MACROBENTHIC COMMUNITY STRUCTURE BEFORE AND AFTER POLLUTION-ABATEMENT IN THE NECHES RIVER ESTUARY (TEXAS)

Macrobenthos and physicochemical conditions in the lower 39 km of the Neches River estuary were studied from August, 1984 to May, 1985. The results were compared with data collected in 1971-1972. Between 1972 and 1984 the permitted BOD waste load in the tidal Neches River was reduced from 123125 kg d to 8717 kg d. River discharge and dissolved oxygen concentrations were consistently higher and salinity was lower, during the same seasons, during the 1984-1985 study. A total of 50 taxa of macrobenthos were collected in 1971-1972 and 104 taxa were collected in 1984-1985. The numbers of taxa per collection at each station in 1984-1985 were at least twice those found in 1971-1972. Minimum densities in 1984-1985 were much higher than the maximum densities in 1971-1972 at all stations. Patterns of dominance, Sorenson's similarity index, and diversity (dBAR) values indicated improved water quality in 1984-1985. Statistical analysis of macrobenthic diversity indicated significant differences between upper estuary and lower estuary stations in 1971-1972. No significant differences were found in 1984-1985. Significant differences in numbers of taxa, macrobenthos densities, and dBAR values between the two studies were found. Reductions of waste loads, increased river discharge, and deepening of the navigation channel were among the factors that probably contributed most to the changes in community structure of the macrobenthos observed.