BENTHIC FAUNAL ASSEMBLAGES OF SHALLOW WATER SAND AND SEAGRASS HABITATS, ST. ANDREW BAY, FLORIDA

Carl. H. Saloman and Steven P. Naughton National Marine Fisheries Service Southeast Fisheries Center 3500 Oelwood Beach Road Panama City, Florida 32407

and

John L. Taylor Taylor Biological Company, Inc. Postal Drawer 730 Lynn Haven, Florida 32444

Performed for U.S. Fish and Wildlife Service Division of Ecological Services 1612 June Avenue Panama City, Florida 32405

April 1982 [This Page Intentionally Left Blank] CONTENTS

FIGURES . v TABLES ...•.•...... v ACKNOWLEDGMENTS . vi INTRODUCTION . 1 LOCALITY AND STUDY SITES 1 Local ity .. 1 Study Sites . 4 PROCEDURE . 4 RESULTS . 6 Benthos . 6 Sediment ..•.... 11 DISCUSSION AND CONCLUSIONS 11 EXPLANATION OF TERMS . 24 REFERENCES . 25 APPENDICES (under separate cover) I Phylogenetic list of species, and number and percentage of individuals collected: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) . 29 II Station listings of benthos, together with number of individuals collected, percentage occurrences, faunal statistics, habitat type, and sediment characteristics: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) . 35 III Species occurrence and frequency, by phylogenetic group, together with related benthic conditions: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) . 251 IV Species dominance ranking by habitat type, including count, percentange of all individual counts, cumulative percent, and station occurrences: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) •.•....••....•...... 525

iii CONTENTS (continued)

v Dendrogram showing faunal similarities among all stations: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) 543 VI Sediment characteristics by station and habitat type: shallow water sand and seagrass habitats - St. Andrew Bay, Florida (June-August 1974) 545

iv FIGURES

Number 1 St. Andrew Bay System, Bay County, Florida 2 2 St. Andrew Bay, Florida, showing sampling locations (149) for study of benthic faunal assemblages in shallow water sand and seagrass habitats (June=August 1974) . 5

T,l\.BLES

Number 1 Dominant organisms collected at 149 stations in shallow water sand and seagrass habitats of St. Andrew Bay, Florida (June-August 1974) •...••...•.... 7 2 Averages and ranges of faunal diversity, abundance, and equitability for 149 stations in shallow water sand and seagrass habitats of St. Andrew Bay, Florida (June= August 1974) .....•..•..•...•....• 9 3 Dominant species recorded for each habitat type at 149 shallow water sand and seagrass stations in St. Andrew Bay, Florida (June=August 1974) .•...... 10 4 Sedimentological characteristics, by habitat, recorded at 149 sand and seagrass stations in St. Andrew Bay, Florida (June=August 1974) ...••.•••••... 13 5 Comparative faunal and environmental data from studies of faunal assemblages in shallow water sand and seagrass habitats of St. Andrew Bay, and other areas of

Flori da 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 l) 0 0 0 Q 0 0 0 14

v ACKNOWLEDGMENTS

William J. Troxel, U.S. Fish and Wildlife Service, Panama City, Florida, assisted with the compilation of the data and review of manuscripts.

vi INTRODUCTION

The purpose of this report ;s to present information on the taxonomy and ecology of benthic fauna found in nearshore sand and seagrass habitats of St. Andrew Bay, Florida. This information should be taken into account in the development of effective regional management plans for recreational and com- mercial fisheries and in planning for a wide range of socioeconomic activities in coastal areas throughout the Southeastern United States. Also, this infor- mation is especially important in determining the impact of proposed altera- tions or modifications of coastal habitats. The study was conducted by the National Marine Fisheries Service as part of an intensive and comprehensive ecological investigation of fishery re- sources in the St. Andrew estuarine system (Brusher and Ogren 1976; May et ale 1976; Nakamura 1976; Ogren and Brusher 1977; Pristas and Trent 1978; Suther- land 1977; Naughton and Saloman 1978). The benthic collections were processed and the data prepared for publication with the support of the U. S. Fish and Wildlife Service and the services of Taylor Biological Company, Inc. Prior to this investigation, information on the benthos of the St. Andrew Bay system was available in only a few papers that described general features of the area, and dealt with several groups of crustaceans, as well as a small collection of polychaete worms (Hartman 1959; McNulty et al. 1972; Saloman 1976). Some unpublished information may also be obtained from the Florida Department of Environmental Regulation, the U. S. Naval Coastal Systems Center at Panama City Beach, and Taylor Biological Company, Inc., Lynn Haven, Florida.

LOCALITY AND STUDY SITES

LOCALITY The St. Andrew Bay system (Figure 1) is situated in Bay County on the gulf coast of northwestern Florida between west longitudes 85°23' and 85°53', and north latitudes 30°00' and 30°20'. Within this estuarine area, St. Andrew Bay is central and opens directly to the Gulf of Mexico through East and West Passes. Connecting embayments include North, West, and East Bays, as well as Grand Lagoon and St. Andrew Sound. North Bay extends inland to Deerpoint Dam and Reservoir; West Bay and East Bay narrow in opposite directions and merge with segments of the Intracoastal Waterway; and St. Andrew Sound lies east of East Pass in a pocket between Crooked Island and Tyndall Military Reservation (McNulty et al. 1972: National Oceanic and Atmospheric Administration Nauti- cal Chart No. 868SC; Figure 1).

