Field, and Montgomery (1971) characterized this inshore "turbulent 

 zone" as one with relatively fewer species and greater fluctuations in 

 abundance and composition. Parr and Diener (1978) drew similar con- 

 clusions in comparing 7.6- and 18.3-meter depths on an exposed 

 bottom. Barnard (1963) and Day, Field, and Montgomery (1971) have 

 commented on the absence of gallery- forming faunas on inshore sands 

 where the substrate is not sufficiently compact to permit much deep 

 burrowing and tube building by infaunal organisms. 



2. Biological Factors . 



Sand-bottom communities are not amenable to direct observa- 

 tion and experimental manipulations are difficult. Only one sand 

 beach study by Boaden (1962) is cited by Connell (1974) in his review 

 of field experiments in marine ecology. This lack of information on 

 biological interactions has naturally led to an overemphasis of more 

 easily measured physical-sediment parameters. Correlations with these 

 variables are often weak and questions of causality left unanswered. 



In an analysis of sediment communities from shelf depths along 

 the entire southern California coast, Jones (1969) found shallow-water 

 fauna to be of heterogeneous taxonomic composition and only very 

 loosely defined relationships to physical sediment parameters were 

 evident. Thus, "patchiness" was an integral part of Hartman's (1966) 

 interpretation of these same communities. Rhoads (1974) was the first 

 to measure effects of biological activities on physical -sediment 

 parameters (bioturbation) . Fager (1964) and Mills (1969) showed how 

 single species may influence substrate stability. Diener and Parr 

 (1977) studied a nearshore community dominant tube-building polychaete 

 and found localized effects of increased sediment coarseness and 

 species diversity in its immediate vicinity. Recently, through experi- 

 mental manipulation, studies have documented the significance of key 

 species interactions, habitat modification, predation, and competition 

 (Blake and Jeffries, 1971; Woodin, 1974; Hall, 1977; Virnstein, 1977). 

 Biological activities may be dominant factors underlying observed 

 patterns of infaunal distribution, with an increase in their influence 

 proceeding from the unstable and more physically mediated beach and 

 surf zones to more stable regions offshore. 



3. The Importance of Life-History Information . 



As an adaptation to an unstable habitat, organisms tend to be 

 short-lived (e.g., most beach fauna are annuals; Hedgepeth, 1957), and 

 either have high fecundity with wide powers of dispersal via planktonic 

 larvae or have low fecundity with brood protection of young ensuring 

 a higher rate of survival. 



For those species with planktonic larvae (about 60 percent 

 according to Thorson, 1946) , an unmeasurable source of variation is 



15 



