During the last year of study, dominance in biota cover had changed 
once again. Although ascidians were still common, especially on the 
channel side of the jetty, algae represented the dominant biota cover in 
1982 (Tables 4 and 5, Figs. 6 and 7). Red algae was much more prevalent 
than green algae, with lush stands of Rk. pseudopalmata, G. folitfera and 
H. musctformis covering the hard substrata. Rhodymenta pseudopalmata 
was more abundant on the exposed side, and it was the most prominent 
alga in the shallower depths (-1 m). Hydroids, such as Dynamena spp., 
Obelta spp., and Sertularta spp., were common on the algae and rocks of 
the exposed side. Hydroids were also common on the channel side of the 
jetty, but to a lesser extent. However, one hydroid (Halocordyle 
ditsttcha) appeared to be more abundant on the channel side than on the 
exposed side. Eudtstoma caroltnense and D. bermudensts were the most 
common ascidians on the rocks during the summer of 1982. 
Cluster analysis of line-transect data on the entire north jetty 
sessile community (Fig. 8) supports the hypothesis that the overall 
community structure changed substantially over the four-year period. 
All stations sampled in the first year grouped together with a 
relatively high degree of similarity in faunal and floral composition 
(Group 1). Within that group, the inner stations were more similar to 
each other than to the outer stations, indicating differences in 
community composition between those station groups. These differences 
were probably related to the 6-month difference in time of rock submer- 
sion and the difference in the number of levels sampled at the outer 
stations. With one exception (NPO; SU, 1980), community structure in 
1979 was relatively dissimilar to the community structure observed in 
later years (Groups 2 and 3). Station collections from 1980 and 1981 
formed Group 2, demonstrating more similarity among collections from 
those years than from the first and last years of the study. Within 
that group, 1981 collections were generally more similar to each other 
than to 1980 collections. The two 1980 collections at the inner stations 
remained relatively dissimilar to the other collections in that year and 
in 1981. Community structure at stations sampled in 1982 was very low in 
similarity to the same stations sampled in previous years (Group 3). 
Additionally, there was a distinct separation of protected and exposed 
stations based on faunal similarity. These major shifts in overall 
community composition between years, combined with the documented yearly 
changes in dominant biota cover (Figs. 6 and 7) strongly suggest that the 
sessile community on the jetty rock had not stabilized by the fourth 
year after construction. 
(b), South Jetty 
Species composition and structure of the sessile 
community on the south jetty also changed considerably between sampling 
periods (Tables 6 and 7, Figs. 9-11). Additionally, many of these changes 
differed from those noted on the north jetty, primarily because this 
jetty was sampled seasonally during the first year after construction. 
The initial May 1980 assessment documented that the intertidal rocks 
were still relatively devoid of fauna, and algal coverage in that zone 
was only moderate (Figs. 9 and 10). The dominant algae were Porphyra sp. 
30 
