Dissolved Trace Metals in Lakes Superior, Erie, and Ontario

Abstract

In spite of continuing large inputs from anthropogenic sources, average concentrations of many trace metals in the Great Lakes remain quite low: 2.8-4.5 ng L -1 for Cd, 3.2-11 ng L -1 for Pb, and 87-277 ng L -1 for Zn. These metals are rapidly scavenged by the seston (suspended particulates) and have a rapid turnover rate in the water column. Factors that affect the distribution of dissolved trace metals include water depth, seston abundance, and biological processes. Higher concentrations are generally found in nearshore stations and especially near the urban centers and polluted river mouths. In summer, there is a marked depletion of Zn (and other bioactive metals) in the epilimnion of the offshore waters. The patchiness in the concentrations of the metals is attributed to spatial differences in the biological processes. With the exception of Cr, there is no systematic increase in concentration down the drainage basin from Lake Superior to Lake Ontario. Most of the Pb, Cd, and Zn loadings into the lakes are retained in the basin, but there is a significant export of dissolved Cu, Ni, and Cr via the St. Lawrence River.

Phosphorus and trace metal limitation of algae and bacteria in Lake Superior

“…The most conservative interpretation of our results is that even very small P-induced growth demands of only about 0.1 d Ϫ1 (doubling time ϳ7 d) cannot be met by the available iron. Dissolved iron in Lake Superior is highly dynamic in space and time (Nriagu et al 1996). In particular locations, there is a pronounced spatial gradient from nearshore to offshore, with concentrations in excess of 100 nmol L Ϫ1 near river outflows but consistently low concentrations of Ͻ5 nmol L Ϫ1 offshore (Sherrell et al unpubl.…”

“…Several early studies of Lake Superior pointed to the potential importance of bioactive metals to algal dynamics (Schelske et al 1972;Shapiro and Glass 1975). The possibility of metal limitation in the Laurentian Great Lakes was made even more compelling through the work of Nriagu et al (1996), who used metal-clean techniques and reported far lower concentrations of trace metals than previous, probably contaminated, studies (Table 1). Coincident with the work reported here, we used highly sensitive analytical techniques (Field and Sherrell 2003) to determine trace metal concentrations in Lake Superior (Table 1).…”

Diurnal variations of trace metals and heterotrophic bacterioplankton concentration in a small boreal lake of the White Sea basin

“…Less in known about the fate of trace metals, except those involved in redox cycles linked to photoreduction that has been extensively investigated (McMahon, 1969;Emmenegger et al, 2001). There is a large body of literature on trace element geochemistry in temperate lakes (e.g., Hamilton-Taylor and Willis, 1990;Noel et al, 1990;Balistrieri, 1992;Viollier et al, 1995Viollier et al, , 1997Hamilton-Taylor et al, 1996Nriagu et al, 1996;Falkner et al, 1997;Albe´ric et al, 2000), including detailed seasonal observations. However the diurnal patterns of trace metal concentration remain poorly investigated.…”

Differential effects of phosphorus limitation on cellular metals in Chlorella and Microcystis

“…Both species are isolated from Lake Erie and represent important classes of primary producers that have been documented in the North American Great Lakes (Munawar and Munawar 1982). The current study was carried out to complement ongoing field studies in Lake Superior, an extremely P-deficient aquatic system (Sterner et al 2004;Anagnostou 2005;Anagnostou and Sherrell 2008) in which Zn cycling has been shown to be particularly intense (Nriagu et al 1996;Sherrell unpubl.). The principal goals of this work are two fold: 1) to investigate how phosphate bioavailability regulates phytoplankton metal quotas for seven bioactive elements (Fe, Mn, Co, Ni, Cu, Zn, and Cd); and 2) to determine whether this regulation is similar or different in a representative eukaryote vs. a cyanobacterium, examples of groups that evolved in very different periods of Earth's geochemical history (Falkowski et al 2004) and have different overall mean metal requirements and metal toxicity sensitivities (Saito et al 2003).…”