The role of seasonal hypoxia in structuring the biology, 

 biogenic mixing depths, depths of the mean apparent RPD, and 

 Organism Sediment Indices is unknown. The recent discovery of 

 regional hypoxia in the central Sound has cast a new light on the 

 DAMOS monitoring protocol. It appears imperative to add near- 

 bottom dissolved oxygen measurements to all REMOTS® measurements 

 and to do hydrographic profiling (CTD/DO profiles) of the water 

 column to relate water column stratification to hypoxic water 

 thickness whenever possible. This would provide documentation of 

 the spatial extent of hypoxic near-bottom water relative to REMOTS® 

 benthic analyses at and near the disposal sites. 



The MQR mound continued to have one of the slowest rates 

 of benthic ecosystem recovery among the mounds at the CLIS site; 

 this phenomenon has been noted in past REMOTS® surveys. Results 

 from the sediment chemistry analyses (Tables 3-21 and 3-22) showed 

 this mound to be the only mound with significantly elevated levels 

 of all contaminants measured as compared with the reference 

 station. The relatively higher levels of chemical contamination 

 combined with the potential hypoxia effects could both contribute 

 to the slow rate of infaunal succession documented at this 

 location. 



As previously indicated, there was no definitive evidence 

 of disposed material in either Ghost Site 1 or 2. Both areas had 

 average OSI values close to +9 and were not significantly different 

 from the new CLIS reference station (Table 4-1) . If material was 

 disposed in these areas in the past, three possibilities exist: 

 1) REMOTS® sampling stations (spaced at 100 m intervals) were not 

 located on this material; 2) the material was disposed a long time 

 ago, and subsequent colonization and reworking has caused the 

 material to converge in its biological and physical properties with 

 the ambient seafloor; or 3) small volumes of material from any 

 recent disposal activities were spread out in thin layers, so that 

 the ambient infauna were able to rework the material into the 

 bottom, erasing its "optical signature". 



After a period of 13 years, the sand cap on the New 

 Haven-74 disposal mound could no longer be seen as a discrete 

 sedimentary layer. The sand has been mixed with fine-grained 

 sediment, leaving the sand fraction as only a minor textural 

 component. It seems reasonable to assume that distinct features 

 of sand or mud caps (e.g., irregular sediment fabrics, layers 

 having distinct grain-size and/or optical reflectance, etc.) which 

 are thin relative to the bioturbation depth of Stage III taxa would 

 be short-lived, due to sediment reworking by these organisms. The 

 upper 20 cm of the sand cap at CS-2, after only 3 years, has also 

 been thoroughly mixed with fine-grained sediment. The only station 

 to show clear evidence of the sand cap in the upper sedimentary 

 layer was located at 600N (CS-1) . 



36 



