numbers (84 percent) and species (49 percent].. Motility appears to be 

 an important adaptation to this zone. Statements on the overriding 

 importance o£ polychaetes in infaunal communities (Dauer and Simon, 

 1976) do not apply to these exposed coastal shallow sediments within the 

 surf zone. At the 3.7-meter depths, crustaceans comprised over 41 

 percent of the numbers and 48 percent of the species; at the 6.1-m.eter 

 depths, crustaceans comprised 45.5 percent of the numbers and 35 percent 

 of the species. These were mostly motile brood- carrying pericarid 

 crustaceans (e.g., amphipods, cumaceans) similar to those in the inter- 

 tidal zone. Polychaetes at 6.1-meter depths comprise 38 percent of the 

 abundance and 46 percent of the species. Since most polychaetes recruit 

 from the plankton, increased sediment stability with depth may be impor- 

 tant to larval settlement and probably underlies this observed relation- 

 ship. Polychaetes are reported to predominate in offshore environments 

 (Knox, 1977) where sediments are more stable. 



i. Relationship of Abundance and Diversity for Specific Sedi- 

 ment Parameters . An increase was expected in fine sediment fractions 

 and possibly of organic matter from the San Diego Bay sediments used to 

 replenish Imperial Beach. 



Within each depth stratum all surveys were combined and sig- 

 nificance of the correlations of numbers of species and average abun- 

 dance with organic carbon content, silt-clay fraction, and very fine 

 sand fraction was determined. Correlation of silt with carbon was also 

 determined (Table 20) . 



Correlations were determined using regression analyses (Sokal 

 and Rohlf, 1969). Tests for significance of correlation between factors 

 were set at a 95-percent confidence level. Results were as follows: 



(a) Intertidal (n = ]3 comparisons) 



No significant correlation between variables. 



(b) 3.7-meter depth (n - 13 comparisons) 



(1) Significant increase in total species present with 

 increased silt. 



(2) Significant increase of average abundance per 

 sample with increased silt. 



(3) Significant increase in organic carbon with 

 increased silt. 



(c) 6.1-meter depth (n ,= 11 comparisons) 



(1) Significant increase in average abundance per 

 sample with increased silt. 



