An ecological and taxonomic investigation of Ephydatia fluviatilis was conducted . E ., fluviatilis was found in alkaline fresh waters and slightly brackish waters . Extreme variation was found in the gemmoscleres of E . fiuviatilis from different Louisiana habitats . The variation appeared to be ecomorphic and related to the chemical characteristics of the habitats . Laboratory investigations, based on the formation of gemmules by sponges maintained under different conditions were used to determine the nature and extent of this variation . The experimental studies demonstrated that gemmoscleres of different forms can develop in sponges from the same locality if exposed to different environmental conditions and that Ephydatia robusta (POTTS, 1887) as revised by PENNEY & RACER (1968), is synonymous with Ephydatia fuviatilis . Results of these studies demonstrate the difficulty of using such characteristics for the recognition of species, subspecies and other evolutionary units .
*ACKNOWLEDGEMENT
In 2005, Hurricane Katrina produced a distinct, acute ecological disturbance of the benthic invertebrate community of Lake Pontchartrain, LA, USA. The bivalve Rangia cuneata and other community dominants were lost from 50% (815 km 2 ) of the lake bottom. The storm surge directly killed benthic organisms and produced salinity stratification that caused episodes of detrimental low dissolved oxygen concentration at depths >3.7 m. Past disturbance of the bottom by shell dredging and intrusion of higher salinity bottom water through deep shipping channels appears to have contributed to the severity of this impact. Colonization by tolerant opportunistic taxa occurred, but low rainfall after Katrina has slowed the recovery of the typical rangia community. A decrease in water transparency and an increase in turbidity and chlorophyll a were associated with the loss of clam biomass. Other hurricanes may have produced less obvious but similar effects on smaller spatial and temporal scales.
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