Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 12. Effects on the Benthic Invertebrate 



Community 



Frank W. Steimle, Jr.. and David J. Radosh' 



' Sandy Hook Laboratory, Northeast Fisheries Cen- 

 ter, National Marine Fisheries Service, NOAA, High- 

 lands, NJ 07732 



INTRODUCTION 



Assessment of the impact of the 1976 oxygen depletion 

 on benthic invertebrates is based on: 1) in-situ diver ob- 

 servations; 2) incidental collections of benthic inverte- 

 brates in finfish trawling and shellfish dredging surveys; 

 and 3) benthic grab collections. 



Diver observations were composed of reports from 

 NMFS divers and reliable sport divers of the species and 

 relative numbers affected around wrecks in New York 

 Bight. These reports included observations on the behav- 

 ior of organisms that appeared to be affected and on other 

 conditions apparently relevant to the phenomenon — for 

 example, a dark, organic flocculent layer on the bottom. 



Trawl surveys assessing the effect on finfish and shellfish 

 resources began a few days after the initial reports of 

 mortalities; dredge surveys began a few weeks later. Al- 

 though commercially valuable species were the primary 

 targets of the surveys, many noncommercial benthic in- 

 vertebrates also were collected and used to assess the im- 

 pact on larger invertebrate species. 



Five surveys examined the effects on benthic infauna. 

 Whenever possible stations that were occupied before the 

 oxygen depletion event were reoccupied, but many sta- 

 tions were sampled for the first time. Thirty stations were 

 examined between July and November 1976. Three 0.1- 

 m' Smith-Mclntyre grab samples were collected at each 

 station. Each sample was washed through a 0.1-mm mesh 

 screen, fixed in 10-percent buffered Formalin, and later 

 transferred to 70-percent ethanol for storage. At least one 

 of the triplicate samples, or a total of 46 samples, has been 

 processed (fig. 12-1), with species identified and counted. 

 The surveys selected both control stations and stations 

 that could be expected to be affected greatly, i.e., in the 

 area of the most severe anoxic and hydrogen sulfide con- 

 ditions. The processed data were analyzed for H' diversity 

 (Shannon and Weaver 1963) and J'equitability (Pielou 

 1969). 



281 



