The fact that young of the year Donax spp. constituted the earliest 
recruits is significant in that it establishes that this clam breeds offshore 
in its overwintering grounds. Chanley (1969) reported that although adult 
D. variabilts displayed ripe gonads all during the summer, the time of 
breeding had not been established. He reported that the pediveliger metamor- 
phosed at a length of approximately 270 to 350 micrometers and at an age 
greater than 22 days. Results of the present study indicate that the Donax 
spp. breeding season begins in early March when water temperatures first begin 
to rise (Fig. 14). 
Neither adult Donax or their young stages were observed at Fort Macon 
beach during the first spring recruitment following beach nourishment. In fact, 
no Donax spp. were found on the Fort Macon beach until 29 July, nearly 2 months 
after the cessation of nourishment. Those individuals that did return were 
young of the year, but were not from pelagic larval stocks. They were post- 
metamorphal adults which had diffused from another beach via littoral drift 
into the Fort Macon area. The transport of 1.3- to 3.9-millimeter-long post- 
metamorphal Donax spp. in the plankton was observed by Williams and Porter 
(1971). Donax spp. are able to "leap" from the substrate (Ropes, 1967; Ansell, 
1969) and be carried by the current to a suitable new substrate. 
The results of this study indicate that adult Donax spp. were killed in 
their offshore overwintering ground and that beach nourishment activities, 
probably greater turbidity, prevented the normal recruitment of pelagic larvae. 
Adult Donax are not as mobile as F. talpotda, and therefore, probably could 
not relocate to any great extent. Thus adult individuals in the intertidal 
zone were destroyed by burial, while adults overwintering in the nearshore- 
offshore were probably eliminated by high turbidity and burial. The effects 
of burial on Donax spp. are unknown, although death resulting from burial of 
other bivalves has been well documented (Needler and Ingallis, 1944; Glude, 
1954; Smith, 1960; Medcof and MacPhail, 1964; Gallucci and Kawaratani, 1975). 
Absence of Donax spp. from the beach for any extended length of time could 
result in serious ecological consequences. Leber (1977) pointed out that 
Donax spp. contributed up to an order of magnitude greater biomass than any 
migrating consumer, and up to 12 percent of the total available secondary 
productivity. 
c. Haustortus canadensts. Haustortus canadensts was more important in 
the Fort Macon beach community than in the Emerald Isle beach community before 
nourishment. However, it was present and important to both beaches (Fig. 26). 
Population density at the Fort Macon beach was fairly constant before nourish- 
ment, while the Emerald Isle beach exhibited a single population peak. 
The H. canadensts is a burrowing amphipod that normally inhabits wetter 
parts of the beach. Unlike the invertebrates previously mentioned, the 4. 
eanadensts broods its eggs and young and has no pelagic larval life history. 
It is a poor swimmer but a good burrower. The significance of these charac-— 
teristics was evident in the slow recovery displayed by this species on the 
nourished beach. No amphipods had been found on the nourished part of the 
beach until two were discovered along the permanent transect being sampled to 
determine the rate of recovery of a segment of beach. They were discovered 
along a part of the beach close to Beaufort Inlet, Possibly these individuals 
49 
