The Possible Transport of Trace Metals via Moulted Copepod Exoskeletons1

Abstract

Concentrations of Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, Sr, and Zn in 10 surface‐zooplankton samples were compared with the values determined for 12 samples collected at 100 or more meters. Average values for Cu, Fe, Mn, Ni, Pb, Sr, and Zn were higher in the deep samples. It was postulated that more of these elements had become adsorbed to copepod exoskeletons at greater depths because food‐dependent moulting rates were lower; thus more time was available for elemental adsorption to take place. If this hypothesis is correct, moulted copepod exoskeletons may be important in biogeochemical cycles. Copepods are the most abundant multicellular animals in the world, and there are 11 cast exoskeletons for every adult; these slow‐sinking exuvia may well be capable of taking up elements by adsorption‐exchange long after leaving the living animals. Thus, a large total surface‐area is provided on which important chemical reactions may take place.

Environmental Impact of Cadmium: A Review by the Panel on Hazardous Trace Substances

“…Tables 37 and 38 indicate that marine organisms concentrate cadmium to levels much higher than those in seawater. Concentration factors (ppm in fresh organism/ppm in seawater) appear to be of the order of 6000 for zooplankton [mainly copepods (222) There is little evidence that cadmium is concentrated to a substantial extent in marine food chains. Martin's (222) figure of 6000 for the concentration factor in zooplankton is some seven times those recorded for marine phytoplankton (229).…”

Trace metal assimilation and release budget in Daphnia magna

“…Numerous studies have therefore focused on the flux of dissolved organic carbon (C), nitrogen (N), and phosphorus (P) controlled by zooplankton through such means as excretion, egestion, and sloppy feeding (Lampert 1978;Lehman 1980;Gardner and Scavia 1981;Olsen and Ostgaard 1985). Although it has been documented that a few essential trace metals (such as Fe and Zn) are potentially limiting factors in the primary productivity of several oceanic and freshwater systems (Martin et al 1991;Morel et al 1994;Twiss et al 2000), the biologically mediated regeneration of trace elements in freshwater systems has been less well studied (Twiss and Campbell 1995;Twiss et al 1996).…”

“…When accumulated by the animals, the metals are lost through molting, egestion, or excretion into the ambient environment, or are retained in the animals and usually transferred to higher trophic levels. Molting of the animals might also contribute substantially to metal flux in aquatic systems (Martin 1970). It is well recognized that nutrient cycling driven by zooplankton provides an important source of regenerated nutrients essential for phytoplankton growth (Lehman and Sandgren 1985;Sterner 1989;Elser et al 1988;Persson 1997).…”

Influence of pollution on the harpacticoid copepods of two North Sea estuaries

“…They may take up trace metals, concentrated in detritus, diatoms and bacteria, via the digestive tract or in solution via the body surface (absorption) Peres, 1976), Adsorption of heavy metals to the exoskeleton of copepods (a .o . Euterpina acutifrons) has also been demonstrated (Martin, 1970) .…”