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Large summer harmful algal bloom predicted for western Lake Erie

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Posted July 12, 2019

University of Michigan researchers and their partners are forecasting that western Lake Erie will experience a significant harmful algal bloom this summer.

Scientists expect this year’s bloom to measure 7.5 on the severity index, but it could possibly range between 6 and 9. An index above 5 indicates blooms having greater impact. The severity index is based on the bloom’s biomass—the amount of algae—over a sustained period.

Illustration by Aerial Associates Photography, Inc. (Zachary Haslick) via NOAA cc 2.0

The largest blooms occurred in 2011, with a severity index of 10, and 2015, at 10.5. Last year’s bloom had a severity index of 3.6, while 2017 was 8.0. This year’s forecast was released by the National Oceanic and Atmospheric Administration, which funds the research.

This year, the lake temperature has remained relatively cool due to the higher-than-average rainfall in the region, so the bloom is not expected to start until late July when the water temperature reaches 65 to 70 degrees Fahrenheit. This contrasts with 2018, when exceptionally warm weather at the beginning of June caused an early start.

“Because of the excessive spring precipitation, this year’s bloom is likely to be large,” said University of Michigan aquatic ecologist Don Scavia, a member of the forecast team.

“But bloom predictions—regardless of size—do not necessarily correlate with public health risk,” said Scavia, a professor emeritus at the School for Environment and Sustainability. “Local weather conditions such as precipitation, wind direction and water temperature also play a role.

“Even so, we cannot continue to cross our fingers and hope that drier weather will keep us safe. These blooms are driven by diffuse phosphorus sources from the agriculturally dominated Maumee River watershed. Until the phosphorus inputs are reduced significantly and consistently so that only the mildest blooms occur, the people, the ecosystem and the economy of this region are being threatened.”

Lake Erie blooms consist of cyanobacteria, also called blue-green algae, that are capable of producing the liver toxin microcystin, which poses a risk to human and wildlife health. Such blooms may result in higher costs for cities and local governments that need to treat drinking water, prevent people from enjoying fishing, swimming, boating and visiting the shoreline, and harm the region’s vital summer tourism economy. These effects will vary in location and severity due to winds that may concentrate or dissipate the bloom.

Lake Erie harmful algal bloom forecasts since 2002. Image credit: NOAA

Calm winds in July, especially in western Lake Erie, tend to allow the algal toxins to concentrate, making blooms more harmful. The bloom typically peaks in the western part of the lake in September. Most of the rest of the lake will not be affected.

“This extremely wet spring has shed light on the movement of nutrients from the land into Lake Erie,” said Christopher Winslow, director of Ohio Sea Grant and Stone Laboratory. “Despite the predicted size of this year’s bloom, portions of the lake will be algae free during the bloom season and the lake will remain a key asset for the state.

“Ongoing research continues to help us understand bloom movement and toxin production, and remains vital to providing our water treatment facilities with the tools, technology and training they need to keep our drinking water safe.”

The size of a bloom isn’t necessarily an indication of how toxic it is. For example, the toxins in a large bloom may not be as concentrated as in a smaller bloom. Each algal bloom is unique in terms of size, toxicity, and ultimately its impact to local communities. NOAA is actively developing tools to detect and predict how toxic blooms will be.

“This spring brought regular, heavy rainfall to the Maumee River watershed, which carried a lot of nutrients into the lake,” said Richard Stumpf, NOAA’s National Centers for Coastal Ocean Science’s lead scientist for the seasonal Lake Erie bloom forecast. “However, due to the amount of rain this year, farmers were unable to plant their fields, which reduced the nutrient concentration. That, combined with higher than normal lake levels, presents an opportunity to test the accuracy of our models.”

Western Lake Erie and an algae bloom as seen from a Landsat-8 satellite in September 2017. Image credit: NASA/USGS

The Lake Erie forecast is part of a NOAA ecological forecasting initiative that aims to deliver accurate, relevant, timely and reliable ecological forecasts directly to coastal resource managers and the public. In addition to the early season projections from NOAA and its partners, NOAA also issues HAB bulletins twice a week during the bloom season.

NOAA continues to expand the use of satellite data into its Lake Erie Harmful Algal Bloom Forecast System, which is helping improve the accuracy of bloom forecast products. The data comes from the European Union’s Copernicus Sentinel-3 satellite, which has instruments that measure coastal water color, and have proven to be especially useful for detecting and tracking algal blooms. NOAA is also continuing to work with its research labs and academic partners to refine and improve the models used to develop the forecasts.

“Communities along Lake Erie rely upon clean, healthy water to support their community’s well-being and economic livelihoods,” said Nicole LeBoeuf, acting director of NOAA’s National Ocean Service. “This forecast provides timely and trusted science-based information to water managers and public health officials so they can better anticipate blooms, mitigate impacts and reduce future outbreaks.”

Source: University of Michigan

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