The Distribution of Macrobenthos in Barataria Basin, Louisiana

Macrobenthos and environmental variables were measured in the Barataria basin, Louisiana, at 32 stations in November 1978. Three of the stations (Lake Salvador, Little Lake and St. Denis Bayou) were sampled bimonthly from November 1977 through November 1978. Abundance, diversity, and biomass results indicated two different areas: fresh, low-salinity habitats in the upper and middle basin with high biomass, abundance, and diversity, and high-salinity habitats in the lower basin with low biomass, abundance, and diversity. Over the whole basin, crustaceans were the most abundant organisms, while the mollusks dominated the biomass. Insects, nematodes, and oligochaetes were characteristic of freshwater habitats, while polychaetes occurred in saline waters. Seasonal variation in abundance seemed to be regulated by salinity, while seasonal biomass changes were dependent only on the biomass of Rangia cuneata. Numerical classification was used to analyze spatial and temporal patterns. The natural and modified environments sampled clustered into distinctive groups. The . natural stations further clustered into open water and bayou areas. The analyses also indicate a distinctly different seasonality between Middle Lake Salvador, Little Lake, and St. Denis Bayou. Benthic abundance and diversity in freshwater stations are similar to those in the Atchafalaya delta, while higher salinity stations were similar to those in Lake Pontchartrain. The results support the idea that benthos are an important food source for nekton and that benthic populations are partially regulated by nekton. Peak benthic biomass coincides with the heaviest use of the area by migrating nekton. Benthic populations are lowest in the lower basin where predation is probably highest