Phosphorus-only fertilization rapidly initiates large nitrogen-fixing cyanobacteria blooms in two oligotrophic lakes

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Two small, oligotrophic lakes at the IISD-Experimental Lakes Area in northwestern Ontario, Canada were fertilized weekly with only phosphorus (P) in the summer and early fall of 2019. The P fertilization rates were high enough (13.3 µg L-1 added weekly) to produce dense, month-long blooms of N2-fixing Dolichospermum species in both lakes within 9-12 weeks after fertilization began, turning them visibly green without the addition of nitrogen. P-only fertilization increased average seasonal chlorophyll a concentrations and cyanobacteria biomass well above the pre-fertilization levels of 2017 and 2018. Nitrogen (N) content in the epilimnion of thermally stratified Lake 304 and the water column of shallow Lake 303 doubled and P storage in the water column temporarily increased during the blooms. These whole-lake fertilization experiments demonstrate that large cyanobacteria blooms can develop rapidly under high P loading without anthropogenic N inputs, suggesting that aggressive N control programs are unlikely to prevent bloom formation and that P controls should remain the cornerstone for cyanobacteria management.

This data is collected as part of the Pillar 3 GWF project "FORMBLOOM: Forecasting Tools and Mitigation Options for Diverse Bloom-Affected Lakes".

Molot, Lewis A., Higgins, Scott N., Schiff, Sherry, Venkiteswaran, Jason, Paterson, Michael J., Baulch, Helen M. (2021). Phosphorus-only fertilization rapidly initiates large nitrogen-fixing cyanobacteria blooms in two oligotrophic lakes [Dataset]. Scholars Portal Dataverse. https://doi.org/10.5683/SP2/Q7FYSI Molot, Lewis A., Higgins, Scott N., Schiff, Sherry, Venkiteswaran, Jason, Paterson, Michael J., Baulch, Helen M. (2021). Phosphorus-only fertilization rapidly initiates large nitrogen-fixing cyanobacteria blooms in two oligotrophic lakes. Environmental Research Letters. https://doi.org/10.1088/1748-9326/ac0564

Lakes 303 & 304, IISD - Experimental Lakes Area

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Data available at https://doi.org/10.5683/SP2/Q7FYSI