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Moffett, JW, Brand LE, Croot PL, Barbeau KA.  1997.  Cu Speciation and Cyanobacterial Distribution in Harbors Subject to Anthropogenic Cu Inputs. Limnology and Oceanography. 42:789-799.: American Society of Limnology and Oceanography   10.2307/2838883   AbstractWebsite

Cu speciation was studied in four harbors on the south coast of Cape Cod, Massachusetts, that are exposed to varying degress of Cu contamination from anthropogenic sources. Copper in waters outside the harbors was complexed by ∼ 10 nM of very strong chelators, twofold higher than ambient Cu concentrations. In Eel Pond (Woods Hole) and Falmouth Inner Harbor, total dissolved Cu concentrations were 7-10-fold higher. However, because the strong chelators were saturated in these two harbors, the free Cu increased by 1,000-fold, from $\thicksim 10^13 M$ to $\thicksim 10^-10 M$ . There was no evidence for any enhanced biological production of chelators in response to the elevated Cu concentrations. However, cell densities of cyanobacteria, which have been proposed as a source of strong Cu chelators in seawater, decline drastically in the high Cu harbors. These trends are consistent with culture studies showing that Synechococcus sp., the predominant cyanophyte in these waters, shows a dramatic decrease in growth rates above a free Cu2+ level of 10-11 M. In Great Pond and Waquoit Bay, which showed no significant Cu contamination or saturation of strong ligands, cyanobacterial cell densities showed little or no decrease. Results suggest that significant anthropogenic inputs of Cu may overwhelm processes occurring in seawater that lead Cu and strong chelator concentrations to approach comparable levels.

Barbeau, K, Moffett JW, Caron DA, Croot PL, Erdner DL.  1996.  Role of protozoan grazing in relieving iron limitation of phytoplankton. Nature. 380:61-64.   10.1038/380061a0   AbstractWebsite

RECENT evidence indicates that iron is a limiting factor in primary production in some areas of the oceans(1,2). In sea water, iron is largely present in the form of particulate and colloidal phases which are apparently unavailable for uptake by phytoplankton(3-5). Several mechanisms have been proposed whereby non-reactive iron may be converted into more labile forms (for example, thermal dissolution(6), photochemical reactions(7,8) and ligand complexation(9)). Here we report that digestion of colloidal iron in the acidic food vacuoles of protozoan grazers may be a mechanism for the generation of 'bioavailable' iron from refractory iron phases. We have demonstrated several grazer-mediated effects on colloidal ferrihydrite, including a decrease in colloid size, an increase in colloid lability as determined by competitive ligand-exchange techniques, and an increase in the bioavailability of colloids to iron-limited diatoms. These results indicate that protozoan grazers may significantly enhance the supply of iron to marine phytoplankton from terrestrial sources.

Barbeau, K, Wollast R.  1994.  Microautoradiography (with Combined Liquid Scintillation) Applied to the Study of Trace-Metal Uptake by Suspended Particles - Initial Results Using NI-63 as a Tracer. Limnology and Oceanography. 39:1211-1222. AbstractWebsite

We report the development of a microautoradiographic method for the study of trace metal-particle interactions in natural waters. This technique, in combination with conventional liquid scintillation counting methods, was applied to surface water samples from the Belgian coastal zone and Scheldt estuary. Ni-63 was used as the metallic radio-tracer. Ni partitioning in our experimental system was shown to be a primarily abiotic process, driven by passive sorption reactions and limited in extent on a 24-h time scale by the slow reaction kinetics of Ni. Small particles (< 1 mum) were important as sorption sites, while large particles exhibited variable and particle-specific scavenging potential.