Aquatic Sciences Meeting, Albuquerque 2001

CS39 Trace Metal Limitation of Biogeochemistry

Date: Tuesday, February 13, 2001, Time: 10:00:00 AM

Location: Dona Ana

McKay, R, M, Bowling Green State University, Bowling Green, USA, rmmckay@bgnet.bgsu.edu

Twiss, M, R, Ryerson Polytechnic University, Toronto, Canada, m2twiss@acs.ryerson.ca

Bourbonniere, R, , Environment Canada, Burlington, Canada, Rick.Bourbon@cciw.ca

Trick, C, G, University of Western Ontario, London, Canada, cyano@julian.uwo.ca

Wilhelm, S, W, University of Tennessee, Knoxville, USA, wilhelm@utk.edu

FURTHER EVIDENCE OF TRACE ELEMENT LIMITATION OF PHYTOPLANKTON GROWTH IN PELAGIC LAKE ERIE

An increasing body of evidence supports the concept of trace metal deficiency in freshwater lakes. Of particular note is the observation that levels of bioactive Zn are depressed in surface waters of Lake Erie during the summer thermal stratification. To address this, we conducted field studies in Lake Erie during research cruises in July 1999 and 2000. Diffusion gradient gel (DGT)-probes deployed at a central basin station demonstrated that labile Zn levels were extremely low (0.5 - 2 pM). The significance of the apparent depletion of Zn from surface waters was elucidated from on-deck bioassays. Bottles amended with Zn, Cd or Co did not exhibit increases in biomass over that of control bottles following short-term (22 h) incubation. However, assessment of photosynthetic efficiency demonstrated striking metal stimulated increases (Cd>Zn>Co), particularly among the picoplankton component. These results indicate that phytoplankton productivity is constrained by low availability of these trace metals in pelagic Lake Erie. One interpretation is that Cd and Co can substitute for Zn when Zn is depleted. This supports the observation of a concomitant drawdown in Cd in Lake Erie when Zn levels fall below 2 nM.

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Aquatic Sciences Meeting, Albuquerque 2001

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