By Dusty Sonnenberg, Ohio Field Leader
“So where is it coming from, and what more can we do?” This is a question many northwest Ohio farmers ask themselves, knowing they will likely be the ones to take the blame as the subject of the Lake Erie algal bloom regularly makes headlines in the paper and on the evening news. Considering the weather challenges faced during the planting season of 2019, many farmers are left perplexed.
According to Jason Williamson of the Williamson Insurance Agency, the question is valid. “Looking at the prevent plant numbers released by the USDA, 30% of the acres in the counties we cover in Northwest Ohio are prevent plant,” he said. “Wood County alone reported over 50% prevent plant.”
Those are acres where farmers did not get a crop in the ground, and the vast majority did not apply any fertilizer this spring or summer. With that being said, the lake is on track to have its fourth or fifth largest harmful algal bloom (HAB) on record. Farmers are asking where the phosphorus is coming from, and what more can they do if this happens when they didn’t apply fertilizer or manure.
According to the National Oceanic and Atmospheric Administration’s (NOAA) Lake Erie Harmful Algal Bloom Bulletin, released on Sept. 3, “The Microcystis cyanobacteria bloom continues in the western basin of Lake Erie. Recent satellite imagery showed the bloom extending from Maumee Bay north along the Michigan coast, to Brest Bay; east along the Ohio coast to the Marblehead Peninsula, and offshore through the Bass Islands, and up to 10 miles east of Pelee Island.”
“So far, we are on par with the July prediction of a 7.5 or 8 for the severity of the bloom, which would make it possibly the fourth or fifth largest,” said Chris Winslow, director for Ohio Sea Grant and Ohio State’s Stone Laboratory.
In July, NOAA and its research partners predicted western Lake Erie would experience a harmful algal bloom of cyanobacteria this summer significantly larger than the mild bloom in 2018. Scientists predicted this year’s bloom to measure greater than a 7 on the severity index. The severity index is based on a bloom’s biomass — the amount of its harmful algae — over a sustained period. The largest blooms, 2011 and 2015, were 10 and 10.5, respectively. Last year’s bloom had a severity of 3.6 which is considered a mild bloom.
Ohio soybean farmers, along with other commodity groups in the state, have invested millions of dollars in research aimed at determining the cause of the algal bloom, and finding potential management practices to functionally mitigate the problem. Farmers are working closely with universities, government agencies, and environmental groups to make changes to protect the water. Practices like cover crops, nutrient management plans, soil sampling and more are increasing every year, and farmers are applying less fertilizer than ever before.
So where is all this coming from? When asked this question, Winslow said the phosphorus in the lake that is causing the bloom is largely coming from “three buckets” as he likes to refer to them. The “first bucket” as he refers to it is what he identifies as current use phosphorus.
“This is real-time phosphorus. This phosphorus would come from fertilizer applied in the spring that is available to the plants and can get in the water right now. Due to the lack of planting this spring and limited fertilizer application as a result of the weather, this first bucket is most likely not a substantial contributor this year,” Winslow said. “The second bucket is from the legacy phosphorus. This is the phosphorus that was already found in the lake or is held in the soils’ that have high phosphorus levels. This is phosphorus available to the algal bloom every year. The third bucket of phosphorus results from the heavy rainfall events and large amounts of precipitation we frequently receive.”
These large rain events move phosphorus found in the soil and environment into the lake. Winslow surmises that the phosphorus contributing to this year’s bloom is largely from the legacy phosphorus and any phosphorus the large rain events have carried to the lake.
“Our prediction was that 24% less phosphorus would be entering the lake (due to less fertilizer being applied) this year. We have equipment that pulls river water samples at various locations all across the watersheds in the Western Lake Erie Basin. We can detect when, and in general where, we get phosphorus (P) and nitrogen (N) spikes as the water travels to the lake. We know what the water samples show at the beginning, and as the various tributaries empty into the watershed along the way,” Winslow said. “For example, in a normal year, we can tell when farmers are sidedressing their corn because if we get a large rain event, we see a spike in the N level in the samples from those areas at that time. With our sampling equipment, we know the levels of N and P before and after each event.”
Winslow explained that this year was beneficial to the researchers because they were able to observe a change in one of the variables, or “buckets” as he describes them. The decline in the amount of “real-time” phosphorus that was applied in the spring and summer on a large scale has allowed researchers to observe the response of the bloom with the other two “buckets” remaining relatively the same. Winslow said having the “three buckets” makes finding simple solutions to the algal bloom situation challenging for farmers.
“If we did not have the ‘third bucket’ of large and frequent rain events this year, we would have had a regular planting season and more normal fertilizer application, which is the source in the ‘first bucket.’ Due to the frequent and heavy rains in the ‘third bucket,’ we did not have as much of the ‘first bucket’ real-time phosphorus applied, but still had the “second bucket” legacy phosphorus, and still more of the ‘third bucket’ heavy rains,” Winslow said. “Any combination of the buckets is a problem.”
When explaining how the forecast for the harmful algal bloom is made, he noted that the formula to forecast the bloom is based on the river water samples from the first of March to the end of July in a given year.
“Anything prior to the first of March, and the lake is too cool for it to have any real impact on the algae. By August and September, the lake is beginning to cool again, and additional phosphorus by that point will have little to no effect on the current bloom,” he said. “Typically, the peak of the bloom is around the end of August or early September. Sometime later in October NOAA will issue their final number rating.”
Winslow pointed out that the size of a bloom is not necessarily an indication of how toxic it is and the location of the bloom is important to consider as well.
“Research has found that high concentrations of phosphorus in the water can increase the size of the bloom. High concentrations of nitrogen in the water can increase the toxicity of the bloom,” he said. “Winds drive the location of the bloom. The strong easterly wind has kept the bloom largely in the WLEB.”
He also noted that the waves mix the water and algae bloom. This can impact drinking water quality for many of the cities that get their water from the lake because the water intakes are located near the bottom of the lake.
“On a calm and still day, the bloom is largely on or near the surface. As the winds pick up and the water churns, it causes the bloom to mix and be distributed across the various layers of the water,” Winslow said. “If the water is calm and the bloom is near the surface, it is not a concern. It becomes more of a concern when the water churns and the bloom mixes in the different layers that it could potentially be a factor for the water intake structures near the bottom.”
According to NOAA, the observed conditions the end of August and beginning of September promoted mixing and eastern transport of surface bloom concentration, now present in the central basin. Measured toxin concentrations were below recreational thresholds throughout most of the bloom extent.