After removing variation attributed to abiotic 

 factors, significant trends over sampling years were 

 evident at EF and GN. At EF, there was a 

 significant increasing trend which principally re- 

 flected the low abundances collected in 1980 and 

 1981. At this station, the 1986 and 1987 means 

 were significantly different from only 1980, when 

 lowest oligochaete densities were found. Abun- 

 dances at GN, were also lower in earlier sampling 

 periods. Oligochaete densities in 1986 and 1987 

 were significantly higher than 1983 when histori- 

 cally low densities occurred in 3 of 4 quarters. In 

 addition, the 1986 value was significantly higher 

 than 1984. At JC, the 1986 mean was significantly 

 lower than 1980, while 1987 was significantly 

 lowerthan 1980 and 1982-1985. Oligochaete den- 

 sities at IN in 1986 and 1987 were lower than 

 those collected from 1980-83; only the 1987 mean 

 was significantly lower than 1980, 1982, and 1983. 



Mediomastus ambiseta 



This capitellid polychaete has been reported in 

 areas of environmental stress caused by distur- 

 bance or high nutrient input; it is also common 

 in subtidal areas composed of silty sediments 

 (Boesch and Rosenburg 1982) along the entire 

 U.S. east coast. Classified as an 'opportunist', 

 Mediomastus ambiseta is capable of large popu- 

 lation increases in response to environmental 

 stress associated with oil spills (Grassle and Grassle 

 1974; Sanders et al. 1980) and organic enrichments 

 (Boesch and Rosenburg 1982). 



Mediomastus ambiseta was the most consistently 

 dominant species at all subtidal stations during 

 1986-87, ranking 1st at GN, IN and JC and 2nd 

 at EF in terms of the 2-year BIV. Quarterly mean 

 abundance (#/core) over the last two years ranged 

 from 25 - 101/core at GN , 7 - 19/core at EF, 8 

 - 41/core at IN and 21 - 411/core at JC. At all 

 stations but IN, the abundance of this species 

 dramatically increased in September 1983 and 

 generally remained at high levels through 1987. 

 Over 1986-87, only June 1986 density at JC ex- 

 ceeded the range of previous years' values. 



Multiple regression analyses revealed significant 

 increases in the density of this species at all sta- 

 tions. Annual abundance of Mediomastus 

 ambiseta peaked in 1984 at JC, EF and GN and 

 remained high through 1987 (Fig. 12 E-M). At 

 IN, highest annual abundance occurred in 1987. 

 Results of pair-wise comparisons between years 

 (t-tests) were as follows: at JC, 1986 and 1987 

 were significantly higher than 1981-1983. The 

 1986 and 1987 annual means were significantly 

 higher than aU previous years at EF (except 1 986 

 vs 1985 at EF), GN (except for 1987 vs. 1984) 

 and IN. 



Aricidea catherinae 



Aricidea catherinae is commonly a member of 

 littoral (Whitlatch 1974; Kinnerand Maurer 1978) 

 and offshore (Maurer and Leathem 1980) tem- 

 perate communities. This species was a dominant 

 component of subtidal communities throughout 

 the baseline period, and in 1986-87, ranked 3rd 

 in terms of 1986-87 BIV at GN and JC (Table 

 5). At both IN and EF, this species did not rank 

 among the top ten in either 1986 or 1987 despite 

 its high ranking in the 1980-85 period. 



Densities of Aricidea catherinae during the last 

 two years ranged from 19 - 66/core at GN, 4 - 

 40/core at JC, 1 - 2/core at at EF and 1 - 4/core 

 at IN (Fig. 12 I-L). At GN and IN, values were 

 within the range of those obtained during the 

 pre-operational period (NUSCO 1987). However, 

 at both EF and JC, values since March 1986 

 (December 1985 at EF) were lower than those 

 found in previous years. 



Regression analysis revealed significant differ- 

 ences in the abundance of this species at all sta- 

 tions. At EF, annual densities in 1986 and 1987 

 were significantly lower than 1980-1984. At JC, 

 both 1986 and 1987 were significantly lower than 

 1981 (also 1986 vs 1983 and 1984). Abundance 

 of this species at GN and IN was less variable 

 and few significant differences among years were 

 evident. At IN, the 1987 annual density was sig- 

 nificantly higher than 1984, while at GN the 1987 



Benthic Infauna 



99 



