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Long-Term Study of Benthic Communities on the Continental Shelf Off Cameron, Louisiana: A Review of Brine Effects and Hypoxia

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A long-term data set compiled from our studies and a variety of investigations was analyzed to determine the effects of nine years of discharged brine (concentrated salt water) on benthic organisms surrounding a brine diffuser off Cameron, Louisiana (USA). These investigations began three months before brine discharge was initiated in 1981. A preliminary summary by Giammona and Darnell (1990) relied on just three years of discharge data and gave misleading reports of brine impacts.

Brine effects over the nine years of study were minimal, in part because the fine sediments of the study area were numerically dominated by opportunistic species. mostly estuarine taxa, that showed dramatic population fluctuations both spatially and temporally. These fluctuations in benthic densities were the most salient characteristic of the study area. They resulted from summer hypoxia and anoxia in bottom waters, not from brine. The hypoxia was related to Mississippi River discharge and subsequent salinity stratification. Hypoxia eliminated some taxa and severely reduced populations of most benthic species. The only significant differences between communities near the diffuser and those outside the influence of its discharged brine resulted from water-column mixing by the discharged brine, which oxygenated waters around the diffuser and stabilized the salinity of bottom water at the stations near the diffuser. This enhanced benthic diversity around the diffuser and resulted in greater populations during some seasons.

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