colonizing benthos on pore water chemistry through tube and burrow 
irrigation. 
At the NL-85 disposal mound, the lowest successional 
seres were found in the southeast quadrant (Figure 3-47); this 
generally coincided with the areas exhibiting shallow apparent RPD 
depths. Stage II (Ampelisca sp.) seres were evident in over half 
of the stations located on the NL-85 mound (Figure 3-48). This 
assemblage also dominated in the NL-85 baseline study conducted in 
November 1985. At the Reference station, evidence of Stage III 
infauna was present in 11 of the 20 photographs. Stage II 
assemblages (amphipod tube mats) were also evident in 18 of the 20 
reference photographs. All of the amphipod tube mats at the 
Reference station, however, appeared to be physically disturbed, 
with many of the tubes lying flat on the bottom or rolled up into 
aggregates (Figure 3-49). The apparently retrograde condition for 
this assemblage may have been a result of local physical factors 
and/or biogenic disturbances, such as large-scale bioturbational 
mixing by Stage III infauna or foraging by epibenthic predators. 
All twenty Reference photographs also showed the presence of 
hydroids and/or small mussels at the sediment surface (Figure 
3-49). The REMOTS® photographs from the NL-I mound and the 
portions of the NL-RELIC, NL-II and NL-III mounds which were 
sampled showed widespread evidence of Stage III infauna, similar 
to the Reference station in contrast to that observed at the NL-85 
mound. Also, mussels were seen at center and 200E of mound NI-I. 
The presence of the high-order successional seres at these mounds 
indicated the absence of recent disturbances. In July 1986, 
disposal operations had not occurred at these mounds for several 
years (the most recent occurred at NL-III in 1984). 
Because of shallow camera prism penetration depth caused 
by the high shell content of the sediment and high shell density 
at the sediment-water interface, it was not possible to determine 
the successional status in many of the photographs at the southwest 
reconnaissance grid (Figure 3-50). The northern and southern edges 
of the site appeared to be populated by Stage I polychaetes. 
Hydroids were again common because the abundance of shell fragments 
provided solid surfaces for their attachment. This area appeared 
to experience periodic (or chronic) physical disturbance related 
to the transport of shell debris from the northeast (upslope). 
The northern and western flanks of the NL-85 disposal 
mound exhibited relatively high OSI's (Figure 3-51), which indicate 
rapid recolonization. Conversely, most of the central area and 
eastern edge of the mound exhibited relatively low OSI values (< 
+6). An OSI value of less than or equal to +6 generally indicates 
bottoms that are either recently disturbed or in a low order 
successional stage. In November 1985 (predisposal survey), the 
NL-85 disposal point showed generally high OSI values, except in 
the extreme southeast quadrant. This gradient was attributed to 
the low oxygen conditions which apparently developed in the deeper 
26 
