How to rein in toxic bloom’s perfect storm

CORNELL (US) — The combination of climate change and nutrient runoff is expected to escalate toxic aquatic blooms, but localized efforts may be successful in controlling their spread from farms and lawns to streams, lakes, and ultimately oceans.

Cyanobacterial blooms, which occur in fresh and marine waters, can be toxic to animals, including humans, that swim in or drink contaminated water. The blooms can lead to substantial economic losses due to water treatment costs, declining property values, and lost tourism and recreational revenues.

Cyanobacterial blooms are part of a mix of toxic phytoplankton that create dead zones in the Gulf of Mexico each summer, for example.


Published in the journal Science, an analysis of prior experiments, historical data, and modeling studies, shows that warming waters are favorable to cyanobacterial blooms only in the presence of high nutrient concentrations. When lakes receive lower nutrient inputs, cyanobacterial blooms can be kept in check in spite of warming water.

“Nutrients are consistently the more important driver of blooms in lakes,” as compared to climate change, says Cayelan Carey, a graduate student in ecology and evolutionary biology at Cornell University and a co-author of the paper with Justin Brookes, associate professor of ecology at the University of Adelaide, Australia.

“This is good news, because decreasing nutrient loading, which operates on a local and decadal scale, is a much more feasible option for controlling cyanobacterial than decreasing global temperatures, which requires international cooperation and century-long time scales,” she adds.

As a result, increasing cyanobacterial blooms are not inevitable if local communities work together to minimize nutrient runoff.

For example, people often overuse fertilizers and can reduce the amount they use on lawns, gardens, and farm fields, Carey says. For lawns that reach the edge of a stream, lake or pond, planting a buffer of wetland plants will absorb nutrients before they run off into the water.

Also, such impervious surfaces as roads and parking lots lead to greater runoff; increasing vegetation and removing impervious surfaces allow water to soak into the ground and slow such runoff.

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