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Occurrence of postmetamorphal bivalves known to have swimming ability is seasonally predictable in surface meroplankton in nocturnally flooding tidal currents near inlets inside the barrier islands of North Carolina. Samples from three stations-Institute of Marine Sciences pieer near Beaufort Inlet, inside Drum Inlet 20 mi N E of Cape Lookout, and inside Lockwoods Folly Inlet 10 mi W of Cape Fear River-were comparable.Ensis directus occurred abundantly from December to June at each of the stations;Tagelus divisus abundantly from May to September and sparsely in December at the Institute pier, and sparsely also at Lockwoods Folly Inlet in September;Solemya velum regularly from April to August at the Institute pier, rarely at Drum Inlet; andSolen viridis sparsely in midsummer at the Institute pier. Though these species are known to swim, no regularly recorded occurrence has ever been documented. A set of non-swimming molluscan species present in the samples were perhaps eroded from nearby source beds by strong currents. At Drum Inlet stationDonax variabilits occurred regularly during summer-fall, andPetricola pholadiformis during winter-spring. At Lockwoods Folly Inlet stationSpisula raveneli occurred regularly during spring-summer. Other species were rare. Seasonal occurrence of these species in the plankton samples remains unexplained. |
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