It is hard to miss this summer’s plague of blue-green algae blooms on our Madison lakes. Blue-green algae can produce toxins that harm people, livestock and fish. People and pets should avoid swimming during severe blooms. Fish, as some recent kills have shown, have no alternative.
Like the biblical plague of frogs, the algae blooms came with high water, triggered by heavy rains that washed huge amounts of phosphorus-laden manure, soil and debris into our lakes. Phosphorus is used to fertilize crops, but it’s even better at growing algae. And, when heavy rains are followed by hot weather, it cooks up a simmering stew of blue-green algae, according to Wednesday’s State Journal editorial, “Mucky lakes are a stark reminder,” and a report from the Center for Limnology.
Current blooms mask real progress to improve land management orchestrated by Dane County, Madison Metropolitan Sewerage District, municipalities in the Yahara watershed, farmers and other partners. Without their investments of money and labor, the blooms would likely be worse because of other changes driving phosphorus flow to the lakes.
Precipitation has increased, and big storms are more frequent with heavier rain, especially in summer. When heavy rains hit phosphorus-saturated soil, big pulses of phosphorus enter the streams and lakes. Our management of phosphorus is barely keeping pace with the changing rainfall. Warm days drive the growth of blue-green algae, and we get plenty of those in summer.
New invasive species also damage water quality. Spiny water fleas, for example, eat Daphnia, a small, native animal that eats algae and prevents blooms. When the Daphnia population in Lake Mendota collapsed due to the “spiny” invasion, the increase in blue-green algae canceled the benefits of $80 million to $160 million in phosphorus control. Making matters worse, zebra mussels may worsen blue-green algae blooms and explain the increase in green glop on beaches.
Those of us who live in our lakes’ watershed cannot manage climate, but we can manage phosphorus to cope with a changing climate. Unprecedented situations call for innovative approaches. Fortunately, Dane County is a hotbed of innovation for phosphorus management. County government is experimenting with removal of polluted streambed sediment. Manure is now being processed at industrial scales, and these technologies will evolve and improve.
Farmers drive the work of Yahara Pride to improve land management and reduce phosphorus pollution. Madison’s sewerage district, municipalities, farmers and other partners organized Yahara WINS, a novel collaboration that will meet more stringent phosphorus targets. These and other innovative approaches are crucial for adapting to the twin challenges of high phosphorus and heavy rainfall.
The plague of frogs quickly vanished, but it will take time to end the plague of blue-green algae blooms. Do not be fooled by occasional good years such as 2016, when moderate rains and a short-lived decline in spiny water flea populations triggered a brief hiatus in the blooms. Droughts such as 2012 will also bring temporary improvements, but most years will be average, and the average trend is wetter with bigger storms that will lead to more big blooms.
Reducing soil phosphorus is a marathon, not a sprint. It will be a long run with some unexpected hills and turns. We need determination to succeed, the ability to adapt to unexpected changes in climate and invasive species, and the willingness to experiment with new ideas. Recent events show our people and local institutions have these qualities. With patience and perseverance, we can gradually bring phosphorus under control.