Nitrogen Constrains the Growth of Late Summer Cyanobacterial Blooms in Lake Erie - Advances in Microbiology

AiM > Vol.3 No.6, October 2013

Nitrogen Constrains the Growth of Late Summer Cyanobacterial Blooms in Lake Erie ()

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DOI: 10.4236/aim.2013.36A003 6,717 Downloads 11,933 Views Citations

Author(s)

Justin D. Chaffin, Thomas B. Bridgeman, Darren L. Bade

Affiliation(s)

.
Department of Environmental Sciences and Lake Erie Center, University of Toledo, Toledo, USA.

ABSTRACT

Phosphorus (P) is generally considered to be the main limiting nutrient to freshwater phytoplankton productivity. However, recent research is drawing attention to the importance of nitrogen (N) in freshwater eutrophication and N often constrains growth of cyanobacteria in small lakes. In this study we determined phytoplankton nutrient limitation in a large lake, Lake Erie during two growing seasons. During 2010 and 2011, nutrient enrichment bioassays (+P, +N and, +P and N) were conducted monthly from June through September with water collected in Maumee Bay (site MB18) and in the center of the western basin (site WB_C). Nutrient concentrations were monitored every other week. At MB18, total P concentration was often >3 mmol/L and nitrate concentration decreased from >250 mmol/L in early summer to <1 mmol/L in late summer. Nitrogen and P levels were about five-fold less at WB_C. Bioassays indicated that phytoplankton nutrient limitation varied in summer, spatially, and even among phytoplankton groups. For site MB18, +P increased chlorophyll concentration in one of the eight bioassays, indicating that P did not typically limit production. For site WB_C, +P increased chlorophyll concentration in six of the eight bioassays. As a result of very low ambient nitrate concentration (<5 mmol/L) in late summer, +N (without P) increased chlorophyll concentration, suggesting symptoms of N-limitation. The N-fixing cyanobacterium Anabaena became dominant following N-limitation. This study highlights the need to reduce P loading to restore water quality. Furthermore, due to low nitrate concentration, the severity of the cyanobacterial blooms could be worse if not for N-limitation in western Lake Erie.

KEYWORDS

Cyanobacteria; Eutrophication; Nitrogen; Phosphorus; Phytoplankton

Share and Cite:

J. Chaffin, T. Bridgeman and D. Bade, "Nitrogen Constrains the Growth of Late Summer Cyanobacterial Blooms in Lake Erie," Advances in Microbiology, Vol. 3 No. 6A, 2013, pp. 16-26. doi: 10.4236/aim.2013.36A003.

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