OUVER ET AL.: RELATIONSHIPS BETWEEN WAVE DISTURBANCE AND ZONATION 



3000 



2000 



1000 



A — A Sand Flat 1971-75 

 o — o Sand Flat Dec. 1972 

 n--n Canyon Dec. 1972 



A 4500 



CRUSTACEA 



3000 r 



Figure ll. — Variations in abundance of crustaceans and 

 polychaetes along the canyon ridge ( A-D) and sandflat transects 

 (M) in December 1972, and along the sandflat from 1971 to 1975 

 in Monterey Bay, Calif. 



Eohaustorius sencillus, Euphilomedes car- 

 charodonta) . Finally, several polychaetes (Noth- 

 ria elegans, Amaeana occidentalis , Lumbrineris 

 luti, Magelona spp.) that were common in deeper 

 water were most abundant at ridge stations B and 

 especially A (farthest from sediment slumping). 



There were only a few statistically significant 

 correlations between the abundance of individual 

 species along the sandflat and canyon transects 

 (P<0.05). Since the correlations involved four 

 pairs of stations, there were just 2 degrees of 

 freedom in determining the significance of a 

 product-moment correlation coefficient (Snedecor 

 and Cochran 1967). With 2 degrees of freedom, a 

 significant (P<0.05) coefficient must be at least r 

 = 0.95. However, there were more positive corre- 

 lation coefficients computed for the individual 



species than expected by chance alone. Eighteen of 

 the most abundant 23 species (those inhabiting 

 both transects at >l/core) had positive co- 

 efficients. Assuming no correlation between the 

 two transects (i.e., independence), the probability 

 of 18 positive correlation coefficients is 0.019 (sign 

 test, Snedecor and Cochran 1967 ). The probability 

 is less when only the species with relatively dis- 

 tinct zonation patterns are considered (P<0.01). 

 The average correlation coefficient among these 

 species is 0.54±0.12 (95% CL). Therefore, al- 

 though few individual species showed a statisti- 

 cally significant correlation in abundance along 

 the sandflat and canyon transects, there was a 

 significant trend in positive correlation when the 

 abundant species were considered together. 



In summary, benthic community zonation along 

 the gently sloping sandflats (6-18 m) was similar 

 to the zonation along a constant depth transect on 

 the canyon ridge (14 m). This similarity was ob- 

 served despite differences in substrate distur- 

 bance (oscillating vs. unidirectional creeping) and 

 transect lengths (almost 1 km vs. 40 m). 



SEASONAL PATTERNS 



Seasonal changes in polychaete abundance 

 were more regular than those of the crustaceans 

 (Figures 12, 13). The lowest polychaete abundance 

 generally occurred in the late fall and the winter 

 (Figure 12). The most dramatic population de- 



8000 



2 6000 

 \ 



_i 



3 4000 - 

 9 



> 



Q 



M-4(l8m) 



M^/Wli^ ,^,. 



2000 - ft ' ; \ 4 i t , ,-<}>M-2(9nn) 



M-I(6m) 



YEARS 



Figure 12. — Temporal variations in number of polychaete indi- 

 viduals at three depths along the southern sandflat in Monterey 

 Bay, Calif, (means and 95^ confidence limits). 



449 



