nine different southern California beaches reported by Patterson 

 (1974), who used a larger mesh screen in sample processing. Dexter 

 (1977) sampled a single intertidal locality at Imperial Beach in 

 February and found 15 species. 



In conclusion, the effects of the deposited sediments do not 

 appear to have reduced the numbers of species or individuals of beach 

 infauna. Sediment and biological data indicate a short-term enrichment 

 effect (five surveys of station B) . Evidence of an intermediate term 

 effect (4 months) is lacking (four surveys of station A) . 



There was an accumulation of coarse shell material which accom- 

 panied finer sediments in the dredged material (Fig. 11). These shells 

 represented typical bay species, and are probably large enough to remain 

 on the beach for some time. As more of the finer particles are sorted 

 out by wave activity, the shells may have an increasing influence on 

 infaunal distribution patterns. Coarse sediments on the beach, if 

 prevalent, would be inimical to the settlement of many species. 



c. Intertidal Faunal Similarity . Similarity indices were calcu- 

 lated at station B for each of the five surveys (Table 13) . The greatest 

 changes occurred just after beach replenishment when abundance and 

 diversity were increasing. This index, as calculated, appears overly 

 sensitive to species which are extremely abundant. 



Table 13. Station similarity indices' between surveys 

 at dredge-disposal terminus station B. 





SURVEY 



I-II 



II-III 



III-IV 



iv-v 1 







INTERTIDAL 



0.194 



0.066 0.761 



0.588 



3.7-Meter Depth 



0.39S 



0.363 0.346 



0.066 



6.1-Meter Depth 



0.2S3 



0.347 0.402 



0.181 



'The similarity index used is Cj (Czekanowski ' s coefficient; Bray and 

 Curtis, 1957). The coefficient compares species similarity between 

 two sampling periods or two separate localities. Cj = 2W/M + \; 

 W = sura of the lower measures of each species co-occurring during 

 the two sampling periods or localities; M and N' = total abundance 

 of all species from each sampling period or separate locality 

 I..M and \) . 



d. Subtidal Abundance and Diversity . The average abundances at 

 3.7- and 6.1-meter depths for all surveys combined were, respectively, 

 5,470 and 6,118 organisms per square meter. Dexter (1977) reported 



67 



