Toxic Sulfide Pub

Toxic Sulfide Concentrations in the Sediments and Water Column of the Suwannee River Estuary and Its Influence on Hard Clam Survival

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Summary

The hard clam Mercenaria mercenaria is an important aquaculture species that is grown to market size in estuarine environments. Hydrogen sulfide, a natural metabolic poison known to decrease the survival and growth of many bivalve species, is often produced as a byproduct of organic matter decomposition in marine soft bottoms particularly in estuaries prone to periodic or sustained eutrophication. This study combined field surveys and laboratory experiments to de4termine whether sulfide is present in hard clam aquaculture areas and whether sulfide decreases the survivorship of two class sizes of hard clams used in field aquaculture areas in the Suwannee River estuary. Sulfide was found in sediment porewater near and within high density lease areas (HDLAs) at concentrations averaging 0.079mM and as high as 0.567mM. The Derrick's Key, Gulf Jackson and Horseshoe Beach HDLAs were found to have significantly higher sediment porewater sulfide concentrations than the Pine Island and Pelican Reef HDLAs. Sulfide concentrations did not tend to vary predictably with sediment organic matter content, sediment grain size or most water quality parameters. Sulfide did vary predictability with salinity at some HDLAs. The survivorship of hard clam nursery seed (4-6mm) and grow-out seed (12-15mm) was reduced when exposed to sulfide in laboratory experiments. Addition of the antibiotic chloramphenicol tended to increase hard clam survivorship, suggesting that sulfide indirectly affects hard clam survivorship by facilitating bacterial proliferation. It was concluded that sulfide is present in the sediments of Florida's hard clam aquaculture areas at concentrations capable of reducing hard clam survivorship. However, with our current understanding, predicting which HDLAs and which lease areas within an HDLA area most at risk and when they are most at risk for potential toxic sulfide levels will require sampling of sediment porewater at specific planting locations and planting times.

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