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theses

Barnegat Bay-Little Egg Harbor (BBLEH) is a highly eutrophic estuary on the New Jersey coast that has experienced parallel seagrass loss in past decades. Further damage to the ecologically and economically important seagrass communities are likely to occur as eutrophication continues. Previous eutrophication studies in BBLEH have not addressed the sediment chemistry, and therefore could be missing a critical component in understanding the current, and potential future, health of the estuary. Of particular importance is the possible accumulation of toxic dissolved sulfide in sediment pore waters. This study investigated the impacts of eutrophication on sedimentary sulfide as a threat to seagrass populations and the underlying redox state and buffering capacity of the sediments in controlling sulfide accumulation in BBLEH. Sediments in BBLEH are becoming sulfidic year-round within the top 7cm. Sulfide accumulation is low in summer and fall (below 250µM) but concentrations reach 2000µM in spring throughout the estuary. Concentrations are similar between barren and seagrass sediments. However, dissolved H2S and Fe2+, and solid phase Mn, U, and Mo indicate that sediments in the northern, more eutrophic, segment are more reducing, transition to an anoxic state and begin to accumulate H2S at shallower sediment depths (2-4cm), where it is more likely to intrude into seagrass roots, than in the central and south segments (4-7cm) of the estuary. Furthermore, Fe-S chemistry suggest that reactive Fe is lower in the north with Fe-oxyhydroxides and FeS having been converted to pyrite, while Fe-oxyhydroxides and FeS are still present in the central and south segment. Thus, the buffering capacity has been exhausted and sulfide removal is diminished in the north, but not in the central and south. This study shows that continued eutrophication since the 1990’s has made the northern segment of the BBLEH more susceptible to future sulfide toxicity, thereby posing a greater threat to the survival of seagrass in that region. Findings suggest that greater emphasis needs to be placed on sediment conditions that may negatively impact seagrass and coastal ecosystems in future eutrophication assessments.

ETD_6131

doi:10.7282/T3GT5PWJ

M.S.

Includes bibliographical references

by Nicole L. Waite

ETD graduate

The author owns the copyright to this work.