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Abstract Efforts to reduce the frequency, extent, and toxicity of harmful algal blooms (HABs) require knowledge about drivers of algal growth, toxin production, and shifts in phytoplankton community composition to cyanobacterial dominance. Although labile nitrogen (N) and phosphorus (P) fuel primary production, micronutrients also play roles as the enzymatic engines that facilitate rapid and efficient growth and toxin production. Macro‐ and micronutrient availability can shape community composition and function by selecting for particular taxa. To address how phytoplankton in two Great Lakes subbasins respond to macro‐ and micronutrients, we conducted bottle incubation enrichment experiments using water collected from two blooming and two nonblooming sites in Lakes Erie and Michigan during late summer (August). Three of the four sites exhibited multi‐nutrient limitation of growth. Both blooming sites responded strongest to enrichment. Both nonblooming sites responded the strongest to enrichment, and three of the four sites responded in some way to a mix of micronutrients (Fe, Mn, Mo, Ni, and Zn).Microcystis aeruginosarelative abundance increased most with N enrichment, while P enrichment increased the abundance of diatoms and chlorophytes. At the Fox River, N‐enriched communities grew 10%–20% more than non‐N enriched communities (measured as chlorophylla), and N‐enriched communities had, on average, over twice as much microcystin (non‐N communities average MC = 2.45 μg · L−1, +N communities MC = 5.35 μg · L−1). These overarching trends support the idea that control of HABs may not be effective with a P‐only approach.
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This content will become publicly available on November 1, 2026
Atmospheric oxidation of cyanobacterial aerosols emitted from lakes and estuaries during harmful algal blooms
Harmful algal blooms (HABs) in lakes and estuaries, caused by cyanobacteria, pose various threats to humans and the environment. Cyanobacteria produce microcystins (MCs) that make animals and people sick. Once airborne, cyanobacterial aerosols are rapidly transformed through heterogeneous reactions with atmospheric oxidants, which tend to occur much faster in air than in water. The important aspects of these transformations include the degradation of MCs and the production of reactive oxygen species (ROS) from oxidized organic matter (OM) in cyanobacterial aerosol. In this study, MCs in aerosols and water samples, collected in lakes (Lake Okeechobee, Georges Lake, and Doctors Lake) of Florida during HABs, were measured using enzyme-linked immunosorbent assay kits. Organic hydroperoxides (OHP) and the oxidative potential (OP) associated with aerosols collected at Doctors Lake were measured with 4-nitrophenylboronic acid and dithiothreitol assays, respectively. The decay of MCs and the evolution of ROS in cyanobacterial aerosols were also demonstrated in an outdoor chamber under ambient sunlight. MC concentrations (0.4–2.1 μg/L) during HAB periods were higher than the US EPA guideline (0.3 μg/L for pre-school age and 1.6 μg/L for school-age and above). Airborne MC concentrations ranged from 0.2 to 5.7 ng/m3. Regulations for airborne MC concentrations are yet to be established. In both field and chamber data, MCs decomposed but ROS substantially increased as aerosols atmospherically oxidized. Aerosolized OM concentrations during HABs were higher than those in dormant periods. OM in cyanobacterial aerosols was enriched at estuary Doctors Lake with high inorganic salt concentrations due to salting-out of water-soluble organics into lake-surface layers. Aerosolized OM concentrations were positively corelated to OP and OHP (r = 0.96 and 0.85, respectively) at Doctors Lake suggesting that cyanobacterial aerosols might adversely influence respiratory health. The longitudinal health impacts of aerosolized cyanobacteria emitted from HABs should be investigated in the future.
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- Award ID(s):
- 2044921
- PAR ID:
- 10628492
- Publisher / Repository:
- Environmental Pollution
- Date Published:
- Journal Name:
- Environmental Pollution
- Volume:
- 384
- Issue:
- C
- ISSN:
- 0269-7491
- Page Range / eLocation ID:
- 126959
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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