the even apportionment of individuals among the few species present. In 

 October 1971, evenness dropped slightly, but the number of species in- 

 creased from 10 to 22; diversity also increased (Fig. 13). In November 



1971, the dominant species were Cccc-ttalla and Armandia. By January 1972, 

 the number of species had decreased and Armandia was the only abundant 

 animal (Fig. 12). Both diversity and evenness dropped by winter. From 

 January to June 1972, the number of species more than doubled (Fig. 13); 

 Armandia and several species of bivalves (mostly juveniles) were present 

 in large numbers. Despite the fact that the density of Phoronopsis was an 

 order of magnitude greater than the second most abundant animal (Fig. 12; 

 Table 5), both evenness and diversity increased (Fig. 13). In September 



1972, Armandia and bivalve densities were very low; the number of species 

 decreased from 64 to 38 (Fig. 13), and Phoronopsis was the only abundant 

 species. Evenness and diversity both decreased (Fig. 13). From September 

 to December 1972, Phoronopsis density decreased from 412 per core to 154 

 per core (Fig. 12), causing an increase in evenness and diversity (Fig. 

 13) . Finally in April 1973, the large spring recruitment tripled the 

 density of Phoronopsis (Fig. 12) , and evenness and diversity decreased 

 again (Fig. 13) . 



By comparing Figures 12 and 13 it is apparent that species diversity 

 cannot be properly interpreted without information on the number of 

 species (richness) and their relative abundances (evenness) . 



Some of the decreases in species diversity were related to life history 

 characteristics, mortality caused by physical stress, or perhaps predation 

 and competition. Increases were associated with the same phenomena under 

 differing conditions, except there was no indication that competition in- 

 creased diversity. 



At the disposal station, there was a marked increase in the number 

 of species, species diversity, and evenness during the later phase of 

 recovery (Fig. 14). At the dredged station, there was an increase in 

 species diversity and evenness after almost complete removal of the native 

 fauna; 1.5 years later the diversity was still much lower than it was be- 

 fore dredging because of Phoronopsis dominance (Fig. 13). Thus, the 

 effect of dredging and disposal was not a decrease in species diversity. 

 The reestablished or recuperated assemblages differed considerably from 

 the originals; in one case, the diversity was higher and in the other, 

 lower. 



There is no positive correlation between species diversity and the 

 "health" or "desirability" of any of the above situations. Therefore, 

 the use of this parameter in summarizing community structure or changes 

 in this structure due to man's activity is not recommended. 



The sequence of recolonization at the dredged station involved two 

 relatively distinct phases. In the earlier phase, the opportunistic or 

 fugitive species quickly colonized the open space; i.e., Capitetta and 

 Armandia. They are generally considered poor competitors, and are rela- 

 tively small, with short reproductive cycles, fast growth rates, and high 



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