ABSTRACT

Twenty-eight modern bottom samples from the Hancock County, Mississippi and Pearl River estuary yielded variable foraminiferal populations (total = live plus dead) during May and June, 1981. Fourteen stations were sampled twice - at "peak" high and low tides.

We identified 22 benthic species of Foraminifera in the samples (counts of approximately 300 specimens/sample); no planktic species occurred. Diversity patterns (S - number of species, H(S) - Shannon-Weiner information function, E - species equability) among the 14 doubly-sample stations indicate the following ranges and averages () exist at high tide: S - 2 to 13, = 7.5; H(S) - 0.311 to 2.046, = 1.25; E - 0.306 to 0.720, = 0.522. Low tide samples have these ranges and averages: S - 2 to 12, 7.0; H(S) - 1.721 to 3.750, = 1.08; E - 0.326 to 0.727, = 0.488. In comparison to low tide samples, high tide ones have a higher species diversity, slightly lower dominance, and are more equable.

Three microbiotopes occur among the 14 stations: (1) beach (B) at 3 stations, (2) lacustrine (L) at 3 stations, and (3) bayou-fluvial (BF) at 8 stations. Among the microbiotopes, the beach marshes have the highest diversity (S = 10), the least dominance (H(S) = 1.36), and are least equable (E = 0.400). Lacustrine environments exhibit the greatest dominance (H(S) = 0.969) and equability (E = 0.635), although the diversity is midrange (S = 6.5). The bayou-fluvial marshes show a lower diversity (S = 6.12) and have midrange values for dominance and equability (S = 1.17 and E = 0.510).

In the beach and bayou-fluvial marshes, arenaceous Foraminifera dominate; however, a calcareous form, Discorbis sp., dominates the lacustrine marshes. Numerical abundance (number of individuals) and the diversity of the less common species appear to cause the greatest differences between microbiotopes.