(a). North Jetty 
Samples collected during the first summer after north- 
jetty construction contained only 13 of the 23 dominant species, two of 
which, Paradella quadripunctata and Elasmopus levis, were substantially 
more abundant than the others (Fig. 18). Paradella quadripunctata 
reached maximum abundance at the +l-m level and was largely restricted 
to the intertidal zone (Fig. 20). It has previously been recorded only 
from Puerto Rico (Bowman, pers. comm.), where it was commonly found 
on red algae in rocky intertidal environments (Menzies and Glynn, 1968). 
The other dominant, #. levis, was found at all levels, but it was most 
abundant at the MLW and -l-m levels. This species is a known inhabitant 
of rocky intertidal and shallow-water zones of New England and the Gulf 
of Mexico (Bousfield, 1973; McKinney, 1977). 
Densities of both P. quadripunctata and HE. levis were greatly reduced 
by the summer of 1980, and remained low for the rest of the study period 
(Fig. 18). An increase occurred in the number of species collected 
during the second year, with 19 of the 23 most abundant species being 
present. However, the densities of most of these species were lower 
than in other years, with the exception of the gastropod Astyrts lunata. 
This mollusk is a common inhabitant of shallow coastal waters of South 
Carolina (Zingmark, 1978), and was most abundant at subtidal levels 
(Fig. 20). 
By 1981, densities of most species had increased and all of the 23 
dominants were present on the rocks (Fig. 18). Astyrts lunata remained 
abundant, but three species of amphipods were even more common. Caprella 
penantts, morphologically adapted for clinging to fouling biota (Bynum, 
1978), was most abundant at the subtidal levels, as were Erichthonius 
brastltensts and Melitta appendiculata. The latter two species reached 
maximum densities during 1981 along with the ophiuroid Amphtodtia sp. 
All but one of the 23 dominant species were still present on the 
jetty rocks during the last sampling period. Caprella penantts remained 
the most abundant species and, together with the amphipod Corophium sp, 
(probably C. ascherusicum) and two species of isopods (P. quadripunctata 
and Paracerceis caudata), numerically dominated the motile fauna (Fig. 18). 
The two morphologically similar sphaeromatid isopods, P. quadripunctata 
and P. caudata, showed considerable niche separation, with the former being 
found in the intertidal region and the latter being largely restricted to 
the subtidal zone (Fig. 20). Menzies and Glynn (1968) also reported that 
P. caudata occurred mainly among algae, seagrass, sponges and the like in 
subtidal waters. Corophtwn sp. showed significantly greater abundance 
on the protected side of the north jetty than on the exposed side (p < 
0.05, Mann-Whitney U-test), but was the only dominant species to show a 
significant difference. 
Cluster analysis of north jetty suction data provides further evidence 
of annual changes in overall community structure of the motile epifauna 
(Fig. 21). Collections from the four stations sampled in 1979 grouped 
Sy 
