Every summer, Lake Erie’s western basin turns the same shade of green, and the reason has not changed in years. Too much phosphorus washes off the land, feeds cyanobacteria, and fuels the harmful algal blooms that close beaches, worry pet owners, and put pressure on the region’s drinking water. The problem can feel stubborn. This month brought a reminder that it is not unsolvable.
Near the city of St. Marys, at the southern edge of the Lake Erie watershed, a new 31-acre constructed wetland is quietly doing exactly what it was built to do. The project — nicknamed the “Pat McGowan Treatment Train” and built through Ohio’s H2Ohio program with the Ohio Department of Natural Resources and the City of St. Marys — treats canal water before it ever heads downstream toward the lake. After two years of independent monitoring by the Lake Erie and Aquatic Research Network, the results are in: an 82 percent reduction in phosphorus and a 68 percent reduction in nitrogen.
Those are not small numbers. Phosphorus is the single biggest driver of Lake Erie’s blooms, and cutting it by more than three-quarters at one site, before the water moves on, is the kind of measurable outcome that has been hard to come by.
Here is why a wetland well upstream matters to everyone who lives on, works near, or drinks from Lake Erie. Nutrients do not respect city limits. The Maumee River alone supplies only about 5 percent of Lake Erie’s water but carries nearly half of its nutrient load. Reducing phosphorus in the tributaries and canals that feed the system is how you change what happens at the shoreline. And it appears to be working at a broader scale, too. Ohio Sea Grant reports that phosphorus entering the lake by way of the Maumee has fallen roughly 10 percent in recent years, crediting much of the improvement to H2Ohio farming practices such as fertilizer-timing limits, wetland buffers, and tree-lined ditches.
None of this means the problem is solved. Blooms are still large, phosphorus-reduction targets have not yet been met, and, as NOAA’s late-season updates remind us, toxins in the western basin can climb above the recreational limit even when the bloom itself is shrinking. Progress and vigilance are not opposites. But two straight years of strong results from a single wetland — one of more than 500 H2Ohio natural-infrastructure projects covering nearly 20,000 acres since 2019 — is real evidence that steady investment produces steady returns.
This is the story the Lake Erie Foundation cares about most: not just naming the problem, but testing and proving the solutions. The St. Marys wetland uses natural infrastructure to capture nutrients across a wide area. The Foundation’s own Phosphorus Runoff and P-Filter Project, in the Maumee River watershed near Defiance, takes a complementary, targeted approach — using engineering to pull phosphorus out of drainage water leaving specific high-phosphorus fields. Three filters were installed in the fall of 2025, and early monitoring has been promising; in project testing, the filters have removed more than 90 percent of phosphorus under the conditions measured. The project is grant funded, and the participating farm remains private.
Put those two approaches side by side — broad natural wetlands and precise, field-level filters — and you can see the outline of a smarter phosphorus strategy. Not every field or every waterway contributes equally. Treating water where it does the most good, with the right tool for the site, stretches every public and private dollar further. It is also why the Foundation continues to advocate for stable, long-term H2Ohio funding. Programs that produce measurable results deserve to be supported, evaluated honestly, and strengthened — not left uncertain from one budget cycle to the next.
The takeaway from St. Marys is simple and, for once, hopeful. When we invest in practical, science-based solutions, Lake Erie responds. If you want to help move that work forward — and see more filters in the ground and more nutrients captured before they reach the lake — support the Lake Erie Foundation’s practical solutions work today. Progress like this is built one project, and one supporter, at a time.