1 , 15

N

GULF OF MEXICO CROOKED ISLAND Sf. ANDREW SOUND

Figure 1. St. Andrew Bay System, Bay County, Florida. The regional climate is humid and subtropical. Average air temperature is 68°F (20°C); the mean summer temperature is 82°F (27.8°C), while the mean winter temperature is 54°F (12.2°C). Normal rainfall is slightly under 60 inches (1.5 m) per year; the wettest months generally are March, April, July, August, and September. Winter rain is usually associated with weather fronts, but thundershowers and tropical depressions account for most of the rain in other seasons. Severe storms occur over the estuary about once in 10 to 15 years. Generally, \.vindvelocity seldom exceeds 10 kn. Net wind direction is mostly onshore (southerly) between spring and late summer, and offshore (northerly) in fall and winter (Salsman and Ciesluk 1978; Schmidt and Clark 1980). The estuary is a drowned river basin that became inundated and reached its present approxif'ate configuration some 3,000 years ago. Total surface area is about 90 mi (233 km2); maximum and average depths are 65 ft (19.8 m) and 17 ft (5.2 m) or less; and volume at mean high water is about 829,000 acre-ft (Jones and Ichiye 1961; McNulty et al. 1972; Salsman and Ciesluk 1978). Tides in St. Andrew Bay are essentially diurnal. Their range is gen- erally below 4 ft (1.2 m), and tidal currents rarely exceed 1 kn except in narrows and passes where they may be as high as 3 or 4 kn. Wave height is usually 1 ft (0.3 m) or 1ess, but as with tides and currents, waves may be strongly influenced by wind direction and velocity (Salsman and Ciesluk 1978). Sediments in shallow water consist of shell fragments and fine to coarse quartz sand. In the many bayous of the estuary and in open water areas below 20 ft (6.1 m), sediments contain substantial amounts of silt and clay (Ogren and Brusher 1977; Salsman and Ciesluk 1978). The bay system may be classified as a positive estuary, since incoming fresh water from land drainage exceeds losses by evaporation (Pritchard 1967). Thus, following heavy rains salinity frequently declines below 10 ppt in the upper sections of North, West, and East Bays. At such tiwes, a well-defined halocline of considerable magnitude may develop between relatively fresh water of the surface and a lower wedge of highly saline tidal water. Under average conditions, the salinity of surface and bottom water in North, West, and East Bays varies between about 10 and 30 ppt. In St. Andrew Bay, owing to its proximity to the sea, salinity rarely drops below 30 ppt and is usually 33 ppt or higher (McNulty et al. 1972; Ogren and Brusher 1977). Water temperature closely follows cyclic, annual changes in air tempera- ture. Summer water temperatures fluctuate between 80° (26.7°C) and 90°F (32.2°C), while spring and fall temperatures average about 70°F (21.1°C), and winter water temperatures fall to 55°F (12.8°C) or less. Thermoclines are common in the bay system, but these seldom exceed a surface to bottom tempera- ture difference of more than a few degrees (Salsman and Ciesluk 1978). Relatively clear water is one of the characteristic features of St. Andrew Bay. Except during periods of severe weather, turbidity seldom is above 4 turbidity units. Secchi Disc readings are 20 ft (6.1 m) or more near gulf passes and are nearly always greater than 6 ft (1.8 m) in North, West, and East Bays (Hopkins 1966; Ogren and Brusher 1977). Several factors con- tribute to the estuary's clarity. First, incoming tidal \'Jateris clear and

3 major tributaries are spring fed. Second, the surrounding upland is mostly forested, and local soils consist of porous sand that contains little of the silt-clay fraction often responsible for turbidity in coastal waters. Third, within the estuary, tidal marshes and seagrasses act as natural filters that collect and stabilize suspended sedirrents and particulate detritus (Tolbert and Austin 1959; Musgrove et al. 1965; McNulty et al. 1972; Ogren and Brusher 1977; Schmidt and Clark 1980). Industrial and domestic pollution has not yet caused chronic water qual- ity or biological problems in the St. Andrew Bay system. Point source effluents number about 30, and most of these have a daily discharge volume below one million gallons per day (mgd). Major industrial outfalls are in St. Andrew Bay (paper mill and associated chemical works: 25 mgd); and West Bay (thermal effluent from power production: 200, 000 gallons per minute). Out- falls for domestic sewage (secondary) occur in North Bay (City of Lynn Haven: 1 mgd; and City of Panama City: 2 mgd); West Bay (City of Panama City Beach: 1 mgd); and St. Andrew Bay (City of Panama City: 4 mgd). Local, periodic water-quality problems that have been attributed to pollution include low levels of dissolved oxygen, high nutrient levels, high levels of certain metals, and high counts of fecal coliform bacteria (U. S. Environmental Protection Agency 1975; Environmental Science and Engineering, Inc. 1978). Recently, recorr.mendations have been made to upgrade water qual ity in the estuary and provide better sanitary sewer service to the county's 100,000 residents and nearly two million annual tourists (Bay County 201 and 208 Programs, Environmental Protection Agency, Atlanta, Georgia). Physical alterations in the estuary include dredging and construction of rock jetties at West Pass; periodic dredging and spoil disposal for Port Panama City and several sections of the Gulf Coast Intracoastal Waterway; about 100 to 200 acres (40.5 to 81 ha) of dredged fill for highway, bridge, and commercial construction; installation of the Deerpoint Dam; and pond construction for shrimp farming in 600 acres (242.9 ha) of West Bay marsh.

STUDYSITES

Sampl ing was done one time at 149 stations during the summer of 1974 (Figure 2). At most sampling sites, two stations were established so that one was in unvegetated sand and the other in seagrass. However, at a few sites, only a single sampling station was established in the sand due to the absence of vegetation.

