Journal
CHEMOSPHERE
Volume 234, Issue -, Pages 34-42Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2019.06.047
Keywords
Nitrogen; Phosphorus; Phytoplankton; Microcystins; Spring lake; Michigan
Categories
Funding
- Robert B. Annis Educational Foundation
- China Postdoctoral Science Foundation [2019M651754]
- Open Research Fund of Jiangsu Province Key Laboratory of Environmental Engineering [ZX2018007]
- UCAS Joint PhD Training Program
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Due to excessive loadings of nitrogen (N) and phosphorus (P), frequent blooms of harmful cyanobacteria and their associated cyanotoxins pose serious threats to recreational usage and human health. However, whether cyanobacteria growth and toxin production are limited by N, P, or both N + P is still not clear. Thus, we conducted a nutrient enrichment bioassay in situ in Spring Lake, a eutrophic lake in west Michigan, USA, to examine the influence of nutrient limitation on the proliferation of algal blooms and the production of microcystins (MC). N or P addition alone resulted in a slight increase in the concentration of chlorophyll-a (Chl-a), suggesting a positive effect on phytoplankton growth, but alone, neither were sufficient to induce algal blooms. In contrast, the combination of N and P had a significant and positive influence on phytoplankton growth and MC production. Compared to controls, the N + P treatment resulted in high concentrations of Chl-a and MC, as well as high pH and dissolved oxygen. In addition, significant increases were observed in different MC analogues for each treatment; the highest concentrations of intracellular MC-LR, -RR, -YR, and TMC (total MC) were found in the N + P treatment with values of 9.16, 6.10, 2.57, and 17.82 mu g/L, respectively. This study suggests that at least in this temperate coastal lake, cyanobacterial blooms and associated MC are influenced more by combined N and P enrichment than by N or P alone, indicating that managing both nutrients is important for effectively reducing algal blooms and MC production. (C) 2019 Elsevier Ltd. All rights reserved.
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