Metal distributions in Tigriopus brevicornis (Crustacea, Copepoda) exposed to copper, zinc, nickel, cadmium, silver, and mercury, and implication for subsequent transfer in the food web.
The marine copepod Tigriopus brevicornis is a benthic microcrustacean inhabiting splashed rock pools in the intertidal zone. The genus has a worldwide distribution, and some species play an important role as a link in trophic webs. It is well established that many crustaceans are able to survive in contaminated environments by storing metallic pollutants in detoxified form, and thus, they may represent a source of contaminants for their predators. The present study was designed to determine the distribution of bioaccumulated metals, both essential and nonessential, with a view to assessing their availability to the next trophic level. Groups of 1000-1500 adult copepods were exposed for 1-14 days to Ag, Cd, Cu, Hg, Ni, and Zn in water. Three concentrations, chosen to be realistic in comparison with those encountered in polluted environments, were tested for each metal. Copepods were homogenized and metals were analyzed in supernatants (i.e., metals stored in soluble form in soft tissues or easily remobilized from the exoskeleton) and pellets (including metal-rich detoxificatory granules or with cellular debris) recovered after centrifugation. Another experiment, consisting of desorption tests, was designed to evaluate the fraction of metals loosely bound onto the exoskeleton. The bioaccumulation ability is highly variable, as shown by the ratios between the concentrations reached in T. brevicornis experimentally exposed to different metals (at higher dose and at day 14) and those in controls (7, 12, 18, 26, 53, and 99, respectively, for Zn, Cu, Ni, Cd, Ag, and Hg). Cu, Zn, and Ni concentrations in copepods increased linearly with time over the whole range of exposure concentrations, whereas a plateau body metal concentration was reached with time particularly at the highest exposure concentrations for Cd, Ag, and Hg. Metals bound onto the exoskeleton were remobilized to different extents, the percentages of desorption being 11, 14, 16, 19, 31, and 32, respectively, for Zn, Cd, Cu, Ni, Ag, and Hg. Metals mainly present in the supernatant (Cd, Ni, Zn) are probably more able to be transferred along a food chain than those which were equally distributed between soluble and insoluble fractions (Ag, Cu, and Hg).
Barka
Sabria
S
Institut Océanographique, LPEM, CNRS/GDR 1117, Paris, France. sabriabarka2@yahoo.fr
Pavillon
Jean-François
JF
Amiard-Triquet
Claude
C
D000818:Animals; D002104:Cadmium / Q000032:analysis / Q000493:pharmacokinetics; D033342:Copepoda / Q000378:metabolism*; D003300:Copper / Q000032:analysis / Q000493:pharmacokinetics; D004784:Environmental Monitoring; D020387:Food Chain; D008628:Mercury / Q000032:analysis / Q000493:pharmacokinetics; D019216:Metals, Heavy / Q000493:pharmacokinetics*; D009532:Nickel / Q000032:analysis / Q000493:pharmacokinetics; D012834:Silver / Q000032:analysis / Q000493:pharmacokinetics; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics*; D015032:Zinc / Q000032:analysis / Q000493:pharmacokinetics
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D002104:Cadmium; D012834:Silver; D003300:Copper; D009532:Nickel; D008628:Mercury; D015032:Zinc