PROCEDURE

At each station, the absence or presence of seagrass was recorded, and benthic organisms wer sampled with a plug sampler (box corer), which covered a bottom area 1/64 m2 and penetrated the sediment to a depth of 23 crn. A station sample consisted of six replicate plugs of bottom materia1 collected randomly. Each plug was washed separately on a screen of 0.701 mm2 mesh, and the residual material was preserved in the field in Formalin diluted to 10% with seawater. Rose Bengal dye was added to the sample to aid in later sepa- ration of stained fauna from unstained inorganic debris (Mason and Yevich

4 NAUTICAL MILES 2 ~2 I J 1-----1 o 1 2 3 I(ILOMETERS

30 10 N

·08'

·06 GULF Of MEXICO

46' 44' 42' 8S·40'W 38' 36'

Figure 2. St. Andrew Bay, Florida, showing sampling locations (149) for study of benthic faunal assemblages in shallow water sand and seagrass habitats (June - August 1974). 1967; $a10man 1976). In the laboratory, fauna from each station was identi- fied to the lowest possible taxon, and enumerated. Species diversity and abundance data for replicate samples were summed to give station totals. These figures were subsequently key-punched for processing by computer.! Sediment samples were obtained by inserting an 8-oz jar into the sub- strate to collect the upper 3 to 4 inches of sediment. Samples If/ere stored frozen and later analyzed by standard methods for grain size distribution and carbon chemistry; and for statistical propel~ties that included mean grain size, standard. deviation (as a measure of sorting), skewness, and kurtosis (Folk 1974; Sa10man 1976).

Hydrological data were not recorded during this study. Information from other sources indicated that yearly averages of surface water temperatures and salinities vary slightly within boundaries of the study area. Salinity tends to be highest near passes and in the central part of St. Andrew Bay, and low- est in upper sections of East, West, and North Bays. Salinities well below 10 ppt have been sometimes recorded in backwaters such as Watson Bayou (Envi- ronmental Science and Engineering, Inc. 1978).

RESULTS

BENTHOS Faunal collections from the 149 stations consisted of 42,313 individual organisms representing approximately 272 species. Annelids ranked highest in diversity and abundance with 96 species and 27,327 individuals, or about 35% of all species and 65% of all individuals. Crustaceans ranked second with 89 species and 9,592 individuals, or about 33% of all species and 23% of all individuals. Molluscs were third with 69 species and 3,904 individuals, or about 26% of the speci es and 9% of the i ndi vi dua 1s. Ten groups made up the remaining small percentages of species (6%) and individuals (3%). Species and abundance data for these 10 groups were noteworthy because they show that conditions in the study area may 1imit many members of large phyla such as Coe1enterata and Echi nodermata, whil e the same conditi ons apparently favor a few speci es that make up small er phyla such as Nemertinea, Phoroni da, and Cepha10chordata (Appendix I). Dominant species for the entire study area were defined as those that made up at least 1% of all individuals, or those that occurred at one-third (50) or more of all stations (Table 1). The 10 most abundant species were the po1ychaetes Axiothe1la mucosa, Nereis pelagica, Laeonereis culveri, Prionospio heterobranchia, Spio filicornis, Syllis cornuta, and Aricidea taylor;; the amphipod crustaceans Lepidactylus sp.; the tanaid Kalliapseudes sp.; and the isopod Apanthura magnifica. The 10 most widely distributed species recorded throughout the study area included an unidentified nemertean; the po1ychaetes lA11 appended statistical data are the product of program designs and computer analyses by Dr. Stephen A. Bloom, Dept. of Zoology, University of Florida, Gainesville, Florida 32611.

6 Table 1. Dominant organisms collected at 149 stations in shallow water sand and seagrass habitats of St. Andrew Bay, Florida (June-August 1974). Groups Total and number Percentage Total species collected all counts stations Nemertinea Unidentified sp. 613 1.5 135 Phoronida Phoronis architecta 104 0.3 53 r~ollusca Anodontia alba 855 2.0 93 Nassarius vibex 94 0.2 51 Tellina tampaensis 170 0.4 65 Tellina versicolor 224 0.5 67 Annelida Aricidea taylori 1167 2.8 99 Aricidea sp. 167 0.4 55 Axiothella mucosa 5633 13.3 110 Capitella capitata 947 2.2 73 Ceratonereis mirabilis 415 1.0 52 Eteone heteropoda 360 0.9 61 Glycera americana 165 0.4 76 Glycinde solitaria 226 0.5 81 Haploscoloplos robustus 91 0.2 51 Heteromastus filiformis 423 1.0 79 Laeonereis culveri 3656 8.6 93 Neanthes acuminata 540 1.3 69 Nereis pelagica 3706 8.8 69 Onuphis nebulosa 590 1.4 73 Platynereis dumerilii 473 1.1 58 Podarke obscura 121 0.3 58 Prionospio heterobranchia 2047 4.8 103 Spio filicornis 1421 3.4 103 Streblosoma hartmanae 445 1.1 25 Syll is cornuta 1228 2.9 68 Unidentified Oligochaete 399 0.9 75 Arthropoda Acanthohaustorius sp. 720 1.7 38 Ampelisca sp. A 340 0.8 62 Ampelisca sp. B 531 1.3 58 Apanthura magnifica 1137 2.7 87 Cymadusa compta 645 1.5 53 Kalliapseudes sp. 1328 3.1 54 Lepidactylus sp. 1941 4.6 17 Echinodermata Ophiophragmus filograneus 145 0.3 58 Cephalochordata Branchiostoma floridae 380 0.9 75

