experimental boxes, exhibited no clear patterns. The low-oil concentration box was characterized by anomalously low faunal abundance as compared with all other experimental boxes. This low density may have been the result of severe erosion in this box during recovery. Oiled boxes not subjected to scour were also less densely populated than control boxes due primarily to reduced crustacean and molluscan abundances. At Station B3 major faunal groups were present in experimental boxes in proportions similar to those in the natural community. Total faunal densi~y in experimental boxes was approximately an order of magnitude less than densities sampled in the natural community. Oiled boxes differed from control boxes by having reduced or virtually absent molluscan populations. Biomass Total wet weight biomass of macrobenthos was greater in the natural communities at stations A5 and B3 than it was in experimental treatments (Figure 6-2). The major constituents of total biomass in the natural community at AS were echinoderms, the ophiuroid Amphioplus macilentus, and asteroids, Asterias vulgaris and Astropecten americanus, which were virtually absent in experimental boxes. Annelid and mollusc biomass was also depressed in boxes relative to the levels observed in the natural community. Decapod crustacean biomass levels were equal to or greater than those observed in the natural environment due primarily to the presence of large Cancer borealis and Munida iris iris which apparently sought refuge within the boxes. Annelid biomaSSWas generally lower in oiled boxes as compared with controls. The natural community at Station B3 supported a much higher wet weight biomass level than did the experimental treatments. This was due primarily to the abundance of molluscs such as Astarte undata, Cyclocardia borealis and Arctica islandica, the peracaridans, Ampelisca agassizi and Unciola irrorata, and numerous species of large annelids. Annelid biomass was generally highest of all groups in the boxes. Decapods such as juvenile Cancer borealis, Eualis pusiolus and Pagurus acadianus were patchily distributed in boxes and occasionally 6-5 STATION A5 2761 STATION B3 2000 Crustoceons Cr ustoceons Annelids Annelids Molluscs . Molluscs Echinoderms Others 1800 IOthers i 1600 1400 N E ci 'en 1200 ..J 0 D R R R R R D R R R R R NATURAL CONT. --OIL-- NATURAL CONT. --OIL-- MIO LOW HIOH MIO LOW HIOH Figure 6-1. Density of macrobenthos in the natural community at deployment (D) and recovery (R) and in recovered sediment boxes from Stations AS and B3. 6-6 t ) STATION A5 STATION 83 7 60 271 200 Decopodo Oecopodo Perocorido Perocorido 180 Annelida Annelida Mollusca Mollusca 160 E cllinodermoto Echinodermata Others Otllers 140 120 0\ I N --.J E '- 100 Cf) :::E 60 40 20 D R R R R R D R R R R R NATURAL CON TROL OIL--- NATURAL CONTROL ---OIL MID LOW H I GH N IO LOW HIGH Figure 6-2 . Biomass of macr obenthos in the natural community at deployment (D) and r ecovery (R) and i n recovered sediment boxes at Stati ons AS and B3 . contributed a significant portion of total wet weight biomass. Mollusc biomass in the control boxes was relatively high due to the abundance of Placopecten magellanicus and Anomia simplex. These species were apparently attracted to the array superstructure to which they were found attached in great abundances upon retrieval. Thus, these high biomass values reflect the somewhat artificial experimental conditions. Assemblage Composition Comparisons of assemblage compositions in experimental boxes with compositions observed in the natural community were accomplished using reciprocal-averaging ordination. This technique facilitated a visualization of relationships among experimental treatments in addition to the relationships between treatments and the natural community. The ordination of samples from Station AS is presented in Figure 6-3. Most of the variation on axes 1 and 2 is explained by differences between the depauperate low-concentration oiled box and all other samples. As a result of this artificial condition, little information is supplied about the actual relationships among non eroded samples. A second ordination was accomplished in which the low concentration oiled sample was excluded (Figure 6-4). Experimental samples are clearly separated from the natural community on the first extracted axis which accounts for 56 percent of the total variation within the data set. The sources of variation explained by axes 2 and 3 (18 and 16 percent of the total variation, respectively) are less obvious. Within the experimental treatments there is an apparent tendency for increasing concentration of oil to coincide with increasingly higher scores on axes 2 and 3. The samples from the natural community also exhibit strong variation on axis 2 which may be related to sedimentary changes over the experimental period. To further clarify the results of station ordination, species were cast into the space defined by axes 1 and 2 (Figure 6-5). The result is a continuum of species aligned with the first axis. Those species found primarily in boxes, such as the polychaetes Capitella capitata, Polydora socialis and Ophelina acuminata (Table 6-1), have the lowest scores on axis 1 while those found primarily in the natural community, including the echinoderms Axiognathus squamata, and Amphioplus macilentus, and the polychaetes Clymenella torquata and Exogone hebes (Table 6-1), have the highest scores on axis 1. The ordination of species along axis 2 suggests the importance of sedimentary changes in the natural community between deployment and recovery. Thus, species such as the molluscs Lucinoma filosa and Siphonodentalium sp., which prefer relatively fine sediments, have high scores on axis 2 while species such as the polychaetes Exogone 6-8 ) ) ) ) ) j NATURAL COMMUNITY A 0~ 6 CONTROL 0 OIL - LOW I) OIL - MID • OIL - HIGH I Cl) °'\0 X <( 0 AXIS Figure 6-3. Reciprocal averaging.ordination of collections of macrobenthos from experimental boxes and the.natural community at Station AS. • • NATURAL COMMUNITY 6 CONTROL C) OIL - MIO • OIL - HIGH I) en X <( AXIS figure 6-4. Reciprocal averaging ordination of collections of macrobenthos from experimental boxes (excluding the low concentration oiled box) and the natural community at Station AS. () I IJ. I J). ·) J j ) } ) ) Polychaeta - Capitellidae and Spionidae •e Polychaeta - Phyllodocidae and Syllidae Polychaeta - Ampharetidae and Terebellidae '-() Polychaeta - Errantia Peracarida - epifaunal or nesting genera •A Peracarida - Lyssianisidae T Decapoda and Echinodermata - epibenthic • Mollusca - epifaunal • T • spp. not included in above * * e* • t) I. () ()•• (\J • • • Cl) • * ~ • • * O'\ t) .)f • I X • • )f • ],. ~ AXIS I Figure 6-5._ Reciprocal averaging ordination of species of macrobenthos from collections (excluding the low concentration-0iled box) at Station AS •. Table 6-1. Species used in reciprocal averaging ordination of collections from Station A5 (excluding low concentration oiled box). Scaled scores on axes 1 and 2 are giv~n for each species. Scaled Score Species Axis 1 Axis 2 Cyclopecten nanus 0.0 51.7 Aglaophamus circinata 0.1 55.4 Goniada sp. 0.6 47.0 Ophelina acuminata 1.2 63.4 Arctica islandica 1.2 35.6 Polycirrus eximius 1.9 24.8 Nicolea venustula 1.9 24.8 Nephthys sp. 1.9 24.8 Nephthys squamosa 1.9 24.8 Placopecten magellanicus 1.9 54.4 Erichthonius rubricornis 1.9 57.9 Polydora socialis 1.9 63.8 Munida iris iris 1.9 63.8 Capitellacapitata 2.3 81.4 Eualus pusiolus 2.9 76.1 Cerastoderma pinnulatum 10.5 34.6 Polydora concharum 12.8 55.0 Amphilimna olivacea 14.0 32.3 Anemia simplex 15.8 53.3 Terebellides stroemi 19.1 69.8 Ampharete arctica 30.8 48.7 Lumbrineris latreilli 33.1 42.3 Leptocheirus pingius 33.2 39.5 Phoxocephalus holbolli 34.1 32.1 Onuphis pallidula 35.0 65.5 Ninoe nigripes 38.0 42.5 Goniada brunnea 40.2 54.2 Aricidea neosuecica 40.3 52.0 Euchone incolor 43.3 46.7 Asabellides oculata 46.3 56.8 Byblis serrata 43.7 36.1 Phyllodoce mucosa 44.1 13.0 Paradoneis lyra 50.3 40.3 Spiophares wigleyi 50.9 54.2 Notomastus latericeus 51.2 60.6 Scalibregma inflatum 54.4 84.7 Tharyx spp. 57.1 52-.1 Prionospio sp. 57.4 9.3 Thyasira flexuosa 58.1 60.4 Meiodorvillea minuta 62.4 22.9 Photis sp. 65.5 36.2 Unciola irrorata 66.7 48.1 Diastylis bispinosa 66.9 75.0 6~12 Table 6-1. (continued) Scaled Score Species Axis 1 Axis 2 Macrocypris sp. 67.1 Harpinia n. sp. A 67.7 Echinocythereis margaretifera 67.8 Pterygocythereis americana inexpecta 68.6 Nereis grayi 69.1 Paralacydonia paradoxa 70.4 Harpinia n. sp. 5 73.1 Echinocythereis planabasalis 73.8 Ampelisca agassizi 73.8 Harbansus bowenae 76.3 Paraonis gracilis 76.5 Thyasira trisinuata 77 .2 Macroclymene zonalis 78.7 Micrura sp. 79.5 Eriopisa elongata 79.6 Campylaspis rubicunda 80.7 Ophelina cylindricaudata 81.3 Nuculana acuta 81.7 Cirolana polita 83.1 Axiognathus squamata 83.6 Aricidea catherinae 83.9 Amphioplus macilentus 87.0 Nephthys incisa 87.6 Myrtea lens 88.5 Harbansus dayi 88.8 0nuphis atlantisa 89.4 Cirrophorus lyriformis 90.7 Clymenella torquata 90.7 Pandora infl ata 90.7 Thracia conradii 90.7 Cadulus agassizi 90.7 Exogone hebes 90.7 Lasaea rubra 90.7 Typosyllis tegulum 90.7 Oligochaeta 92.8 Cossura longocirrata 94.0 Leiocapitella glabra 94.5 Lumbrineris fragilis 94.6 Indishnopus sp. 94.8 Crenella glandula 94.9 Harpinia propinqua 95.0 Asychis carolinae 95.4 Yoldia sapotilla 95.8 Onchnesoma steenstrupi 96.6 Astropecten americanus 96.6 Drilonereis longa 96. 9;\f'\ ft 6-13 Table 6-1. (concluded) Scaled Score Species Axis I Axis 2 Prionospio steenstrupi 96.9 66.8 Periploma fragile 97.2 70.2 Exogone sp. 97.5 72.7 Actinocythereis vineyardiensis 97.7 75.0 Siphonodentalium sp. 98.3 81.8 Lucinoma filosa 100.0 100.0 Myriochele heeri 100.0 100.0 A_, 6-14 hebes and Typosyllis tegulum, which are characteristic of relatively coarser sediments, have low scores on axis 2 (Table 6-1). Distinct patterns in assemblage composition in boxes versus th~ natural ~onnnunity are evident if the broad taxonomic identities of the fauna are considered. The relative contribution of a few specific groups to total faunal composition is much higher in the boxes than in the natural community. These groups include a number of recognized "opportunistic" poly~haete families such as the Capitellidae (e.g. Capitella capitata), Spionidae (e.g. Polydora socialis), Ampliaretidae (e.g. Polycirrus eximus) and Terebellidae (e.g. Nicolea venustqla), as well as numerous errant families such as Nephthyidae (~.g. Nt!phtys squamosa, Aglaophamus circinata), Goniadidae and Lu~briperidae. Epifaunal molluscs and epibenthic decapods and echinoderms were also relatively more important in the boxes than the natural community, presumably because the experimental boxes provided refuge or substrate otherwise unavailable. ! . The ordination of samples from Station B3 (Figure 6-6) is characterized by a stroQg separation of experimental and natural community s~mples on axis 1 which accounts for 50 percent of the total variation. Unlike the results for Station AS, the intermediate position of the control treatment along axis 1 indicates that this treatment was more like the natural community than were the other experimental treatments. No other strong trends in variation are evi4ent although axes 2 and 3 account for 31 percent (19 and 12 percent, respectively) of the variation in the total data set. Some of tlte variation on axes 2 may be explained by faunal respon~e· to s~diment differences between the natural community sampled at qeployment and recovery of the experiment. The ordination of species on axes 1 and 2 (Figure 6-7) for Station B3 suggest$ a continuum aligned with axis 1, similar to that observed for Station AS. Species with the lowest scores on axis 1, ijuch as the amphipod Orchomenella pinguis (Table 6-2) were found primarily in the oiled treatments. Low to mid-range scQres were cha~acteristic of species found in control samples as well as oiled treatments. These included the polychaetes Capitella capitata~ Ampharete arctica, Polydora concharum and amphipods Unciola spp. and Phoxocephalus holbolli (Table 6-2). The highest scores on axis 1 indicate that a species was found primarily in samples from the natural community. As was evident at Station AS certain taxonomic groups were relatively more important numerically in boxes than they were in the natural community. These included a number of epibenthic and epifaunal groups including decapods (e.g. Cancer spp.), echinoderms, peracaridans and molluscs. Nestling (e.g. Melita dentata, Stenopleustes gracilis) ·and scavenging amphipods were found in n~afly all experimental boxes at B3 although they were rarely found in the box~s at Station AS. Opportunistic families of polychaetes includi~J 6-15 A NATURAL COMMUNITY 6 CONTROL 0 OlL - LOW () OIL MIO • OIL - HIGH °'I ..... C\I °' CJ) X AXIS I Figure 6-6. Reciprocal averaging ordination of collections of macrobenthos from experimental boxes and the natural connnunity_at Station B3. I,}) 1}> I It •o NATURAL COMMUNITY •l::::. CONTROL 0 OlL - LOW I). OIL MID • OIL - HIGH C\I CJ) X AXIS I Figure 6-6. Reciprocal averaging ordination of collections of macrobenthos from experimental boxes and the natural community_at Station B3. : }) \) .J ) ) ) ) e Polychaeta - Capitellidae and Spionidae e. Polychaeta - Phyllodocidae and Syllidae ~ Polychaeta - Ampharetidae and Terebellidae () Polychaeta - Errantia A Peracarida - epifaunal or nesting genera () £. Peracarida - Lyssianisidae T Decapoda and Echinodermata - epibenthic • Mollusca - epifuanal * spp. not included in above T C\I • • Cl) • () * O" -X * )f • ** • I ... * I-' ~ • •• ...... A e () * • £. () ••e * .. •• • e ••• () • AC>• ()* • '- • •• ~ •• A ••• A * • * • • • ' • () I tf* • * * * ;K • •• C) e () • () • () () • • () i' .} IE IE IE C)-@ AXIS Figure 6-7. Reciprocal averaging ordination of species of macrobenthos from collections at Station B3. . __ , Table 6-2. Species used in reciprocal averaging ordination of collections from Station B3. Scaled scores on axes 1 and 2 are given for each species. Scaled Score Species Axis 1 Axis 2 Sclerasterias tanneri 0.0 38.7 Orchomenella pinguis 2.9 41.3 Prionospio sp. 7.0 44.6 Acanthodoris sp. 10.0 32.2 Plactopecten magellanicus 10.5 23.2 Anomia simplex 11.0 22.4 Hippomedon propinquus 12.0 33.7 Anomia squamula 13.4 18.6 Cancer irroratus 15.7 42.7 Cyclopecten nanus 19.8 16.6 Stenopleustes gracilis 20.4 44.5 Capitella capitata 21.5 25.7 Melita dentata 24.5 39.9 Phyllodoce mucosa 25.0 47.1 Glycera dibranchiata 26.8 41. 5 Polydora socialis 26.9 39.9 Crenella decussata 27.0 28.1 Spio setosa 29.6 48.0 Aeginina longicornis 29.9 33.3 Cancer borealis 30.0 50.2 Aglaophamus circinata 37.1 26.8 Janira alta 37.9 51.4 Polydora'c'oncharum 40.2 56.9 Harmothoe extenuata 41.4 44.7 Asterias vulgaris 41.6 68.9 Nereis zonata 42.5 41.8 Phoxocephalus holbolli 42.6 37.8 Spiophanes bombyx 42.9 37.4 Ophelina acuminata 43.2 38.5 Unciola inermis 45.5 38.9 Ampharete arctica1 47.3 33.2 Glycera robusta I 47 .4 19.4 Schistomeringos caeca 47.6 15.1 Cerastoderma pinnulatum 50.3 11.1 Nereis grayi 52.6 40.5 Peracarida - Tanaidacea 52.7 38.1 Erichthonius rubr~cornis 55.0 51.6 Stenopleustes inermis 55.4 69.2 Echinarachnius parma 56.2 58.0 Scalibregma inflatum 56.4 37.5 Byblis serrata 56.4 44.9 Pherusa affinis 58.1 36.6 Unciola irrorata 58.8 37.6 Laonice cirrata 59.5 11.8 6-18 ~ . Table 6-2. (continued) Scaled Score Species Axis 1 Axis 2 Chane infundibuliformis 60.0 42.4 Leptocheirus pinguis 61.4 26.3 ... Ampelis1ca vadorum 62.2 55.1 Thaz:yx spp. 62.4 42.9 Casco b igelowi 63.6 0.2 Axius serratus 64.9 64.6 Macroclymene zonalis 65.8 47.9 Polycirrus eximus 66.2 38.9 Axiognathus squamata 68.0 30.4 Unciola sp. 68.2 28.~ Terebellides stroemi 68.6 37.3 Aricidea catherinae 70.0 47. & Modiolus modiolus 70.4 42.3 Amphioplus macilentus 71.2 44.8 Ptilanthura.tricarina 71.3 53.0 Nucula delphinodonta 72.9 47.3 Exogone hebes 73.8 38.8 Clymenella torquata 74.0 55.8 Cerebratulus sp. 74.1 0.1 Exogone verugera 75.0 41. 7 Goniadella gracilis 75.7 82.9 Lumbrineris impatiens 76.8 6.6 Typosyllis tegulton 76.8 22.3 Photis dentata 77 .1 51. 7 Astarte undata 77 .2 48.1 Eudorella pusilla 77 .2 41.5 Argissa hamatipes 77.4 53.1 Goniada maculata 78. 7 15.1 Photis macrocoxa 79.0 10.0 Euchone incolor 79.2 26.5 Pholoe minuta 79.2 28.3 Asabellides occulata 79.5 9.8 Sphaerodoridium claparedii 80.0 50.6 Diastylis bispinosa 81.2 36.9 Ampelisca agassizi 81.3 39.4 Cyclocardia borealis 81.5 44.7 Ninoe nigripes 81.5 21. 7 Prionospio steenstrupi 81.9 30.2 Euchone elegans 82.0 11.5 Cirrophorus lyriformis 82.5 0.1 Echinocythereis planibasalis 82.7 37.9 Goniada brunnea 82.9 28.6 Actinocythereis vineyardensis 83.0 41.0 Lucinoma filosa 83.5 52.4 Micrura sp. 83.7 32.2 Phascolion strombi 83.8 27.0 6-19 --· Table 6-2. (concluded) ~ Scaled Score ~ Species Axis 1 Axis 2 0ligochaeta 84.4 28.9 Lumbrineris fragilis 85.1 80.9 Psuedocytheretta edwardsi 85.7 100.0 Photis sp. 85.1 100.0 Sabella microphthalmes 85.7 100.0 Notomastus latericeus 86.8 40.5 Melinna cristata 87.5 41.8 Crenella glandula 88.6 79.8 Asterias sp. 90.9 63.6 fir\ Cytherella sp. 1 92.1 55.3 ~ Myriochele heiri 92.9 50.0 Diastylis sculpta 92.9 50.0 Periploma fragile 93.2 47.8 Rhodine gracilor 93.6 44.7 Campylaspis rubicunda 94.1 41.4 ~ Eriopisa elongata 94.1 41.4 Drilonereis longa 94.3 39.6 Harpinia propinqua 94.9 36.0 Edotea triloba 95.6 38.8 Spiophanes wigleyi 96.3 26.0 Paraonis gracilis 96.7 23.0 ,a Meiodorvillea minuta 97.5 17.1 Muellerina canadensis 98.0 13.6 Thyasira flexuosa 100.0 o.o Golfingia elongata 100.0 0.0 Golfingia sp. 100.0 o.o Eumida sp. A 100.0 0.0 A Nepthys incisa 100.0 0.0 Prionospio cirrifera 100.0 0.0 Pterygocythereis americana inexpecta 100.0 0.0 Philine quadrata 100.0 o.o Macrocypris sp. 100.0 0.0 Cytheropteron sp. 1 100.0 0.0 (/!!!1t Cancer sp. 100.0 0.0 6-20 the Capitellidae (e.g. Capitella capitata) and Spionidae were well represented numerically as were errant forms from the families Nereidae, Nepthyidae (e.g. Aglaophamus circinata) and Glyceridae (e.g. Glycera robusta). The ordination of all samples in the same ordination space (Figure 6-8) further clarifies the relationships already observed. Additionally, it should be noted that the relationships among samples, and between samples and the natural community are different at the two stations. At Station B3 the control sample is clearly more like the natural environment than are the oiled treatments. The high concent~ation oiled treatment is least like the natural community. At Station AS patterns with respect to treatment are obscured. The samples are less like the natural community at AS than the B3 experimental samples are like the natural community at B3, suggesting that the community at B3 is recovering at a faster rate. Dominant Species Few of the dominant species characterizing fauna! assemblages in the natural community at Station AS were abundant in the experimental treatments (Table 6-3). Thus the ophiuroid echinoderms Amphioplus macilentus and Axiognathus squamata, as well as several species of ostracods, ranked among the ten most abundant species in the natural community but were rare or absent in experimental boxes. The only dominant species common to both the natural community and experimental treatments were the polychaetes Lumbrineris latreilli and Tharyx sp. Control boxes at AS were also dominated by the amphipod Leptocheirus pinquis and several species of polychaetes not among the most abundant in the natural community. The high abundances of Placopecten magellanicus, a species not common in the natural community, in control boxes was related to their settling on and attachment to the hard surfaces of the boxes and array superstructure. Oiled experimental boxes at Station AS were generally dominated by polychaetes, including the opportunistic species Capitella capitata which was never found in the natural community. The most numerically abundant species in the natural community at Station B3, Ampelisca agassizi, ranked among the top ten in all oiled boxes. This ranking is somewhat misleading because nearly all individuals of this species recovered in the boxes were fully mature males which had presumably moved into the water column for mating. With the exception of epifaunal or nestling species, such as. Aeginina longicornis and Anomia spp., which were provided substrate by the hard surfaces of the array, most dominant species in control boxes were also dominant in the natural community. However, an important dominant member of the natural community, the polychaete Exogone hebes, was not found abundantly in any experimental box at Station B3. 