Twiss, M. R.. Department of Applied Chemical and Biological Sciences, Ryerson Polytechnic University, email@example.com
Auclair, J. R.. INRS-Eau, Université du Québec, Jean-Christian_Auclair@INRS-EAU.UQuebec.ca
Charlton, M. N.. National Water Research Institute, Environment Canada, Murray.Charlton@CCIW.ca
IRON-STIMULATED PHYTOPLANKTON PRODUCTIVITY IN THE SURFACE WATER OF EASTERN AND CENTRAL LAKE ERIE DURING THERMAL STRATIFICATION: AN INVESTIGATION USING TRACE METAL CLEAN TECHNIQUES
Following an observation in 1996 that 20 nM Fe additions greatly stimulated primary productivity at a pelagic Lake Erie station (Auclair and Twiss, ASLO-97), we tested further the hypothesis that phytoplankton productivity in pelagic Lake Erie is limited by low iron bioavailability. Simultaneous phosphorus (200 nM phosphate) and iron (20 and 200 nM) enrichment experiments carried out in July 1997 and August 1998 at three pelagic stations revealed that phosphorus enrichment alone stimulated phytoplankton growth. However, phytoplankton yield was greater in combined phosphorus and iron amended experiments relative to phosphorus-enriched treatments. Delayed water column stratification in 1997 and enhanced wind-induced vertical mixing in 1997 and 1998 may have prevented severe iron limitation in the phytoplankton community as surface waters were mixed with Fe-rich hypolimnetic waters. The results from these field experiments over 3 field seasons, and the heterogeneous distribution of dissolved iron in the pelagic surface waters, suggest that Fe limitation was a rare event, having been observed only once in seven experiments. It is hypothesized that Fe limitation may be more prevalent during thermal stratification in the deeper Great Lakes (e.g. Lake Ontario).
Day: Thursday, Feb. 4
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