Metal concentrations and stable isotopic signatures of groundwater and biota in Edgartown Great Pond, MA, US

Estuaries provide critical ecosystem services by supporting biodiversity, maintaining water quality, and supplying seafood resources. Anthropogenic activities introduce trace metals into estuarine systems, potentially threatening these services. Edgartown Great Pond, Martha’s Vineyard, MA, is a shallow, hydrologically restricted estuary hosting abundant benthic primary producers, including seagrasses (Zostera marina, Ruppia maritima) and macroalgae (Polysiphonia sp. and others). We quantified metal concentrations in groundwater entering the pond and analyzed metal accumulation in benthic producers and higher trophic levels. Stable isotope signatures (δ13C, δ15N) were used to reconstruct the food web and determine trophic positions, allowing assessment of metal transfer through the system.
Groundwater inputs contained measurable, though generally low, concentrations of metals including Cu, Zn, Pb, Ni, and Cd, with marginally elevated Cu and Zn in specific coves. Benthic primary producers accumulated all metals at concentrations several orders of magnitude higher than those in groundwater. Food web reconstruction indicated that seagrasses and macroalgae form the base of the EGP food web, supporting herbivores, detritivores, and predators. Regression analysis of metal concentrations and δ15N signatures revealed negative or non-significant relationships for all metals, consistent with biodilution rather than biomagnification.
These results demonstrate that benthic primary producers efficiently sequester metals and limit their transfer to consumers, including humans, reducing pollutant accumulation within the food web. This ecosystem service is critical for maintaining environmental quality and seafood safety. The protection, maintenance, and re-establishment of benthic primary producer populations may be essential to management and restoration strategies for developed coastal systems like Edgartown Great Pond.