7 Axiothella mucosa, Prionospio heterobranchia, Spio filicornis, Aricidea taylori, Laeonereis culveri, Glycinde solitaria, Heteromastus filiformis; the mollusc Anodontia alba; and the isopod Apanthura magnifica. Eighty-nine stations had no seagrass, and those stations that were un- paired with a grassbed station occurred mostly in areas of very brackish water, in areas of above-average current or wave action, on emergent spoil, or in areas where pollution has been reported (U.S. Environmental Protection Agency 1975). Of the vegetated stations, 23 had only shoalgrass (Halodule wrighti;); 9 had only turtle grass (Thalassia testudinum), and 28 had both plant species. Within these seagrass habitats there were some marked differ- ences in average faunal variety and abundance, diversity index (Shannon- Weaver), and equitability (WjLog S). Turtle grass stations yielded the greatest numbers of species and individuals, had the highest diversity index, and were equivalent to the mixed seagrass habitat in equitability. Diversity and abundance figures were second highest at stations having a mixture of shoal and turtle grasses, third highest at shoalgrass stations, and lowest at stations with no vegetation (Table 2). Within each seagrass habitat, highest species diversity and abundance were recorded in relatively high salinity regions of the study area (Grand Lagoon, East Pass, Shell Island Sound, and central St. Andrew Bay), while lowest values were recorded in eastern and western arms of the bay where salinity is comparatively lower and less stable (Appendix II). The distribution and abundance of benthic species together with data for habitat type and sediment composition (Appendix III) may be useful in infer- ring the limitations or advantages of environmental factors for various species in St. Andrew Bay. Dominant species in each habitat were defined as those that made up 1% or more of all individual counts (Appendix IV). This designation included 36 species, which comprised more than 70% of all species in the four habitats. Dominants that occurred only at unvegetated stations included the annelids Capitella capitata, Eteone heteropoda, Heteromastus filiformis, Paraonis fulgens, and Scolelepis squamata; the amphipods Acantho- haustorius sp. and Lepidact~ sp.; and the lancelet Branchiostoma floridae. Those species that showed dominance only at vegetated stations were the mol- luscs Caecum floridanum and Crepidula maculata; the annelids Ceratonereis mirabilis, Exogone di~, Neanthes acuminata, Nereis pelagica, Onuphis nebu- 1osa, Platynereis dumeri 1ii, Scyphoproctus p1atyproctus , and Streb 1osoma hartmanae; and the crustaceans Ampelisca sp. A and sp. B, Cymadusa compta, Cymadusa sp., Lysianopsis sp., and Hippolyte pleuracantha (Table 3). Faunal affinities among habitats were defined by using Czekanowski's Quantitative Index to construct a dendrogram (Appendix V) of similarity be- tween assemblages recorded at each station (Bloom et al. 1977; Bloom 1981). This dendrogram shows five principal station clusters. The first is composed of primarily vegetated stations and contains six sub-clusters. As a group~ these are separable from clusters two through five, which are comprised solely of unvegetated stations. In addition to showing that distinct faunal dif- ferences exist between stations in sand and seagrass, the dendrogram also suggests that shoalgrass and turtle grass faunas are distinct, but that neither fauna can be statistically separated from the fauna found at stations with a mixture of both seagrasses.

8 Table 2. Averages and ranges of faunal diversity, abundance. and equitability for 149 stations in shallow water sand and seagrass habitats of St. Andrew Bay. Florida (June-August 1974).

Unvegetated stations (89) ----Parameter Average Range Number of species 22.0 2 to 46

Number ln. d'lV. /m 2 2013.0 43 to 9920 Shannon-Weaver Div. Ind. 2.1 0.3 to 3.2

Equi tabi 1ity (H'flog S) 0.7 0.2 to 1.0 Shoal grass stations - Halodule wrightii (23)

Number of species 39.0 23 to 67 Number indiv./m2 3370.0 1131 to 11.563 Shannon-Weaver Div. Ind. 2.6 2.1 to 3.2 Equitabil ity 0.7 0.6 to 0.9 Turtle grass stations - Thalassia testudinum (9)

Number of species 67.0 36 to 89

Number indiv./m2 7567.0 2282 to 17.909 Shannon-Weaver Div. Ind. 3.2 2.9 to 3.5 Equitabil ity 0.8 0.7 to 0.8 Mixed shoal- and turtle grass stations (28) Number of species 51. 0 18 to 86

Nurn ber In. d'lV. / m2 4192.0 907 to 8949

Shannon-Weaver Div. Ind. 3.0 2.1 to 3.6 Equitability 0.8 0.7 to 0.9

9 Table 3. Dominant species recorded for each habitat type at 149 shallow water sand and seagrass stations in St. Andrew Bay, Florida (June-August 1974).

Habitat type Shoal- Turtle Mixed Group and species Unveg. grass grass grasses

Nemertinea Unidentified sp. x x Mollusca Anodontia alba x x x x Caecum floridanum x Crepidula maculata x x Annelida Aricidea taylori x x Axiothella mucosa x x x x Capitella capitata x Ceratonereis mirabilis x x x Eteone heteropoda x Exogone dispar x Heteromastus filiformis x Laeonereis culveri x x Neanthes acuminata x x Nereis pelagica x x x Onuphis nebulosa x x x Paraonis fulgens x Platynereis dumerilii x x Prionospio heterobranchia x x x x Scolelepis squamata x Scyphoproctus platyproctus x Spio filicornis x x x x Streblosoma hartmanae x x Syllis corn uta x x x x Unidentified Oligochaete x x Arthropoda Acanthohaustorius sp. x Ampe1i s ca sp • A x x Ampe1i s ca s p . B x x x Apanthura magnifica x x x x Cymadusa compta x x x Cymadusa sp. x x Erichsonella sp. x x x Hippolyte pleuracantha x Kalliapseudes sp. x x x x Lepidactylus sp. x Lysianopsis sp. x x Cephalochordata Branchiostoma floridae x

10 SEDIMENT

In general, sediments in the study area consisted of fine sand that was moderately sorted, coarsely skewed, and leptokurtic. Chemical analyses gave an average total carbon content of slightly under 1%. About 70% of sediment carbon cons i sted of plant detritus, whi 1e about 30% represented shell frag- ments and other animal remains.

