MARINE SNOW AS A POTENTIAL TRANSPORT VECTOR AND SOURCE OF BIOACCUMULATION OF MERCURY IN THE BIVALVE MYTILUS EDULIS

Bioaccumulation of mercury in the aquatic food web is a continuing concern to public health. Extensive research has been conducted regarding the uptake of mercury by various aquatic animals via three main vectors: sediment, food (bioseston) and water, but virtually no research exists with respect to uptake of inorganic Hg or methylmercury from aggregated particulate organic matter. Marine snow composed of transparent exopolymers, plankton cells, detritus and dissolved organic matter has been studied as an effective vertical transporter of nutrients and metals scavenged from the euphotic zone to the benthos. Various aquatic species utilize marine snow as a food source, particularly suspension feeding bivalve molluscs. Therefore, if Hg is incorporated into marine snow these organisms could potentially assimilate and accumulate the heavy metal into their tissues. For this study, marine snow was produced from sieved seawater (210 µm) in 1L glass bottles at 18^oC using the roller-table method. Prior to rolling, water was spiked with inorganic mercury and methylmercury standards. Marine snow was then fed to blue mussels, Mytilus edulis, for a maximum of two hours. Following the assay, feces were collected to analyze for mercury assimilation and the animals were dissected for tissue analysis. Feces were analyzed by cold vapor atomic fluorescence spectrometry (CVAFS). Mussel tissues were analyzed using a Direct Mercury Analyzer (DMA-80). Tissues were analyzed in groups: the mantle and the gill, the foot and adductor muscles, and the visceral mass, thereby defining a total mercury body burden in each animal. Results indicate formation of marine snow increased incorporation of inorganic mercury and methylmercury into particulates compared to unrolled control water. Inorganic mercury data indicates a lack of accumulation from acute exposure. Methylmercury analyses of tissue and feces are being conducted and will be presented at the conference. This research will help to elucidate another important mechanism of mercury transport in the food chain.