6-21 AB-R A-DA NATURAL COMMUNITY A B-D • 6 CONTROL 0 OIL - LOW () OIL - MID A-R • OIL HIGH 6B-R (\J B-R O'\ I Qt) B-R N CJ) N X B-R <( A-R () 6A-R • A-R A-R AXIS I Figure 6-8. Reciprocal averaging ordination of collections of macrobenthos from the experimental boxes and natural communities at Stations A5 and B3. 1.t (} ( 1) .. j ) J ) • Table -6- 3. Numerically.dominant ..species in the .n-atural- community and 'Colonization experiments ·at station A5 and BJ. (A=amphipod,. B=bivalve., Op=ophuiroid, Os=ostraeod, p::;polychaete). Species are ranked by· density, also given is living-position-feeding category (B=burrower, D=subsurface ·deposit [etc 1979 BLM Report Table 6-12J). Mean Density Living-Position Station/Sample Species Rank (no./m2) Feeding Category A5 Natural Community - Deployment Amphioplus macilentus (Op) 1 2533 B-P Tharyx spp. (P) 2 462 B-S Harbansus bowenae (Os) 3 339 E-S Echinocythereis margaretifera (Os) 4 180 E-S Macrocypris .!P.· (Os) 5 203 E-S Ampelisca agassizi (A) 6 160 T-S Thyasira flexuosa (B) 7 143 B-P Axiognathus squamata (Op) 8 135 B-S Lumbrineris latreilli (P) 9 132 B-D Macroclymene zonalis (P) 10 124 B-D I °'N w Natural Community - Recovery Amphioplus macilentus (Op) 1 2045 B-P Tharyx spp. (PJ 2 669 B-S Lumbrineris latreilli (P) 3 257 B-D Axiognathus squamata (Op) 4 209 B-S Paradoneis lyra (P) 5 207 B-D Macroclymene zonalis (P) 6 142 B-D Amphiuridae juveniles (Op) 7 100 B Ophelina cylindricaudata 8 93 B-D Oligochaeta (01) 9 75 B-D Echinocythereis margaretifera (Os) 10 52 E-S Control Lumbrineris latreilli (P) I 257 B-D Tharyx spp. (P) 2 208 B-S Leptocheirus pinguis 1A) 3 132 p Placopecten magellanicus (B) 4 127 E-P Ampharete arctica (P) 5 109 T-S Polydora concharum (P) 6 70 T-S,P Table 6-3. (continued) Mean Density Living-Position Station/Sample Species Rank (no./m2) Feeding Category Spiophanes wigleyi (P) 7 50 T-S Cerastoderma pinnulatum (B) 8 44 B-P Aricidea neosuecica (P) 9 41 B-D Paradoneis lyra (P) 10 38 B-D Oil-Mid Lumbrineris latreilli (P) 1 95 B-D Tharyx spp. (P) 2 48 B-S Ophelina acuminata (P) 3 42 B-D Placopecten magellanicus (B) 4 26 E-P Ampharete arctica (P) 5 24 ·T-S Scalibregma inflatum (P) 6.5 23 B-D Capitella capitata (P) 6.5 23 B-D Terebellides stroemi (P) 8 22 T-S Amphioplus macilentus (Op) 9 20 B-P Leptocheirus pinguis (A) 10 14 p I °'N ~ Oil-Low Placopecten magellanicus (B) 1 64 E-P Echinocythereis margaretifera (Os) 2 56 E-S Leptocheirus pinguis (A) 3.5 16 P? Munida iris iris (D) 3.5 16 E Erichthonius rubricornis (A) 7 1 T-S,P Anomia simplex (B) 7 1 E-P Cyclopecten nanus (B) 7 1 E-D Lumbrinereis latreilli (p) 7 1 B-D Spiophanes wigleyi (P) 7 1 T-S Oil-High Tharyx spp. (P) 1 144 B-S Lumbrineris latreilli (P) 2 80 B-D Polydora concharum (P) 3 56 T-S,P Capitella capitata (P) 5.5 40 B-D Paradoneis lyra (P) 5.5 40 B-D Harbansus bowenae (Os) 5.5 40 E-S Macrocypris sp. ··(Os) 5 .5 · 40 E-S Echinocythereis margaretifera (Os) 8.5 32 E-S Onuphis pallidula 8.5 32 T.-S ,) j J J I Table 6-3. (continued) Mean Density Living-Position Station/Sample Species Rank (no./m2) Feeding Category B3 Natural Community - Deployment Ampelisca agassizi (A) 1 4115 T-S Euchone incolor (P) 2 563 T-P Lumbrineris impatiens (P) 3 386 B-D Erichthonius rubricornis (A) 4 359 T-S,P Unciola irrorata (A) 5 215 T-S Eudorella pusilla (C) 6 213 F Exogone hebes (P) 7 198 I Phoxocephalus holbolli (A) 8 178 F Photis dentata (A) 9 137 T-S Prionospio steenstrupi (P) 10 120 T-S Natural Community - Recovery Ampelisca agassizi (A) 1 12,813 T-S Euchone incolor (P) 2 5933 T-P Exogone hebes (p) 3 670 I Polygordius sp. 1 (P) 4 600 I °'I N Prionospio steenstrupi (p) 5 593 T-S u, Lumbrineris impatiens (P) 6 525 B-D Unciola irrorata (A) 7 462 T-S Eudorella pusilla (C) 8 434 F Phloe minuta (P) 9 289 E Phoxocephalus holbolli (A) 10 283 F Control Placopecten magellanicus (B) 1 178 E-P Polygordius sp. 1 (P) 2 148 I Euchone incolor (P) 3 134 T;,_P Anomia simplex (B) 4 117 E-P Aeginina longicornis (A) 5 ·82 E-S Lumbrineris impatiens (P) 6 81 B-D Prionospio steenstru.pi (P) -7 74 T-S Ampelisca agassizi (A) 8 64 T-S Phoxocephalus holbolli (A) 9 61 .F Anomia squamula (B) 10 58 E Table 6-3. (concluded) Mean Density Living-Position Station/Sample Specie~ Rank (no./m2) Feeding Category Oil-Mid Aeginina ·1ongicornis (A) 1 230 E-S Phoxocephalus holbolli (A) 2 182 F Stenopleustes gracilis (A) 3 164 E-S Melita dentata lA) 4 156 E-S Ampelisca agassizi (A) 5 85 T-S Erichthonius rubricornis (A) 6 79 T-S,P Unciola irrorata (A) 7 78 T-S Capitella capitata (P) 8 4·2 B-D Harmothoe extenuata (P) 9 41 E Ophelina accuminata (P) 10 38 B-D Oil-Low Phoxocephalus holbolli (A) 1 120 F Capitella capitata (P) 2 88 B-D Unciola inermis (A) 2 88 T-S Aeginina longicornis (A) 2 88 E-S CJ\ I Ampelisca agassizi (A) 5.5 72 T-S N CJ\ Unciola irrorata (A} 5.5 72 T-S Placopecten magellanicus (B) 8 32 E-P Ophelina acuminata (P) 8 32 B-D Scalibregma inflatum (P) 8 32 B-D Oil-High Aeginina longicornis (A) 1 144 E-S Phoxocephalus holbolli (A) 3 120 F Stenopleustes gracilis (AJ 3 120 E-S Melita dentata (A) 3 120 E-S Placopecten magellanicus (B) 5 104 E-P Anomia simplex (B) 6 72 E-P Unciola irrorata lA) 7.5 48 T-S Euchone incolor (P) 7.5 ·48 T-P Polydora socialis (P) 10 40 T-S,P Ampelisca agassizi (A) 10 40 T-S Erichthonius rubricornis (A)_ 10 40 T-S,P ,) Species important in oiled treatments were generally the same as those dominant in control boxes. The opportunistic polychaete, Capitella capitata, ranked among the top ten species in the mid-oil boxes, but was otherwise only sparsely distributed. Individual Species Patterns Three patterns of species response were evident in the recolonization of artificially defaunated sediments at Station AS. The first pattern was exhibi~ed by a number of species found consistently in the natural community which were virtually absent from the experimental boxes. Included in this group were the echinoderm Amphioplus macilentus and the polychaetes Macroclymene zonalis and Ophelina cylindricaudata (Figure 6-9). A second group of species including the mollusca Thyasira flexuosa, and polychaetes Tharyx spp. and Lumbrineris latreilli, was present in both the natural community and experimental boxes (Figure 6-10). The density of these species in the experimental boxes g~nerally approached or approximated levels observed in the natural community. The density of Lumbrineris latreilli appeared slightly depr~ssed in oiled boxes relative to the controls. All three species had extremely low abundances in the low-concentration oiled box which was moderately eroded, either by organisms in situ, or by water currents during recovery. A third group of species exhibited greater abundances in the boxes than they did in the natural community. This group (Figures 6-11 and 6-12) included the polychaetes Ampharete artica, Polydora concharum, Aricidea neosuecica and Capitella capitata. A. arctica and A. neosuecica were most abundant in the control boxes, as was the amphipod Leptocheirus pinguis (Figure 6-12). P. concharum was fo~nd in both the control and high-concentration oil box. c. capitata was found primarily in the oiled boxes. The ostracod, Echinocythereis margaretifera (Figure 6-12), was anamolously more abundant in the low-concentration oil box than in the other boxes. Four patterns of species response were evident in the recolonization of sediment at Station B3. Some species abundant in the natural community, including the amphipod Ampelisca agassizi and polych~etes Euchone incolor and Exogone hebes were rare or absent in the experimental boxes (Figure 6-13). A second group of species, primarily comprised of amphipods, were evenly distributed in all boxes at abundances generally lowe~ but occasionally approaching those found in the natural community (Figure 6-14). This group included the amphipods Unciola irrorata, Erichthonius rubicornis and Phoxocephalus hobolli. These species exhibited no marked response to the varying oil treatments. 6-27 Amphioplus mocilenlus Mocroclymene zono/is Ophelino cylindricoudola 400· 80 80 OI 350· 70 70 E 0 300· 60 60 U) '..J <( I :::, °'t-,) C 250- 50 50 (X) > -- C ~ 200· ... 40 40 u. -- 0 a: II.I 150· 30 30 m 2 :::, z 100· 20 20 50- 10 10 .!J! D R R -R R R D R R R R R D R R R R R NATURAL CONTROL ---OIL NATURAL CONTROL ---OIL NATURAL CONTROL --OIL MID LOW HIGH MID LOW HIGH IIID LOW HIQH Figure 6-9. Population densities of various species of macrobenthos in recovered sediment boxes and the natural connnunity at deployment (D) and recovery (R) at Station AS. .• ) I l) • j ) Thyosiro flexuoso Tharyx spp. Lumbrineris lofreilli 104 80 80 80 N 70 70 70 E 0 60 60 60 'en ..J ::,"\ <( I :, 50 50 50 N C \0 > 0 ~ 40 40 40 ~ 0 0: 30 30 30 LIJ m ~ :, z 20 20 20 10 10 10 D R R R R R D R R R R R D R R R R R NATURAL CONTROL --OIL --- NATURAL CONTROL --OIL-- NATURAL CONTROL --OIL--- MID LOW Hl8H MID LOW Hl8H MID LOW HIGH Figure 6-10. Population densities of various species of macrobenthos in recovered sediment boxes and the natural connnunity at deployment (D) and recovery (R) at Station AS. Amphorele orclico Polydoro conchorum Aricideo neosuecico 40 40 40 35 35 35 OI e 30 30 30 0 ...... (/) ...J 25 25 25 °'I D R R R R R D R R R R R D R R R R R NATURAL CONTROL ---OIL NATURAL CONTROL --OIL--- NATURAL CONTROL ---OIL--- MID LOW HIGH MID LOW Hl8H 111D LOW HIGH Figure 6-11. Population densities of various species of macrobenthos in recovered sediment boxes and the natural connnunity at deployment (D) and recovery (R) at Station AS. (J) tD ,) J J J Capilello capilala Leplocheirus pinguis Echinocylhereis margorelifera 48 50 40 40 40 35 35 tll 35 E ci 30 30 30 Cl) 'J Q'\ <( I => 25 25 25 w 9 I-' > 0 ~ 20 20 20 lL 0 a: 15 15 15 UJ m :E z~ 10 10 10 5 5 5 D R R R R -R 0 R R R R R 0 R R R R R NATURAL CONTROL --OlL --- NATURAL CONTROL ---OIL --- NATURAL CONTROL --OIL --- MID LOW -HIGH MIO LOW HIGH MID LOW HIGH Figure 6-12. Population densities of various species of macrobenthos in recovered sediment boxes and the natural. community at deployment (D) and recovery (R) at Station A5. Ampelisco ogossizi Euchone ,ncolor Exogone herbes aa 98 1600 800 80 N E 1400 700 70 0 (/) '..J 1200 600 60 cl :J 0 O"I > 50 I 1000 500 v,) 0 N ~ u. 0 800 400 40 a: LLJ m :i 600 300 30 z=> 400 200 20 200 100 10 D R R R R R D R R R R R D R R R R R NATURAL CONTROL --OIL --- NATURAL CONTROL --OIL NATURAL CONTROL -- OIL--- MID LOW H18H MID LOW Hl8H MID LOW Hl8H Figure 6-13. Population densities of various species of macrobenthos in recovered sediment boxes and the natural community at deployment (D) and recovery (R) at Station B3. , / ,) :}) ():) J J J J ) J 1./nciolo irrorolo Erichlhonius rubricornis Phoxcepholus ho/JJolli 1011 130 80 80 80 OI E 70 70 70 0 en '...J 60 60 60 <( :::, 0 °'I > 50 50 50 w~ 5 ~ . u.. 4 40 40 0 a: llJ m 30 30 30 :E :::, z 20 2 20 10 10 10 D R R R R R D R R R R R D R R R R R NATURAL CONTROL --OIL NATURAL CONTROL --OIL--- NATURAL CONTROL --OIL--- MID LOW HIGH MID LOW HIGH MID LOW H18H Figure 6-14. Population-densities of various species of macrobenthos in recovered sediment boxes and the natural community at deployment (D) and recovery (R) at Station B3. Species found in both the natural community and control boxes, but not in oiled treatments, comprised the third group. This response pattern was exhibited by the polychaetes Lumbrineris impatiens, Prionospio steenstrupi and archiannelid Polygordius sp. 1 as shown in Figure 6-15. The abundances of Lumbrineris impatiens in the control boxes was generally lower than that exhibited in the natural community while the abundance of the other two species was similar to or greater than thQse found during deployment. The last group of species was found more abundantly in boxes than in the natural community (Figure 6-16). Capitella capita·ta, an opportunistic polychaete, was patchily distributed in boxes, but was generally most abundant in the oiled treatments. Both Placopecten magellanicus and Melita dentata were found abundantly in boxes. The patterns exhibited by these species are representative of a suite of species which were apparently associated with the frame of the array. This group included primarily attached molluscan species, epifaunal or inquilinous amphipods, and hydroids. Species Diversity Community structure statistics, including Shannon diversity, species evenness, areal richness and numerical richness, computed for both the natural community and experiment treatments are summarized in Figures 6-17 to 6-19. Individual estimates of areal richness were based on varying sample sizes as follows: natural community - no. of spp./0.1 m2~ control and mid-concentration oil treatments - no. of spp./0.25 m ~low-and high-concentration oil treatments - no. of spp./0.125 m. In the natural community at Station AS (Figure 6-17) Shannon diversity ranged between 3.25 and 4.25 bits/individual. Species evenness ranged between 0.58 and 0.72. Shannon diversity was generally h·ighest in experimental boxes (4.0 to 4 .6 bits/individual) due primarily to high evenness values (0.72 to 0.88). The low concentration oiled treatment exhibited lower diversity than the natural community due to the low numbers of species and individuals contained in the box. Areal richness values for the natural community ranged between 47 and 71 species in 0.1 m2 • Control boxes contained more species on an areal basis (45 to 58 spp./0.25 m2) than did the high and mid concentration oiled treatment boxes (28 spp./0.125 m2 , 34 to A 38 spp./0.25 m2). All experimental treatments were species poor as compared with the natural community, especially considering the · smaller area represented in these estimates. The low-concentration oiled box contained only nine species in an 0.125 m2 area. The number of species expected in a sample of 89 individuals was calculated using the Hurlbert (1971) rarefaction technique for each 6-34 J ) J •• Lumbrineris impatiens Prionospio sleenslrupi Po/ygordius sp. I 88 80 80 80 70 70 70 CII E 60 60 60 d ...... en 0\ ..J 50 50 50 I <( w ::, U1 0 > 40 40 40 0 ~ lL. 30 30 0 30 0: UJ m 20 20 20 ~ ::, z 10 10 10 D R R R R R D R R R R R D R R R R R NATURAL CONTROL -- OIL --- NATURAL CONTROL --OIL--- NATURAL CONTROL --OIL MID LOW HIGH MID LOW HIGH MID LOW HIGH Figure 6-15. Population densities of various species of macrobenthos in recovered sediment boxes and the natural community at deployment (D) .and recovery (R) at Station B3. Copifello copifolo Plocopeclen mogel/onicus Melilo denlolo IH 80 80 80 °"E 70 70 70 ci ...... en .J 60 <( 60 60 ::, Q\ 0 I > 50 w 0 50 50 Q\ z IL 0 40 40 40 0:: UJ m 30 30 30 ~ ::, z 20 20 20 10 10 10 D R R R R R D R R R R R D R R R R R NATURAL CONTROL --OIL NATURAL CONTROL --OIL NATURAL CONTROL --OIL MID LOW HIGH MID LOW HIGH MID LOW HIGH Figure 6-16. Population densities of various species of macrobenthos in recovered sediment boxes and the natural connnunity at deployment (D) and recovery (R) at Station BJ. ,) 1) I_} NATURAL I~ CONTROL IR ---+ H' (bits/individual ) /MID R +- OIL - LOW R • ' HIGH R • 2 3 4 5 6 NATURAL I~ CONTROL IR -+- J' EVENNESS /MID R -+- OIL- LOW R • '\ HIGH R • 0.40 0.50 0.60 0.70 0.80 0.90 NATURAL ,~ 71 CONTROL IR AREAL RICHNESS /MID R * +- OIL- LOW R '\ HIGH • R • 10 20 30 40 50 60 NATURAL I~ CONTROL IR ( E5 89) /MID R NUMERICAL RICHNESS OIL- LOW R ** '\ HIGH R • - 15 20 25 30 35 40 Figure 6-17. Distribution of Shannon diversity, species ~v~nness, areal and numerical species richness for collections of macrobenthos from Station AS. Horizontal lines represent range of values, vertical lines represent the median. 6-37 ~ NATURAL I~ CONTROL IR 1 --+-- H (bits/ individual) f!b, /MID R· ~ ,✓ OIL-LOW R • \HIGH R • 2 3 4 5 6 {..:!!>. NATURAL I~ CONTROL IR -+- 1 /MID R J EVENNESS -+ OIL-LOW R A '\ HIGH R • 0.40 0.50 0.60 0.70 0.80 0.90 ~ NATURAL I~ CONTROL IR AREAL * /MID R RICHNESS OIL - LOW R • \ HIGH R • 40 50 60 70 80 90 D NATURAL R ~ ·-✓ CONTROL R E (89) 5 MID R / NUMERICAL RICHNESS OIL - LOW R • \HIGH R • pi.. 15 20 25 30 35 40 Figure 6-18. Distribution of Shannon diversity, species evenness, areal and numerical species richness for collections of macrobenthos from Station B3. Horizontal lines represent range of values, vertical lines represent the median. 6-38 STATION A5 CONTROL 80 NATURAL-RECOVERY NATURAL-DEPLOYMENT (/) I.LI 60 (J l1J CJ,. (/) La. 0 40 20 200 400 600 800 1000 STATION 83 OIL- MIO 80 CONTROL NATURAL-DEPLOYMENT -• NATURAL- RECOVERY (/) l1J 60 .,,.,,,,...,,,------r-- -- (J l1J / a. "/ (/) / / u.. / 0 / / a:: 40 / LLJ / al / :E / z~ / ./ 20 ,./ ~ I I 200 400 600 800 1000 NUMBER OF INDIVIDUALS Figure 6-19. Diversity values computed using Hurlburt's (1971) modification of Sanders' (1968) rarefaction technique for collections from Stations AS and B3. 6-39 sample except the low-concentration oiled box which contained only 24 individuals. Values for all samples ranged between 23.0 and 31.5 species/89 individuals. These values exhibited a pattern similar to those computed for Shannon diversity. Numerical richness was higher for experimental treatments than for the natural com munity; values for control and oiled treatments were comparable. Thi_s trend is also evident in the complete rarefaction curves· shown in Figure 6-19. Shannon diversity in the natural community at Station B3 (Figure 6-18) ranged between 2.6 and 4.0 bits/individual. Evenness in this community was low (0.41 to 0.67) due to heavy numerical dominance by the amphipod Ampelisca agassizi and polychaete Euchone incolor. High species evenness in experimental boxes (0.78 to 0.88) is reflected in high Shannon diversity values (4.1 to 4.8 bits/ individual). Experimental boxes generally contained fewer species on an areal basis than did the natural community. The widely ranging areal richness values in the natural community at the time of deployment were related to a greater than usual patchiness in faunal distribution. This fauna! patchiness was not reflected in the Shannon diversity values because low values of areal richness were moderated by high values of evenness. Numerical richness (Figures 6-18 and 6-19) predicted a pattern similar to Shannon diversity. Numerical richness was highest for oiled treatments. Control boxes exhibited greater numerical richness values than did the natural community. DISCUSSION Complex interactions of biotic and abiotic factors lead to spatial and temporal variations in the macrobenthic communities of the continental shelf (Boesch 1979, Schaffner 1980). To adequately predict the potential impact of anthropogenic stress resulting from oil and gas development on the shelf, one must understand the specific processes governing the redevelopment of community structure following disturbance. The extensive theoretical and empirical literature on responses to distu~bance in communities has recently emphasized the marine environment. Many of these studies are considered in an extensive A review by Pearson and Rosenberg (1978) of the processes following chronic and catastrophic disturbances in marine benthic habitats; Additionally, the continued occurrence of accidental oil spills has resulted in a number of studies focusing on the effect of oil on benthic communities (Sanders 1978, Sanders et al. 1980, Anderson and Malina 1978, Anderson et al. 1978, Giere 1979). 