NO A A PROFESSIONAL PAPER 11 



See figure 12-1 for station locations. 



surf clam meats in trawl nets and dead or dying specimens 

 of other species, for example, the polychaetes, Glycera 

 dibranchiata and Sigalion arenicola; the sipunculan, Phas- 

 colopsis gouldii; the mantis shrimp, Platysquilla enodis; 

 and unidentified burrowing anemones. They also ob- 

 served that the bivalve, Astarle castanea, and the gastro- 

 pod, Nassarius trivittatus, appeared unaffected. 



Another study, at an inshore area off Little Egg Harbor, 

 N.J., also found benthic and epibenthic mortalities during 

 the late summer; the species affected were similar to those 

 reported here (Garlo, Milstein, and Jahn 1979). 



Mortalities caused by the oxygen depletion are only the 

 immediate manifestation of the total impact to the benthic 

 invertebrate community. One latent aspect of the impact 

 is the recovery time of the benthos. After the 1968 fishkill, 

 Ogren and Chess (1969) reported that the megafauna 

 (e.g., crabs and lobsters) appeared to have completely 

 recovered the following summer. Recolonization studies 

 have indicated incomplete recovery in 1977 and, to a lesser 

 extent, in 1978. This is evident in the blooms of some 

 opportunistic organisms and continued low numbers of 

 other previously abundant species. The abundant species 

 in 1977 were small, tube-dwelling polychaetes, Asahellides 

 oculata, Polydora socialis, and Spiophanes bombyx, which 

 were collected in the 1976 oxygen depleted area during 

 March, June, and July. The last two species belong to the 

 family Spionidae, which contains many species classified 

 as opportunistic (Ziegelmeier 1970; Grassle and Grassle 

 1974). In an earlier unpublished study, AsabelUdes, al- 

 though not previously regarded as an opportunistic spe- 

 cies, was reported in large numbers at an ocean sewer 

 outfall off Deal, N.J. (J. Pearce and J. Caracciolo, NMFS, 



Highlands, N.J., personal communication). Opportunists 

 commonly dominate stressed, unstable areas, such as 

 sewer outfalls. Boesch et al. (1977a) also reported a pop- 

 ulation increase of Spiophanes in their November 1976 

 and February 1977 collections off Atlantic City. Some 

 recolonization by juvenile surf clams and sand dollars was 

 reported. 



Total recovery of the affected benthic community may 

 take several years, because of the extensive dimensions 

 of the affected area. Recolonization by some species can 

 be expected to be rapid, especially those with planktonic 

 eggs or larvae. The population expansion o{ AsabelUdes, 

 Spiophanes, and Polydora and the appearance of juvenile 

 sand dollars and surf clams are probably expressions of 

 this mode of dispersal. Recovery will be slower for other 

 species without a planktonic phase, for instance many spe- 

 cies of amphipods that brood their young. In the end we 

 may not even be able to determine definitely when re- 

 covery is complete, because of such factors as the heter- 

 ogeneity of the environment and the dynamic aspects of 

 the inshore benthic community. 



SUMMARY 



The oxygen depletion event of 1976 killed many benthic 

 invertebrates, especially surf clams off central New Jersey. 

 Some organisms, mostly polychaetes, showed tolerance. 

 Recolonization and stabilization of the benthic inverte- 

 brate population appeared to be incomplete 1 year after 

 the disturbance. Several years may be required for some 

 species — e.g., those with nonplanktonic larval dispersal — 



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