JPR Advance Access originally published online on June 21, 2009
Journal of Plankton Research 2009 31(9):993-1008; doi:10.1093/plankt/fbp048
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Cyanobacteria and microcystin-LR in a complex lake system representing a range in trophic status: Lake of the Woods, Ontario, Canada
1 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 2 Faculty of Forestry and the Forest Environment, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1 3 Lake of the Woods Fisheries Assessment Unit, Ontario Ministry of Natural Resources, 808 Robertson Street, Kenora, Ontario, Canada P9N 3X9
* CORRESPONDING AUTHOR: eprepas{at}lakeheadu.ca
Received on January 12, 2009; accepted on May 23, 2009
| Abstract |
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Euphotic water samples were collected monthly from 16 sites in Lake of the Woods, Ontario, Canada from July to September, 2006 and 2007. Sites represented a range of inorganic nitrogen and phosphorus concentrations and mixing regimes, which was reflected in the spatial variability in phytoplankton biomass and community composition, and cyanobacterial toxin [microcystin-LR (MC-LR)] concentrations. Nutrient concentrations decreased along a south to north transect, concomitant with distance from the main river inlet at the south end of the lake. Filamentous, nitrogen-fixing Aphanizomenon spp. and Anabaena spp. were dominant at most sites: Aphanizomenon was more abundant at southern sites and Anabaena was more abundant at northern sites. MC-LR was detected at all sites at least once (maximum concentration 0.69 µg L–1). However, there was no correlation between MC-LR concentration and the biomass of Anabaena, a documented MC-LR producer. For the pooled data set, total phosphorus and ammonium concentrations were the two parameters most strongly related with MC-LR concentration. Principal components analysis was used to analyze the data set; it indicated that two factors accounted for 81% of the variability among the 12 environmental parameters tested. Factor 1 represented physicochemical characteristics and phytoplankton biomass and Factor 2 represented Anabaena and Woronichinia biomass.
Corresponding editor: William Li