Their model involves random colonization of empty spaces compensating for 
random local extinction in other spaces. Prey species become established first 
followed by predator species. The predator then proceeds to drive the prey to 
local extinction just as a new "patch" is being formed. Although patchiness 
is well known in #. talpotda and Donax spp. populations, the patches are 
generally fairly discrete and long lived (Efford, 1965, Dillery and Knapp, 
1970; Diaz, 1974). In addition, C. Peterson (University of North Carolina, 
Institute of Marine Science, Morehead City, North Carolina, personal communi- 
cation, 1978) noted that ghost crab populations (as determined by daytime 
burrow counts) did not correlate at all with clumps of Donax spp., E. talpotda, 
or H. canadensis. Thus the community discussed here does not fit the Gurney- 
Nisbet model exactly. Caswell (1978) however postulated a nonequilibrium model 
for predator-mediated coexistence in which no equilibrium condition is reached, 
and no local extinction is required. A combination of the two models and a 
degree of physical moderation probably most clearly explains the community 
structure on the high-energy sandy beach intertidal. When clumping is present 
it is probably the result of physical parameters on the beach. This clump is 
not a static group of individuals but an aggregation that gains and loses new 
members constantly via littoral drift (Dillery and Knapp, 1970). These groups 
are never preyed upon to extinction; as populations increase the patches meld 
together until the populations of both HF. talpotda and Donax spp. completely 
fill the swash zones for the entire length of the beach (Leber, 1977). When 
this condition is reached, predation by migrating consumers is greatest, and 
population numbers of the intertidal organisms are kept from exceeding the 
spatial carrying capacity of the intertidal zone. 
e. Symbiosis. There was one visable example of symbiosis on the sandy 
beach during the study. It consisted of a colonial hydroid which was found 
occasionally on the posterior ridge of both species of Donax spp. The infes- 
tation was distributed equally between the two species on both beaches and 
affected up to 10 percent of the samples collected in late spring and early 
summer. The hydroids generally disappeared by late summer and were never 
found in individuals collected during the winter. Leber (1977) tentatively 
identified this hydroid as Clytta bakeri; however, it is more likely a new 
species of Lovenella (C. Lytle, personal communication, 1978). 
Leber (1977) called the relationship commensalism. T. Wolcott (North 
Carolina State University, Raleigh, North Carolina, personal communication, 
1977) originally thought that the relationship was more mutualistic, the benefit 
to Donax spp. being that nematocysts of Lovenella sp. might prove to be a 
deterrent to predators. Wolcott's feeding experiments revealed that ghost crabs 
are not affected by the nematocysts and, if anything, are better able to catch 
the Donax spp. because the large growth of Lovenella sp. impares the digging 
efficiency of Donax spp. If this is so the Lovenella sp. and Donax spp. asso- 
ciation is parasitic. 
Lovenella sp. was always low in colony number and, due to its diminutive 
size, small in biomass. It was not apparent on the beach after nourishment, 
but neither was its host. For that reason the impact of nourishment upon this 
relationship and upon the Lovenella sp. was not determined. 
IV. SUMMARY 
The beach at Fort Macon State Park was nourished with dredged materials 
obtained from the Morehead City State Port Harbor deepening and widening project. 
35 
