In the summer and fall of 2011, a green tide of blue-green algae enshrouded 230 square miles of Lake Erie's western basin. This algae "bloom" poisoned the water with toxins, suffocating the aquatic life of oxygen, burdening the city of Toledo, Ohio's water treatment plant and threatening a $11.5 billion tourism industry in Ohio.

This algal bloom broke the record for Lake Erie, in terms of both size and concentration. And with climate change, these blooms could become a regular occurrence in the next century, says a team of scientists in a paper published yesterday in the Proceedings of the National Academy of Sciences.

The bloom began on July 15, 2011. By September, it was clear it was the biggest one on record, said Anna Michalak, who headed the research team and now works as an environmental scientist in the Department of Global Ecology at the Carnegie Institution for Science.

"It was certainly clear that this was unlike anything we'd seen," said Michalak. Algal blooms are created when high levels of nutrients, like nitrogen and phosphorus, enter a waterway and stay put for an extended period. Cyanobacteria, commonly known as blue-green algae, feed off streams of phosphorus and nitrogen, usually from plant fertilizers, manure, sewage, commercial detergents and industrial waste.

Weak circulation of waters and warm temperatures encourage the cyanobacteria to thrive in nutrient-rich waters. In 2011, unusually heavy spring rains washed a lot of phosphorus fertilizer into Lake Erie's western basin. That summer, water that had arrived from the Maumee River tributary did not mix with Detroit River water as usual, said Michalak, causing a poor circulation of water. The nutrient-rich waters did not flow out of the western basin, and the algae were allowed to proliferate.

The scientists determined the record impact of the algal bloom by measuring the volume of cyanobacteria in the water and with NASA satellite images. Using 12 climate change models, the researchers concluded that the heavy precipitation, coupled with warming over the region and weaker wind speeds, will mean more algal blooms for the region.

During the 2011 bloom, the volume of microcytosis blue-green algae, which are toxic to the liver, peaked at 224 times the World Health Organization's guidelines. Increases in anabaena toxin, which affects the neurological system, are also expected as blooms become more common. Algae can also clog boat motors and hamper fishing.

Farming in the Great Swamp
The Native Indians of Ohio called the area that is now northwestern Ohio and southeastern Michigan the "Great Black Swamp" -- a land of marshy wetlands. The early pioneers were able to dredge the land and turn it into the rich, productive region it is today. Corn and soybeans dominate in the region, and high prices for both commodities in recent years have encouraged farmers to keep sowing more rows, said Joe Logan, director of agricultural programs for the Ohio Environmental Council.

"There is a compelling economic interest for farmers to maximize productivity," Logan said.

Below the surface of the fields lie networks of perforated tubing, which pull excess water from the soil and send it to the lake, rich in phosphorus, Logan said.

Before the 1970s, phosphorus runoff to Lake Erie's western basin was mostly due to municipal sewers and industry, said David Baker, who founded the National Center for Water Quality Research at Heidelberg University in Tiffin, Ohio, in 1969. By 1980, the phosphorus from agricultural runoff was almost twice the amount from municipal sources, he said.

The patterns also changed. While municipal sources of pollution tend to be consistent throughout the year, agricultural runoff increases tremendously in the spring with the swelling of rivers and streams from the rain.

Since the 1990s, dissolved phosphorus has gone up dramatically from agricultural runoff, and between the years of 1981 and 2008, the ratio between agricultural phosphorus and municipal phosphorus has been 3-to-1.

"The spring loads of 2011 were the largest we'd ever seen since we began monitoring in 1975," said Baker. That increase undermined the successes in reducing municipal phosphorus through an agreement with Canada and with amendments to the Great Lakes Water Quality Agreement.

Ironically, no-till agriculture, a practice designed to improve the environment by not degrading the quality of the soil, has helped facilitate the carriage of nitrogen to the lake. Phosphorus fertilizer lies on top of the soil instead of being dug into it.

Ohio bill to regulate fertilizer in the works
The project to study algal blooms and climate change came before the record algal bloom, said Allison Steiner, an atmospheric scientist at the University of Michigan and a co-author of the study.

"We really were very well poised to address the comprehensive nature of this problem," said Steiner. The group included a geospatial statistician, a water runoff modeler and economists who study land-use change.

Despite the gloomy future for Lake Erie's waters, there is room for mutually beneficial solutions to mitigate the problem, said Michalak. Washing phosphorus out with the rain is not only unhealthy for the lake, but a waste of money for farmers, so efforts to curb runoff would help both the environment and agricultural economy.

State agencies in Ohio are also seeking legislative solutions to better control agricultural runoff, said Logan. A bill has been drafted that would revise agricultural pollution laws to authorize the director of the Department of Natural Resources to designate certain watersheds in "distress," which would require the implementation of a watershed management plan. It would also require farmers who apply fertilizer to be certified by the state Agriculture Department.

Although most of the phosphorus runoff comes from crop fields, Steiner doesn't believe that reducing fertilizer is the best solution to the problem.

"I think that's an easy conclusion to draw," she said. "But the problem is much more complicated than that."

What's needed, Steiner said, is better communication to farmers about changes in rainfall and a better understanding of the adaptation measures.

Michalak of the Carnegie Institution agrees.

"One of the take-home messages is that this is a complex system," Michalak said. "Being too myopic and looking at one factor is clearly not the full story."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500