How temporal niche partitioning and growth on urea selects for cyanobacteria in fresh waters

The National Science Foundation Division of Environmental Biology awarded the University of Tennessee $1,454,878 on January 1, 2027, under the Biological Sciences program (CFDA 47.074) to fund research examining how temporal niche partitioning and urea utilization enable Microcystis to dominate harmful cyanobacterial blooms in freshwater systems.

The research combines laboratory experiments, field studies in Lake Erie, and advanced analyses of nutrient and energy use with AI-assisted predictive modeling to test the hypothesis that Microcystis gains competitive advantage by using urea—a nitrogen-rich agricultural runoff compound—not only as a nitrogen source but also to meet carbon demands. The investigators will assess how this metabolic process changes diurnally, how it affects competition with other algae, and whether it explains bloom persistence and intensification. Deliverables include improved understanding of bloom formation and environmental response mechanisms, better bloom forecasting and management approaches, advances in carbon-flow energetics with potential bioenergy applications, student training across multiple disciplines, and public engagement through citizen science and K–12 education.

Work is performed in Knoxville, Tennessee, with a period of performance from January 1, 2027, through December 31, 2029. The University of Tennessee, operating through its System Office, is the prime recipient and will deliver the research with its own faculty and staff.

Abstract

Harmful cyanobacterial threaten drinking water, fisheries, recreation, and local economies worldwide. Microcystis, a type of algae, often dominates these blooms and can produce microcystin, a toxin harmful to both people and ecosystems. While nutrient pollution is known to drive blooms, a key question remains: why do certain bloom-forming species outcompete other algae? This project examines the role of microcystis under specific bloom conditions. IT is hypothesized that microcystis gains a competitive advantage by using urea, a nitrogen-rich compound common in agricultural watersheds, not only as a nitrogen source but also to help meet its carbon demands. Researchers will test how this process changes over the course of the day, how IT affects competition with other algae, and whether IT helps explain the persistence and intensification of harmful blooms. To address these questions, the investigators will combine laboratory experiments, field studies in lake erie, and advanced analyses of nutrient and energy use, together with AI-assisted predictive modeling. By linking cellular metabolism to bloom dynamics, this project will improve understanding of how blooms form, persist, and respond to the environment. The results will support better bloom forecasting and management, advance understanding of carbon-flow energetics with potential relevance to bioenergy, train students across multiple disciplines, and engage the public through citizen science and k?12 education. This project advances NSF?s priorities in biotechnology and artificial intelligence. Harmful cyanobacterial blooms are increasing globally, yet the mechanisms though which conditions in the environment select for specific bloom-forming taxa remain poorly resolved. While phosphorus and nitrogen broadly constrain phytoplankton biomass, nitrogen speciation is increasingly recognized as a key driver of community composition. Bloom-forming cyanobacteria further modify their environment by depleting dissolved nutrients and elevating PH to levels that suppress competing phototrophs. Microcystis is likely to exploit these self-generated conditions through diel temporal niche partitioning, using urea as both a carbon and nitrogen source during peak daylight, when bloom-driven alkalization reduces dissolved CO2 and promotes nitrogen loss via ammonia volatilization. This metabolism is supported by a shift toward cyclic photophosphorylation late in the solar day, enabling ATP generation when linear photosynthesis is constrained. This project will quantify the efficacy of this strategy, determine how IT alters competition with CO-occurring phototrophs, and incorporate these mechanisms into predictive models linking cell physiology to community outcomes. Preliminary observations indicate that urea-grown microcystis can accumulate more biomass than nitrate-grown cells while exhibiting reduced psii activity, consistent with alternative energetic pathways. To test these ideas, investigators will integrate continuous cultures, field surveys, cell enumeration, image-based analyses, transcriptomics, metabolomics, and AI-driven mechanistic modeling. The resulting framework will resolve how nutrient form, carbonate chemistry, cellular energetics, and interspecific competition interact to determine when and why microcystis dominates freshwater systems. These advances will improve mechanistic forecasting of harmful blooms and provide interdisciplinary graduate and undergraduate training in laboratory, field, multi-omic, and quantitative modeling approaches. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.