The influence of tides on larval availability in shallow waters overlying a mudflat

Levin, LA.  1986.  The influence of tides on larval availability in shallow waters overlying a mudflat. Bulletin of Marine Science. 39:224-233.

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The plankton overlying the Kendall-Frost mudflat (Mission Bay, California) was sampled over four separate 12-h tidal cycles, two during the day and two at night, in order to identify short-term, tidally-induced variations in meroplankton abundance. In daytime samples larvae of four polychaete species and bivalve veligers exhibited a distinct bimodal abundance pattern, suggesting oscillation of a large patch of larvae in the back of Mission Bay. Physical data collected previously support this hypothesis and provide evidence for retention of larvae on or near the adult habitat. Nocturnal samples yielded less consistent, species-specific abundance patterns. Several polychaetes, bivalves and ghost shrimp exhibited peak larval abundances at dusk high tide, brachyuran zoea were released just after high tide and one polychaete exhibited a bimodal pattern similar to the daytime samples. Amphipods and harpacticoid copepods peaked in abundance at low tide. No ontogenetic differences in temporal distributions of precompetent and competent polychaete larvae were observed during the study. The mudflat meroplankton is not a well-mixed soup. Tenfold variations in larval abundance, documented for the polychaete species on an annual and seasonal basis (Levin, 1984), can also be observed at one site within a single tidal cycle. Attempts to estimate larval availability should incorporate short-term tidal and diel variability into the sampling design.