Models predict planned phosphorus load reduction will make Lake Erie more toxic

Area of Science:

• Environmental microbiology
• Aquatic ecology
• Computational toxicology

Background:

• Harmful cyanobacteria, particularly Microcystis, are a global environmental concern.
• Understanding the ecology of toxigenic versus nontoxigenic strains and their toxin production is crucial but limited.

Purpose of the Study:

• To develop a mechanistic model of Microcystis growth and microcystin production.
• To investigate the factors controlling toxigenic and nontoxigenic strain succession during harmful algal blooms.

Main Methods:

• A large-scale meta-analysis of 103 papers was conducted.
• A mechanistic, agent-based model of Microcystis was developed and used for simulations.
• Simulations focused on Lake Erie conditions, including the 2014 Toledo drinking water crisis.

Main Results:

• Cellular oxidative stress mitigation strategies and their susceptibility to nitrogen limitation influenced strain succession.
• Simulations indicated that phosphorus load reduction may increase toxin production and favor toxigenic Microcystis strains.
• Both mechanistic and empirical models predicted increased toxin concentrations under future nutrient scenarios.

Conclusions:

• Microcystin's role in oxidative stress protection and enzymatic degradation, coupled with nitrogen availability, drives toxigenic strain success.
• Planned phosphorus reductions may inadvertently increase microcystin toxin concentrations in lakes like Erie.
• Further research and management strategies are needed to mitigate harmful cyanobacterial blooms and associated toxins.