CHAPTER 12 



or significant levels of hydrogen sulfide; thus most species 

 have a low tolerance level to these conditions (Theede et 

 al. 1969; Davis 1975; Shick 1976). When the bottom waters 

 of the Bight became depleted of oxygen and significant 

 hydrogen sulfide concentrations subsequently developed, 

 it could be anticipated that mortalities within the benthic 

 community would be extensive. Diver observations and 

 results of biological surveys, using various sampling equip- 

 ment, support this hypothesis. 



The best evidence of impacts to the benthic community 

 are from trawl and dredge collections. These impacts (ta- 

 ble 12-1) indicate that a wide variety of benthic species 

 in the area of oxygen depletion had extensive mortalities. 

 Organisms involved included over 20 species of inverte- 

 brates, most incidental to survey target species, that is, 

 commercially important shellfish and finfish. Both epi- 

 faunal (e.g., crabs and lobsters) and macroinfaunal species 

 (e.g., polychaete worms and other deep-burrowing or- 

 ganisms, Axius. PlatysquiUa. Caudina, and sipunculans) 

 were noted. Of interest were deep-burrowers, which have 

 been rare in most previous New York Bight benthic col- 

 lections, mainly because they are generally below the sam- 

 pling range of most standard benthic equipment. For a 

 few species, especially surf clams, the effects were massive 

 in numbers and biomass of animals affected. For other 

 species, like lobsters, the response was mainly avoidance 

 and disruption of normal seasonal migrations. Chapters 

 11 and 13 discuss the effects on commercially valuable 

 species. 



Unfortunately, Smith-Mclntyre grab collections re- 

 sulted in mostly circumstantial evidence of effects on the 

 macrofauna. Actual mortalities were observed in only two 

 samples, station 24, including some sand dollars and one 

 polychaete (Sthenelais limicola), and station B near the 

 head of the Hudson Shelf Valley, where dead holothu- 

 roideans (Thyone sp.) were found in one of the three 

 samples taken. Also available from our grab samples are 

 data on numbers of clapper bivalves present, indicating 

 recent mortalities (table 12-4). 



What appear to be the best indications of effects on the 

 infauna are the low numbers of species, individuals, and 

 diversities (H') found at stations E, F, I, J, L, N, F, Q, 

 and 18 (tables 12-2 and 12-3). Again, this evidence has 

 its limitations, because of variability and inadequate base- 

 lines for most of the area affected by the oxygen-depleted 

 water mass. Triplicate samples were processed for several 

 stations, however, and where numbers of species and in- 

 dividuals were consistently low, we believe this indicates 

 an impact from anoxia. Stations I, L. and N appeared to 

 be particularly affected. Stations P and O may also have 

 been affected, but the data are less convincing, because 

 of variability (F) or lack of replication (O). 



A possible alternate approach to assessing impacts on 

 the infauna is to concentrate on population changes in 



species known to be fairly ubiquitous in the sandy sedi- 

 ments off New Jersey. Such species have been identified 

 in several studies (Boesch et al. 1977a, 1977b; Radosh et 

 al. 1978). Based on these studies and on numbers of station 

 occurrences in table 12-2, these species include Cerian- 

 theopsis americanus. Aglaophamus circinata, Leiochone 

 dispar. Spiophanes homhyx, Byblis serrata, Cirolana pol- 

 ita, and Echinarachnius parma. Spiophanes and Cehan- 

 theopsis, known to be tolerant species occurring in stressed 

 environments like sewage disposal areas, increased mark- 

 edly in abundance. Boesch et al. ( 1977a, 1977b) also found 

 these two species to resist the anoxia and found Spio- 

 phanes to be opportunistic as well. We know the low tol- 

 erances of Echinarachnius and crustaceans (Boesch et al. 

 1977a, 1977b) to anoxia. Based on increases in Spiophanes 

 and Ceriantheopsis and decreases in the other species 

 listed above, there were probably severe anoxia impacts 

 at stations 11 and 13, moderate effects at stations 4, 18, 

 and 24, and little or no impact at stations 6, 7, 8, 12, 14, 

 17, and 19. Figure 12-3 shows the area of greatest impact 

 to the benthic macrofauna, based on tables 12-2 and 12-3. 



The substantial postanoxia increases in populations of 

 Spiophanes and Ceriantheopsis may be due to rapid re- 

 colonization as well as to tolerance of anoxia and sulfide. 

 The polychaete, Goniadella gracilis, was abundant at the 

 heavily impacted stations I, L, and N, implying high tol- 

 erance to oxygen depletion. This was unexpected, since 

 Goniadella is characteristic of ridge environments (Boesch 

 et al. 1977a. 1977b; Radosh et al. 1978) in which anoxic 

 episodes must be relatively rare. There is evidence that 

 the polychaetes, Aricidea cerruti and Tharyx acutus, and 

 the bivalve Astarte castanea may also be tolerant to anoxia. 

 The increased occurrence in our samples of the deep-bur- 

 rowing mantis shrimp, PlatysquiUa enodis, is undoubtedly 

 a sign of stress rather than of resistance. 



The absence of any appreciable effects on the benthic 

 fauna at stations G and H near the center of the anoxic 

 water mass can be attributed to these two stations being 

 on an elevated sand-gravel ridge. The height of this ridge 

 is near the depth of the thermocline (25-30m). and more 

 oxygen is expected to be available here, at least inter- 

 mittently, than in the surrounding deeper waters. 



Two other benthic studies in the area during the low 

 oxygen condition also found affects to the benthic inver- 

 tebrate community. Boesch et al. (1977a. 1977b) reported 

 the megabenthos to be severely affected at a station about 

 30 km east of Atlantic City in August 1976. but little 

 affected in November at a station farther east. They found 

 drastic reductions in the populations of the sand shrimp, 

 Crangon septemspinosus; the rock crab. Cancer irroratus; 

 the small peracaridean crustaceans, Tanaissus liljeborgi, 

 Protohaustorius wigleyi. and Pseudunciola obliquua; the 

 starfish. Asterias forbesi; and the sand dollar. Echinar- 

 achnius parma. They noted large quantities of decayed 



287 



