Water quality monitoring experts, scientists, and estuary caretakers built a long-term collaborative monitoring strategy for estuary nutrients and phytoplankton dynamics at the headwaters of Lake Superior.

The Project The St. Louis River Estuary, located at the headwaters of Lake Superior, is nearing a major milestone: its anticipated delisting as a Great Lakes Area of Concern by 2030. Yet even as remediation and restoration successes are celebrated, new environmental stressors, particularly harmful algal blooms, raise concerns about the estuary's long-term water quality health. In response, a group of local, state, federal, and tribal partners who have long worked in and cared for the estuary began calling for a science-based monitoring strategy that could respond to emerging threats and support ongoing stewardship beyond delisting. Together, they shaped a shared vision: a comprehensive program of observations, analyses, and public reporting that would protect remediation and restoration investments and inform future decision-making.

To advance this vision, this group of partners who had long advocated for a coordinated monitoring effort, collaborated closely with the Lake Superior National Estuarine Research Reserve to launch the project. The Reserve brought together a scientific team that included collaborators from the University of Minnesota's Natural Resources Research Institute, who contributed expertise in phytoplankton and bloom dynamics. The partners co-authored the proposal and remained actively engaged throughout the project, helping select sites, shape the study design, and review statistical analysis and draft recommendations. Together, the partners and project team developed a research approach that combined strong scientific design to build foundational understanding of phytoplankton dynamics with a focus on generating practical, actionable insights for a shared long term monitoring strategy. Eight high-priority sites were intensively sampled in 2023 and 2024, focusing on areas vulnerable to nutrient enrichment, low oxygen, and bloom formation. The study also prioritized public relevance by targeting restoration areas, heavily used public zones, and capturing rarely collected wintertime data.

The project successfully identified predictors of cyanobacteria biovolume in the estuary and actionable monitoring strategies to improve bloom detection and efficient water quality monitoring in the future. Important predictors of blooms included low nitrogen, warm temperatures, low dissolved organic carbon, and high pH. In addition, the team observed significant year-to-year differences in bloom composition and intensity suggesting bloom dynamics are highly responsive to variations in hydrology and nutrient stoichiometry which are driven by precipitation patterns. Further analysis evaluated the efficiency of different monitoring designs by assessing redundancy across space, sampling frequency, and parameters. These findings informed a science-based strategy that identified periods and locations of elevated bloom risk while accounting for the real-world capacity of agencies and partners. The resulting recommendations include a reduced set of priority sites and a tiered approach to sampling. This strategy is designed to be flexible with available funding and effort, while ensuring that high-risk bloom locations are monitored as a minimum standard. The project's result is not only a clearer picture of what drives blooms in the estuary, but also a durable and collaborative roadmap for long-term monitoring, co-created by the people who first called for a collaborative, comprehensive program.