Seagrasses and macroalgae incorporate land-derived metal pollution while limiting its transfer through estuarine food webs

Estuarine areas provide critical ecosystem services by supporting biodiversity, maintaining water quality, and supplying seafood resources. Anthropogenic activities can introduce harmful metals into estuarine systems, potentially threatening these services. Edgartown Great Pond, Martha's Vineyard, MA, is a shallow, hydrologically restricted estuarine system hosting abundant benthic primary producers, including seagrasses ( Zostera marina , Ruppia maritima ) and macroalgae ( Polysiphonia sp. and others). We quantified concentrations of eleven metals in groundwater entering the pond and analyzed metal accumulation in benthic producers and higher trophic levels. Stable isotope signatures (δ 13 C, δ 15 N) 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, metal concentrations, with marginally elevated concentrations in two 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 pond's food web, supporting herbivores, detritivores, and predators. Regression analysis of metal concentrations and δ 15 N signatures revealed negative or non-significant relationships for all metals, consistent with biodilution rather than biomagnification. These results demonstrate that benthic primary producers may be able to sequester metal pollution and limit its transfer to consumers, possibly reducing pollutant accumulation within the food web. An ecosystem service like this could be 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.