Sediments from each habi tat had vi rtua lly the same average characteri s- tics, but in each of the four habitat types, one or more stations had some high values in certain particle size classes and organic carbon content. High percentages of granule size particles were attributed to localized concentra- tions of oyster shell, and occurred at Stations 61, 66, 71, 73, 75, 81, 83, 87, 97, 103, 117, and 139. Stations with above-average amounts of silt, clay, and organic carbon were located in areas of poor or modified circulation (Stations 13 and 56), and at grassbed Stations 16, 17, 18, 20, 21, 22, 24, 29, 31, and 33. Faunal diversity and abundance data for most of these stations appear to be unrelated to sediment type. Possible exceptions were Station 56 at the head of Watson Bayou and Station 20 west of Courtney Point. Station 56 was characterized by variable salinities which may have been more important ecologically than high concentrations of silt and organic carbon. Station 20 had high silt-clay percentages which was in contrast to Station 24 where the silt-clay was higher where a typical invertebrate assemblage was collected (Table 4 and Appendix VI).

DISCUSSIONANDCONCLUSIONS

In Florida, quantitative study of benthic fauna in shallow water sand and seagrass habitats was first done in the Miami area by 0 'Gower and Wacasey (1967). This was followed by a subsequent study in the same region by Brook (1968). In other parts of the State simi lar research has been done in Tampa Bay by Santos and Simon (1974), in Apalachee Bay by Stoner (1980), and in the Indian River area by Young and Young (1977). For comparision, results of the present study have been tabulated with findings of the investigations noted above (Table 5). Examination of these data suggests that certain species are widely distributed in vegetated and unvegetated habitats of Florida's coastal waters. This generalization is especially true of the following polychaetes: Axiothella (= Clymenella) mucosa, Heteromastus filiformis, Laeonereis culveri, Prionospio hetero= branchia, and Streblospio benedicti. The bulk of the species and individual numbers consist of polychaetes, crustaceans, molluscs, and in some instances echinoderms. Data for species diversity and abundance show that St. Andrew Bay has a greater variety of infauna, and supports numbers of individuals equiva- lent to other estuarine areas of Florida, with the possible exception of nutrient-rich Tampa Bay (Santos and Simon 1974). Finally, results of this research are in agreement with other Florida studies in showing that turtle grass contains a greater variety and abundance of infauna than is found in unvegetated bottom nearer shoreo This is probably due to predation and limi- tations on habitat availability as well as habitat instability caused by water movements and periodic exposure (Orth 1977).

11 Comparative work on a world-wide scale underscores findings in St. Andrew Bay and other areas of Florida that seagrasses support a very great variety and abundance of bottom-dwelling invertebrates (Young and Young 1977). Conse- quently, as communities, seagrasses are of great biological importance be- cause, in addition to the infauna, diverse, abundant, and highly productive groups of both higher and lower organisms are also nurtured by this unique and cosmopolitan biotope (Phillips and McRoy 1980). From this study and others that have been cited, certain conclusions are summarized in the following statements regarding benthic fauna of sand and seagrass habitats. 1. Species diversity is generally greater in seagrass habitats than in adjacent, unvegetated habitats. 2. Individual abundance and biomass are generally greater in seagrass habitats than in adjacent, unvegetated habitats. 3. Inter-regi ona 1 sand and seagrass habitats are generally composed of statistically distinct faunal assemblages. 4. Lower species diversity and abundance in unvegetated, nearshore habitats are largely due to habitat instability caused by water movements and periodic exposure. Conversely, greater species divers ity and abundance in seagrass habitats are related to more favorable hydrological conditions, sediment stability, more feeding opportunities, and protection from predation. 5. Among various seagrass habitats, infaunal diversity and abundance may be influenced by factors that include degree of seagrass development, type or types of seagrass present, water depth and movements, salinity, season and latitude, turbidity, sediment properties, and activities of man that may influence water quality and sediment composition. 6. As communities, seagrasses are of great biological importance, because, in addition to infauna, diverse, abundant, and highly productive groups of both lower and higher organisms are also nurtured by this unique and cosmopolitan biotope.

12 Table 4. Sedimentological characteristics, by habitat, recorded at 149 sand and seagrass stations in St. Andrew Bay, Florida (June-August 1974).

Shoal- Turtle Nixed Unveg. grass grass grass Parameters sta. (89) staG (23) s ta. (9) s ta. (28) Texture (wt. %) Granule Average 0.573 4.130 1.333 3.250 Range 0.000 to 0.000 to 0.000 to 0.000 to 18.000 14.000 6.000 14.000 Sand Average 98.607 94.217 96.444 92.857 Range 82.000 to 77.000 to 87.000 to 86.000 to 100.000 100.000 100.000 100.000 Si It Average 0.573 0.783 1.222 1.821 Range 0.000 to 0.000 to 0.000 to 0.000 to 6.000 7.000 6.000 9.000 Clay Average 0.247 0.870 1.000 2.107 Range 0.000 to 0.000 to 0.000 to 0.000 to 3.000 15.000 7.000 10.000 Mean grain size (~) Average 2.083 2.119 2.070 2.123 Range 0.942 to 1.488 to 1.757 to 1.674 to 2.850 3.653 2.266 2.402 Std. deviation (~) Average 0.579 0.920 0.686 1.013 Range 0.323 to 0.324 to 0.334 to 0.406 to 1.665 2.785 1.642 2.198 Skewness Average -0.123 -0.295 -0.100 -0.079 Range -0.733 to -0.683 to -0.404 to -0.620 to 0.332 0.695 0.503 0.475 Kurtosis Average 1.166 1.939 1.837 2.476 Range 0.899 to 0.764 to 0.999 to 0.932 to 2.432 3.984 4.958 4.959 Carbon Chern. (wt. %) Total carbon Average 0.543 1.053 0.867 1.138 Range 0.060 to 0.150 to 0.290 to 0.390 to 7.370 3.910 2.030 3.800 T. organi c C Average 0.400 0.793 0.512 0.772 Range 0.010 to 0.070 to 0.200 to 0.180 to 7.300 3.120 0.950 3.160 T. carbo C Average 0.143 0.260 0.354 0.372 Range 0.000 to 0.000 to 0.070 to 0.000 to 1.720 0.790 1.540 1. 240

13 Table 5. Comparative faunal and environmental data from studies of faunal assemblages in shallow water sand and seagrass habitats of St. Andrew Bay and other areas of Florida.

