1963; Connell, 1972). It has a short reproductive cycle (1 month) and 

 probably has poor competitive and high dispersal abilities (personal 

 communication, Dr. Reish, Long Beach State College, 1972). The worm is 

 often found in polluted marine harbors, near sewage discharges, and in 

 other areas of natural or unnatural stress (Reish, 1955, 1957; Felice, 

 1959; Rosenberg, 1972); it is also common in the mudflats and muddy bot- 

 toms in Elkhom Slough and Moss Landing Harbor. 



The dredge spoil disturbance caused a slight drop in the number of 

 species. During recovery the total number of species rose to a high in 

 June 1972, and decreased steadily thereafter. The number of species and 

 individuals at the control (Fig. 11) and the dredged harbor stations (Figs. 

 12 and 13) were also highest in June 1972. These June peaks may be related 

 to_ seasonal or possibly long-term variations rather than any time sequence 

 characteristic of recovery. The sequence and rate of recovery (or recol- 

 onization) are probably a function of the initial time of exposure and the 

 particular set of ecological conditions present during the recovery pe- 

 riod. 



During recovery, species composition was more stable than relative 

 abundance. The common species and their abundances for each sampling 

 period are listed in Table 4. Mollusks and crustaceans were irregular 

 members of the assemblage; many of the worm species were present through- 

 out the study period. 



In June 1972, the polychaete worm, A. occidentalism settled at the 

 disposal and control stations. It was uncommon at both locations before 

 June, but was more abundant later at the disposal station. This large 

 terebellid polychaete lives in a semipermanent U-shaped burrow, and is 

 capable of burrowing deep into the sediment. Its tentacles are usually 

 spread just below the bottom surface and their expanded distal ends extend 

 into the water column. 



Changes in species diversity and evenness followed a trend similar to 

 that for the number of species (Fig. 14) . Disposal had little effect on 

 their values. The bloom of Capitella in October 1971 lowered evenness 

 and consequently diversity. Both parameters increased until June 1972. 

 After the dumping, density was much lower (Fig. 15) , but the dominants 

 accounted for a similar percentage of the total. In June, no dominant 

 mollusks (Fig. 15) were present and the number of species was highest 

 (Fig. 14). A large population of juvenile Tresus settled in December 1972 

 (Fig. 15), and both parameters decreased (Fig. 14). The combination of 

 an increase in the number of species and a decrease in the abundance of 

 the two predisposal dominants Eetevomastus and Capitella, caused evenness 

 and diversity to increase. Thus, recovery from disposal resulted in a 

 more diverse fauna, although an earlier large decrease was observed be- 

 cause of the large number of juvenile Capitella. This general increase 

 in diversity is undoubtedly related to the increase in substrate stability 

 and structural diversity due to the presence of Amaeana. 



45 



