THE STJBT1DAL BENTHIC MACROFAUNA OF CAPE COD BAY by Allan D. Michael Margaret A. Mills Joel S. O'Connor R800656 Marine Biological^Xaboratory Woods Hole Massachusetts 02543 PUBLICATION: flfc,772-257-10-3-87-CR Second Printing Approved by the State Purchasing Agent FOREWORD The large-scale marine benthic survey, comprising intensive quantitative sampling over an extended period of time, is rapidly passing into obscurity. As we move into an era of applied, rather than basic research, studies which consume large amounts of manpower and material without producing data which are immediately applicable to a particular problem are the first to fail to receive continued funding. This is unfortunate, as often these are the programs which historically have provided the basic information against which present environmental conditions may be compared. In many cases the limited programs which are now being instituted to provide baseline environmental data for potentially damaging projects are providing no baselines at all, since the area may have already been degraded far beyond its orig- t inal condition. _ ,-__ . Since we have every reason tolbelieve that the present fiscal.con-, straints on basic research will continue indefinitely, it may well be that the Biotic Census of Cape Cod Bay represents one of the last projects of its kind to be completed. The present project was initiated in June of 1964 under a contract from the Office of Naval Research, which contin- ued to provide funding for nearly seven years, during which time the bulk of the work was completed. The remainder of the study, including primarily the completion of sample processing, data analysis and report preparation was funded by the Massachusetts Division of Water Pollution Control and the Environmental Protection Agency. Cape Cod Bay was chosen as the site of these studies since it provides a discrete, yet continuous working unit of the Gulf of Maine, an area of increasing economic importance both then and now. In addi- tion, the Bay provides a readily accessible source of fauna represen- tative of the boreal biogeographic province rather than the much more extensively studied Virginian province, which is generally considered to reach its northern limit at Cape Cod. At the inception of the study, Cape Cod Bay was unique in representing a truly pristine marine environ^ ment in close proximity to a major metropolitan area. In spite of the wealth of talent and resources in the nearby Woods Hole area, only two previous general surveys have been conducted in the Cape Cod Region. In 1871 Verrill and Smith undertook a now classic study of benthic populations in Vineyard Sound and adjoining waters, which es- tablished the basic faunal inventory for those areas. Some 35 years later t Sumner et al, conducted a similar but more intensive study of both plant - and animal populations in Vineyard Sound and Buzzards -Bay, which supplements the previous investigation. • The present study, due to both the lack of previous work north of the Cape and the unprecedented cooperation of numerous excellent systematists unquestionably represents the definitive faunal study of Cape Cod Bay. Richard A. McGrath 14 August, 1978 ABSTRACT The benthic infauna at Cape Cod Bay was sampled over a period of three years (1966-1969). One hundred stations were identified on a grid system, and each was sampled once. Four different types of sampling gear were employed: a Smith-Mclntyre grab, an epibenthic sled,_ a naturalist dredge and a clam dredge. The benthos retained after sieving through a 1 mm mesh was sorted and sent to 45 systematists. More than 800 taxonomic groups were identified. Polychaetes, amphi- pods and bivalves were the dominant faunal components. The average grab sample contained 650 individuals of 37 species. Significant variation in several community parameters was found in spatial, seasonal and annual analyses. The highest number of species and individuals were found in winter samples. Shallow areas (< 10 m depth) were characterized by sands of medium to coarse grades. These areas had the fewest species. "Annual temperature range may be as much o :^=i as 23 C. Depths of greater than^-30 m, which had the greatest numbers of species, are subjected to a limited temperature range and sediments are primarily silts and clays. A substantial portion of the bay falls within the 15-30 m depth range. Sediments are mixtures of silts-and sands. This environment showed the most seasonal variation with significantly more species and individuals in winter thanin summer. A well developed tHermocline exists during the summer months and intercepts the sea floor at depths of 15-25-jn. 111 The study was originally intended as an inventory, and the design serves that purpose best. Only a limited amount of quantitative analysis could be executed because of the considerable variation that occurs in time and space. The study provides a comprehensive list of the benthic infauna and some insight to the range of variation