deposit- feeding capitellids and bivalves were absent; the biomass was 

 drastically reduced. 



In October 1971 the polychaetes, A. bioculata and C. capitata, settled 

 in large numbers. Both animals have a larval settling peak in the fall, 

 are small (1 centimeter) surface deposit feeders, and are common in the 

 slough and harbor. Capitella capitata is generally found in muddy de- 

 posits, but is known to invade disturbed habitats. By January 1972, all 

 the C. capitata were gone. 



The density of A. bioculata remained about the same from November 1971 

 to January 1972, decreased in March and June 1972, and further decreased 

 in September 1972 (Fig. 12) . From November to January there was a definite 

 increase in individual size. Avmandia hioouiata had another settling peak 

 in the spring and additional recruitment probably occurred at that time. 



The decline in the number of A. bioculata was undoubtedly precipitated 

 by the tremendous settling of Phoronopsis viridis in March 1972 (Fig. 12) . 

 Phoponopsis viridis is a suspension-feeding phoronid worm that builds and 

 lives in a permanent sand tube. The new population reached adult size 

 by June 1972, with a density of about 1,000 individuals per 0.018 square 

 meter. As the phoronids grew, their tubes occupied more space, drastically 

 reducing the amount of the deposit-feeding habitat, thus, decreasing the 

 number of A. bioculata. Woodin (1972) supports this conclusion with exper- 

 imental evidence. She found that the density of A. brevis on San Juan 

 Island, Washington, increased when the larvae of several tube-building 

 polychaetes were prevented from settling. She concluded that the increase 

 in A. brevis abundance was the result of decreased interspecific competi- 

 tion for space. 



Little is known about the ecology of A. bioculata which has the char- 

 acteristic of an opportunistic species, similar to C. capitata. 



From March 1972 until April 1973, P. viridis dominated the benthic 

 assemblage. Its density dropped steadily from the March settlement to 

 December 1972, and in April 1973 there was a second large recruitment. 

 Phoronopsis viridis may spawn into the early summer* however, in both 

 years early recruitment and fast growth left little space for additional 

 settlement. In March 1972, about 1,200 individuals per core settled, and 

 200 A. bioculata per core were present. In April 1973, about 500 phoronids 

 per core settled in a population of large adults (200 per core) . The 

 difference in recruitment between successive springs again suggests that 

 available space limits the number of settling larvae. 



Several species of bivalves settled in relatively large numbers at 

 times during recolonization (Table 5) . Most were gone by the next sampl- 

 ing period and very few reached adult size. The situation was similar at 

 the disposal station. Settling conditions were optimal for a short period, 

 and subsequent events caused heavy mortality. Apparently, the environment 

 was marginal for most of the bivalves. 



