Factors influencing the assimilation of arsenic in a deposit-feeding polychaete

We investigated mechanisms leading to the assimilation of particle-bound arsenic (As) ingested by the deposit-feeding polychaete Alitta succinea using a radiotracer approach. The release of As from different particle types into extracted gut fluid or bovine serum albumin (BSA), a gut fluid mimic, was measured. In addition, gut fluid proteins were analyzed by separating proteins via 2D gel electrophoresis, and protein peptide sequences were determined by mass spectrometry. Major ions in the gut fluid were measured by ion chromatography and metals by mass spectrometry. Percentages of particulate As release were related to As assimilation efficiencies (AEs) in polychaetes feeding on different particle types. AEs of As were highest from radiolabeled pure diatoms (72%) and radiolabeled diatoms added to sediment (51%), lower from radiolabeled sediment (10%), and lowest from a radiolabeled iron oxide mineral, goethite (2%). It appears that As release from particles is a necessary but not sufficient requirement of As assimilation. For example, 15% of As was released from goethite into the gut fluid but only 2% was assimilated by A. succinea. Our results suggest that the likelihood of As assimilation is higher when it is bound to an organic compound of nutritional value in the ingested particles.