Phosphorus legacy causes recurring blooms according to ELA lake study

Friday, June 20, 2014

 David O'Connell.For 40 years scientists have studied the effects of adding phosphorus to Lake 227, the world’s longest continuous experiment in phosphate pollution. Located in the Experimental Lakes Area (ELA) research facility, Lake 227 is most famous for demonstrating that excess phosphate in the water causes algal blooms, leading to bans worldwide on phosphates in laundry detergents.

Yet harmful algal blooms in hundreds of Canada’s water bodies like Lake Erie and Lake Winnipeg persist.

Researchers from the University of Waterloo’s Ecohydrology Research Group have turned to Lake 227 once again for answers and found that phosphorus in the lake sediments is being recycled back into the water, which can cause the algal blooms to return even if phosphate inputs are stopped or drastically reduced.

This is the first detailed study into the various organic forms of phosphorus in the lake’s sediments and their potential role in the internal recycling of phosphorus.

Lake 227 is like the Rosetta Stone of human-induced phosphorus pollution,” said Philippe Van Cappellen, Canada Excellence Research Chair in Ecohydrology and head of the Ecohydrology Research Group. “Sediments from the ELA are providing us with unparalleled environmental archives that allow us to reconstruct the response of lake ecosystems to human pressures.”

Results show that a significant fraction of the phosphate added to the lake is bound to natural organic matter. These phosphorus complexes eventually settle to the bottom where they accumulate in the sediments until they are broken down by microorganisms. When this happens, the phosphorus is released and may eventually find its way back into the lake water where it can stimulate algal growth.

Even if we stop adding phosphate now, that doesn’t immediately solve the problem,” said research associate Dr. David O’Connell who led the study. “The sediments contain a legacy of past phosphorus pollution. You’re often left dealing with a delay of 10 years or more during which the sediments act as an internal source of phosphorus and sustain algal blooms in the lake.”

The study was presented as a talk at the 2014 Goldschmidt conference last week in Sacramento, California. The study’s authors include Nienke Ansems, Hannah Chessel, Johan Wiklund from the Department of Biology, Thilo Behrends of Utrecht University in the Netherlands, ELA founding director David Schindler and Diane Orihel from the University of Alberta.

Funding for the project was provided by the Canada Excellence Research Chair Program.

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