Weekly Lake Erie Algal Bloom Outlook | Protecting our water

TOLEDO, Ohio Each summer, blue-green algae build up in Lake Erie, affecting water quality and outdoor recreation to varying degrees. Weather conditions affect the size and severity of harmful algal blooms (HABs). In early May, NOAA released its first western Lake Erie algal bloom forecast of the season. Based on the weather conditions of the last few weeks, an updated forecast was released on Thursday, May 23.

In this article, meteorologist John Burchfield will preview the 2024 harmful algal bloom and provide weekly updates based on the latest data.

Algal blooms are fed by nutrient runoff in the Maumee River and Lake Erie. Nutrients such as phosphorus and nitrogen enable blue-green algae to spread rapidly during the summer months. Heavy rain and warm temperatures accelerate the development of harmful algal blooms.

So how have weather conditions this spring affected the start of this year’s algal bloom? Heavy spring rains have increased runoff in Lake Erie, flooding its waters with high levels of nutrients. During April, the Maumee River’s phosphorus levels were the second highest on record since 2003.

April was the wettest on record in the Toledo area with 7.94 inches of precipitation, marking just the fourth time on record April precipitation exceeded half a foot. This precipitation leached phosphorus and nitrogen from the farm fields of northwestern Ohio into the Maumee River and eventually into Lake Erie.

Researchers measure total bioavailable phosphorus (TBP) levels in the Maumee River near Waterville to predict how nutrient runoff will fuel blue-green algae growth during the summer. TBP, measured in metric tons, can be compared to past years to predict future algal blooms.

RELATED: Heavy spring rain expected to lead to massive algal blooms in Lake Erie

As of May 21, TBP levels were measured at 263, similar to 2022 and 2023. Given that both past seasons featured moderate to larger than average algal blooms, this similarity in phosphorus levels is a useful metric for determining severity.

TBP levels can vary widely in late May, ranging from less than 100 (2012) to over 700 (2015). High TBP levels early in the season, such as in 2015, are a worrisome sign regarding the development of a potentially harmful algal bloom. With moderately high phosphorus levels early this season, experts are predicting an average or slightly larger than average algae bloom.

Despite the large nutrient load that occurred during the historically rainy April, the frequency and intensity of rainfall decreased significantly during May. With only 1.58 inches of precipitation, May’s rainfall is well below average. Because of this decrease in precipitation, TBP levels have increased only slightly since NOAA’s initial forecast in early May. As a result, the initial forecast remains largely on track.

The bloom, which is usually concentrated in the western Lake Erie basin, usually begins to form in mid- to late July. It is distributed in the fall, but the timing depends on the frequency of wind events in September, according to NOAA.

RELATED: Lucas County Commissioners, Toledo City Sue US EPA Over Mega Farm Runoff Regulations

So what can you expect for this year’s harmful algal bloom? An average to slightly above average bloom is expected, with the final result depending on June rainfall and temperatures. A wetter, warmer start to summer will lead to more severe algal blooms, and drier, cooler conditions may inhibit the spread of blue-green algae.

Bloom severity is quantified on a scale of 1-10, with higher numbers representing more significant impacts on lake water. Experts predict a range of 4.5-7.5 this year similar to the initial forecast in early May. This range expresses a good deal of uncertainty, and algal blooms will depend heavily on weather conditions in the coming weeks.

While harmful algal blooms are likely to fall well below levels experienced a decade ago during the historic water crisis, warm, wet weather could lead to another severe algal bloom affecting water quality and recreation in nature.

Stay tuned to the WTOL 11 Weather Team and check this story each week for updates on the 2024 Harmful Algal Bloom.

Harmful algal blooms affect Northwest Ohio wineries. Health risks caused by microcystin can cause cities to close beaches, preventing and limiting boating, fishing and swimming tourism. According to researchers, Lake Erie tourists spend more than $15 billion annually, generating $1.9 billion in state taxes. It also supports over 100,000 tourism-related jobs.

HAB could even affect coastal property values, analysts said. For every 1 g/L (microgram per liter) increase in harmful algal blooms in Lake Erie, lakefront homeowners can expect their property values ​​to decrease by 1.7 percent, or $2,205.

HABs also produce microcystin, a known toxin that can affect humans and wildlife, according to NOAA.

A decade ago, WTOL 11 pledged to seek answers and hold officials accountable in our ongoing fight to protect our water. Now, as we mark 10 years since the water crisis in Toledo, we continue that promise we made to our community. Join us as we explore the changes that have been made, find out which promises have been fulfilled, and determine if we are truly better off now than we were in the summer of 2014.