Bioaccumulation of Mercury (Hg) in "Agihis" (Donax sp.) Shellfish: Contamination from a Trophic Ecology and Human Health Perspective

Abstract

INTRODUCTION

"Agihis"(Donax sp.) is an important small shellfish bivalve mollusk that is fed to mud crabs and prawns in fishponds in Hinatuan and Bislig in Surigao del Sur. These are fed to prawns and mud crabs as fattener and alternate to commercial feeds. The crabs and prawns from Hinatuan and Bislig have been exported to other countries in the world. As sediment dweller mollusk, "Agihis" is exposed to heavy metals like Hg that are coming from the riverine system in terrestrial areas where small-scale gold mining activities are existing.

METHODS

Total Hg contamination in sediments and tissues of "Agihis" were determined to define and measure the presence and effects of pollutants on the aquatic system. The density distribution and biomass of "Agihis was determined. This is along with the physicochemical parameters of waters in Hinatuan and Bislig bays.

RESULTS

Results of the study showed that all physic-chemical parameters in both bays are favorable for the growth of aquatic organisms dwelling both in water and in sediments.

While the density of “Agihis” in two bays differ significantly. Meanwhile, the biomass has no significant difference. "Agihis" in Hinatuan is heavier than in Bislig attributed by the larger size. With high densities and biomass of "Agihis" in two bays, itis concluded that there is still an abundance of "Agihis" shellfish in two bays. The results obtained in the current study reveal that Hg concentration in sediments of Hinatuan and Bislig bays are currently low. Bislig bay sediment is lower in Hg concentration than in Hinatuan Bay.

DISCUSSIONS

Hg values in sediments are well below the prescribed ERL value (0.15Âμg g-1), sediment-dwelling biota, "Agihis" are also low in terms of Hg in the body tissues. Concentration is also lower than the European Union maximum permissible value (0.5Âμg g-1) and USEPA for mollusk tissue residue, which is the maximum tolerable intake levels. Nevertheless, it is recommended that constant monitoring will be done for heavy metal concentration in sediments and tissues ofmollusks in the two bays.