The diel light cycle modulates microcystin content in continuous cultures and natural communities of Microcystis: Implications for bloom monitoring
- 1Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
- 2Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse NY 13210, USA
- 3F.T. Stone Laboratory and Ohio Sea Grant, The Ohio State University, Put-In-Bay, OH 43456, USA
Abstract
Harmful algal blooms dominated by Microcystis spp. threaten fisheries, recreation, and drinking-water supplies because many strains produce the hepatotoxin microcystin. Monitoring programs compare microcystin concentrations among samples collected at different times of day, yet the extent that diel variation affects these estimates remains poorly resolved. We tested whether microcystin concentrations varied over a diel cycle under laboratory conditions and evaluated the effect of short-term sunlight exposure on a natural bloom community. Axenic Microcystis aeruginosa PCC 7806 was maintained in cyclostats with controlled nutrients and temperature under a 16 h light:8 h dark cycle. Microcystin concentrations normalized to culture volume (g L-1) and biovolume (ag m-E-3 were significantly higher (p [≤] 0.05) at the end of the dark period (64 {+/-} 8 g MC L-1; 630 {+/-} 40 ag MC m-3) than at the end of the light period (45 {+/-} 7 g MC L-1; 390 {+/-} 60 ag MC m-3), and this pattern was reproducible across consecutive days. Cell abundance and photosynthetic efficiency remained constant, indicating variation was not explained by changes in growth or photosynthetic performance. In parallel, water from a Lake Erie Microcystis bloom was exposed to sunlight or paired dark controls, and microcystin concentrations declined ~19% after just 60 min of sunlight exposure (p = 0.048). Together, these results demonstrate that microcystin measurements can vary predictably across the diel cycle and that light contributes to daytime declines. Although the underlying mechanism(s) remain unresolved, time of day should be considered, or standardized, when monitoring microcystins.
Related
- Indigenous communities' perceptions of ecosystem services of a montane forest ecosystem in Nigeria: Implications for restoration planning
- Premature Ventricular Contractions at Extreme Altitude: Continuous Electrocardiographic Monitoring on Mount Everest.
- Continuous monitoring of deficit irrigation in avocado across two contrasting rainfall years using sensor networks, telemetry, and machine learning
- Sugarcane–peanut intercropping improves rhizosphere fungal communities and metabolites following long-term continuous peanut monoculture
- Comparison of the Genotoxic Potential of Three Microcystin Variants (‐ LR , ‐ RR , and ‐ LF ) by High Content Analysis and Micronucleus Assay in a Human Hepatic Cell Line
BibTeX
@misc{maggard2026diel,
title = {{The diel light cycle modulates microcystin content in continuous cultures and natural communities of Microcystis: Implications for bloom monitoring}},
author = {Isabella J. Maggard and Robbie M. Martin and Kelly E. Joyce and Zac Triumph and Emily M. Garlock and Gregory L. Boyer and Justin D. Chaffin and David Talmy and Steven W. Wilhelm},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.24.761440},
url = {https://www.biorxiv.org/content/10.64898/2026.10.24.761440v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - The diel light cycle modulates microcystin content in continuous cultures and natural communities of Microcystis: Implications for bloom monitoring
AU - Isabella J. Maggard
AU - Robbie M. Martin
AU - Kelly E. Joyce
AU - Zac Triumph
AU - Emily M. Garlock
AU - Gregory L. Boyer
AU - Justin D. Chaffin
AU - David Talmy
AU - Steven W. Wilhelm
PY - 2026
DA - 2026/10/24
PB - bioRxiv
DO - 10.64898/2026.10.24.761440
UR - https://www.biorxiv.org/content/10.64898/2026.10.24.761440v1
AB - Harmful algal blooms dominated by Microcystis spp. threaten fisheries, recreation, and drinking-water supplies because many strains produce the hepatotoxin microcystin. Monitoring programs compare microcystin concentrations among samples collected at different times of day, yet the extent that diel variation affects these estimates remains poorly resolved. We tested whether microcystin concentrations varied over a diel cycle under laboratory conditions and evaluated the effect of short-term sunlight exposure on a natural bloom community. Axenic Microcystis aeruginosa PCC 7806 was maintained in cyclostats with controlled nutrients and temperature under a 16 h light:8 h dark cycle. Microcystin concentrations normalized to culture volume (g L-1) and biovolume (ag m-E-3 were significantly higher (p [≤] 0.05) at the end of the dark period (64 {+/-} 8 g MC L-1; 630 {+/-} 40 ag MC m-3) than at the end of the light period (45 {+/-} 7 g MC L-1; 390 {+/-} 60 ag MC m-3), and this pattern was reproducible across consecutive days. Cell abundance and photosynthetic efficiency remained constant, indicating variation was not explained by changes in growth or photosynthetic performance. In parallel, water from a Lake Erie Microcystis bloom was exposed to sunlight or paired dark controls, and microcystin concentrations declined ~19% after just 60 min of sunlight exposure (p = 0.048). Together, these results demonstrate that microcystin measurements can vary predictably across the diel cycle and that light contributes to daytime declines. Although the underlying mechanism(s) remain unresolved, time of day should be considered, or standardized, when monitoring microcystins.
SN - 2692-8205
ER -