by Bob Heath
For a full day, the topic of discussion among academics, federal and state government officials, ecosystem managers, non- governmental organizations, the public, and even a few retired professors attending the Understanding Harmful Algal Blooms: State of the Science conference hosted by the University of Toledo on September 12, was the damaging effects of recurrent algal blooms on the Lake Erie ecosystem and current efforts to abate them. The conference was produced by The Ohio State University and Ohio Sea Grant, an organization that promotes research in the Lake Erie and the Great Lakes with funding from National Oceanic and Atmospheric Administration.
The premise of the conference was that the Lake Erie ecosystem begins at the crests of the watershed on both sides of the border. Remediation of the recurrent cyanobacterial (i.e. blue-green algae) blooms that damage water quality, harm wildlife and threaten human health requires understanding the causes of these blooms and removing those causes from the watershed with the goal of a healthier ecosystem for the physical, social and economic benefit of all stakeholders. Below is a synopsis and synthesis of the 14 papers presented at the conference.
Better Prediction of HABs (Hazardous Algal Blooms) in Lake Erie
The ability to predict the timing and extent of cyanobacterial blooms in the western basin of Lake Erie is a measure of how well scientists understand the causes of these blooms, sometimes referred to as hazardous algal blooms (HABs). The better that scientists understand the causes of HABs, the better they can predict them. Past predictions were so-so. In some years, the predictions were accurate but, in other years, they missed the mark. Something was missing in the equations used to predict these algal-bloom events, but what was it?
Dr. Rick Stumpf, an oceanographer at NOAA, presented improvements in the ability of scientists to predict when HABs occur and how intense they will be. The size of the annual HAB in the western basin of Lake Erie is determined by the amount of bioavailable phosphorus (BAP) that is loaded into the basin, largely through the Maumee River. Only BAP loaded into the lake from early March through mid-June leads to the bloom. Recent studies have shown that the extent of the bloom also is determined by the temperature of the water in June through mid-July, even though the bloom reaches its largest size in mid-August through early September.
Using only the spring BAP loading to the lake, the HAB in 2019 would have been predicted to be among the largest on record. On a scale of 1 to 10, it would have been predicted to be about a 9.0 or 9.5. However–and this is the important point–because June was wetter and cooler than normal, the bloom was predicted to be modest, at 7.5. Observations to date indicate that the bloom appears to be about 7.5, exactly as predicted. This indicates that scientists are understanding the causes of these events better because the predictions are borne out by the observed extent of the HAB.
Progress to Abate P (Phosphorus) Loading to Lake Erie
In addition to the ability to predict HABs, scientists want to be able to prevent the blooms–or at least to diminish them. Many years of study into the land-use effects on Lake Erie’s water quality have shown that the majority of phosphorus loaded into the lake is from agricultural activities, primarily from the Maumee River watershed. BAP runs off fields in one of two ways: from the surface of the field as erosion or from drainage through tiles placed below ground that empty into streams and eventually into Lake Erie. Abatement is achieved best by having tile drainage pass through a phosphorus filter, a device that traps phosphate on industrial slag before it runs into streams. The filter is an efficient device but also an extremely expensive one, precluding its use on all farm fields.
Not all farm fields, however, bleed phosphorus equally. Some fields are much more potent sources of phosphorus. Scientists are looking for ways to identify these phosphorus hot spots and remediate them with phosphorus filters or other techniques. These other techniques include riparian buffer strips between fields and streams, the use of cover crops to retain phosphorus, and constructed wetlands. None of these techniques alone is sufficiently effective. The best approaches seem to be a combination of these techniques used in sub-watershed hot spots.
Identification of the source of the phosphorus has been relatively easy, and technological advances have readily identified procedures and practices that are likely to be effective. Implementation of these procedures and practices, however, will require substantial public funding and cooperation by a majority of individual farmers. Implementation also will require a well-informed public to provide the necessary political will and societal patience to achieve the eventual outcome of a healthier Lake Erie. Likely, it will take at least a generation to achieve the intended results.
Can that happen, or is this a hopeless pipe dream? The success of the Chesapeake Bay Watershed Management Plan shows that it is possible to achieve the necessary cooperation between many layers of government and society. The Chesapeake Bay experience may well serve as a template scenario of management development and implementation.