The 2024 Harmful Algal Bloom (HAB) Season in Review
With a record high number of bloom and illness reports, the 2024 bloom season was one of the busiest yet! This month's issue has all the details about the blooms and illnesses we saw this year, a recent HAB program adventure in Maine, and upcoming conferences geared toward water enthusiasts.
Bloom data
Our partners at the Wisconsin Department of Natural Resources (DNR) work diligently to collect bloom reports from water bodies across the state. This year, they documented 253 bloom reports — a whopping 45% more than in 2023! Of these reports, 75% were confirmed cyanobacterial blooms.
According to the DNR, blooms were reported in every month of this year except for February. The first blooms were spotted in January and had the appearance of "pink ice" under the lake's frozen surface. These blooms were identified as Planktothrix rubescens. Since this species is adapted for cold and dark conditions, forming blooms under the ice are not uncommon for them. The most recent cyanobacterial bloom was observed just last week (December 2) in a lake in Fond Du Lac County. It is believed that this bloom was likely the result of nutrients mixed into the water during fall turnover.
Most bloom reports came from southern and northern regions of Wisconsin in areas where there are more lakes, while the least amount of reports came from areas with the fewest lakes. These blooms encompassed everything from small accumulations lasting only a couple of hours to longer or repeated blooms in lakes with high nutrients. Check out the map below (courtesy of the DNR) to learn more about the types of blooms that were reported and where they were located.
 Why did we see so many more blooms this year compared to last year?
According to DNR's algae expert, Gina LaLiberte, the warm winter, spring, and fall extended the growing season for cyanobacteria. If cyanobacterial populations do not die off in fall and winter, and then get a jump start on growth in warm springs with heavy rainfall, it can lead to the growth of more blooms.
Did you know? This year's winter was the warmest winter documented since record-keeping began in Wisconsin in 1895! Source: Winter 2023–2024 Climate Summary.
What else did we find in the water?
Gonyostomum semen
A Gonyostomum bloom was reported in a 100-acre lake in Barron County this past summer. Gonyostomum semen, a species of freshwater algae, grows best in waters that are eutrophic and stained like tea. Its cell wall contains organelles that eject slime threads when disturbed, causing a slimy coating on swimmers’ skin.
|
Wild Celery Plants
A lake in southern Wisconsin showed accumulations of wild celery plant (Vallisneria americana) male flowers. These flowers are tiny and granular, and can form whitish to light tan scums if a lot of them are floating together. Consequently, they could resemble and be mistaken for cyanobacterial blooms.
The image on the left is courtesy of Gina LaLiberte.
|
Health data
Similar to bloom reports, the DHS HAB Program saw an uptick in illness complaints. We received 39 health complaints consisting of 35 human and four animal illnesses. After thorough investigation, we determined that 11 of the human illnesses were likely related to HAB toxicity. A water sample was tested for one of these cases and the results showed high levels of microcystin at 10 ug/L, which is above the EPA's swimming advisory level. Surprisingly, we did not document any HAB toxicity animal cases. Other interesting statistics from this years HAB illness case include:
- Reported exposures to cyanoHABs occurred in water bodies located in Dane, Barron, Calumet, Green Lake and Racine counties.
- The majority of cases reported exposure at private residential properties.
- The most commonly reported symptoms were diarrhea and fever.
- Ages ranged from 8 to 35 years old.
|
Interested in seeing how this year's illness reports compared to previous years? The graph below shows historical data from the past nine years.
Last month, HAB Program manager, Jordan, traveled to Portland, Maine to attend the US Symposium on Harmful Algae. This week-long conference spanned every HAB topic imaginable and brought together researchers from across the world. Jordan had a busy week learning about emerging HAB issues and ongoing projects in marine and freshwater systems, presenting about HABs in Wisconsin (pictured on the right), and connecting with other leaders in HAB research.
|
Save the Dates!
January 9–10, 2025: The 5th Annual Virtual Harmful Algal Bloom Symposium
This year’s symposium will focus on four key themes related to HABs: monitoring, forecasting and detection, prevention and treatment, human dimensions, and climate change impacts. Visit the symposium's website for updates on registration and the agenda.
March 26–28, 2025: The Wisconsin Lakes and Rivers Convention
This popular conference joins science, education, and citizens to empower people to work together to care for our water resources. It will take place at the Holiday Inn Convention Center, in Stevens Point. Wisconsin's HAB Team (Jordan, DHS, and Gina, DNR) will talk about HABs in Wisconsin. They will be joined by Tristin Faust from the Eau Claire City-County Health Department, who will be talking about their beach monitoring program. We'd love to see you there! Visit the Wisconsin Water Week webpage for more information.
Stay in Touch
Missed a past issue? Previous issues are available on our Resources for Health Professionals webpage.
Email us your burning questions! If others can benefit from hearing the answer to your question, we’ll feature it in a future issue.
Remember that we are always available for consultation on any HAB health-related issue by email or phone (608-266-1120).
|
|
