CYANOBACTERIA PHYSIOLOGICAL RESPONSES TO RESOURCE IMBALANCE IN EUTROPHIC LAKES AS REVEALED BY CELLULAR PIGMENT CONTENT
Phytoplankters can modify both the quantity and composition of their photosynthetic pigments in response to external growth conditions. Phytoplankton taxa may have differing capacities to alter their photosynthetic apparatus to the constantly fluctuating balance between nutrients and light in lakes, thereby resulting in differing competitive advantages under varying growth conditions. Standard microscopic techniques may not reveal changes in phytoplankton physiology to these drivers, especially for small Cyanobacteria cells that commonly dominate in eutrophic lakes. To test this, we quantified both phytoplankton pigments via HPLC and taxonomic biovolume via light microscopy for 30 eutrophic lakes in the agricultural Midwestern US to explore patterns in cellular pigment content across nutrient and light availability gradients. We hypothesized that the proportion of pigments diagnostic of total Cyanobacteria (e.g., echinenone, myxoxanthophyll) under balanced growth conditions would shift towards higher proportions of pigments diagnostic of N-fixing Cyanobacteria (e.g., aphanizophyll, canthaxanthin) under N-limited growth conditions, but the cellular content of these pigments relative to biovolume would increase with decreasing light availability. Principal components analysis revealed that nutrient imbalance was the strongest predictor of Cyanobacteria taxa, whereas nutrient and light interacted to explain variability in cellular pigment content, suggesting that Cyanobacteria may be better adapted to thrive under diverse growth conditions relative to other taxa.
Filstrup, C. T., University of Minnesota-Duluth, USA, firstname.lastname@example.org
Leavitt, P. R., University of Regina, Canada, Peter.Leavitt@uregina.ca
Downing, J. A., University of Minnesota-Duluth, USA, email@example.com
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