by Dexter (1977) . Estimated densities of the abundant species and the 

 rank order of abundance in the intertidal area are presented in Tables 

 10 and 11. Summer periods (June, July, and September) had the highest 

 densities of organisms, while winter periods (November and February) 

 were lower. Seasonal total abundance patterns at all three intertidal 

 stations (Fig. 18) showed drops in abundance from summer to winter 

 preceding the beach replenishment operation. This correlates well with 

 measurements of increased wave action offshore (Fig. 7) and with observa- 

 tions of beach erosion during this period (Fig. 4, Table 3). Surf 

 temperatures averaged only 1.5° Celsius lower in winter (Table 5). 

 Thus, twofold or more seasonal changes in total abundance occurred here 

 in response to natural events. Before beach replenishment, intertidal 

 abundance varied significantly between stations (p<.05) along the 2.1- 

 kilometer stretch of nearly straight sand beach (Figs. 18 to 21). 

 Localized erosion-deposition patterns may have been responsible. Based 

 upon beach profiles, it was determined whether beach stations had built 

 up or been eroded between surveys. This was compared with abundance 

 data. A significant (p<.05) correlation was found between these vari- 

 ables, (sign test, Tate and Clelland, 1957); i.e., abundances generally 

 increased during calm depositional periods and decreased with beach 

 erosion. Upper intertidal sediments had been eroded at all beach sta- 

 tions before survey II (February), but this was most severe at station 

 B. It is here that relatively few organisms were found (Fig. 20, see 

 also Fig. 4). Localized wave and current patterns along beaches may 

 significantly affect species composition and abundance; e.g., a rock 

 groin is located 170 meters north of station A and wave and current 

 patterns may be different here. Observations of physical events 

 should accompany biological studies in order to help sort out natural 

 versus induced effects on populations. 



Beach replenishment occurred in the spring (22 March to 20 June 

 1977), followed by increases in abundance at all stations the follow- 

 ing summer (Fig. 18). At station A (impacted station) and station C 

 (control) abundances were not significantly different from each other 

 and were similar to those in the previous late summer. Similarities 

 between these impacted and control intertidal stations suggest that 

 deposition effects are not long term. Note that fine sediments were 

 not present in sediment samples from station A 4 months after 

 sediment deposition while they were evident 1 month after deposition 

 at station B (Figs. 8 and 9). This indicates that fine sediments 

 were sorted out of beach material within 4 months after deposition. 

 Concomitant offshore increases in fine sediments substantiate this 

 (Figs. 8 and 9). 



Sampling at station B indicated a possible short-term effect of 

 beach replenishment. Summer populations were sampled just 290 meters 



54 