found in such environ- ments . IV ACKNOWLEDGEMENTS The authors would like to acknowledge the efforts of those that conducted the earlier work on this study. This includes Dr. David C. Grant who was in charge of the study through August 1968 and Dr. David K. Young who headed the program from then through December 1969. ~~A special vote of thanks is due to Mr. James P. Ostergard, the captain of the research vessel A.E. VEKRILL. His skill and hard work enabled the scientific party to accomplish the field" tasks in an effective manner. There were many whose patient efforts in sorting the sample material were a necessary part in the completion of the laboratory analysis. The list is too long to be included here but their efforts are sincerely appreciated. Two people whose efforts were~~~critical" to the project are Dr. Melbourne Carriker and the late Mrs. Katharine D. Hobson. Dr. Carriker was the organizational and driving force in getting the project off the ground and seeing it through tcTjthe completion of the laboratory analysis. Mrs. Katharine Hobson in addition to the systematic work on polychaetes was an industrious worker and a key factor in the completion of the laboratory phase. We would also like to thank the participating systematists whose cooperation enabled the taxonomic work to be completed with a high level of quality. v TABLE OF CONTENTS Section Page FOREWARD i ABSTRACT iii 1. INTRODUCTION 1 2. METHODS 3 3. RESULTS 11 4. SUMMARY 101 REFERENCES 103 APPENDIX 106 LIST OF TABLES Table Page 1. Selected sediment parameters for sediment samples from El stations 21 2. Numbers of species and individuals in various - station groups 45 3. Faunal parameters reported in two Cape Cod Bay Benthic Studies 47 4. Variation for three parameters in quadrate replicates. 48 5. Comparison of dominant species in Cape Cod Bay in two studies 49 6. Species collected at Station 0620 El 52 7. Species collected at Station 1628 El 53 8. Species collected at Station 1930 El 54 9. Species collected at Station 2012 E5 55 t 10. Species collected at Station 2212 E2_± 56 11. Species collected at Station 2224 KS" 57 12. Species occurrence in four'types of":sampling gear. ... 59 13. Diversity values for El stations 69 14. Diversity values for station group categories 72 15. Diversity values obtained at the same sites in Cape Cod Bay 75. 16. Parameters for station groups 86 17. T tests for comparison of station group parameters ... 87 Vll LIST OF TABLES (continued) Table Page 18. Summary of numbers of species and taxa found in four types of sampling gear 96 19. Species most frequently occurring in epibenthic sled. ... 98 20. Species oust frequently occurring in clam dredge 99 21. Species most frequently occurring in naturalist dredge. 100 Vlll LIST OF FIGURES Figure Page 1. Cape Cod Bay sampling quadrats .............. 4 2. Temperature profiles in spring .............. 12 3. Temperature profiles in summer .............. 13 4. Temperature profiles in fall ............... 14 5. Temperature profiles in winter .............. 15 6. Predicted minimum bottom temperatures ........... 16 7. Predicted maximum bottom temperatures ........... 17 8. Sediment map prepared by Hough (1942) ........... 27 9. Sediment distribution based on median particle size. ... 28 10. Sediment distribution based on the mode of particle sizes. 31 11. Sediment map based on standard sediment classes (Shepard, 1954) ............... -; ......... 32 12. Major current patterns (re-drawn from Da^L, -1958) ...... 33 12a. Outline of Cape Cod and Kantucket ............. 39 13 through 32. Distribution of species ............ 63 33. Station groups from classification including all taxa. 79 34. Station groups from classification including polychaetes only .......................... 80 35. Station groups from classification including amphipods and molluscs ...................... 81 IX LIST OF FIGURES (continued) Figure Page 36. Station groups from classification including molluscs only 82 37. Station groups from classification including amphipods (log 1Q transformation) 83 38. Dendrogram from cluster analysis 85 39. Separation of station groups I - V 89 40. Dominant factor map 92 41. Dominant factors - summer 93 42. Dominant factors - winter 94 SECTION I. INTRODUCTION Study area Cape Cod Bay is an open embayment approximately 41 km in dia- meter. The surface area covers 580 km (300 square miles) and depths average 30 m (Hough, 1942). Neap tidal amplitude is 4 m at Plymouth, Massachusetts and 3 m at the entrace to Barnstable Harbour. The av- erage annual precipitation of-the area is about 40 inches and land drainage area is approximately 36% that of the bay. the soils are generally sandy permitting infiltration so that the resulting run off has an insignificant effect on the salinity of the bay as a whole. The circulation of the bay has never been described accurately, but on the basis of Bigelow's study of the Gulf of Maine in 1928 and recent drift bottle experiments, some generalizations can be made.