Cyanobacteria blooms and toxin production are an urgent contemporary problem in the US and worldwide. Water quality models are important tools for managing these problems, but currently the utility of available models is strictly for management and research. This research will lead to better predictions of cyanobacteria blooms and toxin production, which will benefit the management of Lake Erie and other systems plagued by cyanoHABs.

Why We Care

University of Tennessee graduate student Lauren Krausfeldt on a research vessel collecting samples from Microcystis blooms (right) in Lake Erie during summer 2015. Credit S. Wilhelm, UT.

There is a disconnect between our current models and current problems (toxin production) in the Great Lakes. Water quality models are important environmental engineering tools for managing these problems, but the available operational models are based on outdated biological theories, do not include many important processes (e.g., overwintering in the sediment bed) and do not make predictions of important parameters (e.g., toxin production). This limits their utility for management and research.

This project aims to take a significant step towards remedying this situation by developing a modern model for Microcystis growth and toxin production, which will resolve intracellular mechanisms of metabolism and toxin production at the gene, transcript, protein and metabolite level. The model will be developed based on available laboratory data, integrated into an existing water quality model of western Lake Erie and compared to field observations of Microcystis and toxin concentrations. Further, the model will be used to explore hypotheses about the ecological role of toxins, including as a grazing deterrent or to protect against redox damage.

The research will lead to better predictions of cyanobacteria blooms and toxin production, which will benefit the management of Lake Erie and other systems plagued by cyanoHABs, thus helping to restore and protect their beneficial use. Further, the modeling technology developed in this project is unique and different from existing models: Intracellular mechanisms are dynamically simulated at the molecular level. This model can therefore serve as a case study and may cross-fertilize and inspire similar changes in other microbial ecology models, including those used for research and management of other HAB problems (e.g., red tide).

Microcystis and microcystin-LR (MC-LR). (A) Microcystis colony. (B) Microcystin-LR structure. (C) Intracellular microcystin (and other toxins) metabolism pathways showing link with nitrogen. From Gobler et al. 2016. https://doi.org/10.1016/j.hal.2016.01.010

What We Are Doing

This project will build a model of Microcystis growth and toxin production, based on a previously-developed model for Anabaena - nitrogen interaction. Model development will be based on the available data from lab experiments and field observations, which will be compiled as part of this project. The development of the model will follow standard protocols for the definition and parameterization of complex agent-based models.

The model will include explicit representation of genes, transcripts and enzymes involved in microcystin-LR (MC-LR) toxin production, a mechanistic representation of reactive oxygen species generation and damage to the cell, and the protection by MC-LR. Continuous culture Chemostat (static, controlled cell culture environment) experiments will be performed, which will generate molecular level observations (i.e., transcripts, metabolites), and can be compared directly to the model. Data from these experiments and available field data will be used to formally validate the model.

The model will also be used to explore hypotheses about the ecological role of toxin production, including: (1) microcystin is a defense mechanism against grazers; (2) microcystin protects the cell from redox damage. Two workshops will engage the water quality modeling community and the Lake Erie community.

Dr. Ameet Pinto,  formally of Northeastern University, initially led this project. Co-leads are Dr. Ferdi Hellweger (Berlin University) and Dr. Steven Wilhelm (University of Tennessee). The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Bloom (ECOHAB) Program.