Date of Award
Program or Major
Doctor of Philosophy
Frederick T Short
The potential of eelgrass, Zostera marina L., as a sentinel indicator of lead (Pb) pollution in the water column was investigated. Eelgrass was grown in mesocosms that contained ambient sediment collected from sites near the Portsmouth Naval Shipyard Jamaica Island Landfill (JIL) of Kittery, Maine, to test viability of eelgrass in the Shipyard's marine sediment. Eelgrass was also grown in mesocosms at three shoot densities in marine sediment of three Pb concentrations to determine to what extent Pb affects eelgrass growth and whether Pb uptake by eelgrass is affected by plant density. Additionally, eelgrass was used to detect water-borne sources of Pb. Eelgrass was deployed in the water column adjacent to water seepages along the JIL to see if Pb could be detected and whether the seepages near the JIL were indicated as sources of Pb to the estuary.
Mesocosm research showed that eelgrass grew well in Shipyard marine sediment, however physiological evidence indicated eelgrass experienced some level of toxicity when exposed to high levels of Pb. Shoots growing in sediment with high Pb concentrations had significantly lower levels of chlorophyll and low Fv/Fm values. Additionally, as shoot density increased, Pb uptake decreased in both rhizomes and leaves of shoots growing in Pb enriched sediment, indicating a density effect on Pb uptake.
Leaves of deployed eelgrass accumulated Pb relative to reference shoots (with background Pb levels) at five of the six stations sampled. Highest Pb concentration occurred in shoots that were deployed closest to water seepages, suggesting that the seeps were a source of Pb and that eelgrass tissue Pb reflected Pb exposure. Analysis of stable isotopic composition of Pb in deployed eelgrass leaves and Pb in seep water and sediment indicated that two seepages near JIL were sources of anthropogenic Pb to Jamaica Cove.
If eelgrass habitat is restored in Pb contaminated sediment, high eelgrass densities could be planted to bioaccumulate Pb, while maintaining a low tissue Pb burden per plant. Additionally, using Pb isotope ratios in eelgrass expands the use of eelgrass as a sentinel accumulator in the detection of water-borne sources of Pb.
Hoven, Heidi Morrill, "Eelgrass (Zostera marina L) as a sentinel accumulator of lead in Portsmouth Harbor, New Hampshire - Maine" (1998). Doctoral Dissertations. 2044.