WRRCTMR No.42 Mercury Cycling in a Small Hawaiian Estuary

Abstract

Uptake from food and water and loss of 203HgCl2 were studied in two detritus feeders, the polychaete Nereis succinea and the shrimp Palaemon debilis, from a small Hawaiian estuary. During 1973 to 1974, total mercury analyses were also conducted on sediment and biota samples collected from the estuary. Detritus feeders concentrated dissolved 203Hg from 160 to 310 times over the concentration in sea water. Little 203Hg was accumulated from labelled estuarine sediment; the steady state concentration of 203Hg in the animals was 0.0025 to 0.015 times the concentration in the sediment the animals ingested. Net excretion of 203Hg was slow relative to accumulation in both species. The total mercury content of shrimp and worms collected from the estuary showed a temporal pattern of variation. Samples of shrimp collected at five day intervals were used, with a mathematical description of the accumulation and loss of metal by the shrimp to simulate biotia mercury dynamics in the estuary. The simulation showed that mercury levels in shrimp in the Ala Wai Canal were never at steady state over the 1973-74 sampling period, and indicated the most important source of biologically available mercury in the estuary was some inorganic, solute form of the metal.