Species area curves . A general leveling off in the accumulation of 

 species over the six replicate panels is illustrated by species area 

 curves for communities collected at Giants Neck and Effluent (Fig. 9). 

 Similar trends occur at all stations in May and August, when the numbers 

 of species peaked for the year at Effluent and Giants Neck (Fig. 10). 

 Three replicate panels accounted for a low of 74% of the species on six 

 replicate panels in August at Effluent to a high of 95% in August at 

 Giants Neck. Over the year, three replicate panels generally accumulated 

 82% of the species on the six replicate panels and four replicates 

 accumulated approximately 90%. 



Total community estimates . Variance associated with the estimate 



of total abundance for the parameters canopy cover, primary cover, and 



density is reduced quickly with the accumulation of the first three 



replicates and more slowly over the last three (Fig. 11). These trumpet 



diagrams were created by plotting the 95% confidence interval (CI) about 



the mean as a percent of the mean (% = _ x 100). The collection 



mean 

 periods in 1980 and 1981 were selected because they represented peak 



periods for each measurement. 



Canopy cover is the percentage of a panel surface which is covered 



(shaded) by the vertical growth of an attached organism and the CI is 



reduced to 61-74% of the mean after six replicates. Primary cover is 



the percentage of a panel surface which is directly obscured by an 



organism's attachment and the CI is reduced to 28-40% of the mean after 



six replicates. Density refers to the total number of solitary organisms, 



both free and attached, on a panel and has the greatest precision of the 



three parameters with the CI reduced to within 21-23% of the mean after 



six replicates. In comparison, after three replicates these CI's are 



reduced to 94-163%, 57-58%, and 37-64%, respectively. 



21 



