High concentrations of complexed metals in the guts of deposit feeders

Sediment particles passing through the guts of deposit feeders an subject t o an environment unusually rich in dissolved organic material, especially p roteinaceous materials, capable of binding metals. Concentrations of many h eavy metals are high in gut fluids of various deposit feeders from pristine environments. Concentrations of Cu and Cd show strong correlations with to tal acid-hydrolyzed amino acids (TAHAA) in gut fluids in a cross-phyletic s urvey of 35 deposit feeder species. Similar correspondence with TAHAA obtai ns among individuals, along longitudinal gut sections, and among molecular weight fractions. Multiple incubations of sediments with a commercial prote in solution having similar TAHAA concentration as gut fluid solubilized man y metals, showing convergence toward similar composition as gut fluid. Adhe rence of gut-dissolved metal concentrations to the Irving-Williams order su ggests that the rich milieu of soft ligands contained in gut fluids provide s a mechanism for mobilization of softer metals in sediments.