18 NOAA Technical Report NMFS 18 A Temporal and Spatial Study of Invertebrate Communities Associated With Hard-Bottom Habitats in the South Atlantic Bight E. L. Wenner, P. Hinde, D. M. Knott, and R. F. Van Dolah November 1984 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service NOAA TECHNICAL REPORTS NMFS The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of these resources, and to establish levels for optimum use of the resources. 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NOAA Technical Report NMFS 18 A Temporal and Spatial Study of Invertebrate Communities Associated With Hard-Bottom Habitats in the South Atlantic Bight E. L. Wenner, P. Hinde, D. M. Knott, and R. F. Van Dolah November 1984 u.s. DEPARTMENT OF COMMERCE Malcolm Baldrige, Secretary National Oceanic and Atmospheric Administration John V. Byrne, Administrator National Marine Fisheries Service William G. Gordon, Assistant Administrator for Fisheries The National Marine Fisheries Service (NMFS) does not approve, recom­ mend or endorse any propriety product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this publica­ tion furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends or endorses any proprietary product or proprietary material mentioned herein, or which has as its purpose an intent to cause directly or indirectly the advertised pro­ duct to be used or purchased because of this NMFS publication. CONTENTS Introduction . I Materials and methods . I Collection of samples . I Data analysis . 2 Results and discussion . 3 Hydrographic measurements and description of study sites . 3 Large macrofauna sampled by dredge and trawl . 3 Biomass of larger macroinvertebrates . 8 Smaller macroinvertebrates sampled by suction and grab . 8 Conclusions . 13 Acknowledgments . 15 Literature cited . 15 Appendices . 17-104 Figures 1. Location of hard-bottom stations sampled during 1981 .......................................................... 2 2. Normal cluster dendrogram showing station groups formed using the Jaccard similarity coefficient and flexible sorting. 4 3. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station-species group coincidence based on seasonal dredge collections. ........................................................................ 6 4. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station-species group coincidence based on seasonal trawl collections. ......................................................................... 8 5. Normal cluster dendrogram of station groups formed using the Bray-Curtis similarity coefficient, log transformation, and flex- ible sorting ............................................................................................. 13 6. Inverse classification hierarchies and nodal diagram showing constancy and fidelity of station-species group coincidence based on seasonal suction and grab collections. ................................................................ 15 Tables 1. Number of species and percent contribution for each taxonomic group collected by dredge and trawl at each station and season. ................................................................................................ 3 2. Species groups resulting from numerical classification ofdata from samples collected by dredge during 1981 5 3. Species groups resulting from numerical classification ofdata from samples collected by trawl during 1981 7 4. Percent contribution to epifaunal biomass oftaxonomic groups in dredge and trawl collections. ......................... 9 5. Average density and percent of total number for 10 numerically dominant invertebrates collected by suction and grab. ...... 10 6. The 10 most abundant invertebrate species collected by suction and grab samplers at each station ....................... II 7. Seasonal community structure values for pooled replicate samples of invertebrates at each station .... ................... 12 8. Species groups resulting from numerical classification of data from samples collected by suction and grab samplers during all seasons, 1981 ........................................................................................... 14 iii A Temporal and Spatial Study of Invertebrate Communities Associated With Hard-Bottom Habitats in the South Atlantic Bightl E. L. WENNER, P. HINDE, D. M. KNOTT, and R. F. VAN DOLAH2 ABSTRACT Species composition, biomass, density, and diversity of bentblc invertebrates from six bard-bottom areas were evaluated. Seasonal collections using a dredge, trawl, and suction and grab samplers yielded 432, 525, and 845 taxa, respectively. Based on collections wltb tbe diCCerent gear types, species composition of invertebrates was found to cbange batbymetrically. Inner· and mlddle-sbelf sites were more similar to eacb otber In terms of invertebrate species composition tban tbey were to outer-sbelf sites, regardless of season. Sites on tbe Inner and outer sbelf were grouped according to latitude; bowever, results suggest tbat deptb Is apparently a more impor­ tant determinant of Invertebrate species composition tban eltber season or latitude. Sponges generally dominated dredge and trawl collections In terms of biomass. Generally, cnldarlans, bryozoans, and sponges dominated at sites In terms of number of taxa collected. Tbe most abundant smaUer macrofauna collected In suction and grab samples were polycbaetes, ampbl. pods, and mollusks. Densities of tbe numerically dominant species cbanged botb seasonally and batbymetrlcally, witb very few of tbese species restricted to a specific batbymetrlc zone. Tbe blgb diversity of invertebrates from bard·bottom sites Is attributed to tbe large number of rare species. No consistent seasonal cbanges in diversity or number of species were noted for individual stations or deptb zones. In addition, n' and Its components sbowed no definite patterns related to deptb or latitude. However, more species were collected at mlddle-sbelf sites tban at Inner- or outer·sbelf sites, wbicb may be related to more stable bottom temperature or greater babltat complexity In tbat area. INTRODUCTION MATERIALS AND METHODS Although other studies have provided species lists of inverte­ Collection of Samples brates from hard-bottom areas [see Continental Shelf Associates (1979) for literature review], Wenner et al. (1983) provided the Two study sites were selected between lat. 31 °24' and 32°49'N first detailed information on structure of hard-bottom invertebrate from each of three bathymetric zones: Inner shelf (ISO I, 17 -18 m; communities in the South Atlantic Bight. Results indicated that IS02, 17-22 m), middle shelf (MS02, 23-29 m; MS06, 32-36 m), the invertebrate fauna of these areas was more diverse than the and outer shelf (OSOI, 59-67 m; OS06, 46-69 m) (Fig. 1). Four of surrounding sand biotope, Species composition was apparently the sites (ISOl, IS02, MS02, OSOI) were previously assessed dur­ related more to station depth than to season, although species ing the initial study (Wenner et al. 1983). All sites were sampled associations did vary between winter and summer. Because sam­ quarterly during 1981 as follows: Winter (25 February to 17 pling during their study was limited to only two seasons, it was not March), spring (26 April to 28 May), summer (25 July to 13 possible to determine seasonal trends in community composition, August), and fall (6 October to 16 November). structure, and biomass which might be occurring over an annual Prior to sampling for invertebrates, hydrographic profiles of cycle. temperature, salinity, and dissolved oxygen were obtained at each