6-40 Pearson and Rosenberg (1978) note that in nearly all studies of environmental disturbance due to organic enrichment of the benthic realm there is a consistent pattern in faunal change. This same pattern of response has been observed by McCall (1977, 1978) in artificially defaunated sediments in Long Island Sound, and in the natural environment following a spill of No. 2 fuel oil in Falmouth, Massachusetts (Grassle and Grassle 1974, Sanders 1978, Sanders et al. 1980). The pattern is characterized by the early arrival and initial colonization of substrates by small surface-resource (surface deposit - feeding and suspension feeding) dependent organisms. Such species, capable of rapidly exploiting newly created habitats, are generally known as "opportunists" (Grassle and Grassle 1974). Characterized by rapid growth and maturation, high fecundity and great capabilities for dispersal, these are species with life histories emphasizing r-selected, reproductive processes, rather than K-selected, maintenance processes (Gadgil and Bossert 1970). Boesch (1979) noted that the opportunistic life history is manifested in various ways depending on the phylogenetic framework within which organisms are constrained. Thus, some opportunistic species maximize reproductive output by producing large numbers of planktonic larvae (i.e. most bivalves, s~me polychaetes) while others produce smaller numbers of offspring and offer broad protection (i.e. peracaridan crustaceans, some polychaetes) which increases the likelihood of survival. The first phase in a colonization sequence, characterized_ by high abunclances·of species of this type is called the 0 peak of opportunists" or PO by Pearson and Rosenberg (1978). The second ~hase begins at an °ecotone point ... At this point along a temporal or spatial gradient of pollution total abundance is low, but evenness diversity is high. The authors note that the transitory ,communities following the ecotone point are unpredictable, largely because they are dependent on the availability of recruitable species from the water column. The possibility of attaining "multiple stable points" (Sutherland 1974) in the successional path is certainly related to these stochastic recruitment processes. Thus, the application of the classic concepts of succession which suggest that early colonists are exclusively capable of utilizing newly available habitats and must in some way alter them before further colonization can occur (Odum 1969) has been questioned (Connell and Slatyer 1977, Sutherland and Karlson 1977). Connell and Slatyer (1977) suggest that at least two successional mechanisms exist in addition to the classic concept. They indicate that in some cases initial colonizers may inhibit rather than enhan·ce the influx of subsequent arrivals. In a third model, species are equally capable of utilizing the habitat following disturba~ce but arrive at varying rates depending on life history strategies. It is difficult to predict the pathway of succession and recovery from only one point in time. Yet, the data from this study and the previous recolonization study suggest that recovery patt.erns on the . 6-41 shelf should be similar to those outlined for estuarine and coastal water environments. During the earlier colonization study on the outer shelf (B·oesch 1979) we noted that unscreened boxes exposed in situ for 9 weeks supported higher densities of organisms that did those exposed for 43 weeks. The dominant organisms in boxes exposed for 9 weeks included the polychaete Capitella capitata, and the amphipods Erichthonius rubricornis and Unciola inermis. After 43 weeks the abundances of Capitella were greatly reduced. Shannon diversity increased with time in response to a trend in increasing species evenness. The boxes exposed for 43 weeks were characterized by higher Shannon diversity and species evenness than that exhibited by the natural community. These patterns are strongly suggestive of the general successional patterns expected following disturbance as outlined by Pearson and Rosenberg (1978). Boxes retrieved after 9 weeks may have characterized the "peak of opportunists" phase while those retrieved after 43 weeks represented some stage in the transitory phase. In the present study the limited success in experiment recovery and artifacts related to sediment erosion in experimental boxes prevent definitive testing of the hypotheses outlined in the Introduction and conceptualization of specific recovery processes as outlined in the foregoing discussion. However, the results may be weighed as evidence in support of or against the outlined hypotheses. Hypothesis 1: The rate of colonization by macrobenthos is more rapid and the colonizing fauna is more like that of the natural community in more frequently disturbed outer shelf habitats than in shelf-break habitats. The extent of colonization observed at the swale Station BJ was similar to that observed in previous recolonization experiments in situ for 43 weeks at Station BS (Boesch 1~79). A number of factors suggest that the fauna retrieved in the boxes at Station B3 represented a transitory phase (Pearson and Rosenberg 1978) in the recovery process. These include: 1) the presence of presumably diminished populations of opportunists such as Capitella capitata, coupled with generally low total faunal abundances, 2) Shannon diversity values higher than those exhibited by the natural community, due primarily to high species evenness, and 3) the presence of numerous species normally found in the natural community, such as the amphipod Phoxocephalus holbolli and polychaetes Lumbrineris impatiens and Prionospio steenstrupi. Although other amphipod crustaceans colonized these boxes they were generally less successful than i~ the previous experiment. This reflects differences in species composition and behavior of dominant amphipods at the two sites. Ampelisca agassizi, the dominant amphipod at the deep swale station B3, was not a successful colonizer of box sediments at the shallow swale station BS, although it was found abundantly in the natural community there. 6-42 The most successful colonists at Statipn BS (Erichthonius rubricornis, and Unciola spp.) were not abundant in the natural community or experimental boxes at B3. These general trends in recovery were also observed in the box assemblages retrieved from Station AS, although some differences were apparent. Most notably, fewer constituents of the natural community at AS were found in experimental boxes thus supporting the initial hypothesis that the rate of colonization is faster at the more frequently disturbed outer shelf habitat represented at B3. The dominant species at Station AS include two species of ophiuroids, Amphioplus macilentus and Axiognathus squamata, both of which were rarely found in the control boxes. This is presumably a result of their life history strategies which involve planktonic dispersal (probably of long-lived larvae), slow growth and late maturity. The more complete colonization of the control sediments at Station BJ was also suggested by the results of the reciprocal average ordination analysis which depicts the assemblage in the B3 azoic controls as more similar to the natural community at BJ than were the comparable experimental treatments at A5 to the natural community at Station AS (Figure 6-11). Hypothesis II: Colonization is more complete in uncontaminated than oil-contaminated sediments because colonization of more sensitive forms such as crustaceans is delayed. The effects of erosion in the experimental sediment boxes at Station B3 and the incomplete colonization in the control boxes at both stations makes it difficult to arrive at conclusions about the effects of oil in the sediments on macrofaunal colonization. Nonetheless, the results do not support the conclusion that oil had a substantial toxic effect on a wide variety of species in the natural community. Certain species were clearly less abundant in the oiled treatment than in the control sediment boxes, but these patterns d~d not r~flect any patterns of known sensitivity. Although the amphipod Leptocheirus pinguis was less abundant in the oiled treatment than in the Gontrol treatment at Station AS, amphipod crustaceans were present in the sediment of all oiled treatments. Most amphipods found in the boxes. were surface dwelling forms which would have had only limited con~act with the high concentrations of potentially toxic oil incorporated in box sediments. Yet, the fossorial amphipod, Phoxocephalus holbolli, was more abundant in oiled boxes than in control boxes at Station B3. Multivariate representation of the community in the experimental treatments at Station B3 suggests that the assemblages in co~trol boxes were more similar to the natural community than those in the oiled treatments, primarily dµe to greater abundance of certain polychaetes. However, this relationship is not clearcut and may, in fact, represent differences in sediment composition as a result of diffe~ential erosion in the experimental boxes. 6-43 In summary, although there seem to be clear indications of an effect of experimental oil contamination of the sediments for a few species, based upon comparison of oiled and unoiled sediment, colonization of azoic sediments was generally not; substantially slowed by inclusion of Prudhoe Bay crude oil in the concentrations usedo Hypothesis III: The effect of crude oil contamination on colonization is proportional to the concentration of oil in the sediments. - The results fail to provide evidence to support this hypothesis. There were few cases of clearcut relationships of species or community response to the experimental concentration levels. Conclusions, however, must be tempered by recognition of possible artifacts in the experimental treatments arising when several of the unreplicated boxes with high and low concentrations of crude oil were eroded, either in situ or during retrieval. This obviously reduced the power to discern a relationship between concentration and biological effect. Hypothesis IV: Because sediments with high silt and clay content better accommodate the oil and reduce its rate of weathering, the effect of contamination on colonization is greater at Station AS than at Station B3. The results of our macrobenthos studies fail to provide significant evidence to support this hypothesis either in terms of community structure statistics, multivariate representation of the community, or individual species patterns. The premise on which this hypothesis is based, i.e. that weathering of oil is greater at Station B3 than at Station A5 is, in fact, not strongly supported by the hydrocarbon characterization in these experiments (Chapter 4). Interpretation of both the hydrocarbon data and the biological data with regard to this hypothesis is made difficult by differential erosion of sediment from the boxes at s-tations B3 and AS. Severe erosion of sediment at Station B3 presumably enhanced the loss of hydrocarbons from the sediment. The relative lack of erosion and mixing of sediments in boxes at Station AS probably had the effect of slowing the rate of weathering of petroleum hydrocarbons with depth in the sediment relative to that observed at B3. ACKNOWLEDGEMENTS Cindy Miekley and Louise Theberge are gratefully acknowledged for the time and effort they spent sorting and identifying the samples for this study. Gary Gaston identified the Polychaeta and assisted in the compilation and editing of data. Karl Nilsen confirmed many of the mollusc identifications. Timely assistance on taxonomic difficulties with the Echinodermata was provided by D. Keith Serafy. William Blystone provided assistance with the compilation, editing and analyses of data for this study. 6-44 LITERATURE CITED Anderson, J. w. and D. c. Malins. 1978. Physiological stresses and response in chronically oiled organisms. J. Fish. Res. Bd. Canada 35:679-680. Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydrocarbon concentrations in the sediment. J. Fish. Res. Bd. Canada 35: 776-790. Boesch, D. F. 1979. Benthic ecological studies: Macrobenthos. In: Middle Atlantic Outer Continental Shelf Environmental Studies." Volume IIB. Chemical and Biological Benchmark Studies. Virginia Institute of Mari~e Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62). Chap. 6, 301 p. Boesch, D. F. and R. Rosenberg. In Press. Re~ponse to stress in marine benthic communities. In: G. M. Barrett and R. Rosenberg (eds.), Stress Effects on Natural Ecosystems. John Wiley & Sons, Inc., New York. Cabioch, L., J. -c. Dauvin and F. Gentil. 1978. Preliminary observations on pollution of the sea bed and disturbance of sub-littoral communities in Northern Brittany by oil from the Amoco·cadiz. Mar. Pollut. Bull. 9:303-307. Chardy, P., M. Glemarac and A. Lauree. 1976. Application of inertia methods to benthic ecology: practical implications of the basic options. Estuar. Coast. Mar. Sci. 4:179-205. Connell, J. and R. o. Slatyer. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. Am. Natur. 111:1119-1144. Gadgil, M. and o. T. Bossert. 1970. Life historical consequences of natural selection. Am. Natur. 104:1-24. Gauch, H. G., Jr. 1977. Ordiflex - a flexible computer program for four ordination techniques: weighted averages, polar ordination, principal components analysis, and reciprocal averaging. Cornell University, Ithaca, New York, 123 pp. Gauch, H. G., R.H. Whittaker and T. R. Wentworth. 1977. A comparative study of reciprocal averaging and other ordination techniques. J. Ecol. 65:157-174. Giere, o. 1979. The impact of oil pollution on intertidal meiofauna. Field studies after the La Coruna spill, May 1976. Cah. Biol. Mar. 20:231-251. - 6-45 Grassle, J. F. 1977. Slow recolonization of deep-sea sediment. Nature 265:618-619. Grassle, J. F. and J.P. Grassle. 1974. Opportunistic life histories and genetic systems in marine benthic polychaetes. J. Mar. Res. 32:253-284. Hill, M. o. 1973. Reciprocal averaging: an eigenvector method of ordination. J. Ecol. 61:237-249. Hurlburt, s. H. 1971. The non-concept of species diversity: a critique and alternate parameters. Ecology 52:577-586. McCall, P. L. 1977. Community patterns and adaptive strategies of the infauna! benthos of Long Island Sound. J. Mar. Res. 35:221-266. McCall, P. L. 1978. Spatial-temporal distributions of Long Island Sound infauna: the role of bottom disturbance in a nearshore marine habitat. In: M. L. Wiley (ed.), Estuarine Interactions. Academic Press, New York, pp. 157-172. Odum, E. P. 1969. The strategy of ecosystem development. Science 164:262-270. Pearson, T. H. and R. Rosenberg. 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Bio. Ann. Rev. 16:229-311. Pielou, E. c. 1975. Ecological diversity. Wiley-Interscience, New York, 165 PP• Sanders, H. L. 1968. Marine benthic diversity: a comparative study. Am. Nat. 102:243-282. Sanders, H. L. 1978. Florida oil impact on the Buzzards Bay benthic fauna: West Falmouth. J. Fish. Res. Bd. Canada. 35:717-730. Sanders, H. L., J. F. Grassle, G. R. Hampson, L. s. Morse, s. Garner-Price and c. c. Jones. 1980. Anatomy of an oil spill: long-term effects from the grounding of the barge Florida off West Falmouth, Massachusetts. J. Mar. Res. 38:265-380. Santos, s. L. and J. Simon. 1980. Marine soft-bottom community establishment following annual defaunation: larval or adult recruitment. Mar. Ecol. Prog. Ser. 2:235-241. Schaffner, L. c. 1980. Resource use by Amphipoda (Crustacea: Peracarida) on the outer continental shelf of the Middle Atlantic Bight: Implications to community structure. Masters Thesis, College of William and Mary, Virginia, 176 pp. 6-46 SQtherland, J.P. 1974. Multiple stabl~ points in natural communities. Am. ~atur. 108:859-87-3. Sqtherland, ~. P. and R.H. Karlson. 1977. Developme~t and s~abi~ity of ~he fouting community at Beaufort, North Carolina. Ecol. Monogr~ 47:42~-446. :JI\ 6-47 CHAPTER 7 MEIOBENTHOS COLONIZATION Daniel M. Alongi and Donald F. Boesch - - CHAPTER 7 TABLE OF CONTENTS INTRODUCTION. . 7-1 METHODS . 7-1 Processing of Samples • 7-1 Taxonomic Analysis . • 7-2 Data Analysis. • 7-2 RESULTS . 7-4 Abundance and Biomass . • • • . 7-4 Faunal Composition •••. ••••• 7-13 Nematoda • • • . . . . ••.•• 7-13 Harpacticoida Copepoda...... • 7-16 DISCUSSION .· . •· 7-26 ACKNOWLEDGEMENTS. •. 7-36 LITERATURE. CITED . . 7-36 CHAPTER 7 MEIOBENTHOS COLONIZATION Daniel M. Alongi and Donald F. Boesch INTRODUCTION Relatively few studies have examined the recruitment capabilities of meiobenthos (Boaden 1962; Scheibel 1974; Conrad 1976; Rhoads et al. 1977; Sherman and Coull 1980; Thistle 1980; Desbruyeres et. al. 1980). The sparse data presently available suggest a rapid colonization sequence (less than-one month for return to ambient conditions) for meiobenthic organisms. Their rapid dispersal has recently been ascribed primarily to transport via resuspended sediment in. conjunction with active migration and habitat selection (Gerlach 1977; Sherman and Coull 1980; Thistle 1980). Before,the onset of such studies, however, the meiobenthos was hypothesized as being slow, rather inefficient colonizers due to .the general abs~nce of a pelagic dispersal stage. This problem is apparently negated by their generally small size, rapid maturation and consequently high intrinsic rate of population increase. Our ability to conceptualize the mechanisms of m~iofaunal dispersal is hampered by lack of data under a suite of environmental conditions and types of disturbance. All of the above-mentioned studies were conducted in relatively shallow (0-28 m) non-polluted estuarine habitats. As an attempt to alleviate these discrepancies, the following study was conducted on the Middle Atlantic outer continental shelf to examine the means by which meiofauna disperse and react to pollution-induced disturbance. METHODS Processing of Samples Subsamples for meiofauna were taken at each station in the following manner. From each of three (3) 0.1 m2 Smith-McIntyre bottom grabs, two (2) 6.25 cm2 cores were collected. From the azoic control arrays (4 boxes), two (2) cores were collected from each of three (3) boxes, providing a total of six replicate cores. From. the oil-treated box arrays (4 boxes - 1 partitioned), two (2) cores were ta~en from each of the three boxes containing the midconcentration-oil treatment, and one (1) core from each portion of the box containing the low and high-oil treatments. This sampling design allowed equal replication (6 cores)--except for the low- and high-oil treatments--for each treatment (natural community, azoic control, mid-oil concentration) 7-1 and subsequently allowed partitioning of variance within and among grabs and boxes. Cores were taken by inserting Plexiglas core tubes into the sediment to a depth of 5 cm or to the maximum depth possible if less than 5 cm of sediment was present, and withdrawing them with as little disturbance as possible. Maximum penetration depth, appearance of the redox potential discontinuity (RPD) and sediment temperature from each grab or experimental treatment was measured and recorded. An additional core was taken from each station grab or experimental treatment for archiving for possible future treatment of the soft-bodied meiofauna (i.e. turbellarians, gastrotrichs, tardigrades). Cores collected for hard-bodied meiofauna (nematodes, harpacticoid copepods) were agitated with an isotonic solution of magnesium chloride (MgCl2), the supernatant decanted through 0.5 mm and 0.063 mm sieves, and preserved in 5% buffered formalin. The agitaion procedure was repeated three times. Samples were stained with Rose Bengal to facilitate sorting. In the laboratory, samples were sorted into major taxa. The abundance of each major taxon was recorded durin! sorting and the values converted to numbers of individuals/10 cm to facilitate comparisons with other studies. Biomass values for each major taxon and total biomass values were computed as µg dry weight/individual using values obtained from previous workers (see Table 7-1). Taxonomic Analysis Nematodes were identified to family level; occurrence of dominant genera was noted. Previous studies on nematode populations have indicated considerable sensitivity at even the family level to relatively small changes in sedimentary and/or physio-chemical parameters. Taxonomic analysis of the harpacticoid copepods was carried out to the species level, where possible, by Dr. John w. Fleeger of Louisiana State University at Baton Rouge, Louisiana. Data Analysis Several indices were calculated to reflect community structure. Species diversity was measured for the harpacticoid copepods by t~e Shannon-Wiener information function (Pielou 1966, 1969, 1975). Evenness (J') was calculated after Pielou (1966, 1969, 1975) and species richness (SR) was estimated by SR=S-1/lnN, where Sis the number of species and N the number of individuals in a sample (Margalef, 1958). 