Scientists want more focus on dissolved reactive phosphorus to help fix Lake Erie

11/15/2017

MONROE — To better understand what’s happening to western Lake Erie, think of how kids crave sweet, sugary snacks.

Laura Johnson, director of Heidelberg University’s National Center for Water Quality Research, said here Wednesday that’s sort of how algae responds to a sub-category of nutrient called dissolved reactive phosphorus, which essentially is phosphate bound to sediment that has dissolved over time and become readily available to algae in the water column. It differs from phosphorus particles, but —  according to the Ohio Environmental Protection Agency — is found in both manure and commercial fertilizers.

Algae loves it. Unlike phosphorus particles, the dissolved variety is entirely consumed by algae. It’s like candy to a kid: There are no leftovers, Ms. Johnson said.

The distinction between dissolved reactive phosphorus and total phosphorus is important because scientists such as Ms. Johnson have believed for several years now that the impact of the former has been underrated. Yet policymakers continue to rely more on the latter, using total phosphorus for their reduction goals.

Ms. Johnson, one of several speakers at an event held at Monroe County Community College, noted that annual phosphorus levels in the Maumee River, Sandusky River, Portage River, and River Raisin have either stabilized or gone down since 2008, while those of dissolved reactive phosphorus have shot up. And the region’s no closer to solving the algae mystery, with the four largest blooms on record occurring since 2011.

The symposium was arranged by the Toledo Metropolitan Area Council of Governments and the Southeast Michigan Council of Governments.

Chris Winslow, Ohio Sea Grant and Ohio State University Stone Laboratory director, discussed an updated state report that shows 87 percent of algae-forming phosphorus released into the Maumee and Sandusky river watersheds comes from non-point runoff, which is mostly — though not exclusively — from agriculture.

“This is not a finger-pointing exercise at agriculture,” Mr. Winslow said. “It’s just that we know more now than we did before.”

Libby Dayton, an OSU research scientist who specializes in edge-of-field studies tracking nutrient flow off farms, said it’s important to collect data and “provide unambiguous information” for policy decisions. 

Seventy percent of the Maumee River and Sandusky River watershed land is agriculture, Mr. Winslow said.

The goal of a 40 percent phosphorus reduction embraced by Ohio, Michigan, and Ontario will not eliminate western Lake Erie algal blooms but bring the region back to a more “normal” state if implemented, he said.

That goal is based on 2008 total phosphorus levels and is to be met by 2025, with an interim goal of at least a 20 percent reduction by 2020.

Scientists, though, note those goals do not account for dissolved reactive phosphorus or climate change.

“There are going to be some years in which Mother Nature throws that curve ball at us,” Mr. Winslow said, referring to the likelihood of more frequent and heavier storms because of climate change.

Laura Campbell, Michigan Farm Bureau ag ecology manager, said there are still questions that need to be answered.

“Once we get to 40 percent, is that our number?” she asked. “That's the great unspoken thing today.”

Contact Tom Henry at thenry@theblade.com, 419-724-6079, or via Twitter @ecowriterohio.