present at station A, 3.7 meters, survey IV, the same population is 

 assumed to have moved offshore to station A, 6.1 meters, survey V. 

 The timing of this migration indicates a seasonal response rather than 

 an avoidance of perturbations induced by beach nourishment. This is 

 most evident since by survey V the physical conditions had returned to 

 levels comparable to those at the onset of this study. 



Since the sampling program was not specifically designed to 

 follow D. exoentvious movement, it is impossible to quantify the direct 

 effects of the beach deposition program on the beds. Beach replenish- 

 ment buried some large beds of sand dollars with very fine sediment, but 

 no direct mortality was seen. Onshore-offshore migrations may have been 

 affected by deposition of fines but offshore migration was evident 5 

 months after beach replenishment and correlated well with the onset of 

 the first winter storms. 



b. Crustaceans . Crustaceans in nearshore sediments are dominated 

 by species which do not disperse by planktonic larvae (amphipods, iso- 

 pods, cumaceans) . Many are capable of leaving the sediments to form 

 reproductive swarms or seek food or another habitat. Densities are more 

 variable since patchiness may result from response preferences, repro- 

 ductive aggregations, localized brood release, and response to food 

 source. The following is a discussion of the response of selected 

 crustaceans or species groups to beach replenishment. 



(1) Synahel-Jdiim spp. (Amphipod) . This species group, composed 

 of an undescribed intertidal species (personal communication, J.L. 

 Barnard, 1977) and offshore species including S. shoemakevi , ranked 1, 

 10, and 13 in abundance for intertidal, 3.7- and 6.1-meter depth sta- 

 tions, respectively (Table 11). The abundance of Synahelidiym in the 

 intertidal varied from 13 to over 1,400 per square meter (Fig. 32, 

 Table 10). Egg-carrying individuals were found at all stations in all 

 five surveys. 



Abundance of Synohelidivm did not differ between stations 

 in the intertidal zone during survey 1. There was a significant drop in 

 abundances at intertidal station B, survey II, which correlated with 

 extensive erosion that exposed cobbles at this station (Figs. 4 and 31, 

 Table 3). Survey III (station B only) was concurrent with beach replen- 

 ishment. Estimates of over 1,250 individuals per square meter indi- 

 cated that beach replenishment did not preclude Synahelidium . In 

 survey IV (postdisposal) intertidal abundances were high at all sta- 

 tions. Station B had significantly higher abundances than station A but 

 neither differed significantly from station C. Five months after dis- 

 posal (survey V) , abundances at all stations were lower, and station B 

 was significantly higher than stations A and C. 



The general abundance pattern observed for this species 

 group of amphipods suggests a seasonal pattern with low abundances in 

 winter and high in summer only to decrease again with the onset of 



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