and Enteromorpha sp. (Tables 6 and 7). Kapraun and Zechman (1982) also 
noted these genera colonizing North Carolina jetty rocks during the 
winter and early spring months. Two barnacle species, Chthamalus 
fragtlts and Balanus improvisus, the hydroid Tubularta crocea, and the 
bryozoan Bugula neritina were the only fauna found on the rocks in May. 
Larval recruitment of these species is known to begin in the cooler 
water temperatures which prevailed at Murrells Inlet during the period 
preceding first sampling (Woods Hole Oceanographic Institution, 1952; 
Sutherland and Karlson, 1977), thus accounting for their presence. 
Three months later biota coverage had increased considerably. The 
most abundant three organisms (Cyanophyta, C. fragilis, and B. exustus), 
which had settled on the rocks during the intervening period, were the 
same as those noted on the north jetty at that time (Tables 4 and 6). 
Chthamalus fragitlts and blue-green algae were more prevalent on the 
exposed side during that summer, but by autumn, this difference between 
sides was reduced. Mussel coverage also increased during the summer 
months of 1980, reaching peak densities on both sides by November 
(Figs. 9 and 10). Mussels, barnacles and blue-green algae continued 
to dominate the community in terms of rock coverage until the summer of 
1982 when coverage by most taxa declined. 
Reduced biota coverage on the rocks in 1982 reflected, in part, the 
reduced number of intertidal levels which could be sampled in that year. 
For example, coverage of the intertidal rocks by the mussel B. exustus 
appears to be considerably less in 1982 as compared with the preceding 
sampling periods (Figs. 9 and 10). However, this species was observed 
only in the lower portion of the intertidal zone on both jetties, and 
these sampling levels were buried in sand at the inner stations (SPI, 
SEI) by 1982. Additional causes for the reduced biota cover observed 
on this jetty may include such factors as competition, predation, and 
natural mortality. Even at stations where the lower levels were not 
buried, mussel densities had declined considerably at the lower levels 
by 1982 (Appendices C and D). Additionally, although the rocks at 
higher intertidal levels appeared to be covered with barnacles, close 
inspection revealed that most were just shell plates from dead adults 
and the majority of living specimens were newly settled juvenile forms, 
The natural life span of the dominant species, C. fragilis, is not known 
for this area. However, a 2- to 3-year life span has been noted for other 
barnacle species (Woods Hole Oceanographic Institution, 1952), which 
correlates well with the mortality noted on the south jetty. 
As noted for the north jetty biota, subtidal fauna and flora on the 
south jetty rocks changed considerably over the study period (Tables 
6 and 7, Fig. 11). Three months after completion of rock emplacement, 
several species had colonized the rocks, but the hydroid Tubularta crocea 
dominated in terms of faunal cover. The peak settling period for this 
species is during the spring (Woods Hole Oceanographic Institution, 1952; 
Sutherland and Karlson, 1977), thus explaining early dominance on the 
rocks. By summer, 7. crocea had disappeared from the rocks, probably 
because this species undergoes cycles of activity in temperate areas of 
the western Atlantic, and it is inactive during the summer in South 
Carolina (Calder, unpublished). 
37 
