The Cycle of Living and Dead Particulate Organic Matter in the Pelagic Environment in Relation to Trace Metals

Abstract

The distribution and cycling of many trace elements in the pelagic environment appear to be tightly coupled to biological processes. Therefore, the elucidation of these processes is essential if we are to understand the various interactions between biogenic particles and trace elements. Using particle traps, we have been studying the cycling of total organic material, “living” biomass (as measured by adenosine triphosphate) and various particulate components such as fecal pellets, which represent important potential carriers of many macro-nutrients and trace elements. Our results indicate that most of the macro-nutrients (i.e., C, N and P) are cycled in the upper 200 m of the water column; trace elements such as Cd follow the same pathways. Surface-produced fecal pellets, long thought to be important trace element carriers, appear to be recycled in tilt upper 1000 m of the water column. However, we have found evidence suggesting that significant amounts of fresh pellets are produced from in situ activity leading to variable fluxes of many elements throughout the water column. The distribution of living organic material as measured in “suspended” particulates (i.e., those collected with conventional water bottles) present the usual classical picture, ranging from > 30% of the total suspended organic carbon at the surface to < 2% at 1500 m. However, the rarer, but rapidly sinking particles collected by our traps, indicate that in the deep ocean (i.e., > 1000 m), the living fraction represents > 400 times more biomass than the suspended material.

This paper presents current information concerning the for?mation, make-up, distribution and transport of biogenic particles in the belief that this knowledge will provide greater under?standing of the role of these particles in the cycling of trace elements.