Harmful Algal Blooms
on the Rise
Scientists, agencies, communities, and lawmakers are working to understand the drivers behind the proliferation of harmful algal blooms (HABs) and developing science-based solutions to move forward from a reactive to a proactive approach.
The crisis ended after a little more than 48 hours, but it remains an example of just how severe the challenge of harmful algal blooms can be—and it helped inspire Congress to enact HR 212 in 2015, requiring the EPA to develop a strategic plan to assess and manage risks associated with cyanobacterial harmful algal blooms. More recently, in April of this year Ohio Congressman Robert Latta introduced House Bill 1893, the Great Lakes and Fresh Water Algal Bloom Information Act. The bill would require the National Oceanic and Atmospheric Administration (NOAA) to create a database on algal blooms in the Great Lakes. Track the bill here. State legislation has also followed.
Algae are natural and indispensable components of freshwater ecosystems, but increasing levels of nutrients in many water bodies allow cyanobacteria to thrive in the warmer months of the year, beating out beneficial algae and creating these damaging blooms.
“What happens in the Great Lakes, and is also a big problem in Florida’s Lake Okeechobee, is that rainfall in late winter or early spring loads up the lakes with nutrients,” said Kevin Donovan, senior vice president for Ecology and Environment, Inc. (E & E). “Then in the warmer months, these toxic algae start to grow and multiply to the point where they can cover huge swaths of lakes and rivers.”
Wastewater treatment plants, septic tank leach fields, and runoff from lawns and golf courses contribute nutrients to water bodies, but in most ecosystems the top contributor is agriculture. In western Lake Erie, this has been borne out by decades of research tracking the high concentrations of phosphorus flowing into the lake from the Maumee River watershed, where corn and soybean farmers apply large amounts of phosphate fertilizer and manure.
Even though roughly equal amounts of phosphorus flow into the lake from the urbanized Detroit River watershed, the low concentrations have little impact on CHABs. “The algae don’t respond to low concentrations in the same way,” said Tom Johengen, associate director with the Cooperative Institute for Limnology and Ecosystems Research (CILER) at the University of Michigan. “That’s why we don’t get the blooms associated with the Detroit River, which does contain wastewater inputs, that we do with the Maumee River.” See our Living with Toxic Algal Blooms: Lake Erie article.
One input to Lake Erie which is not supporting CHAB growth is the sediment deposited by the dredges that maintain Toledo Harbor’s channels. Responding to concerns from the Ohio Environmental Council and others, the U.S. Army Corps of Engineers commissioned Limnotech and E & E in 2013 to assess whether open-lake placement of Toledo Harbor dredge spoils was contributing to the troublesome algal blooms.
Using placement area buoys deployed with an Acoustic Doppler Current Profiler (ADCP) and data from University of Toledo and NOAA, “we determined that 97 percent of placed material settle immediately and that the dredge spoils have a negligible impact on algal blooms in Lake Erie,” said Tom Heins, Principal Civil Engineer at E & E. Learn more about the project here.
While scientists who study the causes of CHABs have focused mostly on phosphorus, nitrogen is also a concern that some researchers say should be given more attention. According to a September 2016 article by Hans Paerl, et al, published in Environmental Science and Technology, experiments on several large lakes show that CHABs are often stimulated more by combined phosphorus and nitrogen loading than by either alone.
Researchers also suspect that the increase in the application of urea to U.S. farmland since the 1960s has helped certain species of cyanobacteria to grow more rapidly. “There has been a massive shift in U.S. agricultural use of nitrogenous fertilizer away from ammonium nitrate and toward urea,” said Steve Wilhelm, professor of microbiology at the University of Tennessee and head of UT’s Aquatic Microbial Ecology Research Group. “So we’ve become interested in the role that urea may play in stimulating and maybe even driving the microsystin blooms and how urea discharges may influence the types of algae we see.”
Reducing phosphorus and nitrogen runoff from farms is a complex, costly and long-term undertaking focused mostly on encouraging and financially supporting farmers to implement best management practices (BMPs) that reduce erosion. See our article, The Ag Angle: Addressing Farm Runoff. Researchers and policymakers are concerned that some trends in Midwestern farming methods are making CHABs worse. At the same time, it is thought that more efficient targeting of USDA financial support for BMPs would result in greater reductions of phosphorus and nitrogen erosion into waterways.
Increasing nutrient loads are not the only cause of CHABs. High temperatures and sluggish water movement are major contributing factors—the shallowness of western Lake Erie makes it naturally susceptible to warming and CHABs.
Not surprisingly, climate change is expected to make CHABs more common and more severe. “Cyanobacteria become more competitive the warmer the water is,” said Johengen. “Additionally, as we see more variability in our weather patterns and an increase in extreme rainfall events, we can expect more nutrient loading. Data on Lake Erie from recent years shows that after we’ve had extreme rainfall events, we see extreme loss of nutrients from the watershed, followed by higher levels of harmful algal blooms.”
For smaller lakes and ponds, artificial mixing devices and chemicals can be used to mitigate CHABs. Seasonal hydrogen peroxide treatments have been successful in ridding small lakes of CHABs without harming other aquatic life or leaving biocide traces in sediments and the food chain as occur with metal toxicants like copper salts.
But for larger lakes, these and similar technologies are very unlikely to be useful. “Some of these technologies could be effective in local reservoirs that supply drinking water, but I haven’t seen anything that can be scaled to the size and volume of water in the Great Lakes,” said Johengen. “Managing nutrient inputs to minimize the extent and toxicity of CHABs is really the only cure.”
Learn more about how researchers are using advances in sampling technologies to monitor algal blooms in our Remote Sensing Holds Promise article.
Kevin Donovan – Senior VP
Tom Heins – Regional Engineering Manager
Sharon Ewe – Chief Ecologist
Marcia Galloway – QA Director/Chief Chemist
Harmful Algal Blooms on the Rise
Scientists, agencies, communities, and officials work to understand the drivers behind the harmful algal blooms and develop science-based solutions