Intestinal Solubilization of Particle-Associated Organic and Inorganic Mercury as a Measure of Bioavailability to Benthic Invertebrates

Abstract

The bioavailability of particle-associated inorganic mercury (HgI) and monomethylmercury (MMHg) was evaluated in vitro using digestive fluid of the deposit feeding lugworm, Arenicola marina. Digestive fluid, removed from the midgut of the polychaete, was incubated with contaminated sediment, and the proportion of HgI or MMHg solubilized by the digestive fluid was determined. Digestive fluid was found to be a more effective solvent than seawater in solubilizing particle-associated HgI and MMHg. A greater percentage of MMHg than HgI was solubilized from most sediments, suggesting that sediment-associated MMHg is generally more readily available from sediment for biological uptake. The proportion of MMHg released from the sediment was inversely correlated with sediment organic matter content, decreasing exponentially with increasing organic matter content of the sediment. The results for HgI were equivocal. MMHg bioaccumulation factors (BAFs) from previous studies showed a similar trend with organic content of sediment, suggesting that solubilization may be the process limiting the bioaccumulation of particle-bound MMHg. It is concluded that in vitro extraction with a deposit feeder's digestive fluid provides a potential tool to study the process of Hg bioaccumulation via ingestion routes, although its application to various sediments and organisms needs further investigation.

Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery

“…The digestive lining of fish has been reported to be permeable to MeHg after ingestion of prey and can then accumulate MeHg in all organs (36). Particulate MeHg is also a major source of Hg to bivalves and other benthic invertebrates because of its high assimilation efficiency from ingested sediment-associated particles (37,38). However, the bioavailability of MeHg bound in keratinous material (e.g., hair and feathers) during digestion is largely unknown and merits future investigation because of its potential ecological relevance for nearshore environments, such as that at Año Nuevo.…”

Sediment Extraction Using Deposit-Feeder Gut Fluids: A Potential Rapid Tool for Assessing Biaccumulation Potential of Sediment-Associated Contaminants

“…In order for a contaminant to be accumulated via ingestion, it must generally be desorbed from the ingested particle and solubilized in the fluids of the gut lumen. Recent studies have shown that in vitro incubation of contaminated sediment with deposit-feeder digestive fluid and quantification of contaminant that is extractable in that fluid often provides a reliable measurement of bioavailability (Mayer et al 1996;Weston andMayer 1998a, 1998b;Lawrence et al 1999;Mayer, Weston, and Bock 2001). This measure is consistent with more traditional approaches for measuring bioavailability (Weston and Mayer 1998b) and is a good predictor of contaminant bioaccumulation (Weston and Maruya 2002).…”

“…A second possibility is a change in solution-phase behavior of the solubilizing agents in seawater upon their association with contaminant materials. Some indication of this behavior has been found for certain metals (especially cadmium and mercury, so far), which show an initial dissolution from sediment followed by readsorption (Chen and Mayer 1999;Lawrence et al 1999). This behavior might result from destabilization of protein ligands by the metals, resulting in greater adsorbability of the protein.…”

“…As the percentage of organic carbon among the sediments increased from about 0.1 to 1.4 percent, benzo[a]pyrene solubilization decreased from 52 to 13 percent. Solubilization of methylmercury by digestive fluid has also been shown to be inversely related to organic content (Lawrence et al 1999). As organic carbon content among four sediments increased from 1 to 16 percent, methylmercury solubilization decreased from 38 to 3 percent.…”

Bioavailability of Metals in Contaminated Sediments

“…Extraction with digestive fluid of A. marina has been shown to be a good predictor of mercury bioaccumulation by the deposit feeding amphipod Leptocheirus plumulosus (Lawrence et al, 1999). Gut fluid extractions can be conducted on bulk sediment samples and on the residue from metal fractions produced by sequential extractions.…”