High concentrations of complexed metals in the guts of deposit feeders

cited By 32International audienceSediment particles passing through the guts of deposit feeders are subject to an environment unusually rich in dissolved organic material, especially proteinaceous materials, capable of binding metals. Concentrations of many heavy metals are high in gut fluids of various deposit feeders from pristine environments. Concentrations of Cu and Cd show strong correlations with total acid-hydrolyzed amino acids (TAHAA) in gut fluids in a cross-phyletic survey of 35 deposit feeder species. Similar correspondence with TAHAA obtains among individuals, along longitudinal gut sections, and among molecular weight fractions. Multiple incubations of sediments with a commercial protein solution having similar TAHAA concentration as gut fluid solubilized many metals, showing convergence toward similar composition as gut fluid. Adherence of gut-dissolved metal concentrations to the Irving-Williams order suggests that the rich milieu of soft ligands contained in gut fluids provides a mechanism for mobilization of softer metals in sediments

Bioavailability of sedimentary contaminants subject to deposit-feeder digestion

cited By 173International audienceContaminants in sediments are less available than their concentrations might imply, but measures of this availability have been generally lacking. Sediments ingested by benthic animals can be expected to undergo a unique chemical environment controlled by the digestive chemistry of the organism. We measured solubilization of sedimentary contaminants-Cu, Pb, and polycyclic aromatic hydrocarbons (PAH)-by digestive fluids extracted from marine invertebrates. Bioavailability of these contaminants, thus measured, is a small fraction of total contaminant loading-typically 1-10%. The amounts of metals solubilized by digestive fluids were orders of magnitude greater than would be predicted from water-solid partitioning with clean seawater, although they correlated well with solubilization by seawater. Digestive fluids from two different animal species solubilized different amounts of metals, indicating that bioavailability varies among species even under constant mode of uptake. High concentrations of solubilizing agents, such as amino acids for metals and surfactants for PAH, in the digestive fluids can explain the enhanced solubilization. This biomimetic approach to contaminant measurement provides the basis for more accurate mechanistic and routine assessments of environmental impact