The effect of dissolved organic matter in sea water on the uptake of mixed individual hydrocarbons and number 2 fuel oil by a marine filter-feeding bivalve ( Mercenaria mercenaria)

Abstract

Laboratory studies, using the marine bivalve Mercenaria mercenaria, were performed to examine the role that naturally occurring surfactant dissolved organic matter (DOM) plays in mediating the process of hydrocarbon uptake. The uptake of a simple hydrocarbon mixture consisting of an n-alkane, hexadecane and an aromatic hydrocarbon, phenanthrene was studied as was the uptake of Number 2 fuel oil. Removal of DOM from the seawater uptake media, by activated charcoal, results in: (1) a statistically significant increase in the uptake of hexadecane; (2) no change in the amount of phenanthrene taken up; and (3) a sevenfold increase in the quantity of No. 2 fuel oil taken up by the clam. The uptake of the ‘saturated’ fraction of the fuel oil increased 17 times when DOM was removed and the ‘aromatic’ fraction increased five times. The findings indicate that solubilization of saturated hydrocarbons by the DOM results in their being taken up less readily by the filter-feeding bivalve. When this DOM is removed, these hydrocarbons are retained more readily by the animal's gill due to changes in the hydrocarbons' physical state in seawater. The increase in the uptake of the ‘aromatic’ fraction of fuel oil in the absence of DOM may reflect a co-solubilization of aromatic and saturated hydrocarbon components.