Dominant speci~s by habitat (in decreasing order of dominance) Present study - St. Andrew Bay Habitats Unvegetated sand H. wrightii T. testudi num Halodule-Thalassia mixture

Laeonereis culveri Axiothella mucosa Axiothella mucosa Axiothella mucosa Lepidactylus sp. Nereis pelagica Nereis pelagica Nerei~ pelagica Axiothella mucosa Prionospio 5yllis cornuta Prionospio Capitella capitata heterobranchia Prionospio heterobranchia Apanthura Spio filicornis heterobranchia Spi 0 fil icorni s magnifi ca Aricidea taylori Caecum floridanum Cymadusa compta Kalliapseudes sp. 5y11 I-' ------Acanthohaustorius Onuphis nebulosa is cornuta ..j:::. sp. Kalliapseudes sp. Spio filicornis Crepidula maculata Kalliapseudes sp. Apanthura Exogone dispar Ampelisca sp. B Aricidea taylori magnifi ca Neanthes acuminata Hippolyte 5pio filicornis Platynereis Streblosoma pleuracantha Anodontia alba dumerilii hartJ:1anae Platynereis Prionospio-- Anodontia alba Cymadusa corrpta dumerilii heterobranchia Ampelisca ~B Apanthura Streblosoma Unident. Nemertean Laeonereis culveri P.1agnifica hartmanae Eteone heteropoda Ampelisca sp. A Ceratonereis Aricidea taylori Paraonis fulgens Cymadusa compta rr.irabil is Ceratonereis Heteromastus Syllis cornuta Lysianopsis sp. mirabilis filiformis Unident. Oligochaete Crepidula maculata Anodontia alba Branchiostoma Ceratonereis Onuphis nebulos~ Onuphi s nebUfOsa floridae mirabilis SCY)hoproctus Ampelisca sp. A Syllis corn uta Unident. Nemertean p atyproctus Neanthes acuminata Unident. Oligochaete Erichsonella sp. Ampelisca sp. B Apanthura Erichsonella sp. Cymadusa sp. B magnifi ca Scolelepis Kalliapseudes sp. squamata Cymadusa sp. Erichsonella sp. Lysianopsis sp. (continued) Table 5. (Continued).

Dominant species by habitat (in decreasing order of dominance) OIGower and Wacasey 1967 - Florida Keys Habitats Unvegetated sand li. wrightii 1. testudinum (mixed with I. testudinum) (mixed with-Syrinqodium filiforme)

Key Biscayne Clymenel1a mucosa Onuphis magna Loimia medusa Divaricella quadrisulcata Nothria stigmatis Qnuphis magna Clymenella mucosa Codakia orbicularis Anachis avara Diopatra cuprea Divaricella quadrisulcata Chione cancellata Codakia orbicularis Euclymene coronata Chione cancel lata Alpheus normanni Virginia Key Batillaria minima Phascolion sp. Codakia orbicularis Chione cancel lata Chione cancellata Anodonti a alba Semiodera roberti Amphioplus abditus Amphiodia pulchella Prunum apicinum Loimia medusa Panopeus occidentalis Notomastus luridus Terebellides stroemi

Brook 1978 - Florida Keys (no species dominance data) (continued) Table 5. (Continued).

Dominant species by habitat (in decreasing order of dominance) Santos and Simon 1974 - Tampa Bay (Lassing Park) Unvegetated habitats Sand - inshore Sand - middle Sand - ripple

Streblospio benedicti Heteromastus filiformis Clymenella mucosa Capitella capitata Capitella capitata Laeonereis culveri Laeonereis culveri Laeonereis culveri Lumbrineris tenuis Lumbrineris tenuis Prionospio heterobranchia Heteromastus filiformis Onuphis ~. oculata Lumbrineris tenuis Onuphis ~. oculata Clymenella mucosa Onuphis ~. oculata Streblospio benedicti Heteromastus filiformis Streblospio benedicti Prionospio heterobranchia Prionospio heterobranchia Fabricia sabella Capitella capitata

Seagrass habitats ~. wrightii T. testudinum Prionospio heterobranchia Fabricia sabella Heteromastus filiformis Onuphis ~. oculata Lumbrineris tenu;s Pr;onosp;o heterobranch;a Clymenella mucosa Lumbrineris tenuis Laeonere;s culveri Clymenella mucosa Capitella capitata Heteromastus filiformis Fabricia sabella Capitella capitata Onuphis ~. oculata Laeonereis culveri Streblospio benedicti Streblospio benedict;

(continued) Table 5. (Continued).