7-2 Table 7-1. Values for computation of meiobenthic biomass (from Tenore_!:!~. 1978 and Tietjen, personal communication). Taxon µg dry weight/individual Nematoda 0.3 Copepoda 1.3 Ostracoda 5.0 Polychaeta 5.0 Polychaeta larvae 2.5 Turbellaria 0.1 Bivalvia 5.0 Gastrotricha 0.1 Kinorhyncha 3.0 Tardigrada 0.05 Hydrozoa . 0.5 Oligochaeta 5.0 Amphipoda 7.0 Decapod larvae 5.0 Nauplii 0.1 Sipuncula· s.o Archiannelida 0.3 ------ 7-3 Reciprocal averaging ordination (Hill 1973) was employed for the harpacticoid copepods on reduced sets of square root transformed data. This technique has proved to be efficacious in ecological interpretations (Fasham 1977, Gauch et al. 1977), in that it projects collections (normal analysis) and species (inverse analysis) in the same space. The program ORDIFLEX of the Cornell Ecology Program Series (Gauch 1977) was used to execute reciprocal averaging ordination. RESULTS Abundance and Biomass Density and estimated dry weight biomass of the meiobenthos at both stations were significantly lower in all experimental treatments than in the natural community. Meiofaunal abundance and biomass in the natural community was significantly greater (p(0.05) at Station A5 during deployment (August 1979) than upon retrieval (June 1980). Nematodes were the dominant group at both sampling periods comprising between 82 and 94% of total mean meiofaunal abundance (Table 7-2 and Figure 7-1), and between 44 and 64% of total mean estimated biomass (Table 7-3 and Figure 7-2). Copepods were the next most abundant constituent but were far less common than the nematodes. Ostracods, polychaetes and bivalves were minor constituents at this station. Juvenile macrofauna (polychaetes, bivalves and decapod larvae), however, accounted for approximately 15-25% of the meiofaunal biomass. Nematodes and copepods were co-dominant in all of the experimental treatments at Station A5, with the depressed densities in the treatments attributable to a severely lower density of nematodes. Harpacticoid copepod density and biomass were not significantly different (p)0.05) between the natural community and the control and mid-oil treatment boxes. Meiobenthic density and biomass were significantly depressed (p(0.05) in the low- and high-oil treatment boxes; no significant differences {p)0.05) existed between the control and mid-oil populations. A precipitous decline in nematode population density also accounted for the significantly different (p<0.05) levels of meiobenthic abundance and biomass between the two sampling periods in the natural environment at Station B3 (Tables 7-4 and 7-5; Figures 7-3 and 7-4). As at Station AS, the nematodes and harpacticoid copepods were the most conspicuous meiobenthic taxa, with the nematodes comprising 69-85% and 21-50% of the total mean abundance and total mean estimated biomass, respectively. Ostracods, although only 1-8% of the total densities, accounted for nearly 43% of the estimated biomass of the natural community samples of June 1980. 7-4 Table 7-2. Geometric mean density per 10 cm2 of meiobenthic taxa at Station AS. D = deployment, R = recovery. ,_ Natural Control Oil Mid Low High · Taxon D R R R R R Nematoda 475 201 15 13 3 5 Copepoda 9 24 12 9 2 8 Ostracoda 3 3 2 1 Polychaeta 4 4 2 2 3 Turbellaria 1 Bi val via 5 1 1 2 Gastrotricha 1 1 Kinorhyncha 1 1 1 Hydrozoa 1 1 1 1 2 ,... Oligochaeta 1 1 2 1 Decapod larvae 1 Nauplii 8 3 Sipuncula . 1 2 3 ~ Polychaeta larvae 2 1 2 Archiannelida 1 Total 504 246 38 34 7 21 7-5 NEMATODA COPEPODA a NAUPLII 500 35 400 30 300 25 200 20 100 15 10 50 5 H 0 o-__.__,__...._ ...... __.___._...__ ...... __._ ..... E u 0 ...... OST RACO DA POLYCHAETA S LARVAE en 3- 6 - - ...J - - <[ :::, 5 - 0 - > 2- 4 - 0 - - - ~ 3 - LL. 0 1- 2 - a: IJJ m - :E :::, 0 __._.....,_...... ,,____.,__,_...._...... , ___ z 0 D R R R R R D R R R R R ~NATURAL-fCCNTROL-f--OIL--f J-NATURAL-tCONTROL+- OIL---i MID LOW HIGH MID LOW Hl8H OTHERS 10 8 6 4 2 0 _.__._ ...... __..._.,_...... ___,___._ .... D R R R R R 1-NATURAL-f-CONTRCL-f-OIL----i MID LOW HIGH Figure 7-1. Geometric mean density of meiobenthos (per 10 cm2) in oiled and control sedment boxes and control natural cormnunity at Station AS. 7-6 Table 7-3. Estimated geometric mean biomass of meiobenthic taxa (µg dry weight/IO cm2) at Station AS. Natural Control Oil Mid Low High Taxon D R R R R R Nematoda 143.0 60.4 4.4 4.1 0.9 1.5 Copepoda 10. 9 30.8 15 .4 12.1 2.6 10.4 Ostracoda 7.9 17.3 5.0 3.3 Polychaeta 20 .5 18.7 8.0 5.6 15.0 Turbellaria 0.1 Bivalvia 18.3 1.5 1.3 10.0 Gastrotricha 0.2 0.2 Kinorhyncha 1.4 2.0 1.4 Hydrozoa 1.2 1.0 1.0 1.0 1.0 Oligochaeta 2.2 2.4 2.5 1.5 Decapod la,rvae 13.4 Nauplii 0.5 0.7 Sipuncula 1.5 Polychaeta larvae 3.5 1.4 2.2 1.9 7.5 Archiannelida 0.8 Total 222.6 136.8 40.2 32.9 4.5 44.4 ~ 7-7 NEMATODA COPE POCA 8 NAUPL 11 30 25 20 15 10 5 0 -...... _ ...... __.__.__.....__..__.,_.__ OI E u OSTRACODA POLYCHAETA a LARVAE 0 18 24- 15 ,-. '1- :c 18- (!) 12 w ;: g 12- >- 0::: 6 C s- 0 __._...... _...._.___.___.__._.&.....I ___ 0 ...... _--1-...._. __ ....._, D R R R R R D R R R R R ~NATURAL-iCONTROLr--OIL--+- t-NATURAL-tCONTROLt- OIL---i MID LOW HIGH MID LOW HIGH 40 OTHERS 30 20 10 0 ...... _._....._..__.___._....._...__...... _,_~ D R R R R R I-NATURAL• CONTOL+--OIL----1 MID LOW HIGH Figure 7-2. Mean estimated biomass (µg dry weight/IO cm2) of meiobenthos in oiled and control sediment boxes and control natural connnunity at Station AS. 7-P, Table 7-4. Geometric mean density of meiobenthic taxa per 10 cm2 at Station B3. Natural Control Oil Mid Low High Taxon D R R R R R Nematoda 596 200 8 8 3 5 Copepoda 56 45 6 13 2 13 Ostracoda 6 24 6 3 3 Polychaeta 21 6 1 Turbellaria 1 Bivalvia 7 1 2 2 Gastrotricha 1 Kinorhyncha 1 Tardigrada 1 1 Hydrozoa 2 Oligochaet~ 2 2 1 Amphipoda 1 Decapod Larvae 1 1 Nauplii 3 8 2 4 6 2 Polychaeta Larvae 4 1 1 Archiannelida 1 Total 699 288 27 32 11 25 7-9 Table 7-5. Estimated geometric mean biomass of meiobenthic taxa (µg dry weight/IO cm2) at Station B3. Natural Control Oil Mid Low High (!b. Taxon D R R R R R Nematoda 179.0 59.9 2.3 2.3 0.9 1.5 Copepoda 73.0 58.7 8.3 17.2 2.6 16.9 Ostracoda 31.0 119.2 28.1 8.4 15.0 ~ Polychaeta 10.6 30.7 1. 7 Turbellaria 0 .1 Bivalvia 34.0 1.7 3.4 3.8 Gastrotricha 0.03 Kinorhyncha 1.4 Tardigrada 0.05 0.2 (21 Hydrozoa 1.0 Oligochaeta 10.0 5.3 1.5 Amphipoda 1.0 Decapod Larvae 1.6 1.5 Nauplii 0.6 0.8 0.8 0.4 0.6 0.2 Polychaeta Larvae 11. 7 1.3 2.8 I"\ Archiannelida 1.0 Total 352.7 280.0 48.9 33.8 4.1 34.6 ~ 7-10 NEMATODA COPEPODA a NAUPLII 600 70 500 60 400 50 300 40 200 30 100 20 OI 50 10 E u 0 __.___._..L-.&...... L---&;;;;;i.._~1-.c=i-.c:::i 0--'---L...... L-a....J,--1-,--L--.L-J.....J...... J.....J 0 (/) . '..J OSTRACODA POLYCHAETA a LARV~E 15 OTHERS 12 9 6 3 0 ...... L.-1..-..L-J.....&--L.--L-..1.-JL---.J....J D R R R R R 1-NATURAL-fCC>NTROL+--- OIL---i MIO LOW HIGH Figure 7-3. Geometric mean density of meiobenthos (per 10 cm2) in oiled and control sediment boxes and control natural community at Station B3. 7-11 NEMATODA COPEPOOA 8 NAUPLI I 180 ,e. 70 160 140 60 120 50 100 40 80 30 60 f/!!f\ 40 20 20 10 0 0 OSTRACOOA POLYCHAETA a LARVAE °'e ~ u 120 30 2 100 'I- ::c 80 20 C) L&J 60 3 /F't. >- 40 10 ~ 0 20 C' !:I:. 0 0 0 R R R R R 0 R R R R R ~NATURAL-¾ CONTROL.f--O IL---1 I-NATURAL-f CONTROLf-O1 L~ MID LOW HIGH MID LOW HIGH OTHERS 50 40 30 20 10 0 0 R R R R R I-NATURAL-¼CONTROL~OIL---1 MID LOW HIGH t:E!'I Figure 7-4. Mean estimated biomass (µg dry weight/IO cm2) of meiobenthos in oiled and control sediment boxes and control natural community at Station B3. 7-12 - No significant differences (p)0.05) existed between control and mid-oil boxes at Station B3 in terms of total mean densities and total mean estimated biomass. Extremely depressed meiofaunal abundance in the low oil concentration box may have resulted from severe erosion of the fine sand component. The copepod population densities were significantly lower (p<0.05) in all experimental boxes relative to the natural environment; significantly higher densities (p(0.05) were recorded in the mid- and high-oil treatments. Juvenile macrofauna was conspicuous in its absence in all of the oil--treated boxes and was of low abundance in the control boxes 2 (i C 4/10 cm ) relative to the natural community (x = 34/10 cm2 at deployment; x c 8/10 cm2 at retrieval). Faunal Composition Nematoda The significantly depauperate nematode populations in the experimentai treatments at both stations appeared to be comprised, with f~w exceptions, of only those families abundant in th~ natural colllDlunity. .The paucity of individuals hindered the ability ~~ '.• elucidate familial patterns. :·• . At Station AS the Comesomatidae and Chromadoridae comprised 28.3 and 26.2% of the nematodes present in the natural community, and dominated in the experimental treatments as well (Table 7-6). Although no detailed quantitative analyses were taken, observations have shown the family Comesomatidae to consist predominantly of the genus Sabatieria at this station. Sabatieria was the dominant nematode genus in all treatment types (natural community, control, oiled boxes). The Monhysteridae were relatively less abundant in the control and mid-oil treatments, whereas the 0xystomatidae and Enoplidae were considerably more abundant. Variations in the abundance of these three families accounted for the differences in relative abundance of feeding types per experimental treatment (Figure 7-5 [top]). The higher percentage of omnivore/predators in the mid-oil concentration was due primarily to a greater percentage of Enoplidae, and lower percentage of deposit-feeders. The lower percentage of omnivore/ predators in the control boxes is attributed to the absence of the rarer families, several of which are characterized as omnivore/ predators. The nematode families at Station B3 appeared to exhibit slightly higher diversity and evenness than the shelf-break community (Table 7-6). Nematode populations are generally more diverse in coarser sediments (sensu Wieser 1959). Three families (Comesomatidae, 7-13 Table 7-6. Relative abundance of nematode families (expressed as percentage of geometric mean of replicate cores) at Station AS. Natural Control Oil /!!:I\ Mid Low High Family D R R R R R Oxystomatidae 2.0 0.6 4.7 11.9 Oncholaimidae 0.5 0.5 ~ Desmodoridae 12.0 3.0 4.7 Comesomatidae 28.8 27.8 45.3 11. 9 40.0 Aponchiidae 0.5 0.3 Leptolaimidae 0.4 0.1 Linhomoeidae 6.2 8.0 1.8 Monhysteridae 14. 2 15 .o 5.8 1.8 (21. Enoplidae 0.2 7.1 7.0 31.2 Cyatholaimidae 8.9 3.4 1.1 2.8 Chromadoridae 21.8 30.5 25.6 39.5 100.0 60.0 Axonolaimidae 2.7 2 5.8 Tripyloididae 0.9 0.1 Chioniolaimidae 0.5 0.3 - ~ Monoposthidae 0.1 0.4 Trefusiidae 0.4 0.1 Sphaerolaimidae 0.5 A 7-14 100 90 Selective Deposit 80 Non -selective/ feeders Epiqrowt/J feeders 70 i Omnivore /Predotors 60 50 40 30 0 :,!2 0 20 w (_) I z 10 70 60 50 40 fj - 30 ll 20 10 0 D R R R R R 1--- NATURAL -l CONl'ROL f-----OIL-----4 MID LOW HIGH Figure 7- 5. Relative abundance of nematode feeding types (expressed in percentage) at Stations AS (top) and B3 (bottom). 7-15 Enoplidae, and Chromadoridae) which were abundant in the natural community dominated in all experimental treatments (Table 7-7). Two families appear to present interesting patterns of abundance. The Axonolaimidae, were significantly more numerous in the controls than in the natural community, but absent in the oiled treatments. The Linhomoeidae were equally abundant in the natural community and control boxes, but also absent from the oiled boxes. As presented in Figure· 7-5 (bottom) the relative increase in epigrowth feeders in the control boxes was due to the absence of the less abundant families-the majority of which are deposit-feeders. Harpacticoida Copepoda Species Diversity. All three community structure indices (H', J' and SR) were significantly higher at the shelf-break station (AS) than in the sandier sediments of Station B3. · At both areas, higher values of these statistics were recorded in the natural community relative to all experimental treatments (Table 7-8) even though the samples from the natural community yielded more species. In the natural community at Station AS Shannon diversity values ranged from 3.27 (J' c 0.91) to 3.55 (J' = 0.91) bits/individual. Diversity values were lower in the colonizing community primarily due to lower numbers of individuals and species. Species richness in experimental boxes ranged from 0.62 (high-oil) to 1.90 (mid-oil); a comparable value was recorded for the control (1.50). Diversity values for the natural community at the swale station (B3) ranged from 2.74 (J' = 0.77) to 2.80 (J' = 0.72) bits/individual. As at Station AS, lower diversity values for the experimental treatments reflect the generally depauperate colonizing copepod community in these boxes (Table 7-8). Species richness in the mid-oil treatment (SR= 2.15) was comparable to the natural community; the control and high-oil boxes exhibited significantly lower values of 0.72 and 1.44, respectively. No harpacticoid copepods were found in the low-oil samples at either station possibly because of erosion of sediments during the deployment period or upon retrieval. Assemblages. Further analysis of distributional trends was facilitated by the use of reciprocal averaging ordination. The ordination of collections from Station AS is presented in Figure_7-6. Axes 1 and 2 accounted for 70% of the variance within the data set. Most of the variation along axis 1 reflected assemblage differences in samples from the natural community taken on deployment and recovery, perhaps due to differences in sediment properties. Axis 2 s·eparated samples from the natural community and experiment treatments. The 7-16 Table 7-7. Relative abupdance of n~matode f$11ilie~ (expressed as percentage of geom~t~ic me4n of repliG,tte co~es) at St~tJon B3. · N4tural Control Oil '~id ·· Low. High Faqiily D R R R R R Oxyetol!l4tiqae 5.2 0.8 - .,. Onfholaimidae 6.1 3.~ 2.7 9.6 ... »,IJlllodori~ae 3.8 1.0 4.5 CQme soma tidae 14.2 13.1 4.5 2s .• o 50.0 33.3 Leptolaimi~•e 1.2 1.0 ~ f.,inhomoeidae 17. 3 1.4 18.9 .... Monhysteridae 16.4 9.5 6.8 9.6 Enoplidae ·. 13.~ 19 .1 8.1 ll.5 33.l tho imid ae 1.9 10.9 15.4 . era 1, ..• , . :. . C"i"qmadori4ae 16.2 38.4 50.0 28.9 50.0 ::~ .. :33.) AxptJolaimidae 2.2 0.2 4.5 ... T1;ipyloididae 0.2 0.4 ~ ,.. Trefusiidae 0.1 0.4 Scaptrellidae 1.5 0.3 1hano4erm4tidae 0.2 \ ... 7-17 Table 7-8. Species diversity (H'), evenness (J'), richness (SR) and number of species (N) of harpacticoid copepods at Stations A5 and B3. * Station-Treatment N H' J' SR Station AS Natural D 12 3.27 0.91 3.42 R 15 3.55 0.91 3.54 f!2\ Control R 6 1.87 o. 72 1.50 Mid-Oil R 8 2.33 0.78 1.90 High-Oil R 2 o. 72 o. 72 0.62 ~ Station B3 Natural D 15 2.80 0.72 2.78 R 12 2.74 o. 77 2.34 ,a. Control R 2 0.81 0.81 0.72 - Mid-Oil R 9 2.44 o. 77 2.15 High-Oil R 3 1.50 0.95 1.44 {I!,..,. * No harpacticoid copepods found in low-oil sample at either station. ___,' 7-18 j ) ) t) R N Cl) ...... , X A NATURAL COMMUNITY I <( .... ~ CONTROL \0 ~ OIL-MID • OIL- HIGH RA R = RECOVERY D = DEPLOYMENT IA D "_! AXIS I ... -, Figure 7-6. Reciprocal averaging ordination of collections of harpacticoid copepods, Station AS. high-oil sample was cast alone with a high score on axis 2, while the control and mid-oil treatments possess similar scores along the axes. Comparison with the species ordination (Figure 7-7) shows that several species occurred exclusively in specific treatments, partially accounting for the distinct separation of treatments within the ordination space. Stenhelia longipilosa, Amphiascus sp., Psammis sp., Sicameria sp. and Monocletodes sp. occurred exclusively in the natural environment during June 1980. Another cluster of species-Pseudoameria sp., Diosaccopsis sp. and Fultonia sp.--occurred only in the natural community during August 1979, with Amphiascus minutus pr~sent during both sampling periods. Ancorabolus mirabilis was cast alone with a high score on axis 2, since it was present only in the mid-oil samples. The ordination of collections from Station B3 is presented in Figure 7-8. The ordination along axes 1 and 2 accounted for 51 and 30% of the variance in the data, respectively. With the exception of the sample from the natural community during August 1980 and the mid-oil treatment, the other treatments were clearly dissimilar. The ordination of species cast along axes 1 and 2 (Figure 7-9) help to clarify these discrepancies. Leptomesochra sp., Fultonia sp., Tisbisoma sp., Pseudoameria sp. and Pseudomesochra sp.--species clustered in ordination space--occurred exclusively in the natural community during deployment sampling. The epibenthic Psammis sp. was cast alone having occurred only in the high-oil concentration. The ordination of the total set of harpacticoid collections (Figure 7-10) helped to delineate the differences between stations, as well as the dissimilarities among treatments. Axes 1 and 2 accounted for 50% of the variance. Apparently, the experimental treatments at Stations AS were most similar to each other, with strong dissimilarity between collections from the natural environment during deployment and recovery. At the swale station (B3), mid-oil samples were similar to the natural community with contrastingly strong dissimilarities between the high-oil and control treatments. The ordination of copepod species helped to interpret the complex spatial relationships among the species (Figure 7-11). Three species had conspicuously low scores on axis 2. The burrowers Monocletodes sp. and Sicameria sp. occurred primarily in the natural environs at Station AS; the epibenthic Psammis sp. was absent in the natural community at both stations, but occurred in the high-oil sample at Station B3. Individual Species Patterns. Several patterns of harpacticoid abundance were discernable in the recolonized control and oil treatments at both stations. In all cases, however, the delineation 7-20 ) j J • Ancorobolus mirobilis Oanielssenia • ·sp.. & Sarsocletodes fypico & Enhydrosoma longifurcorum & Tisbisomo sp. Ho/ectinosomo sp.e BODY TYPE • EPI BENTHIC (\J Ho/oschizopero • 1-NTERSTITIAL Cl) oegyptina • X Amerio sp. • & Bulbamphioscus minutus & BURROWING ct • L eptomesochra sp. • Stenhelia /ongipilosa(&)"" I Amphioscus sp.(&) Psammis sp.{e) , Sicomerio sp.(&) Pseudoomeria sp. (•) Monoc/etodes sp. ( &) Oiosoccopsis sp. (&) Fu/Ionia sp. { <•) / Amphiascus mfnutus {&) la AXIS I Figure 7-7. Reciprocal averaging ordination of harpacticoid copepod species, Station AS. ~ ------t------__--LJR t A NATURAL COMMUNITY -..J ~ .CONTROL I N t) OIL- MID N • OIL - HIGH AD t) R R = RECOVERY D = DEPLOYMENT ~R AXIS I Figure 7-8. Reciprocal averaging ordination of collections of harpacticoid copepods, Station BJ. J) () 1) j ) J ) 1 •\[Leptomesochro sp.( •) Fultonio sp.(e) Tisbisomo s p. (&) P.seudoomerio sp.( •) Pseudomesochro sp.( •) Psommisspe & Stenhelio longipiloso BODY TYPE • EPI BENTHIC • 1NTERSTITIAL BURROWING ...... , N • Apodopsy/Jus sp . & I Cl) !-...:> '..,J : • Amerio sp. Amphiascus sp. t £nhydrosomo longifurcotum A Aniphioscus minulus • Donielssenia sp. • eHolectinosomo sp. Holoschizopero oegyptico A Diosoccopsis sp. •Bulbomphioscus minutus .. "'I Sorsocletodes fypico ·- AXIS I Figure 7-9. Reciprocal averaging ordina~ion 0£,harpacticoid copepod species, Station B3. B-RD. t) A-R IA-R ~A-R AA-D ~ B-R B-RA AB-D ...... I (\J A NATURAL COMMUNITY ~ ~- (I) X 6, CONTROL R = RECOVERY D = DEPLOYMENT AA-R eB-R AXIS ·Figure 7-10. Reciprocal averaging ordination of collections of harpacticoid copepods, Stations A5 and B3. 