H2Ohio work moves the needle on harmful algal blooms

Columbus — The H2Ohio Wetland Monitoring Program, implemented by the Lake Erie and Aquatic Research Network (LEARN), released its 2024 annual report, showcasing the effectiveness of wetland restoration efforts across Ohio to reduce nutrient pollution and mitigate harmful algal blooms (HABs) in Lake Erie and other state water bodies.

The findings support the need to continue wetland restoration because of their ability to prevent nutrients that feed HABs from entering lakes and waterways, according to LEARN.

Since 2021, LEARN – a network of Ohio researchers studying Lake Erie, the Ohio River, and related aquatic ecosystems – has monitored wetland projects across the state. Scientists from Kent State University, The University of Toledo, Bowling Green State University, Wright State University, The Ohio State University, and Heidelberg University have assessed 45 wetland restoration, enhancement, and construction projects. These efforts are a critical part of the H2Ohio Initiative, launched by Gov. Mike DeWine and managed by the Ohio DNR (ODNR) to tackle HABs that threaten more than $17 billion in economic activity and over 100,000 Ohio jobs.

“This report improves our understanding of how to design and manage wetlands for maximum environmental benefit to help reduce HABs,” said Dr. Lauren Kinsman-Costello, the program’s lead researcher and member of LEARN. “The findings help ensure that every dollar invested in these projects delivers the greatest return in cleaner water and healthier ecosystems.”

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Key Findings from the 2024 Report:

Consistent Nutrient Reduction: All 45 wetland projects with sufficient data showed effective reductions in phosphorus and nitrogen, the primary drivers of HABs.

Retention Ranges: Wetlands retained between 0.2–29 pounds of phosphorus per acre and as much as 863 pounds of nitrogen per acre.

Design Matters: Projects draining large, nutrient-rich areas and those that hold water for extended periods retain the most nutrients.

Weather Impacts: Due to drought conditions in 2024, less nutrients entered wetlands than in wetter years. Retention effectiveness is expected to increase during wetter years.

Active Management Enhances Performance: Wetlands that had water-level control structures or pumps retained more nutrients.

Soils and Plants Support Long-Term Storage: Wetland soils demonstrated high capacity for additional phosphorus storage. Native plants such as broadleaf arrowhead, soft rush, and pickerelweed enhance both nutrient retention and biodiversity.

The report emphasizes that continued monitoring is necessary to ensure the long-term effectiveness of these wetland projects. Communication between wetland managers and researchers is essential for accurate assessment of wetland value. Since 2022, the program’s monitoring has been informed by on-the-ground expertise, engaging over 30 partners, including county parks, land conservancies, community groups, and private landowners.

Vegetation within newly completed wetlands is still in the early stages of development, and data from the first few years after wetland construction or restoration may underestimate the full nutrient retention potential of these ecosystems.

The researchers also established a volunteer panel to evaluate proposed projects’ nutrient reduction potential, directly informing ODNR’s investment strategies. These findings will continue to guide the next generation of wetland design and restoration across Ohio.

“With new understanding of wetland restoration emerging and continued investment in science-based evaluation,” said Eric Saas, H2Ohio Wetlands Program Manager, “Ohio is leading the way in using wetlands to solve one of the state’s most persistent environmental challenges.”