[Folk and Ward, 1957), a nonparametric Mann-Whitney U test was used 

 to compare mean grain sizes and sorting coefficients. There was a 

 significant difference in mean grain size between beaches with clams 

 and beaches without clams (P = 0.05). Beaches with clams had sand of 

 a smaller grain size. There was no significant difference in the sorting 

 coefficient between beaches with and without clams. 



Tests were made to determine if there was a correlation between clam 

 abundance and grain -size. Samples from all stations were combined to 

 obtain a large enough sample, and a nonparametric Spearman rank correla- 

 tion test was used because the distribution of clams was not always 

 normal. Correlation tests were performed between clams less than 39 

 millimeters long, greater than 39 millimeters long, and all sizes versus 

 mean grain size. Tests were also made to determine correlation between 

 number of clams and sorting coefficient sand. The correlation coefficients 

 (r ) are listed in Table 4. There was no significant correlation between 

 numbers of clams and mean grain size (P = greater than 0.05), but a 

 significant correlation fP = less than 0.05) was found between all sizes 

 of clams versus mean grain size, clams less than 39 millimeters, and 

 the sorting coefficient. There was no significant correlation between 

 clams greater than 39 millimeters and the sorting coefficient. 



Table 4. Correlation coefficients (r ) between 

 clams and sediment parameters. 



Clam size 



Mean grain size 



Sorting coefficient 



All sizes 



0.214 



0.369^ 



<39 mm 



0.098 



0.380^ 



>39 mm 



0.260 



0.133 



1. Significant at P <0.05 



(T^^l^ ^a(0.05) = °-^^^^- 



Slopes of beaches with clams and without clams are listed in Table 5. 

 An estimate of the slopes was derived by smoothing the profile from high 

 water mark to the corrected 0.00 tide level. The Mann-Whitney U test 

 was used, and a significant difference was found between slopes from 

 beaches with clams and without clams (P = less than 0.05). Beaches 

 without clams had a steeper slope than beaches with clams. Graphs of 

 these beach profiles are presented in Figure 4. 



4. Discussion . 



A significant difference in mean grain size was found between beaches 

 with and without clams. The grain size from beaches with clams was smaller 

 (0.25 ±0.09 millimeters) than beaches without clams (0.50 ±0.3 milli- 

 meters). Slopes were significantly steeper for the beaches without clams. 

 The relationship between beach slope and grain size is translated into 



20 



