β Scribed by Dr. Don Maurer; MR. Richard T. Keck; Mr. Jeffrey C. Tinsman; Mr. Wayne A. Leathem; Mr. Christian Wethe; Dr. Charles Lord; Dr. Thomas M. Church
No coin nor oath required. For personal study only.
This account describes the comparative response of four species of benthic invertebrates t o burial in t,erms of vertical migration and mortality, and provides a synthesis of studies and recommendations upon which t o assess future impacts. The species featured were the bivalve Mercennrin mercennrin, the amphipod crustacean Parahnustorius longirnerus, and the polychactes Scoloplos fragilis and Nereis suceinea.
There wns evidence of synergistic effects on burrowing activity and mortality with changes in timc of burial. sediment depth, sediment type and temperature. I n sediment. with silt-clay. h'.
succiiten was the most resistant species followed by ,+I. mercenarin, 8. fragilis and P. longimerus.
I n sediment without silt-clay the order of percent mortality was reversed.
Studies of surface water chemistry and sediment geochemistry showed that dissolved oxygen decreased significantly and ammonia and sulfide increased significantly between the surface and below 2.0 cm within a 15-day period. Based on these results and physiological tolerances from the 1 itrraturc it was concluded that N . niercenaria and N . euccinea would be relatively resistant to chemical effects of spoil disposal, whereas 8. frngi2i.y and P. longirnerus would be less resistant t o such effects.
Yert ical migration of benthic invertebrates through dredge disposal can be a viable mcchanism of recolonization under certain conditions. Some effects of burial of benthos can be predicted hnsed on morphology, behavior and physiology. These biological features were discussed with exnniplea dealing with moll~iscs. crustaceans, and polychaetes. Finally, recommendations were made concerning the type of st,ndies t o provide additional data t o aid management agencies in clecision mttking about future dredging and disposal practices.
π SIMILAR VOLUMES
During the course of study on vertical migration and mortality of benthos in simulated dredged material, changes in pore water chemistry and sediment geochemistry were also examined. Dissolved oxygen, ammonia, and sulfide showed significant changes between overlying water and pore water over the two