Community structure of macro-zooplankton in Trinity and Upper Galveston Bays : with special reference to the cooling water system of Cedar Bayou Electric Generating Station

Abstract

Macro-zooplankton were sampled bi-weekly from October 1969 through May 1973 at 16 stations in Trinity and Upper Galveston Bays, including intake and discharge areas of the Houston Lighting & Power Company's Cedar Bayou Electric Generating Station east of Baytown, Texas. Hydrological measurements including water temperature, conductivity and dissolved oxygen accompanied each biological sample. Sampling sites and species were grouped by cluster analysis using Canberra metric dissimilarity-measure and flexible sorting. The presence of two major seasons in each year based on taxon composition and abundance was revealed by cluster analysis. Sites were more similar to each other within a year than they were between years. Differences between years correlated with variation in salinity and fresh water inflow. Community structure indices (Shannon diversity, species richness and "evenness") were applied to the seasonal data. Shannon diversity and "evenness" were positively correlated with each other, but richness values were often negatively correlated with the other two indices. Low Shannon diversity and "evenness" values at stations in the warm seasons were attributed to dominance by a single taxon, brachyuran zoea. Changes in macro-zooplankton distribution and abundance were correlated with natural and man made changes in the ecosystem. No major changes during the period of study were attributable to the cooling water system of the power plant.