34 



replicates had indeterminate surface roughness values, with five attributed to physical 

 effects and two to biogenic activity. 



3.3.2.2 Benthic Community Assessment 



Although the majority of replicates had a Stage I successional status in September 

 1997, there was an increase in the presence of Stage III indicators, both deposit feeders and 

 feeding voids, since the July 1996 survey (Figure 3-6). The mean RPD depths, however, 

 were shallower than observed in previous surveys, with an overall average of 1.44 cm 

 (Figure 3-7) compared to 2.46 cm from July 1996. The Organism-Sediment Index, which is 

 a combination of the previous factors, was close to the 1996 survey results with an overall 

 median of 4. Two replicates with OSIs of 7 at SOW, which had a zero OSI value in 1996 

 due to low DO, did show improved benthic conditions (Figure 3-7; Table 3-2). No low DO 

 conditions were evident in either September or March surveys. 



In March 1998, the benthic conditions at the 5-station grid had improved 

 significantly since September 1997. Evidence of Stage III organisms was found in 10 of 

 the 15 replicates. Stage I organisms were less abundant at both the H and I mounds in 

 March. Stage I organisms, which are polymorphic filter feeders that can easily adapt and 

 recolonize new resources, tend to die back during winter and then increase again in May. 

 The overall mean RPD in March was 2.3 cm (Figure 3-8). The OSI values ranged from 4 

 to 1 1 with an overall median of 8 (Figure 3-8; Table 3-2). 



3.4 WLIS Reference Areas 



As part of the DAMOS tiered monitoring protocols, we collected reference area 

 data in September 1997 to provide a baseline to compare results from the dredged material 

 mounds. A total of thirteen stations were occupied over two reference areas (SOUTH and 

 SW-REF). Complete REMOTS® results for the WLIS reference areas are available in 

 Appendix B. In March, we investigated SE-REF but did not revisit South and SW-REF 

 due to time constraints. 



3.4.1 Sediment Grain Size and Stratigraphy 



Ambient sediments, characterized by brown silt or very fine sand over mud, were 

 identified in almost all of the replicates. SOUTH Station 1 appeared to contain dredged 

 material, and SW-REF Station 9 was indeterminate. The major mode of grain size was 

 >4 phi for majority replicates, with 3 to 4 phi for 15 replicates. The mean camera 

 penetration at the reference areas, 9.42 cm for SOUTH and 6.24 cm for SW-REF, was 



Monitoring Cruise at the WLIS Disposal Site, September 1997 and March 1998 



