 The particulate matter oysters remove are sand, clay, silt, detritus, and phytoplankton.These particulates all could possibly contain harmful contamination that originates from anthropogenic sources (the land or directly flowing into the body of water).Instead of becoming ingested by other filter feeders that are then digested by bigger organisms, oysters can sequester these possibly harmful pollutants, and excrete them into the sediment at the bottom of waterways.