The Influence of Bioirrigation

Near-shore marine environments are complex ecosystems where much of the global benthic flux of metals and nutrients take place between the seawater and sediment (Meile et al, 2003). Bioirrigation is the increase of solute transport resulting from introduction of oxygenated water from the surface into the more reduced environment deep within the burrow. Fe and Mn hydr-(oxides) accumulate on burrow margins in response to the oxygen flux into suboxic porewaters and has been shown to trap trace metals (Harding and Risk, 1986; Tessier and Campbell, 1988; Tessier et al., 1979, 1982). The diagenesis, mobility, and transport of metals may enhance the bioavailability of metals in the environment, possibly to the extent of harming ecosystems, especially in coastal areas with anthropogenic waste. This study assesses Fe and trace metal speciation influenced by bioirrigation in and near burrows collected off the coasts of Georgia and Washington. Overall, this study found that bioirrigation does play a role in metal distribution and retention near burrows, but sediment mineralogy, grain size and organic matter were also significant factors at the studied sites.