Aquatic Sciences Meeting, Albuquerque 2001

CS39 Trace Metal Limitation of Biogeochemistry

Date: Tuesday, February 13, 2001, Time: 9:45:00 AM

Location: Dona Ana

Sterner, R, W, University of Minnesota, St. Paul, MN, USA, stern007@tc.umn.edu

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

Qin, X, , Bowling Green State University, Bowling Green, OH, USA, xqin@bgnet.bgsu.edu

Smutka, T, , University of Minnesota, St. Paul, MN, USA, smut0005@tc.umn.edu

Brown, E, T, University of Minnesota, Duluth, MN, USA, etbrown@d.umn.edu

Agnich, J, , Univesity of Minnesota, Duluth, MN, USA, etbrown@d.umn.edu

Sherrell, R, M, Rutgers University, New Brunswick, NJ, USA, sherrell@imcs.rutgers.edu

IDENTIFYING FACTORS THAT CONSTRAIN PHYTOPLANKTON GROWTH IN LAKE SUPERIOR: TRACE METALS REVISITED

Limitation of primary production by trace metals is often overlooked in freshwaters. One reason may be that most lakes are subject to strong nearshore and anthropogenic influence. Several recent surveys of metal distributions in the Great Lakes, however, do not support this view. We report here on results obtained following the initial field season of a multifaceted study of trace metal-biota interactions in Lake Superior. Eight stations were occupied during each of 3 research cruises between early June and late September, 2000. Spatial resolution was enhanced by additional underway sampling between stations. Determination of total and dissolved (< 0.45 micron) metals using ICP-MS demonstrated that metals were present at low nanomolar levels with critical bioactive metals such as Fe and Zn ranging between 1-5 nM and 2-4 nM respectively. Low metal levels were underscored by the results of metal-clean bioassays that demonstrated a strong synergistic effect of Fe upon relief of P limitation. Low dissolved Fe was also reflected in the routine presence of the biochemical marker flavodoxin among diatoms sampled at most stations. In addition, the possibility of Zn deficiency was supported by ectoenzyme assay of leucine aminopeptidase and beta-glucosidase activities.

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Aquatic Sciences Meeting, Albuquerque 2001

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