1) :) ' l) ', !) :. !} j J } j • Ancorabolus •mirobilis Diosaccopsis sp. A . Amphioscus Sorsocletodes typic0A Pseudoomeno . minutus .. sp. • .- • eFultoniosp. Enhydrosoma longifurcotumA Ha/oschizopero • aegyptico Ho/ectinosomo . A . _. sp. Tisblsomo spA mertasp. BODY TYPE Oanie/ssenio • Amp/JioscusA s~ s~ • EPI BENTHIC • INTERSTITIAL N Bu /bomphiascus minutus A A BURROWING en • !-eptomesochro sp. X • Pseudomesochra sp. Monocletodes sp. S icamerio sP... ·; • Psom11JiS sp. AXIS Figure 7~H. · Reciprocal averaging or-dina-tion of hattpacticoid copepod species, -stations A5 and B3. of species response patterns was tempered by their comparatively low levels of abundance in the suite of experimental treatments. Several specie present in the natural community at Station AS were absent from th experimental treatments. The burrowers Stenhelia longipilosa, Amphia cus minutus, Diosaccopsis sp. and the epibenthic Fultonia sp. are th major constituents of this group. One species, e robust epibenthic Ancorabolus mirabilis, was found in the' mid-o treatment, but absent in the natural environment. The interstitial f rms Ameria sp. and Aeptomesochia sp. were also present in the mid oil samples though in significantly lesser numbers than in the natura community. Sarsocletodes typ~ca was consistent in its occurrence in he natural comm.unity and all experimental treatments. Eluci ation of species response in the high-oil sample was hindered by ex remely low abundances. The relative abundance and frequency of occur ence of harpacticoids at the station are provided in Table 7-9; dens ties of dominant species are presented in Figure 7-12. The harpactic id copepod community at Station B3 was characterized by t,e dominance of the interstitial Ameria sp. and epibenthic Halectimosoma sp. in the suite of treatment types, except for the absence of Ameria sp. in the control boxes. The patterns of abundance for thes two species are diagrammed in Figures 7-12 (top) and 7-13. The rel tive abundance and frequency of occurrence of all harpacticoid copep ds at this station are presented in Table 7-10. Seven species exhibited a response in which they were present in the natural commun ty, but absent in the experimental boxes. Included in this group were Leptomesochia sp., Fultonia sp., Tisbisoma sp., Pseudoameria sp., seudomesochea sp., Stenhelia longipilosa and Bulbamphiascus min tus. Another conspicuous species pattern was the sole occurrence---- of epipelic Psammis sp. in the high-oil sample. DISCUSSION The low meiof unal densities in the experimental trays recovered after approximate! 9 months at the shelf-break and swale stations suggest incomplete recovery of this benthic component. Both control and oil-contaminat d sediments at both stations supported equally depauperate meiob thic communities, thus there is no evidence that Prudehoe Bay crude oil contamination at the concentrations used affected meiofaun 1 recovery. The rate of ecolonization reported here appears to be at odds with most previou studies (Table 7-11); only Desbruyeres et al. (1980) reported r tes of recovery for meiofauna in defaunated sediments longer han one month. Since their first retrieval was after a 6-month p riod, and meiobenthic densities were greater than 7-26 ) j Table 7-9. Relative abundance (A) and frequency of occurrence (B) -0£ harpacticoid copepods at St-at ion AS.* Natural Control Oil Mid High Species D R R R R A B A B A B A B A B Ameria sp. 4.0 16.7 5.7 50.0 2.5 16.7 Halectinosoma sp. 16.0 16.7 3.8 63.3 7.1 16.7 12.5 66.7 Leptomesochra sp. 4.0 16.7 7.7 16.7 2.5 16.7 Enhydrosoma longifurcatum 12.0 33.3 13.5 66. 7 57.1 66.7 35.0 66.7 ...... Stenhelia longipilosa 15.4 50.0 I N Amphiascus minutus 4.0 16.7 ...... 17.3 50.0 Fultonia sp. 4.0 16.7 Diosaccopsis sp. 8.0 16.7 Danielssenia sp. 3.8 33.3 20.0 100.0 Tisbisoma.sp. 4.0 16.7 3.8 33.3 3.6 16.7 7.5 16.7 Amphiascus sp. 1.9 16.7 Pseudoameria sp. 8.0 16.7 Halos-chizopera aegyptica 8.0 33.3 1.9 16.7 10. 7 50.0 2.5 16.7 Sarsocletodes ~ypica 24.0 33.3 7.7 33.3 17.9 50.0 32.5 33.3 80.0 100.0 Psammis sp. 1.9 16.7 Bulbamphiascus minutus 24.0 1.0 7.7 33.3 3.6 16.7 Sicameria sp. l.9 16.7 Monocletodes sp. 5.7 16.7 Ancorabolus mirabilis 5.0 16.7 * No harpacti~oid copepods found in AS-04 Sample ( low oil). STATION B3 40 Amerio sp. 35 Holecfinosomo sp. 30 Others 25 "' 20 E u 0 15 '- (/) 10 ...J 20 15 10 5 0 D R R R R R f-, NATURAL -I CONTROL t-----OIL -----1 MID LOW H IGH Figure 7- 12 . Comparison in composition of dominant harpacticoid copepod speci es in different tre atments for Stati ons B3 (top) and AS (bott om) . Numbers represent geometric mean densities. 7- 28 25 Amerio sp. 20 15 "' E 10 u Q CJ) '..J 10 5 D R R R R R t- NATURAL~ CONTROL .,__ ___ OIL ----1 MID LOW HIGH Figure 7-13. Geometric mean population densities of dominant harpacticoid copepods Ameria sp. and Halectinosoma sp. at Station B3. 7-29 / Table 7-10. Relative abundance (A) and frequency of occurrence (B) of harpacticoid copepods at Station B3.* Natural Control Oil Mid High Species D R R A B A B A B A B A B Apodopsillus sp. 2.6 16.7 2.7 33.3 Ameria sp. 41.8 100.0 26.1 100.0 46.3 83.3 25.0 100.0 Halectinosoma sp. 20. 9 100.0 33.3 83.3 75.0 33.3 19.5 83.3 50.0 100.0 Le:etomesochra sp. 2.0 16.7 ...... Enhydrosoma longifurcatum 3.9 50.0 5.4 33.3 2.4 16.7 I w Stenhelia longipilosa 4.6 33.3 2.7 33.3 0 Amphiascus minutus 4.6 33.3 5.4 33.3 7.3 16.7 Fultonia sp. 0.66 16.7 Diosaccopsis sp. 2.0 50.0 12.6 66.7 25.0 16.7 4.9 16.7 Danielssenia sp. 1.3 16.7 0.9 16.7 4.9 16.7 Tisbisoma sp. 2.0 16. 7 Amphiascus sp. 2.6 16.7 1.8 33.3 4.9 33.3 Pseudoameria sp. 0.66 16.7 Haloschizopera aegyptica 2.6 16.7 5.4 33.3 4.9 33.3 Sarsocletodes typica 2.7 50.0 4.9 33.3 Psammis sp. 25.0 100.0 Bulbamphiascus minutus 0.9 16.7 Pseudomesochra sp. 7.8 50.0 * No harpacticoid copepods found in B3-04 sample (low oil). 1,) ) ', i) ' J j Table 7-11. Cempilation of previous studies investigating meio~enthi~ recolonization. Nature of Recovery Locality Depth n·isturbance Time Source Sandy beach, North Wales, U.K. Western Baltic Sea 19m Artificial 3 days Scherbel, 1974 Sandy beach, Long Island, U.S.A. Mudbar, North Inlet Estuary, South Carolina, U.S.A. Meriadyed Terrace, Bay of Biscay, France 2160m Artificial within 6 months Desbruyeres ~ .!.!. ·, 1980 the natural commun ty, it is probable the meiofauna recolonized months before retrieval. The general trend in all these studies points to faster recovery in estuarine and coastal waters where the combined effects of tidal ad wind-forced currents and wave disturbance dominate. In deep r shelf waters, only wind-forced currents and those associated with er ss- and long-shelf circulation account for the intermittent ottom transport of sediments (Beardsley et al. 1976; Butman 1979). Present scena ios suggest transportation of meiofauna to d·isturbed habitats primarily by resuspended sediments. The rate of meiobenthic recove y following defaunation is probably dependent upon the spatial extent of the disturbance as well as the strength and duration of physic 1 forces (e.g. tidal and wind-forced currents) capable of produci g suspended sediment loads within the area of disturbance. With the caveat in mind, one can envision a faster meiobenthic respo e in regions where a prevalence of physical forces (e.g. weather-gene ated currents) can permit mass migration of meiobenthos via t resuspended sediment route and, secondarily, by active migration. Conversely, the meiobenthos might take longer to recover from defa nation in relatively quiescent areas where the frequency of sedi ent turbation is considerably less, thus hindering passive transport of meiofauna--the primary means by which meiobenthic organisms diapers • Since most meiobenthic taxa do not have pelagic larvae, the rate f meiofaunal recovery would be considerably reduced if active migrati n was the sole mode of transport, especially in a large scale distu bance. Similarly, m ny macrobenthic species without planktonic dispersal phase·(i.e. larva) such as paracaridan crustaceans have been found to be slow recoloniz rs. For example, Boesch (1979) discovered that the paracaridan crust ceans had not significantly recolonized one and one-half years fo lowing their elimination when anoxic conditions developed over a road area of the inner and central shelf off New Jersey during the summer of 1976. Near-bottom urrents at both shelf habitats have sufficient mean current velocitie permit bedload transport of surficial sediments (Butman et al. 19 Sherman and Coull (1980) have noted that with a mean current velo ity of 15.5 cm· s-1, a calculated boundary sheer stress of 0.735 g • cm-3 is capable of transporting sand particles (density "' 2 .65 g • cm-3) and suspending most meiobenthic taxa as well. However, i is evident by the severe erosion of the fine sanrls in the boxes at S ation B3 that outer shelf currents exceeded velocities necess ry to erode sediments. The erosion coupled with the relative lack of edeposition would account for the low levels of meiobenthic fauna 7-32 The interruption of normal mean bottom transport caused by the effects of box emplacement on the bottom would account for the lack of redeposited sediments, and the hindrance of meiobenthic migration into the boxes. Additionally, it is reasonable to hypothesize that the crawling and/or swimming capabilities of most meiobenthic organisms were impeded since the boxes were placed on the bottom, not into the sediment. Regardless of the balance between passive and active migration, search for a successional pattern of meiofauna has been hampered in previous studies by lack of adequate species identifications of. various taxa. The studies of Sherman and Coull (1980) and Thistle (1980) stress the importance of thorough taxonomic analysis, although rapid colonization precluded a successional sequence ranging from ea+ly colonizing opportunists to later colonizing, equilibrum species. The concept of differential opportunism among meiobenthos is presently not supported by evidence of sequence of colonization, and is hindered by a severe lack of knowledge concerning the population dynamics and life histories of individual species. It is logical to hypothesize that the more motile, epibenthic species are more capable of initial colonization than those organisms adapted to an infauna! lifestyle. Epibenthic copepods have been shown to be tolerant to stressed conditions (Marcotte and Coull 1974, McLachlan 1978, Giere 1979); Hicks (1979) has suggested a selective metabolic superiority of these more motile organisms relative to infauna! species. Calanoids, cyclopoids, and the epibenthic harpacticoids Ancorabolis mirabilis and Psammis sp. were the only copepods able to colonize the oiled treatments at Station AS. Fultonia sp. and Danielssemia sp. (both epibenthic) exhibited no clear patterns at either station. The epibenthic Halectinosoma sp. colonized all treatments at both shelf habitats, having been quantified as an extraordinarily dynamic and robust species (Marcotte 1977). Table 7-12 presents the qualitative changes in relative ~bundance of copepod body types in treatments at both stations, Decreased abundances in the low and high oil concentrations hindered the ability to detect any significant patterns, though a general decrease in burrowing forms was noted in the treatments relative to the natural community at both stations. No significant differences in relative abundance was noted for the interstitial and epibenthic forms in the treatments at both stations--a trend which.does not appear to support the hypotheses that infaunal species would be less capable of migrating either passively or actively as compared to the epibenthic species. The nematode taxocene's response to disturbance may best be examined on the basis of feeding type composition. Interestingly, at the shelf-break habitat the genus Sabatieria (a deposit feeder) dominated the natural environment and control, but not the oil 7-33 Table 7-12. Relative abundances of copepod body types at Stations AS and B3 (expressed as percentage-of geometric mean of total copepod abundance) • Oil Natui::al Communit~ Control Mid Low High Body Type D R R R R R Station AS Harpacticoida Epibenthic 20.0 6.7 4.8 15. 9 · 20.0 Burrowing 40.0 42.7 16.7 36.4 '-,I Interstitial 40.0 19.9 45.2 38.6 80.0 I w Calanoida ~ Epibenthic 30.7 33.3 9.1 100.0 Station 133 Harpac ticoida Epibenthic 22.2 22.4 9.7 18.5 50.0 Burrowing 19.0 20.0 3.2 16.7 Insterstitial .55.6 22.9 40.8 16.7 Calanoida Epibenthic 18.2 83.9 24.0 100.0 33.3 Cyclopoida Epibenthic 3.2 16.5 3.2 - 1} ·.. ) treatments. This genus has been consistent in its dominance under impacted conditions (Tietjen 1977,· 1980; Bouwman 1978; Boucher 1980; Giere 1979), and has been characterized as an opportunist within a pseudocoelomate class considered to be opportunistic in general (John H. Tietjen and Preben Jensen, pers. comm.). The increased . abundance of epigrowth feeders in the low and high oil concentrations was probably due to the increased gravel and coarse sand components in t~e p~rtitioned boxes caused by ~evere erosion. Epigrowth feeders are - usually dominant in coa~ser sediments (Wieser 1959; Tietjen 1969). In the low oil and control boxes at Station B3 there was a significantly greater number of epigrowth feeders--again due to sedimentary changes produced by severe erosional effects. The qematode trophic structure in the other treatments was similar to the surrounding natural coonnunity. To ascribe this difference in nematode community structure in the oiled treatments to an oil effect is problematical since all trophic types have been well represented in stressed enyironments (Marcotte and Coull 1974; Tietjen 1977, 1980; Bouwman 1978;.Boucher 1980; Giere 1979). It is, therefore, doubtful that the levels of abundance and species composition of meiobenthos were influenced by the presence of· petroleum hydrocarbons in the light of past evidence and present tentative conclusions. Although the muddy sands at t~e shelf-break station retained more oil per treatment due to adsorption to fine particles as compared to the sandier sediments at Station B.3, where lack of particulate organics resulted in less retention of the oil, the meiobenthos colonized to comparable levels of abundance in the suite of oiled treatments at both stations. The sensitivity of whole meiofaunal groups to hydrocarbons seems to·vary greatly depending upon oil type and/or a wide variety of abiotic conditions. Wormald (1976) observed a reoccurrence of meiobenthos one month after a diesel oil spill at Hong Kong. Boucher (1980) reported a general decrease in nematode abundance in intertidal sands 7 months after being inundated by the Amoco Cadiz oil spill. However, no changes were detected in nematode and copepod abundances in sublittoral sands adjacent to the spill. Other studies indicate equivalent insensitivity of meiofauna to petroleum (Rutzler and Sterrer 1970; Sanders et al. 1972; Green et al. 1974; Feder et al. 1976; Naidu et al. 1978; Elmgren et al. 1979, 1980), although harpacticoid copepods seem to exhibit more variable sensitivity to oil pollution, as compared to other meiobenthic taxa (Barnett and Kontogiannis 1975; Dalla Venezia and Fossato 1977). The conclusion that the meiobenthic community was not . significantly affected by the presence of Prudhoe Bay crude oil is substantiated by the apparent lack of response within the harpacticoid copepod community. Additionally, Naidu et al. (19?8) have shown the lack of adverse effects on meiofauna utilizing increasing concentrations of Prudhoe Bay crude oil to simulate an intertidal oil 7-35 spill--at concentra ions several orders· of magnit~de higher than used in this study. The general la k of significant change in meiobenthic community composition betwee the controls and oil treatments suggests a response to physic ly-mediated conditions (e.g. storm-generated currents), rather an a response to oil pollution. In spite of the absence of polluti effects,_ interpreting these results as proof of meiobenthic resist nee to pollution-induced disturbance in areas of oil and gas develo ment on the continental shelf is questionable and dangerous. ACKNOWLEDGEMENTS The authors a e indebted to a number of individuals for their help during the co rse of this project. Marcia Bowen assisted in all aspects of the fie d and laboratory work as well as the_~reliminary data analysis. Ta ara Vance assisted in sample sorting. Robert Diaz and Linda Schaffne helped with the ordinations. Special thank to Dr. John w. Fleeger, _Louisiana State University at Baton Rouge, La , for identifying the copepods and providing substantial insigh son copepod ecology, and Dr. John H. Tietjen, City College of New Yor , for providing biomass values and timely ~ssistance with ne atode taxonomic problems. LITERATURE CITED Barnett, c. J. and Kontogiannis. 1975. The effect of crude oil fractionatio son the survival of a tidepool copepod, Tigriopus californicus. Envir. Pollut. 8:45-54 • ~eardsley, R. c., • c. Boicourt and D. v. Hansen. 1976. Physical oceanography the Middle Atlantic Bight. Am. Soc. Limnol. Oceanogr. Sp Symp. 2:53-58. Boaden, P. J. s. 1962. Colonization of graded sand by an inter stitial faun. Cah. Biol. Mar. 3:245~248. Boesch, D. F. 19 9. Benthic ecological studies: macrobenthos. In: Middle tlantic Outer Continental Shelf Environmental Studies, Vol me II B, Chemical and Biological Benchmark Studies. Virginia Ins itute of Marine Science, Gloucester Point, Virginia (BLM Contrac Report No. AA550-CT6-62). Chap. 6, 301 P• Boucher, G. Impact of Amoco Cadiz oil spill on intertidal and sublitto·al meiofauna. Mar. Poll. Bull. 11:95-101. 7-36 Bouwman, L.A. 1978. Investigations on nematodes in the Ems-Dollart estuary. Ann. Soc. v. Zool. Belg-T. 108-fasc. 1-2, 103-105. Butman, B., M. Noble and D. w. Folger. 1979. Long-term observations of bottom current and bottom sediment movement on the Mid-Atlantic Continental Shelf. J. Geophys. Res. 84(3): 1187-1205. Conrad, J.E. 1976. Sand grain angularity as a factor affecting colonization by marine meiofauna. Vie et Milieu, Vol. 26, fasc. 2, ser B, pp. 181-198. Dalla Venezia, I. and V. U. Fossato. 1977. Characteristics of suspensions of Kuwait oil and corexit 7664 and their short and long term effects on Tisbe bulbitosa (Copepoda:Harpacticoida). Mar. Biol. 42:233-237. Desbruyeres, D., J. Y. Bervas and A. Khiripounoff. 1980. Un cas de colonisation rapide L'une sediment proford. Ocean. Acta. 3(3):285-291. Elmgren, R., s. Hansen, U. Larsson and B. Sundelin. 1979. Impact on deep soft bottoms. In: The Tsesis oil spill. A cooperative international investigation. Asko Laboratory Report. Elmgren, R., G. A. Vargo, J. F. Srassle, J.P. Grassle, o. R. Heinle, G. Langlois ands. L. Vargo. 1980. Trophic interactions in experimental marine ecosystems perturbed by oil. In: Microcosms in ecological research, edited by J.P. Siesy. 43pp. Fasham, M. J. R. 1977. A comparison of nonmetric multidimensional scaling, principal components and reciprocal averaging for the. ordination of simulated coenoclines and coenoplanes. Ecology 58:551-561. Feder, H. M., L. M. Cheek, P. Planagen, s. c. Jewitt, M. H. Johnston, A. s. Naider, s. A. Norrell, A. J. Paul, A. Scarborough and D. Shaw. 1976. The sediment environment of Port Valdez, Alaska: The effect of oil on this ecosystem. Ecological Res. Ser. EPA-600/3~76-086, 332 pp. Gauch, H. c. 1977. Ordiflex. A flexible computer program for four ordination techniques. Release B. Cornell University Press, Ithaca, N.Y. 185 pp. Gauch, H. G., R•• Whittaker and T. R. Wentworth. 1977. A comparative study of reciprocal aver~ging and other ordination techniques. J. Ecol. 65:157-174. Gerlach, s. A. 1977. Means of meiofauna dispersal. Mikro. der Meeresbodens 61:89-103. 