Geochemistry of burrow waters vented by a bioturbating shrimp in Bermudian sediments

Waters collected at various times from the burrows of Callianassa spp. shrimp are characterized chemically by concentrations of nutrients, sulfide and organic carbon, intermediate between those of pore waters and overlying waters of Coot Pond, Bermuda. Although the shrimp vigorously flush their burrows, irrigation events are insufficently frequent to maintain a burrow water composition completely like that of oxygenated overlying waters; in instances where departure is extensive, models describing the diffusion of interstitial-water solutes into the water column via burrows would have to take this into account. Measured oxidation potentials are substantially reduced with respect to those of the water column, and relatively high levels of reduced arsenic (As III) are encountered. Burrow irrigation provides a mechanism for the rapid, conservative advection of solutes across the sediment-water interface and therefore is at least partially responsible for the concentration and speciation variations typical of coastal seawater. Of the solutes tested, only total dissolved inorganic arsenic occurs at seawater concentration in the burrows, implying that some specialized mechanism intercepts the diffusion of pore water arsenic into the burrows.