Dominant species by habitat (in decreasing order of dominance) Stoner 1980 - Apalachee Bay (Amphipods and Polychaetes only) Habitats Low density Med. density High density Unvegetated sand 1. testudinum & T. testudinum & 1. testudinulJ1& -So filiforme -S. fil iforme -So filiforme

Ampelisca verrill; Elasmo~ levis Elasmopus 1evis. Lembos sp. A Ampelisca vadorum Lysianopsis alba Cymadusa sp. A Rudilemboides nagle; Batea catharinensis lembos sp. Lysianopsis alba £1asmopus 1ev;s Synchelidium Cymadusa sp. A Rudilemboides ~glei Cymadusa sp. A americanum Melita appendiculata Lembos sp. A Carinobatea Corophium sp. A Pontogeneia sp. A Ampelisca vadorum tl"i car; nata Lysianops;s alba Batea catharinensis Ampel;sca verrilli Pontogeneia sp. A Elasmopus levis Synchelidium Pontogeneia sp. A Ampelisca vadorum Cymadusa sp. A americanum Gitanopsis sp. A Batea catharinensis Pontogene;a sp. A Ampelisca vadorum Carinobatea Lysianops;s h;rsuta Melita append;culata Rudilemboides naglei tricarinata Lysianops;s alba Mediomastus californiensis Aricidea taylori Aricidea taylori Aricidea taylori Lumbrineris tenuis ~1ed;omastus Syllis sp. B Syll is sp. B Ar;cidea taylori californiensis Pr;onospio Exogone dispar G1ycinde solitaria Dorv;llea sociabilis heterobranchia Prionosp;o Paraprionospio Lumbrineris tenu;s Platynereis dumerilii heterobranchia pinnata Platynere;s Clymenella mucosa Platynereis Prionospio dumerilii Sabella sp. A dumerilii heterobranchia Gypt;s brevipalpa Exogone dispar Fabr;cia sp. A Glycera americana Sy11is cornuta Pomatoceros Spiophanes bombyx Gyptis brevipalpa Prionosp;o caerulescens Haplosco1oplos Clymenella mucosa heterobranchia Gyptis brevipalpa fragilis Cirriformia Glycinde solitaria Glycinde solitaria Phyllodoce fragilis filigera Cirriformia il11 gera PO~~~?-~1~~~ens (continued) Table 5. (Continued).

Dominant species by habitat (in decreasing order of dominance) Young and Young 1977 - Indian River Habitats Haulover Canal Link Port St. Lucie Inlet li. wri ghti i li. wrightii li. wri ghti i

Polydora ligni Clymenella mucosa Clymenella mucosa Exogone dispar Cerithium muscarum Unident. Nemertean Phascolion sp. Streblospio benedicti Diastoma varium Paratanaidae sp. A Phascolion sp. Phascolion sp. Clymenella mucosa Laeonereis culveri Fabricia sabella Fabriciola sp. Crepidula fornicata Cymadusa sp. A Cymadusa sp. A Unident. Nemertean Paratanaidae sp. A Prionospio Capitella capitata Streblospio benedicti heterobranchia Polydora 1igni. Polydora socialis Erichsone 11a f. Erichsonella f. Aricidea sp. A isabelensis- isabel ens is- Cymadusa sp. A

Total species collected (mesh of sorting screen)

Present study OIGower & Wacasey Brook 272 (0.7 mm) Key Bis. 182 (3.0 mm) 161 (1.0 mm) Vir. Key 129 (3.0 mm) Santos & Simon Stoner Young & Young 44-Polychaetes only (0.5 mm) 170 (0.5 mm) 230 (1. 0 mm) (continued) Table 5. (Continued).

Species and individuals by group (number and percentage of species)

Present study OIGower & Wacase (Ke O'Gower & Wacase Vir. Annelida 96 (35%) Annelida 81 45% Annelida 65 50% Arthropoda 89 (33%) Arthropoda 25 (14%) Arthropoda 14 (11%) Mollusca 69 (26%) Mollusca 48 (26%) Mollusca 34 (26%) Other 18 (6%) Echinodermata 22 (12%) Echinodermata 11 (9%) Other 6 (3%) Other 5 (4%) Brook Santos & Simon Stoner Mollusca 88 (55%) (Polychaetes only) Annelida 75 (44%) Arthropoda 52 (31%) Mollusca 21 (12%) Other 22 (13%) Young & Young Annelida 83 (36%) Arthropoda 59 (26%) Mollusca 57 (25%) Other 31 (14%)

Individuals by group

Present study O'Gower & Wacasey Brook Annelida 65% (no data) (no data) Arthropoda 23% ~1ollusca 9% Santos & Simon Stoner Young & Young (no data) Annelida 33% to 45% Annelida 54% Amphipoda 37% to 47% ~1ollusca 17%

(continued) Table 5. (Continued).

Species by habitat (average number and range)

Present study OIGower & Wacasey (Key Bis.) OIGower & Wacasey (Vir. Key) Sand Sand Sand Average 22 Average 33 Average 29 Range 2 to 46 !i. wrightii .t!.. wrightii .t!.. wri ghti i Average 117 Average 75 Average 39 1. testudinum 1. testudinum Range 23 to 67 - Average 133 Average 101 T. testudinum Average 67 Range 36 to 89 Halodule-Thalassia mixture No Average 51 Range 18 to 86 Brook (I. testudinum only) Santos & Simon Stoner Bear Cut 81 (no data) Sand West Point 61 Average 24 Featherbed Bank 38 Range 14 to 33 Long Arsnicker 72 Low dens ity veg. Murray Key 52 Average 42 Range 32 to 54 Med. density veg. Young & Young (.t!.. wrightii only) Average 38 Range 17 to 57 Haulover 115 High density veg. Link.Port 104 Average 38 St. Lucie 108 Range 27 to 49

(continued) Table 5. (Continued).

Number of individuals/m2 by habitat (average number and range)

Present study OIGower & Wacasey Brook (I. testudinum only) Sand (no data) Bear Cut 10,644 Average 2013 West Point 4286 Range 43 to 9920 Featherbed Bank 292 !t. wrighti i Long Arsnicker 1010 Average 3370 Murray Key 4508 Range 1131 to 11,563 1. testudinum - Average 7567 Range 2282 to 17,909 Halodule-Thalassia mixture Average 4192 Range 907 to 8948 Santos & Simon Stoner Young & Young (polychaetes only) Inshore sand Sand (no data) Average 17,220 Average 1754 Range 8594 to 29,620 Range 833 to 4386 Middle sand Low density veg. Average 4934 Average 3154 Range 3374 to 8180 Range 1906 to 6054 Ripple sand Med. density veg. Average 3231 Average 3293 Range 2196 to 5602 Range 1498 to 5293 !t. wrighti i High density veg. Average 13,313 Average 3107 Range 7926 to 18,870 Range 1498 to 5293 1. testudinum Average 33,485 Range 9422 to 63,830 (continued) Table 5. (Continued).