7-37 Giere, o. 1979. e impact of oil pollution on intertidal meiofauna. Field studies fter the La Coruna-spill, May 1976. Cah. Biol. Mar. 20:231-25 • Green, D.R., C. B den, w. T. Gretney and C. s. Wano. 1974. The Alert Bay oil spill: A one year study of the recovery of a contaminated Pacific Mar. Sci. Rep. 74(9): 39 pp. Hicks, G. R. F. Pattern and strategy in the reproductive cycles of ben ic harpacticoid copepods. In: E. Nay'lor and R. G. Hartnol (eds.), Cyclic phenomena inmarine plants and animals. Per amon Press, New York, pp. 139-147. Hill, M. O. 1973. Reciprocal averging: An eigenvector method of ordination. • Ecol. 61:237-249. Marcotte, B. M. 1 77. The ecology of meiobenthic harpacticoids (Crustacea:Co epoda) in West Lawrencetown, Nova Scotia. Ph.D. Dissertation, Dalhousie University, 212 pp. Marcotte, B. M. an B. c. Coull. 1974. Pollution, diversity and meiobenthic c mmunities in the North Adriatic (Bay of Peran, Yugoslavia). Vie et Mili~u 24:281-300. Margalef, R. 1958 Information theory in ecology. Gen. Syst. 3:36-71. McLachlan, A. Sediment ·particle size and body size in meiofaunal pacticoid copepoda. South African J. Sci. 74:27-28. Naidu, A. s., H•• Feder ands. A. Norrell. 1978. The effect of Prudhoe Ba crude oil on a tidal flat ecosystem in Port Valdez, Alask • Offshore Technology Conference, pp. 97-103. Pielou, E. C. 19 The measurement of diversity in different types of biologica collections. J. Theoret. Biol. 13:131-144. Pielou, E. c. An Introduction to Mathematical Ecology. Wiley-Inters ience, N.Y. Pielou, E. c. Ecological Diversity. Wiley-Interscience, N.Y. Rhoads, D. C., R. Aller and M. B. Goldhaber. 1977. The influence of colonizin benthos on physical properties and chemical diagenesis o the estuarine seafloor. In: B. c. Coull (ed!), Ecology of M rine Benthos. Univ. SouthCarolina Press, Columbia, S.C., PP• 11 -138. Rutyler, K. and W Sterrer. 1970. Oil pollution: Damage observed in tropical ommunties along the Atlantic seaboard of Panama. Bioscience 2 :222-224. 7-38 Sanders, H. c., J. F. Grassle and G. K. Hampson. 1972. The West Falmouth oil spill. Part I. Biology. Tech. Rep. Woods Hole Oceanogr. Inst. No. 72-20, 23 pp. Scheibe!, w. 1974. Submarine experiments on benthic colonization of sediments in the Western Baltic Sea. II. Meiofauna. Mar. Biol. 28:165-168. Sherman, K. M. and B. c. Coull. 1980. The response of meiofauna to sediment disturbance. J. Exp. Mar. Biol. Ecol. 46:59-71. Tenore, K. R., C. F. Chamberlain, w. M. Dunstan, R. B. Hanson, B. Sherr and J. H. Tietjen. 1978. Possible effects of Gulf Stream intrusions and coastal runoff on the benthos of the continental shelf of the Georgia Bight. In: M. L. Wiley (ed.), Estqarine Interactions. Academic Press--;iew York, pp. 557-598. Thistle, D. 1980. The rsponse of a harpacticoid copepod community to a small-scale natural disturbance. J. Mar. Res. 38(3):381-395. ~-. Tietjen, J. H. 1969. The ecology of shallow water meiofauna in two New England estuarines. Oecologia (Berl.) 2:251-291. Tietjen, J. H. 1977. Population distrubution and structure of the free-living nematodes of Long Island Sound. Mar. Biol. 43:123-136. Tietjen, J. H. 1980. Population structure and species composition of the free-living nematodes inhabiting sands of the New York Bight apex. Est. Coast. Mar. Sci. 10:61-73. Wieser, w. 1959. Free-living marine nematodes. IV. General part. Chile Reports 34, Lunds Univ. Arsskr., N.F. Avd. 2( 55): 1-111. Wormald, A. P. 1976. Effects of a spill of marine diesel oil on th~ meiofauna of a sandy beach at Picnic Bay, Hong Kong. Envir. Pollut. 11:117-130. 7-39 ".~::•• -t~•' :·:· .. ·.',;. : -~~ '.; -- .. ··.i 1:.t -.! - !_'•_ ·-., . ' .v ·. ":· r: ,f:J O • ~ 0 J ~ 0 ~ , ·~; ;·-1;· .._, .r·-:, :--,· , ,, : !l .. ,,.· , ...... ,~ 1.·.' .. ;•' }: .... ·. ~: , I :, ., •·. ~ .·· :.J .. :·... ··.•··-t·-· .. f \_.'.- •·.:·, ...,.ic- · ~- ... -= '. . - ,· --;:_ . -~· ...: ~ • .!, ... ~- ':.. _1i::::, ._, ·; ~.; / .•-_ ·- _ .. ·• _. .. :G:~,- .;-f' l '1 . . I ':: ,·.. ~-.._, .. ·- :l• .. : ,.·I . ,· :.•; . ·:_. ·.. _, I ·: .... i ,, . _. __{_, .. ';, ~ • •• cf .~ . ,:_ ,_: 3. .: _: ... .- .· -~ : .. .: .. : .·,::· =· • ~! _; ,I .• t ~- i. ~. .. : . :.... _•. ..' CHAPTER 8 SYNTHESIS AND CONCLUSIONS Donald F. Boesch and Eugene M. Burreson s=-1 retrieval. The closing cable must be at·tached to the closing bar by SQme means other than a swage fitting and consideratio~ should be given to other types of wire rope. Kevlar or some other plastic coated cable may be preferable to stainless steel. The small stainless steel shackles on the bungees could easily be replaced by nylon tie-wraps since the forces are low even when the covers are closed. The method of attachment for the top-plate bearings also needs changing, but the forces here are also relatively low. It may -. even be possible to eliminate this 'bearing. In short, portions of the array which must move or bear critical weight must be noncorroding or well isolated and protected by anodes. Because of the diversity of materials (sheets, tubes, 'bolts, bars) it is virtually impossible to build experimental arrays from completely galvanically compatible metals. Colonization of Disturbed Sediment The observed colonization of azoic sediments by macrobenthos relative to the structure of the natural community proceeded at a roughly similar rate to that observed in an earlier study on the outer shelf of the Middle Atlantic Bight (Boesch 1979). The rate of colonization thus appeared to be intermediate between that observed in shallow water habitats (McCall 1977) and that observed in the deep sea (Grassle 1977). Although the difference was not overwhelming, the colonization rate at the shelf break station A5 appeared slower than that at station B3, as hypothesized, and thus conforming to the conceptual model relating rate of.community recovery following disturbance (resilience) to environmental constancy and frequency of distrubance (Boesch and Rosenberg in press). Long-lived species relying on planktonic larval dispersal (e.g. the dominant Ophiuroids at station AS) were slower to establish populations than those short-lived forms with effective short range dispersal (brooding amphipods and polychaetes). The colonization of azoic sediments by meiobenthos was apparently much slower than previously reported. This is seen as a result of experimental artifacts as well as real differences among the communities which have been studied. The erosion of sediment from the experimental boxes, especially at B3, probably also resulted in the selective erosion of meiobenthos, this keeping "emigration" high with respect to "immigration." On the other hand, all previO\lS_studies -except one in the deep sea, were conducted in very shallow habitats where waves and tidal currents cause very frequent, if not continuous, transport of meiobenthos via resuspension. There was no evidence that colonization was faster at station B3 compared to AS, but this . comparison is also influenced by more severe erosion of sediments from the experimental boxes at B3. The results at station AS, probably more accurately reflect a situation wherein the meiobenthos .of a small patch of natural seafloor is exterminated. 8-6 CHAPTER 8 SYNTHESIS AND CONCLUSIONS Donald F. Boesch and Eugene M. Burreson ·General Findings The overall results of this experimental study may be sunnnarized in four general statements which will be further discussed in this chapter in the context of the six original objectives listed in the Introduction (Chapter 1): 1. Field experiments in the benthic environment are confronted with formidable technical and logistical problems which seriously compromise their probability of success, but which can be partially mitigated based on the experiences of this . study. 2. Petroleum hydrocarbons constituent in crude oil may, if they are mixed into indigeneous bottom sedime~ts, persist for surprisingly long periods of time (probably over one year) in Middle Atlantic Bight outer continental shelf environments, little altered by degradative processes. 3. Despite the chemical evidence of relatively little degradation of hydrocarbons, populations of petroleum-degrading bacteria increase quickly and persist in oil-contaminated sediments. 4. There was little evidence that persistent contamination by hydrocarbons, including toxic components, affects the speed or manner of colonization of azoic sediments by macrobenthos or meiobenthos in the Middle Atlantic Bight, but these results are compromised by experimental artifacts and the slow colonization of uncontaminated controls. Experimental Techniques Failures of the apparatus designed for deployment and recovery of treated sediment (SADRS) seriously reduced the effectiveness of the experiment by limiting the recoveries to one rather than three as planned. However, because of the surprisingly slow oil degradation it must be concluded that, although intermediate recoveries may have demonstrated some short-term effects and elucidated processes, the overall findings would have probably changed little except perhaps to increase confidence in these findings. 8-1 Nonetheless the problems confronted offer some valuable lessons for the design and operation of in situ experiments in the benthic environment of the continental shelr.--Although some of these problems are predictable now with the benefit of hindsight, most problems stemmed from our inabiiity to predict the fate of the experimental arrays for the duration of the experiment during their design and short-term testing. Frankly, this was in part due to inexperience with long term deployment of equipment in the ocean by the scientific investigators and design engineers as well as to the vagaries of nature. Observations about the condition of the SADRS arrays and reasons for their failure follow. Support Frame After ten months underwater the condition of the support frame was generally good. There was considerable pitting on the tubular quadripod due to crevice corrosion, but the frame was structurally sound. There was little evidence of corrosion on the sheet stainless steel frame surrounding the fiberglass boxes. Biological fouling, primarily hydroids, was light at Station B3 (Figure 8-1 and 8-2) and was virtually nonexistent at Station AS. Cover Closing Mechanism Serious corrosion of certain components of the cover closing mechanism resulted in complete failure of the retrieval mechanism. As outlined in Chapter 2 and Appendix A, the stainless steel cables which pull the closing bars and attached covers over th~ fiberglass boxes also support the weight of the array during retrieval. The cable passed through a hole in each bar and was attached to the bar by means of a swage end-fitting. Corrosion of the cable at this fitting caused the cable to part (Figure 8-2), making it impossible to retrieve the arrays as originally planned, and also.making it impossible to close the covers as originally intended. The swage fitting that clamped the closing cable around a thimble to form the eye to which the.retrie~al •line was attached 'also corroded away. The cable itself was not -corroded, however, and would have functioned properly had it not parted at the closing bar. Other components of the closing system were also badly corroded. The stainless steel bolts attaching the nylon bearings to the top plate of the quadripod were usually corroded through allowing the bearing to be pulled away from the plate. The area beneath the bearing flange (Figure 8-1) was heavily pitted as well. Failure. of this bearing alone probably would not have resulted in system failure because its purpose was only to provide a smooth track for the closing cable as it emerged from the quadripod tube and the angle was not that acute. The critical nylon bearings at the base of the quadripod legs were not affected by corrosion and appeared as if they would have 8-2 operated normally. The small stainless-steel shackles attaching the bungees to the frame beneath the fiberglass boxes were often corroded through. These bungees provide back tension to the dacron covers when they are closed and when they corroded off covers were not taut enough to prevent sediment loss. The bungees themselves were in good condition. Other array components such as the fiberglass recolonization boxes, dacron covers, closing bars, retrieval buoys, rope cannisters and retrieval line were in good condition. ... Artificial Effects Containment of sediments just above the natural seafloor introduces artificial effects with pervasive consequences. Sediment will tend to erode from the containers when bottom currents become strong as it does on the seafloor, however little deposition occurs in containers in the sandy habitats studied. An opposite effect of ... enhanced deposition has been reported in habitats with fine sediments subject to tidal resuspension, for example in estuaries. In the present case there seems to be no practical solution in those habitats subject to significant bottom sediment resuspension (e.g. station B3 as opposed to AS) except to limit the studies to more quiescent periods of time by avoiding winter storm periods. Shorter intervals of exposure and smaller containers of sediment may be especially appropriate for studies of bacterial or meiofaunal response. Such studies of inner shelf sediments which are frequently disturbed by wave-induced oscillatory currents may be impossible. Other artificial effects are introduced by organisms attracted to the experimental apparatus. The incidental inclusion of epifauna such as hydroids, caprellid amphipods, and young scallops can simply be factored out in the analysis of data, but, other than possible caging, no acceptable solution exists to contend with large nestling organisms attracted to the array as a refugium (hakes, Urophycis sp., and other fishes, cancroid and galetheid crabs). Recommendations Results of the analyses indicate that the SADRS design is sound from a biological point of view. Artificial effects resulfed primarily from location or seasonal factors (i.e. mid-shelf during winter) and not from design problems. The experiments provided useful, and somewhat unexpected results which could not have been obtained any other way. The closing mechanism design is also satisfactory, only the materials used need improvement. Construction of the entire array from non-corrosive material such as PVC or fiberglass would prevent corrosion but those materials may not be able to support the weight of the sediment or other lifting forces during 8-3 ·::_; Figure 8-1. Top pl-ate of an a:r·ray showing nyd·to_id fot1l:i..tig,- corrosion beneath bearing· fiange, and .corro;s•ion of flange attachment bolt'~· Figure 8-2 .. :Corx:qsion and failtire of· closing cabt·e at· at-tachment to closing bar. 8-4 - - 5 retrieval. The closing cable must be attached to the closing bar by SQme means other than a swage fitting and consideratio~ should be ·given to other types of wire rope. Kevlar or some othe·r plastic coated cable may be preferable to stainless steel. The smaU. stainless steel shackles on the bungees could easily be replaced by nylon tie-wraps since the forces are low even when the covers are closed. The method of attachment for the top-plate bearings also needs changing, but the forces here are also relatively low. It may even be possible to eliminate this ·bearing. In short, portions of the array which must move or bear critical weight must be noncorroding or well isolated and protected by anodes. Because of the diversity of materials (sheets, tubes, 'bolts, bars) it is virtually impossible to build experimental arrays from completely galvanically compatible metals. Colonization of Disturbed Sediment The observed colonization of azoic sediments by macrobenthos relative to the structure of the natural community proceeded at a roughly similar rate to that observed in an earlier study on the outer shelf of the Middle Atlantic Bight (Boesch 1979). The rate of colonization thus appeared to be intermediate between that observed in shallow water habitats (McCall 1977) and that observed in the deep sea (Grassle 1977). Although the difference was not overwhelming, the colonization rate at the shelf break station 45 appeared slower than that at station B3, as hypothesized, and thus conforming to the conceptual model relating rate of.community recovery following ·disturbance (resilience) to environmental constancy and frequency of distrubance (Boesch and Rosenberg in press). Long-lived species relying on planktonic larval dispersal (e.g. the dominant Ophiuroids at station A5) were slower to establish populations than those short-lived forms with effective short range dispersal (brooding amphipods and polychaetes). The colonization of azoic sediments by meiobenthos was appar~ntly much slower than previously reported. This is seen as a result of experimental artifacts as well as real differences among the communities which have been studied. The erosion of sediment from the experimental boxes, especially at B3, probably also resulted in the selective erosion of meiobenthos, this keeping "emigration" high with respect to "immigration." On the other hand, all previot,J.s. studies except one in the deep sea, were conducted in very shallow habitats where waves and tidal currents cause very frequent, if not continuous, transport of meiobenthos via resuspension. There was no evidence that colonization-was faster at station B3 compared to AS, but this . comparison is also influenced by more severe erosion of sediments from the experimental boxes at B3. The results at station AS, probably more accurately reflect a situation wherein the meiobenthos .of a small patch of natural seafloor is exterminated. 8-6 Effects of Oil on Colonization by Benthic Animals The lack of substantial, demonstrable effect~ of Prudhoe Bay ~rude oil on the colonization by macrobenthos and meiobenthos is surprising in light of the often devastating effects which have been observed in natural communities inhabiting sediments following oil spills (e.g. Sanders et al. 1980). There was no strong suggestion of effects of oil contamination on the colonization success of any dominant macrobenthic species at the, swale station B3. At the shelf break station AS, colonization after ten months seemed to be less successtul in oiled sediments for the amphipod Leptocheirus pingqls and the polychaete Lqmbrineris latreilli. On the contrary, the polychJete Capitella capitata, a species renowned for its opportunistic response to- organic enrichment, was more abundant in oi,le4 sedilJlents. Except for Leptocheirus, benthic amphipods, which because of their documented sensitivity to petroleum hydrocarbons were hypothesized to be slow to colonize contaminated sediments, were about as abundant in oiled treatments as they were in controls. The extent of colonization by amphipods was, however, slight compared to previo~s experiment~ at station BS and different results might have been ·obtained in a conununity dominated by motile corophioip amphipods. I~ ha~ been similarly hypothesized that colonization by the ~ominant crustaceans among the meiobenthos, the copepods, would have been affected by oil contamination. Except for their poor success in oiled sediments at station B3 (only epibenthic forms were found), there was no evidence of effects on the copepod taxocerie. ·The result at station B3 may have been caused by the severe erosion of sediments from the experimental boxes. Several experimental limitatio~s warn against concluding that contamination of the seabed by crude oil produced in the Middle Atlantic outer continental shelf will not harm the benthos. The experiment tested the effects on colonization of azoic sediment, an admittedly artificial condition, not the effects on indigenous colillilunities. The generally slow and incomplete colonization of uncontaminated, azoic sediments and the effects of enhanced sediment erosion in the experimental trays introduce further complicating factors. Finally, the Prudhoe Bay crude oil used has been shown ta ~e of relatively low toxicity compared to some other crude oils. Even so, the presumablymore toxic naphthalenes and phenanthrenes persisted in the experiments in concentrations of a few parts per million, concentrations which · might be toxic if they were.