Influence of food on the assimilation of selected metals in tropical bivalves from the New Caledonia lagoon: qualitative and quantitative aspects.
The present study aimed at examining the influence of food quality and quantity on the assimilation efficiency (AE) of metals in two abundant bivalves in the New Caledonia lagoon, the oyster Isognomon isognomon and the clam Gafrarium tumidum. Bivalves were exposed via their food to the radiotracers of three metals of concern in New Caledonia ((54)Mn, (57)Co and (65)Zn) under different feeding conditions (phytoplankton species, cell density, and cell-associated metal concentration). When bivalves were fed Heterocapsa triquetra, Emiliania huxleyi and Isochrysis galbana, AE of Mn, Co and Zn was strongly influenced by the phytoplankton species and by the metal considered. In contrast, when fed one given phytoplankton species previously exposed to different concentrations of Co, phytoplankton-associated Co load had no influence on the AE and on the retention time of the metal in both bivalves. Metals ingested with I. galbana displayed generally the highest AE in both bivalve species, except for Mn in clams for which the highest AE was observed for H. triquetra. Influence of food quantity was investigated by exposing bivalves to different cell densities of I. galbana (5 x 10(3), 10(4) or 5 x 10(4) cell ml(-1)). As for food quality, food quantity was found to influence AE of Mn, Co and Zn, the highest AE being observed when bivalves were fed the lowest cell density. Overall, results indicate that the two bivalve species are able to adjust their feeding strategies according to the food conditions prevailing in their environment.
Hédouin
Laetitia
L
International Atomic Energy Agency, Marine Environment Laboratories, 4 Quai Antoine Ier, MC-98000 Principality of Monaco, Monaco.
Metian
Marc
M
Lacoue-Labarthe
Thomas
T
Fichez
Renaud
R
Teyssié
Jean-Louis
JL
Bustamante
Paco
P
Warnau
Michel
M
D000818:Animals; D049872:Bivalvia / Q000737:chemistry / Q000378:metabolism*; D017753:Ecosystem; D005502:Food; D008670:Metals / Q000032:analysis / Q000378:metabolism*; D009510:New Caledonia; D010839:Phytoplankton; D011868:Radioisotopes / Q000032:analysis; D014329:Tropical Climate
D008670:Metals; D011868:Radioisotopes