Environmental data

Present study Climate - subtropical Sampling period - summer Salinity - oligohaline to mesohaline Sediment type - predominantly fine sand, moderately sorted Depth - intertidal to shallow subtidal Tide - diurnal; range less than 4 ft; current 0.5 to 4 kn OIGower & Wacasey Climate - tropical Sampling period - spring and summer Salinity - oligohaline to polyhaline Sediment type - fine to coarse sand Depth - intertidal to shallow subtidal Tide - lunar; range probably less than 4 ft; current 5 to 35 ft/min Brook Climate - tropical Sampling period - spring Salinity - polyhaline Sediment type - sand and calcareous rubble to fine calcareous floc Depth - 0.5 to 1.0 m Tide - lunar; range probably less than 4 ft; current strong to weak Santos & Simon Climate - subtropical Sampling period - quarterly for 1 year Salinity - oligohaline to mesohaline Sediment type - moderately well-sorted fine sand Depth - 1 m or less Tide - diurnal; range probably less than 4 ft; current very weak (continued) Table 5. (Concluded).

Environmental data

Stoner Climate - subtropical Sampling period - monthly for 1 year Salinity - oligohaline to polyhaline Sediment type - moderately to poorly sorted medium to fine sand Depth = subtidal Tide - diurnal; range probably under 4 ft; current moderate Young & Young Climate - subtropical Sampling period - fall and winter Salinity = oligohaline to polyhaline Sediment type - well-sorted fine sand Depth - shallow subtidal Tide - semidiurnal; range probably less than 4 ft; current weak to moderate Shannon-Weaver Index of General Diversit. This index (H'=-E(ni/N) log(ni/N is a statistical measure of species diversity within a sample, and is influenced by both the number of species present (richness) and their respective abundance (equitability). Values of three or greater are charac- teristic of unstressed, natural communities. Equitability. In addition to HI, separate calculations are often made to determine sample equitability (JI=HI/logS) and richness (actual species count or d=(S-l)/logN), to isolate population characteristics that contribute to HI. This is done because communities with a few, evenly represented species may have the same or simi 1ar HI value as those composed of a large number of unevenly represented species. Generally JI values above 0.5, and relatively high species counts, or d values above 2.0, are confirmation of HI values that suggest a high degree of community stability and the presence of numerous, evenly distributed species.

Czekanowski's Quantitative Index. This index measures the percent of similarity, or overlap, between fauna of two samples. This information was used to compare infauna at each station with that at every other station and plot the dendrogram in Appendix V.

Skewness. Sediment samples that are positively skewed contain an excess of fine particles, while those that are negatively skewed contain a dispropor- tionate quantity of coarse particles. Kurtosis. This is a measure of sediment sorting within the central and end, or tail, portions of a grain size distribution curve. Curves that show better sorting in the central portion are termed leptokurtic, and those that show better sorting in the tails are called platykurtic. Values less than 0.9 denote a platykurtic condition while those above 1.11 indicate a leptokurtic conditi on. Carbon Chemistry. Sediments were analyzed for total carbon, total organic carbon, and total carbonate carbon to determine the amount of carbon available for microbial metabolism. Available carbon could in turn influence the availability of dissolved oxygen at the sediment-water interface. Organic carbon is utilized by bacteria and other microorganisms, but carbonate carbon is not since it is bound primarily in shell fragments. In areas where water circulation is poor, high levels of organic carbon in sediments and low dis- solved oxygen near the bottom are factors that probably limit variety and abundance of infauna. REFERENCES

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25 Musgrove, R.H., J.B. Foster, and L.G. Toler. 1965. Water resources of the Econfina Creek basin area in northwestern Florida. Florida Geological Survey, Rept. of Investigation No. 41. Nakamura, E.L. 1976. Scombrid fishes in St. Andrew Bay, Florida. Bull. Mar. Sci. 26 (4): 619-621.

Naughton, S.P., and C.H. Saloman. 1978. Fishes of the nearshore zone of St. Andrew Bay, Florida, and adjacent coast. Northeast Gulf Sci. 2(1): 43-55. OIGower, A.K., and J.W. Wacasey. 1967. Animal communities associated with Thalassia, Diplanthera, and sand beds in Biscayne Bay I. Analysis of com- munities in relation to water movements. Bull. Mar. Sci. 17(1): 175-210. Ogren, L.H., and H.A. Brusher. 1977. The distribution and abundance of fishes caught with a trawl in the St. Andrew Bay system, Florida. Northeast Gulf Sci. 1(2): 83-105.

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26 Tolbert, W.H., and G.B. Austin. 1959. On the nearshore marine environment of the Gulf of Mexico at Panama City, Florida. U.S. Navy Mine Defense Lab., Panama City, Fla. TP-161. Trent, L., and P.J. Pristas. 1977. Selectivity of gill nets on estuarine and coastal fishes from St. Andrew Bay, Florida. Fish. Bull. 75: 185-198.

U.S. Environmental Protection Agency. 1975. Water quality study St. Andrew Bay, Florida. National Enforcement Investigation Center, Atlanta, Ga. 70 pp. Young, O.K., and M.W. Young. 1977. Community structure of the macrobenthos associated with seagrass of the Indian River Estuary, Florida. Pages 359-381 in B.C. Coull, ed. Ecology of marine benthos. The Belle W. Baruch Library in Marine Science No.6. University of South Carolina Press, Columbia.

27