- based qn an aqueous concentration (see Anderf?on et al. 1978). A cautious conclusion appears · to be that if crude oil from formations in the Middle Atlantic Bight is similar to Prudhoe Bay crude, contamination of the .seabed on t~e outer continental shelf would pose a less serious biological threat than it may in other OCS·areas and would not result in effects as· severe as those reported ·from more toxic refined products (Sanders et al. 1980) or crude oils (Cabioch et al. 1978). 8-7 Responses of Microbial Community Although alternate freezing and thawing of sediments was undertaken to reduce if not eliminate bacterial densities prior. to deployment, this. technique was ineffective and actually resulted in stimulation of bacterial populations, including the hydrocarbon degraders, just prior to deployment. This was apparently related to a release of more labile organic compounds due to the destruction of animals in the sediment, these including lipids which are probably also suitable substrate for those bacteria which degrade hydrocarbons. Such a result is an experimental artifact but.is probably not dissimilar from an in situ event causing animal mortalities. : Populations of petroleum degrading· bacteria were increased relative to total populations when sediments were contaminated with crude oil, both in the short term (prior to deployment) and for the duration of the experiment (except at the lowest concentration of oil us.ed). The vertical distribution of hydrocarbon degraders in oiled sediments exposed in situ for 10 months, suggests oxygen limited biodegradation.of oil below the. top few centimeters of sediment. The proportion of the bacterial population capable of degrading petroleum hydrocarbons has been shown from these in situ experiments, as in in vivo experiments, to: be. sensitive to oilcontamination. Populations of hydrocarbon degraders were increased by approximately two orders of magnitude and the proportion of the total bacterial populations capable of degrading o~l was higher than that previously observed at the two stations at least at nominal concentrations of oil )50 mg/kg. Weathering qf Petroleum Hydrocarbons Assessments of the weathering of oil (i.e. the change$ in its quantitative and qualitative composition) in the marine environment are based mainly on observation of surface slicks and laboratory experiments. These generally indicate relatively rapid weathering as a result of evaporation, dissolution, biodegradation and- . photooxidation. The persistence of oil in sediments in the experimental boxes placed in situ at two outer-shelf locations is therefore a surprising result-:---iot only did -the total concentrations of oil, estimated based on the concentration of three n-alkanes assuming proportional constancy, decrease little - except for one treatment between 45%· and 91% of·added oil remained, but the oil maintained its qualitative integrity. Al~hough there is evidence of selective loss of more soluble components, the lack of a strong. indication of biodegradation is particularly notable. The potentially toxic naphthalenes and phenanthrenes were selectively lost frpm the sediments relative to the indicator n-alkanes, however concentrations of these former compounds remained approximately one-third of one-half A those originally added. 8-8 The low envifonmental t~mperatures.(probably below 12°C during the experiment), the incorporation aJ;td ;"binding" of the oil in the sediment, and the oxygen and possibly nutrient limited biodegradation of the oil in the sediment all probably contributed to the slow weathering of crude oil in these outer shelf sediments.• Significance Because of the limitations discussed above it is ·impossible to directly apply these results in a model ~f- response to a hypothetical oil spill or chronic input of petroleum hydrocarbons as a r~sult of oil development activities of the outer continental shelf. A model of response.to-oil contamin~tion that could be developed· from the· literature would be that the oil would be fairly ·rapidly altered through selective dissolution and biodegradation leav~ng rela~ively innocuous higher molecular weight components and breakdown products and that as a result of this process, an initially acute effect on colonization by, benthos would gradually lessen. ·Instead,. slow weathering of oil but little observable effects on animal colonizatioq. of oiled s,ediments after 10 months was observed·. Bacterial. response was, however, more predictable. Except for the lowest concentration of oil applied (50 ~g/kg), the muddy sands at the shelf break station A5 retained more oil after 10 months than the fine sands at the swale station B3 (74 vs. 38% for the 250 mg/kg nominal concentration and 91 vs. 45% for the 2500 mg/kg nominal concentratiQn). Also the more frequent and severe resuspension of bottom sediments by storm generated waves at the . shallower station would redistribute contaminated sediments allowing greater dissolution and biodegradation. The effect on macrofaunai colonization was also greater at station AS than at B3. The~e results are consistent with the hypothesis that habitats consisting of finer grained sediments which are less frequently disturbed (e.g. the shelf break versus the outer shelf, swales versus ridges) are more susceptible and sensitive to oil contamination. LITERATURE CITED Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydroc~rbon concentrations in the sediment. J. Fish. Res. Bd. Canada 35:776-790. Boesch, D. F. 1979. Benthic ecological studies: macroben~hos. In: Middle Atlantic Outer Continental Shelf Environmental Studies, Volume IIB, Chemical and Biological Benchmark Studies. Virginia Institute of Marine Science, Gloucester Point, Virginia (BLM Contract Report No. AA550-CT6-62). Chap. 6, 301 p. 8-9 Boesch, D. F. and R •. Ros~nberg. ··In pr~ss. Response to stress in maritie benthic communiUe~- In G. M. Barret~ and R. Rosenberg (eds.),- Stress Effects· on Natural Ecosyst~ms. J. Wiley, New Yoik. Cabioch, L., J. c. Oauvin and F. GeQtil. 1978. Preliminary observa~ions 9n pollution of the sea-bed and disturbance of sub~littoral co~unities in No~thern Brittany by oil from the Amoco Cadiz. M,r. Poll, Bull. 9:303-307. Grassle, J. F. 1977. Slow recolonizat1ron of d~ep-t3ea sediment. Nature 265:6i8-61~. McCall·, P. L. 1977. Community patterns and adaptive strategi,s of the infauna! benthos of Long Island Sound. J. Mar. Res. 3~:2i1-266. Sanders, H. L., J. F. Grassle, G. R. Hampson, L. s. ~orse, s. Garner Price~ and c. o. Jones. 1980. Anatomy of an oil spill: long-term effects from the grounding of the barge Florida off West ·Falniouth, Massachusetts. J. Mar. Res, 38:265-380. APPENDIX A PHASE I FINAL REPORT - DEVELOPMENT AND FINAL DESIGN OF THE SURFACE ACTIVATED DEPLOYMENT AND RECOVERY SYSTE~ DESIGN CRITERIA System Specifications. To be judged acceptable, the SADRS had to meet the following minimum criteria set forth by the BLM. a. The SADRS must be operable from a surface vessel such that deployment and recovery can be accomplished without the use of either divers or a submersible. b. The SADRS must house the sediment-filled recolonization boxes such that they enter the water column and pass through it to the bottom without significant loss of sediment. c. Upon placement on the sea floor, the housing must be removed so that the boxes are exposed to ambient conditions. The· removal of the requisite housing shall be ·triggered, in some fashion, from the surface vessel, or removed automatically after placement. d. Prior to recovery, the recolonization boxes must again be rehoused, in order to prevent sediment loss as the SADRS is retrieved. The rehousing shall be triggered, in some fashion, from the surface vessel, or automatically on the sea-floor. e. The SADRS must be sufficiently rugged to withstand ambient conditions for at least twelve months. 2 APPENDIX A PHASE I FINAL REPORT - DEVELOPMENT AND FINAL DESIGN OF THE SURFACE ACTIVATED DEPLOYMENT AND RECOVERY SYSTE~ - The objective of the Bureau of Land Management's Environmental Studies Program is to provide usable and timely information to support management decisions concerning leasing of submerged Federal lands on the outer continental shelf. One of the major d~ta gaps identified by the BLM concerns the effect of oil on benthic biota; specifically, the sequence of recolonization by benthic organisms and the rate of recovery of an area i~ the event of a pollution episode. This information cannot be obtained by tolerance studies iµ the laboratory; in situ experiments are required. Therefore, the Virginia Institute of Marine ·science was contracted (AA551-CT8-32) to conduct an in situ recolonization --- . e~periment utilizing defaunated sediment from various physiographic provinces on the Middle Atlantic Shelf housed in arrays ~hat are deployable and recoverable from the surface. The program consists of two phases. Phase I entails the de~ign, construction, and testipg of a surface-activat.ed deployment and recovery system (SADRS). Phase II, dependent upon the satisfactory completion of Phase I, entails a series of recolonization experiments and subsidiary studies. The purpose of this report is to present the results of Phase I, - including the initial design of the SADRS, the testing program conducted, modifications to the initial design, the final design, and the method of deployment. The prototype SADRS was designed and constructed by Advex Corporation, Hampton, Virginia. 1 DESIGN CRITERIA System Specifications. To be judged acceptable, the SADRS had to meet the following minimum criteria set forth by the BLM. a. The SADRS must be operable from a surface vessel such that deployment and recovery can be accomplished without the use of either divers or a submersible. b. The SADRS must house the sediment-filled recolonization boxes such that they enter the water column and pass through it to the bottom without significant loss of sediment. c. Upon placement on the sea floor, the housing must be removed so that the boxes are exposed to ambient conditions. The removal-of the requisite housing shall be 'triggered, in some fashion, from the surface vessel, or removed automatically after placement. d. Prior to recovery, the recolonization boxes must again be rehoused, in order to prevent sediment loss as the SADRS is retrieved. The rehousing shall be triggered, in some fa8hion, from the surface vessel, or automatical~y on the sea-floor. e. The SADRS must be sufficiently rugged to withstand ambient conditions for at least twelve months. 2 Biological Considerations. Since the purpose of the study is to assess the recolonization of defaunated, oiled sediment by benthic organisms - both immigrating juveniles and adults, and settling planktonic larvae - it is important that.the SADRS does not interfere with, or alter the behavioral patterns of any organism attempting to colonize the boxes. It is also important th~t replication be provided so that variability can be analyzed. Therefore, the following criteria were set forth by VIMS' benthic ecologists. a) The individual r~colonization boxes must be deep enough to . allow survival of deep-dwelling polychaete worms and bivalve molluscs, and wide enough to prevent an edge effect which might discourage colonization. Based upon previous experience (Boesch, 1979) the following inside dimensions aie satisfactory: 50 cm square and 15 cm deep. b) Each box must have screened areas in the bottom to allow interstitial water circulation through the sediment in the box. c) Each SADRS must contain four (4) boxes situated in the same plane and as close to the sea floor as poss~ble. d) Any superstructure must be as simple and open as possible to allow unobstructed flow of water over the boxes-and to 3 reduce to a minimum the possibility of fouling by fishing vessels. e) The covers and/or closing mechanism must not protrude into.• the water column such that they would either deflect or concentrate sediments or planktonic organisms in the region of the boxes. f) Based upon previous experience (Boesch, 1979) biological fouling should not be a problem during this study. However, the use of mechanisms with very close tolerances, such as objects sliding along narrow grooves or tracks, should be avoided because of the possibility of obstruction by sand, shell, gravel or epifaunal growth. INITIAL DESIGN This section gives a brief description of the initial SADRS A design by Advex Corporation. Engineering drawings and materials ,I specifications are included on the attached blueprints.* Item number and sheet number also refer to these blueprints. *Blueprints available from the Bureau of Land Management, New York OCS Office. 4 Support Frame. The support frame base measures five feet wide by five feet, four inches long by eight ~nches high (5' x 5'4" x 8") (sheet 1, item 1). A welded quadripod superstructure for support of an acoustic release - - buoy syst~ and for attachment of a lowering cable measures five feet, two inches in height. The frame base is constructed of sheet. stainless st~el with four openings in the top to receive the boxes (sheet 3, item 2), and four openings in the bottom covered with sheet fVC eacp with a six inch diameter central screened opening (sheet 2, section A-A; sheet 5, item 1). The quadripod is constructed of tubular stainless steel with a circular stainless steel top plate (sheet 3, items lm and lk). Recolonization Box. ~ach sediment box (fo~r per SADRS unit) is constructed of fiberglass and measures 19 5/8 inches square by~ 7/8 ,inches deep with a surroun4ing two inch lip. Because of an early misunderstanding, the width of the box was drawn too large in the initial design (sheet 4, item 1). Cont~ary to sheet 2, section A-A, the area of the frame that receives the pox lip and the attachment screws are both recessed SUfQ that the box is flush with the frame. Sediment Box Deployment Covers. During deployment each sediment box will be protected by a 1 oz dacron cover attached with a velcro fastener at each corner (sheet 5, 5 item 3; sheet 1, item 2). Each cover will have a metal .grommet sewn in its center, to which is attached a shroud line to be fastened to the deployment release. On deployment when the load is released and the cable hauled the shrouds will pull the dacron covers off the array. Closing Mechanism. Prior to retrieval of the SADRS the closing mechanism and covers are concealed inside the frame beneath the boxes (sheet 2, sections A-A and B-B). Each 2 oz dacron cover (sheet 5, item 4) is attached along its trailing edge to a stainless steel bar (sheet 5, item 2). This bar is attached to the frame by two latex elastics which provide back tension to the covers in the closed position (sheet 2, section B-B). The leading edge of each cover travels around a guide (sheet 2, section A-A; sheet 6, item 1), through a narrow opening formed by a stainless steel sheet (sheet 6, item 2), and attaches to a stainless steel bar (sheet 6, item 4). The two covers on one side of the unit A both attach to the same bar. Thus there are two bars which span the • ,I width of the unit each with two covers attached. A stainless steel cable attaches to the center of each bar, passes between the two boxes on that side, and enters the opposite quadripod leg through a nylon bearing (sheet 2, section A-A). Each cable passes up through the leg and exits through a nylon bearing in the top plate (sheet 1, item 1). At this point the two cables are connected around a thimble with a swage fitting. The cables are here shackled to an end of the recovery A. 6 line stored in a rope cannister attached to one of the quadripod legs. The other end of the recovery line is attached to an acoustic release (Innerspace Model 431) which, on command, surfaces due to flotation provided by a glass buoy. When the recovery line is hauled the cables are pulled through the legs, closing the dacron covers. TESTING AND MODlFICATION Construction of the prototype SADRS was completed on 13 December 1978. The first pool test, to evaluate the efficacy of the deployment covers and the closing mechanism, was held on 18 December 1978 (for a chronology of events see Table 1). Recolonization boxes were not in place so that observation of the entire closing mechanism was possible. The short velcro strips were not sufficient to hold the deployment covers and it was decided to place velcro around the entire edge of each cover. The closing mechanism worked easily, qowever, and the covers were taut when closed. The only other problem encountered was the difficulty moving the SADRS underwater, especially vertically. This caused concern that the 1/4 inch line in the standard Innerspace rope cann~ster would not be strong enough to retrieve the array. Three dock tests were held in January 1979 and resulted in the follofing modifications to the SADRS. The size of the cover closing cable was increased, the retrieval line in the rop~ cannister was increased to 1/2 inch necessitating redesign of the cannister, the rubber elastics were increased in size to provide more back tens~on on 7 Table i. Phase I chronology of events. 1978 Contract signed. 19 October Subcontract signed with Advex Corporation for design and construction of .prototype SADRS. 20 November Preliminary engineering drawings of chosen design reviewed. 28 November Final drawings received. 13 December Construction of prototype SADRS completed. 