58 



WLIS, where the mounds are the steepest monitored under the DAMOS Program. A 6 m 

 horizontal separation between depth measurements over a 3° slope generates a 0.4 m 

 difference in measured height. Therefore, the apparent changes to the height of the WLIS 

 "A" mound were likely the result of small differences in the horizontal transducer position 

 between the 1991 and 1992 surveys. 



Although the range of RPD depths at the WLIS "F" mound was only moderate (from 

 0.1 to 4.3 cm) some of the deepest values were observed in the center region of the 1991- 

 1992 disposal area. RPD depths at these stations were comparable to or exceeded those in 

 the reference areas, indicating the relatively deep oxygenation of sediments at the center of 

 the WLIS "F" mound. Several of these same stations (F100N, WLIS "F", F100SE) were 

 also associated with Stage III benthic infaunal assemblages. The presence of a Stage III 

 community at the center of the mound indicates a rapid recolonization for at least part of 

 WLIS "F". However, an equal number of central stations (F100W, F100SW, F100S) had 

 only Stage I communities present. This is more typical of recently disturbed benthic 

 habitats, and was predicted to be the case for the entire mound prior to the survey. This 

 pattern of recolonization is common for benthic areas in the process of recovery from recent 

 disturbance, such as dredged material mounds. Barring further disturbance, the WLIS "F" 

 mound is expected to exhibit a mature Stage HI community by the summer of 1993. 



The CTD profiles in the vicinity of the WLIS "F" mound did not indicate unusually 

 low dissolved oxygen levels in either the surface or bottom waters. The oxygen, 

 temperature, and salinity stratification observed (Appendix) was typical for this area of the 

 Sound (Welsh and Eller 1991). Although the western Long Island Sound region has 

 experienced cycles of summertime hypoxia (DO less than 3 mg l" 1 ) these conditions did not 

 exist during the present survey. 



4.2 Analysis of Selected WLIS "D" and "A" Stations 



After completion of the 1991 REMOTS® survey at WLIS, it was noted that five ' 

 stations in the vicinity of the WLIS "D" and "A" mounds exhibited very highly reduced, or 

 dark, subsurface sediments. As a result, these stations were resampled in 1992. Both 

 REMOTS® and sediment toxicity data were used to evaluate and compare the two surveys. 

 The REMOTS® sampling showed a modest improvement in habitat quality, but toxicity 

 testing demonstrated no difference between the WLIS "D" and "A" stations, and reference 

 areas. These results were used to evaluate the stations in the context of the DAMOS Tiered 

 Monitoring Plan (Germano, Rhoads, Lunz 1994). 



REMOTS® sampling indicated little change in OSI between the two years, although 

 RPD depths were approximately 0.3 cm deeper in 1992. The increased depth of the RPD 

 may represent a small increase in sediment reworking by benthic organisms present at the 

 time of the survey. However, this change in RPD was not large enough to influence the 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1992 



