Starving algae

Western Lake Erie is too big to cor­rect its nox­ious al­gae prob­lem with large doses of alu­mi­num sul­fate, or alum, alone. Still, alum treat­ments ap­pear to be hav­ing at least a lim­ited pos­i­tive ef­fect on Grand Lake St. Marys.

At 12,500 acres, Grand Lake St. Marys is the larg­est open body of wa­ter in Ohio. Like Lake Erie, its rec­re­ational ac­tiv­i­ties are af­flicted by al­gae.

The state of Ohio has spent $8.5 mil­lion to ap­ply alum to 4,900 acres of Grand Lake St. Marys over the past two sum­mers. The com­pound is sup­posed to keep al­gae from feed­ing on its main food source, phos­pho­rus.

This year’s drought cut off the farm run­off that feeds Lake Erie al­gae. But al­gae in Grand Lake St. Marys rely more heav­ily on phos­pho­rus em­bed­ded in lake sed­i­ment, so this year’s dry con­di­tions did not do as much to curb al­gae there.

Pre­lim­i­nary alum re­sults for Grand Lake St. Marys look good, ac­cord­ing to a re­searcher. But the suc­cess needs to be quan­ti­fied for state of­fi­cials to de­cide whether to ap­ply more.

No mat­ter what re­sults emerge, Ohio may need to take more than a two-and-out ap­proach us­ing alum to gen­er­ate more data, es­pe­cially in non-drought years. More-pro­ac­tive ef­forts are needed to keep run­off and un­treated house­hold waste out of Ohio wa­ter­ways.

The most cost-ef­fec­tive way to man­age nat­u­ral re­sources is to pre­vent pol­lu­tion. Alum treat­ments are, at best, short-term re­sponses to al­gae.

Ohio needs to en­hance wet­lands state­wide and, when nec­es­sary, dredge the most pol­luted sed­i­ment from Grand Lake St. Marys. Alum re­search can help un­lock al­gae mys­ter­ies. But it is no pan­a­cea for what ails Ohio’s lakes.