18 December Pool test. 1979 8 January Pool test. 10 Janaury Dock test. 16 January Dock test. 22,January Dock test. 23-25 January Test cruise "'." Leg I. 2-5 March Test cruise - Leg II. 22 March Dock test. 30 March Dock test. 5 April Dock test. 8 the:covers, 1/4 inch thick nylon strips were placed along each box to make a tighter seal with the cover and also to provide a lock for the closing bar in the closed position, the attachment point of the deployment cover retrieval line was moved from the center to a c9rqer, and closing bar stops were added. The sea test on the R/V Cape Henlopen was aborted at sea on 24 January 1979 because of rough seas and, due to continued poor weather, was not completed until 5 March. The SADRS was successfully deployed and retrieved during the sea test, but underwater television observations revealed that the cover edges flapped and rippled during ascent, and some sediment was lost during passage through the water surface. A more detailed discussion of the test cruise can be found in the Cruise Report for contract AA551-CT8-32 dated March 1979. As a result of observations made during the sea test, the following modifications were incorporated into the SADRS. The elastic attachment bar on the covers was modified so that tension was transmitted directly and entirely to the cover edges, and nitex screen windows were sewn into two covers. A dock test to evaluate these changes revealed that further stiffening of the covers was·ne~essary, and also that the nitex screens allowed scouring of the sediment during ascent. As a result, the nitex windows were removed, 1/4 inch nylon rope was sewn into the cover edges for their e.ntire length, and the,nylon strips were moved inboard about 1/2 inch on two boxes. A dock test revealed that the friction of the rope passing ove~ the cover guide actually reduced tension on the covers. In addition, 9 sediment loss was observed under the leading edge bar and also around . the beveled end of the nylon strips. Further modifications involved limiting the rope edge to that portion of the cover actually over the box, shortening the covers to provide more tension, narrowing the covers, lengthening and raising the nylon strips, and moving the closing bar stops closer to the quadripod support tube. A final dock '-' test was conducted in which virtually no sediment was lost during retrieval, and the SADRS was judged acceptable. FINAL DESIGN The final design of the SADRS incorporates modifications approved during the test phase. However, since these modifications were "added on" to the original design during testing, some have been redesigned as more integral parts of the overall unit, and therefore are more amenable to assembly line techniques. The following section will discuss final design structural ._.., changes only. Modifications that resulted only in increased strength or size of a component will not be mentioned here. Both types of modifications have already been mentioned in the previous section. Support frame. No change. A 10 -· Recolonization Box. Each sediment box will have velcro strips glued on the lip completely ,~ound the opening of the box. On two sides, immediately adjacent to the velcro strips, will be a nrlon strip. These strips will be 3/8 of an inch high at the center and taper to a smooth bevel at the closing bar when in the open position. The opposite end of the strip will taper to a thickness of 3/16 of an inch to provide a locking mechanism for the closing bar when in the closed position. Sediment Box Deployment Covers. For the final design, velcro will be sewn into the entire edge of each cover, _and the retrieval line grommet will be sewn near one corner instead of in the center. This will facilitate removing the covers during deployment. Closing Mechanism. +wo modifications have been incorporated to provide additional tension or stiffness to the closing covers. The elastic attachment has been changed so that they now connect directly to the edges of each cover rather than to the bar. The bar has been modified to function only as a spacer to prevent the cover from collapsing. Rope (1/4 inch nylon) has been sewn into that portion of each cover edge that will be adjacent to a nylon runner when the cover is closed. In addition, the closing bar stops, designed to prevent the closi~g bar from applying force to the tubular legs, have been incorporated into the design of the lower nylon bearing. -~ - 11 METHOD OF DEPLOYMENT Each SADRS will be deployed with an acoustic release-load multiplier system (Innerspace Technology, Inc. Model 431) attached via cable to a shipboard winch. Lines from each deployment cover will also be attached to the acoustic release (Figures I and 3). Each SADRS will ·be lowered to the sea floor. An acoustic signal will then be given which will cause the acoustic release to detach from the SADRS. The release will then be retrieved, pulling the deployme~t covers from the boxes during ascent. A second acoustic release and buoy will remain attached to the SADRS for use during recovery (Figures 2 and 4). METHOD OF RECOVERY To recover an SADRS, an acoustic ~ignal will be given causing the acoustic release and buoy to detach from the unit (Figure 2). The buoy and release will then travel to the surface pulling liqe from the rope cannister as they ascend. Upon reaching the surface, the buoy and release will be retrieved and the line passed through a block and retrieved using a capstan. The other end of the line is attached to the thimble in the closing cables (Figure 2) and thus the entire lifting force is transmitted· through these cables. Since the force required to close the covers is less than that reqqired to lift the SADRS off the bottom, the tension on the cables will pull the two closing bars and attached covers over the sediment boxes before the 12 Acoustic Release/ Load Bar Acoustic Release Deployment Coyer Rope Retrieval Line Cannister Figur~ 1. Schematic of SADRS during deployment without rope cannister attachment shown. 11 Buoy Acoustic Release Figure 2. SADRS shown as deployed on the sea floor. 14 Figure 3. Photograph of SADRS showing deployment release and lines to deployment covers. 15 - - Figure 4 . Photograph of SADRS showing attachment of deployment and retrieval releases and line from rope cannister to retrieval release. 16 unit lifts off the bottom. During ascent, the tension on the closing cables will hold the covers closed, and bungee tension will keep the covers taut. Even if vessel surging causes the cables to slacken during ascent, the nylon strips on each box serve as locks and will prevent the covers from opening . .f'a\ 17 - - APPENQIX B RECOLONIZATION BOX OBSERVATIONS AND PHOTOGRAPHS - .... - - Figure B-1. Control array from Station A5 (A5C2) immediately aft er recovery, showing one cover properly in place (left), one slightly dislodged (right), and two covers missing. - 1 ,.. , I Figure B-2. AS Control box l. Sediment depth uniform 12 .1 cm. Figure B-3. AS ·Control box 2. Sediment depth uniform 12. 7 ·cm. 2 - - - 3 ,. Figure B-4. AS Control box 3. Sediment depth uniform 12.1 cm. This box lost its cover near the surface, but there is no gross evidence of sediment scour or loss. Figure B-5. AS Control box 4. Sediment depth uniform 12.7 cm except two corners are slightly eroded. This box lost its cover near- the surface. 4 - - 5 Figure B- 6. Oiled array from Station A5 (A501) during sampling. 6 Figure B-7. A5 medium oil concentration box I. Maximum sediment depth 12.7 cm, minim\Dll sediment depth 3.8 cm in one corner. Eroded area in lower portion of photo may be result of a large Cancer crab. Figure B-8. A5 medium oil concentration box 2. Maximum sediment depth 10.2 cm, minimtnn sediment depth 5.7 cm. Large Cancer crab present underwater in upper right corner; many Munida also visible. 7 - - 8 Figure B-9. AS medium oil concentration box 3. Maximum sediment depth 10.2 cm, minimum sediment depth 3.2 cm in lower right corner. Large Cancer crab was located in upper right corner; many Munida also visible. Figure B-10 •· AS low oil concentration box 4 ( right) and high oil concentration box 5 (left). Maxim~ sediment depth in box 4 was 10.8 cm, the upper left corner was devoid of sediment and depth was as low as 3.2 cm in lower right corner. Maximum sediment depth in box 5 was 12.7 cm, minimum depths ranged from 6.4 cm in lower right corner to 8.9 cm in upper left corner. 9 0 C .... - Figure B-11. Control array from Station B3 (B3C3) showing moderate loss of sediment. The submersible pilots observed moderate current scour around this array as well as one lobster and at least two large crabs living under the array. One large hake (Urophycis sp.) was nestled in one corner of a box and numerous hake were observed in the immediate vicinity. 11 Figure B-12. B3 control box 1. Sediment depth v~ried from 2.5 cm to 7.0 cm. Figure B-13. B3 control box 2. Sediment de.pth varied from 1. 9 cm to 5.8 cm. 12 ( . ' .·. Flg~re ij-14., B1f qqntrol ·bo~ 3·. ·:;Erdiment- ·ci~pt_h vai,-i~4 from ·:o.-. 0~ :cm to :.3·: a: ·cm. Fig-u.i;~ ~~~.!h · BJ ·r.ontr.ol 1;,qx 4. $eqinient: ·d~pth vai;ieP f~9m O. 6 cm to . g, 8' cm·. Wh-i.te lin·e, -~re support ridges m(?ld.ed into ~o_ttom .qf box. · · 14 - 15 Figure B-16. BJ medium oil conc~ntration box 1 from array B302 (No ~ photograph available of entire array). Sediment depth ranged from 3.2 cm to about 0.5 cm in two corners. Figure B~l7. B3 medium oil concentration box 2. Sediment d~pth ranged from 3.8 cm to 1.3 cm in two corners. 16 - 17 p,.__ , _Figure B-18. B3 nie.dium oil concentr~tion box· ·3. Sedim.ent. .-4.~pth r-ange'd..from 2.5 cm to 0.0 cm in one corner • . •,. . .~ •. ~ .. ,l . :! ...~ .. •. ·'i : , ...... ' • t .• - - ,~ •Figure -B-19· •..B3 l~w oil concen•tration box (left) and high oil . ··c<:>n~·entra-tion _.bax Crig}J.,t). ·. ~edim~nt -qept.h ranged·-· from _._. ·3.-.2 .cni to O·.0 cm in -both boxes. · · ...... -!~:· ) . .; ' .. • : ii, 18 """_,_ "' ..... - -, , - 19 APPENDIX C CHARACTERIZATION OF PRUDHOE BAY CRUDE OIL C. L. Smith - I INTRODUCTION The B~nthic Recolonization Study was designed to Ptovide information on the effects of oil on benthic biota by monitoring the sequence and rate of recolonization of oiled sediment by benthic organisms. The oil chosen by BLM for use in these in situ experiments was Prudhoe Bay crude, a relatively light (high API gravity) oil from the North Slope of Alaska. This report presents the results of oil characterization analyses performed at VIMS·, and compares them to resµlts reported by Dr. Robert G. Riley, Battelle Northwest Laboratories, Richland, WA. (Tables 1 and 2). The primary objective of the VIMS characterization is the identification of the numerous peaks in the chromatograms of the aliphatic and aromatic fractions of the crude oil. Details of quantitative analyses and how the characterization data are to be used in the Recolonization Study will be presented in a separate report. Since the oil analyses to be conducted later would involve extracts from sediment, an extract of freshly oiled se~iment was used for the oil characterization study. METHODS Fresh Prudhoe Bay crude oil was mixed with wet station B3 sediment at a concentration of 2.6 g/kg. Station B3 is one of the, sites selected for the Recolonization Study. Tqe oil dose was arbitrarily selected as adequate to ensure extensive oil recovery, and to overwhelm indigenous sedimentary hydrocarbons. Previous analyses of station B3 sediment (see Middle Atlantic OCS Baseline Studies) demonstrated total hydrocarbon concentrations to be less than 5 mg/kg - some 500 fold lower than the oil dose. This qil dose is not related to that to be used in the Recolonization Study itself. A method of Anderson et al. (1978) modified by Anderson (1979, personal communication) was used for the extraction. Oiled sediment (20 g) in~ 125 ml Erlenmeyer flask with teflon cap was sequentially extracted using an orbital shaker with 20 ml of methanol with 5% lN HCl (2 hr), 30 ml hexane (16 hr), and 20 ml hexane (2 hr). Equal volumes of hexane and distilled water were added to the methanol from the first extraction, and after agitation, the hexane layer was separated. The combined hexane extracts were reduced to 10 ml on a rotary evaporator. As the oil characterization analysis was qualitative, standards were not added and recovery was not determin~d, A 1 ml aliquot of the concentrated extract was separat~d into aliphatic and aromatic fractions by elution chromatography on silica gel according to the technique of Warner (1976) as modified by MacLeod et al. (1978). Each fraction was reduced to 0.5 ml by evaporation under a strea~ of dry nitrogen, and analyzed on a Varian 2740 gas 1 Table 1. Concentrations of Saturate Hydrocarbons in Prudhoe Bay Crude Oil provided by Battelle. Concentrations in mg/gram oil. Concentration in Compound Original Oil 1 Ca 4.20 + 0.12 C9 4.42 + 0.10 C10 4.44 + 0.35 Cu 4.68 + 0.08 C12 4.62 + 0.15 C13 4.46 + 0.26 C14 4.16 + 0.05 C15 3.99 + 0.22 C16 3.74 + 0.24 C17 3.39 + 0.42 Pristane 2.07 + 0.38 C1a 2.50 + 0.24 Phytane 1.05 + 0.24 C19 3.04 + 0.76 C20 1.93 + 0.24 C21 1.58 + 0.20 C22 1.86 + 0.30 C23 1.65 + 0.29 C24 1.27 + 0.26 C25 1.02+0.55 C26 0.76 + 0.23 Total (c1i - C26) 43.39 + 4.27 1compounds Ca - C11 were corrected for recovery on the basis of the recovery of C12 hydrocarbon and, therefore, more than likely are low. 2 Table 2. Concentrations of Aromatic·Hydrocarbons in Prudhoe Bay Crude Oil provided by Battelle. 9oncentration in mg/gram oil. ConcentratioQ in Compound Original Oil! toluene 0.82 + 0.08 ethyl benzene 0.56 + 0.01 m+p-xylene 2.05 + 0.04 o-xylene 0.79+·0.0l isopropylbenzene 0.16 + 0 .oo l-ethy1+4-methylbenzene. 0.29 + 0.00 1,3,5-trimethylbenzene 0 .41 + O .oo 1,2,4-trimethylbenzene l.i4 + 0.01 secbutylbenzene 0.14 + o.oo methyl-4-isopropylbenzene 0.12 + 0.00 indane 0.67 + 0.00 l,3-dimethyl-5-ethylbenzene 0.27 + 0.00 1,2-diet~ylbenzene 0.24 + 0.02 l,2-dimethyl-4-ethylbenzene 0.24 + o.o~ 1,2,4,S~tetramethylbenzene 0.38 + o.oo 1,2,3,5-tetramethylbenzene 0.27 + 0.00 napthalene 0.92 + 0.01 2-methylnapthalene 1.63 + 0·.02 1-methylnapthalene 1.29 + 0.02 l-ethyl+2-ethylnapthalene 0.48 + o.oo 2,6+2,7-dimethylnapthalene 0.69 + 0.01 l,3+1,6-dimethylnapthalene 0.99 + 0.01 1,7-dimethylnapthalene 1.10+0.0l l,4+2,3+1,5-dimethylnapthalene 0.80 + 0.01 1,2-dimethylnapthalene 0.40 + 0.00 2,3,6-trimethylnapthalene 0.51 + 0.07 phenanthrene 0.38 + 0.05 1-methylphenanthrene 0.33 + 0.02 .2-methylphenanthr~ne 0.21 + 0.01 3,5~dimethylphenanthrene 0 .11 + 0 .00 Total (napthalene - 3,6-dimethyl 9.91 + 0.15 phenanthrene) lMonoaromatic hydrocarbons have not been corrected for recovery. 3 chromatograph interfaced to a Dupont 21-492B mass spectrometer. GC separation conditions were: Column - 0.3 mm x 20 m glass capillary. Coating - SE-52 applied to pre-silanized glass (per Grob 1979). Carrier - He at 17 psig. ·Injection - Splitless, hot needle, with toluene solvent plug. Temperature program - 50-240C at 6C/min. The resulting mass spectra and GC retention times were used to identify the peaks on the chromatograms. _RESULTS AND DISCUSSION The aliphatic fraction of the crude oil is dominated by n-alkanes with carbon numbers up to C34, and a few branched/isoprenoid - hydrocarbons. Major peaks in the gas chromatogram (Fig. 1) were identified by mass spectra and retention indices, and are listed in Table 3. Mass spectra for branched alkanes at Kovats Indices 1462 and 1650 are shown in Figures 2 and 3. Positive identification of these compounds is prevented by overlapping compounds and limited mass spectral detail. Peak ratios determined from the gas chromatogram (Table 4) are in crude agreement with those calculated from the Battelle results. The VIMS data show nearly equal amounts of all n-alkanes from Cl3-C26, whereas Battelle found a rather sharp decline in amount with increasing carbon number in that range. These differences are probably due to evaporative losses of the most volatile components from the VIMS sample (uncorrected) and injection loss of the least volatile components from the Battelle sample (no solvent plug injection). The aromatic fraction of the crude oil consists primarily of di and tri-cyclic compounds and their alkyl derivatives. ·Major peaks of the gas chromatogram (Figure 4) are identified in Table 5. None of the substituted benzenes reported by Battelle appear here because of evaporative losses in the sample workup. However, as these compounds will also be lost from the oiled recolonization tray sediments before deployment, this should not prove to be detrimental to the interpretation of the study. Although more isomers of di-, tri-, and higher polycyclic aromatic hyrdrocarbons are listed here than reported by Battelle, there exists considerable overlapping of peaks, and some uncertainty about the exact isomer!~ identities. For this reason, aromatic compounds appearing in natural groupings are classed ~ogether for quantitative purposes under the name of the compound class which seems most typical of the group (Table 6). Identification of some groups, such as the phenanthrenes, is greatly facilitated by inspection of mass chromatograms plotted for their molecular ions. Mass chromatograms for phenanthrene, Cl-phenanthrenes, and 4 ., ) ) A M L B D E G J N () p Q R :S V, H K 0 5 \0 15 20 25 30 3S 40 45 50 SAMPLE: PRUDHOE BAY CRUDE ALIPHATIC RAW FILE YM4TFR PLOTTING TIME : 0 TO 50 MINS. Figure 1. GC of Pr udhoe Bay crude oil a liphati c f raction . See Table 3 for peak identif ication. Table 3. Major al~phatic fraction peaks in Prudhoe Bay crude oil. Peak Kovats Index Identification ~ A 1300 n-Tridecane B 1400 ii-Tetradecane C 1462 Farnesane (isoprenoid) D 1500 n-Pentadecane E 1600 n-Hexadecane F 1650 Branched alkane (non-isoprenoid) G 1700 n-Heptadecane H 1705 Pristane (isoprenoid) I 1754 Branched alkane (non-isoprenoid) J 1800 n-Octadecane K 1810 Phytane (isoprenoid) ~ L 1900 n-Nonadecane _,- M 2000 ii-Eicosane N 2100 n-Heneicosane 0 2200 n-Docosane p 2300 n-Tricosane Q 2400 _E-Tetracosane R 2500 n-Pentacosane s 2600 -n-Hexacosane Table 4. Ratios of aliphatic hydrocarbons. (.P.). Ratiott This Studz* Battelle Cl7/pristane 1. 7 1.6 Cl8/phytane 2.2 2.4 Cl3/C20 0.9 2.3 a:,. C14/C20 0.9 2.2 Cl5/C20 1.1 2.1 C16/C20 1.0 1.9 Cl7 /C20 1.0 1.8 Cl8/C20 1.1 1.3 C19/C20 1.0 1.6 C20/C20 1.0 1.0 ~ C21/C20 0.9 0.8 C22/C20 1.2 1.0 C23/C20 0.9 0.9 C24/C20 0.8 0.7 C25/C20 1.0 0.5 A C26/C20 0.8 0.4 ._/ *Results of this study not corrected for evaporative losses. *Cone. of. C20=2.4 mg/g this study, C20=1.9 mg/g for Battelle. IS 6 SEQUEN 6 PAQE 3 GCID. BL 156 MACK'S a HE)( IGNORE as. 3e~ •e. •• 9'SCALE 188 8AMU'S aee HRDCPY NO SUBTR e BASEPIC e SCAN I ua1 BKGRND 188 BASE 1a1 *2** e ,C TOTAL IONIZ. 18 e SEQUEN 6 PAGE 4 GCID BL 156 ~ACK'S e HE>< aee ase 318 358 •88 figure 2. Mass spectrum of farnesane (KI-1462). 7 SEQUEN 6 PAGE 1? GCID BL 156 MACIC'S e HE>< IGNORE aa. 3a. •e. 4• tcSCALE 1ee *AMU'S a0e HRDCPY NO SUBTR e BASEPIC e SCAN I a?0 BKGRND 269 ,Q!\ BASE aea •a•• e tc TOTAL IONIZ. a1 -- • se 180 158 aee Figure 3. Mass spectrum of branched alkane (KI-1650) found in aliphatic fraction of sediment extract. 8 ) ) ) t kk a e b ti n bb 0 pp ee h ,p hJ'_ . m X 00 ff gq l k \ t s u 0 3 6 9 t2 rs J-8 21 24 30 SAMPl::£ : Prudhoe Boy Crude Aromatic RAW FILE -Y-RATFR PLOTTING TIME : 0 TO 30 MINS. Fiogur e 4. GC -0f Prudhoe Bay crude oil aromatic fraction. See Table 5 for peak identification. Table 5. Aromatic hydrocarbons identified in Prudhoe Bay crude oil. PEAK GROUP COMPOUND ~ Q a Cl-Naph. 2-Methylnaphthalene b It 1-Methylnaphthalene C C2-Naph Biphenyl d C2-Naphthalene e C2-Naphthalene f C2-Naphthalene g C2-Naphthalene h C2-Naphthalene i C2-Naphthalene ---✓ j C3-Naph. Methylbiphenyl k It C3-Naphthalene 1 C.3-Naphthalene m CJ-Naphthalene n C3-Naphthalene 0 CJ-Naphthalene p C3-Naphth~lene q Fluorene r CJ-Naphthalene s C4-Naphthalene t C2-Biphenyl u C4-Naphthalene V C4-Naphthalene w Methylfluorene X Methylfluorene y Methylfluorene z C3-Biphenyl aa Dibenzothiophene bb Phen. Phenanthrene cc C2-Fluorene dd C2-Fluorene ee C2-Fluorene ff ·Unidentified, mw. 210 gg Cl-Phen. :'. · Methylphenanthrene hh Methylphenanthrene If!!!, ii Methylphenanthrene jj Methylphenanthrene kk Septum contaminant 11 C2-Phen. C2-Phenanthrene 10 Table 5 (concluded) PEAK GROUP COMPOUND mm C2-Phen. C2-Phenanthrene nn C2-Phenanthrene oo C2-Phenanthrene pp C3-Phenanthrene qq C4-Phenanthrene Table 6. Concentrations of aromatic hydrocarbon groups in Prudhoe Bay crude oil (in mg/g). CLASS CONCENTRATION Cl-Naphthalenes 1.2 C2-Naphthalenes 3.0 C3-Naphthalenes 5.6 Phenanthrene 0.2 Cl-Phenanthrenes 1.3 C2-Phenanthrenes 0.9 11 /1!'!1. . -· SEQUEN 18 PAGE 1 - DRAW l'IC QC ID BL 134 DATE 11~1~~?9 AQRATE 8 SCTIME 1 RESPWR see HIPIASS see THRESH 1 "ACK~s OILED SEDil"IENT HEM TOL "ASSES 118. •• •SCANS aee HRDCPY ••NO • MSCALE 188 REZERO YIES BASE 8143*1** 8 • &e ... Figure 5. Mass chromatogram showing phenanthrene (m/e-178). 12 S~QUEN 21 PAGE 1 DRAW MC GC ID BL 13• DATE 11 ✓ 1~/?9 AQRATE 6 SCTIME 1 RESPWR see HIMASS see THRESH 1 "ACK>S OILED SEDI~ENT HEk TOL PIASSES SSCANS "SCALE BASE " 50 109 1se aee Figure 6. Mass chromatogram showing methylphenantrenes (m/e-192). 13 Ii•, ;&;,•ht•"•'U'fk'&•htr••,11·•1 .. 200 250 300 360 400 Figure 7. Mass chromatogram showing C2-phenanthrenes (m/e-206). 14 C2-phenanthrenes are shown in Figures 5, 6, and 7. Mass chromatograms such as these will be extremely useful in identifying highly weathered oil, where other characteristics are not obvious. LITERATURE CITED Anderson, J. w., R. G. Riley and R. M. Bean. 1978. Recruitment of benthic animals as a function of petroleum hydrocarbon concentrations in the sediment. J. Fish. Res. Bd. Can. 35 776-790. Grob, K., G. Grob, K. Grob, Jr. 1979. Deactivation of glass capillaries by persilylation. Journal of High Res. Chromatography and Chromatog. Comm. Vol. 2, 677~678. MacLeod, w. D., D. w. Brown, R. G. Jenkins, and L. s. Ramos. 1977. Intertidal sediment hydrocarbon levels at two sites op the Strait of Juan de Fuca, p. 335-396. In D. A. Wolf [ed.] Fate and Effects of Petroleum Hydrocarbons in Marine Organisms and Ecosystems. Pergamon Press, Inc. Hew York, N.Y. Warner, J. s. 1976. Determination of aliphatic and aromatic hydrocarbons in marine organisms. Ana. Chem. 48:578-583. 15 .... APPENDIX D - MACROBENTHOS AND MEIOBENTHOS RAW DATA - Included on Microfiche