MACROINVERTEBRATE ASSOCIATIONS FROM BEACHES OF SELECTED BARRIER ISLANDS IN THE NORTHERN GULF OF MEXICO - IMPORTANT ENVIRONMENTAL RELATIONSHIPS

Patterns of macroinvertebrate community structure were examined from beaches of three barrier islands in the northern Gulf of Mexico. Between October 1986 and July 1988, a total of 562 box cores were taken, providing 92 separate cases. A rotated Principal Component Analysis (PCA) identified seven major faunal associations comprising the 23 most common species and accounted for 73.7% of the cumulative variance in their transformed abundances. The first two faunal associations included 13 of the 23 species and accounted for 41.7% of the cumulative variance. Seven continuous abiotic variables and eight categorical spatial/temporal variables were considered as possible environmental correlates with faunal associations. Stepwise multiple regressions of PCA scores on standardized environmental variables showed that faunal associations varied with beach exposure, sediment grain-size distributions, seasonality, and tidal zonation. Several faunal associations were better represented on either protected or exposed beaches. Regional and seasonal variation in the expression of faunal associations also were important. A community model that represents faunal associations as independent, but not exclusive of each other, accurately describes these data.