PT20 Ecotoxicology of Tropical Aquatic Environments
Exhibit Hall
8:00 AM - Tuesday
(PT285) Delineation of metal uptake routes in bivalves from the New Caledonia lagoon: a radiotracer study.
Warnau, M1, Hedouin, L1, 2, 3, 4, Metian, M1, Teyssie, JL1, Cotret, O1, Fowler, S1, Fichez, R2, 1 International Atomic Energy Agency, Monaco2 IRD-Noumea Center, New Caledonia3 La Rochelle University, France4 Goro-Nickel, New Caledonia
ABSTRACT- The SW lagoon of New Caledonia is subjected to intense metal input from land-based mining industries exploiting metals such as Ni and, secondarily, Cr and Co. However, as is the case for most tropical environments, little is known about the contamination status of this lagoon. In order to allow a better ecotoxicological characterization of the New Caledonian lagoon, three locally common species were selected for laboratory radiotracer experiments. The objective of the study was to characterize their usefulness as bioindicator species in programmes for local pollution surveys and monitoring. The selected species were the edible clam Gafrarium tumidum, and the oysters Isognomon isognomon and Malleus regula. Bioaccumulation and tissue distribution of six elements (Ni, Cd, Co, Cr, Zn, Ag) were determined following exposures via sea water, sediment and food using radiotracers (Ni-63, Cd-109, Co-57, Cr-51, Zn-65, Ag-110m). Transfer from food was efficient; assimilation efficiencies of metals ingested with phytoplankton ranged between 34 and 77%, and these ingested fractions were retained for long periods of time (biological half-lives from 20 to 400 days). In contrast, in terms of transfer efficiency, sediments were a much less important pathway than sea water: concentration factors from sea water were three to five orders of magnitude higher that transfer factors from sediments. The relative contribution of each uptake pathway to the total bioaccumulation of metals in bivalves was estimated using a mathematical model. Computations suggest that sediment always accounts for only a minor part of the total bioaccumulation in the three bivalves (<3%; except for Cd in the oysters: 20%). In the clams, the predominant uptake route for all metals was the food (95-99%). In contrast, both oysters accumulated Co and Cd mainly from food, whereas sea water was the predominant route for Zn accumulation. The two oysters displayed the same behaviour with respect to all the metals except Ag. The latter element was far more efficiently taken up and retained in the soft parts of I. isognomon than in M. regula. The model indicated that I. isognomon took up Ag mainly from sea water (88%) whereas M. regula accumulated it principally from its food (90%). In conclusion, food and, secondarily, sea water appear to be the predominant routes for the uptake of these metals in the three tropical bivalves investigated.
Key words: tropical bivalves, metal bioaccumulation, new caledonia lagoon, mining activities