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Volume 69, Issue 12 p. 2913-2928
Research Article

Dual phosphorus and nitrogen nutrient reduction will be more effective than a phosphorus-only reduction in mitigating diatom and cyanobacterial blooms in Lake Erie, USA–Canada

Hans W. Paerl

Corresponding Author

Hans W. Paerl

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

Correspondence: [email protected]

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Justin D. Chaffin

Justin D. Chaffin

F. T. Stone Laboratory, The Ohio State University, Put-in-Bay, Ohio, USA

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Jack H. Cheshire

Jack H. Cheshire

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

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Haley E. Plaas

Haley E. Plaas

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

Department of Marine, Earth and Atmospheric Sciences, NC State University, Raleigh, North Carolina, USA

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Malcolm A. Barnard

Malcolm A. Barnard

Department of Biology and Center for Reservoir and Aquatic System Research, Baylor University, Waco, Texas, USA

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Lillian B. Goerlitz

Lillian B. Goerlitz

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

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Jeremy S. Braddy

Jeremy S. Braddy

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

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Alexandrea Sabo

Alexandrea Sabo

Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania, USA

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Leah M. Nelson

Leah M. Nelson

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

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Lindsay Yue

Lindsay Yue

Department of Earth, Marine and Environmental Sciences, Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, North Carolina, USA

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First published: 01 November 2024

Author Contribution Statement: HWP: Conceptualization, funding acquisition, investigation, methodology, resources, supervision, writing—original draft, review & editing. JDC: Conceptualization, funding acquisition, investigation, methodology, resources, writing—review & editing. JHC: Data curation, methodology, writing—review & editing. HEP: Conceptualization, investigation, writing—original, review & editing. MAB: Investigation, methodology, writing—review & editing. LBG: Investigation, methodology, writing—review & editing. JSB: Investigation, writing—review & editing. AS: Investigation, formal analysis, methodology, writing—review & editing. LMN: Investigation, formal analysis, methodology, writing—review & editing. LY: Formal analysis, methodology, writing—review & editing.

Associate Editor: John Downing

Abstract

Lake Erie, USA–Canada, plays an important ecological and socioeconomic role but has suffered from chronic eutrophication. In particular, western Lake Erie (WLE) is the site of harmful algal blooms (HABs) which are suspected of being driven by excessive nutrient (phosphorus (P) and nitrogen (N)) inputs. During 2022 and 2023, in situ nutrient dilution and addition bioassays were conducted at a WLE bloom-impacted location to investigate whether a nutrient reduction regime would be effective in limiting phytoplankton growth during the June diatom-dominated spring blooms and August cyanobacteria-dominated summer blooms. The primary objectives of this experiment were to (1) Determine if a proposed 40% P-alone reduction would effectively reduce phytoplankton growth and mitigate blooms and (2) assess whether reductions in both P and N are more effective in controlling phytoplankton biomass than exclusive reductions in either N or P. Samples were analyzed for nutrient concentrations and growth rate responses for specific algal groups, utilizing diagnostic (for major algal groups) photopigments. Results indicated that although both 20% and 40% dilutions led to lower phytoplankton biomass and growth rates, 40% reductions were more effective. Our results support the USA–Canada Great Lakes Water Quality Agreement recommendation of a 40% P reduction, but also indicate that a parallel reduction of N input by 40% would be most effective in controlling bloom magnitudes. Overall, our findings underscore the recommendation that a year-round dual N and P 40% reduction is needed for long-term control of eutrophication and algal blooms, including cyanobacteria and diatoms, in Lake Erie.

Conflict of Interest

None declared.

Data availability statement

Data used in this manuscript are listed and provided in Supporting Information. Data are available upon request from the senior author.