amphipod and ostracod species have more restricted distributional pat- 

 terns. 



Thorson (1946) discussed the importance of temperature as a critical 

 reproductive cue, and the synchrony o£ spawning with yearly plankton 

 blooms. The monthly temperature and standing stock chlorophyll values 

 at several hydrographic stations in Monterey Bay are shown in Figure 9. 

 Although the chlorphyll data are extremely variable, distinct fall and 

 spring blooms are common in the bay and at this latitude. 



V. EFFECT OF DISPOSAL OF DREDGED MATERIAL ON THE BENTHIC FAUNA 



1. The Control Area . 



There are no published studies of the spatial and temporal variations 

 of the fauna within an exposed subtidal sand-bottom community on the west 

 coast. Barnard (1966) described some shallow-water communities from Santa 

 Barbara to San Diego but no seasonal data were presented. Many of the 

 genera and species listed by Barnard were common to this study. Lie and 

 Kisher (1970) surveyed the benthos off the coast of Washington; the shal- 

 lowest station was at the same depth as the present study's deepest, but 

 he had sampled only once. Temporal studies have been made in other benthic 

 environments on this coast. Jones (1961) studied a mudflat in San 

 Francisco Bay and found that the variations within that community had no 

 seasonal trend. Lie (1968) found no such trends in Puget Sound. On the 

 east coast. Smith (1971) observed no seasonal trend in the changes in com- 

 munity structure on a bottom similar to that in the present study area. 



Masse (1972) investigated the fauna in a number of sand bottoms in 

 shallow waters (1.5 to 11 meters) in the Mediterranean. He discussed 

 three major changes that explain the range of variation in quantitative 

 data: (a) Short-term changes that are often correlated with hydro- 

 graphic or trophic conditions and affect mainly motile macrofauna with 

 little effect on biomass; (b) seasonal changes that are correlated with 

 reproductive and recruitment processes that often vary for different 

 species and have little effect on biomass; (c) long-term changes that 

 are correlated with successful recruitment of new or uncommon species 

 that are irregular and unpredictable events which can affect biomass. 

 For many quantitative data, sampling error must also be added to the 

 list; however, this source of variation can be reduced by establishing 

 permanently marked stations and by prior investigation of sampling meth- 

 odology, including the detection of gross patchiness or spatial heteroge- 

 neity of the fauna. 



A quantitative sampling plan was developed at the 20-meter control 

 station in March 1971 and substantiated in March 1972 (App. A). Eight 

 replicate cores sampled 82 percent of the species of worms present in 

 28 cores; cumulative species diversity stabilized after 4 to 5 cores. 

 Samples of 10 replicates from four progressively larger areas did not 

 differ significantly; the benthos appeared homogeneous along the 20-meter 

 depth contour. Variation among samples at nearly the same time is a good 



29 



