Trace elements in zooplankton particulate products

Abstract

IT has become increasingly evident that biogenous processes in oceanic surface layers play an important role in removing trace elements from sea water and transporting them to the sediments^1,2. Plankton are strongly implicated in these processes and investigations of the chemistry of these organisms have demonstrated their ability to accumulate trace elements to relatively high levels^3,4. Zooplankton metabolic activity can be expected to enhance the biogeochemical cycling of trace elements through the release of particulate matter³ such as faecal pellets, moulted exoskeletons and eggs. Furthermore, theoretical models^5,6 on the vertical flux of particulates have emphasised the sinking of large particles, similar to those produced by zooplankton, as a mechanism for rapid transport of particulate matter and associated trace elements out of the mixed layer. Nevertheless, little, if any, data exist on (the trace element composition of these biogenic particles, and Boyle et al.⁷, interpreting their Pacific Ocean Cd profiles in terms of probable Cd regeneration from sinking biogenic debris, have stressed the need for information on the trace element composition of planktonic particulate matter. This note reports the concentrations of 18 trace elements in freshly released faecal pellets, moults and eggs from a representative planktonic crustacean. The high levels of many trace elements found in these biogenic products, relative to concentrations in the plankton which produce them, clearly indicate the importance of these particulates in oceanic trace element biogeochemical cycles.