A mysterious algae first began coating northern Michigan lake beds around 2010. After years of research, scientists and residents still wonder what triggered the growth and whether there’s a solution. Jan Stevenson, a retired professor of integrative biology at Michigan State University, has helped lead research on golden brown algae (aka golden brown crud). Stevenson first thought the cause was environmental change caused by humans. But in 2023, we know more about its composition and more about how it changes during the summer. Stevenson spoke at an ESLA Shore Thing in late September. Here’s a link to the video presentation on ESLA’s YouTube channel HERE.
What is Golden Brown Algae? GBA is a combination of cyanobacteria, fungi and diatoms — tiny individual cells of algae that can colonize. There’s no evidence the cyanobacteria in the algae is hazardous to health. Researchers remain stumped why GBA keeps proliferating.
One hypothesis: Might higher phosphorus levels due to groundwater contamination be linked? Nope. Research shows phosphorus is decreasing and has been in the northern Michigan lakes for decades.
Explain: Typically, more phosphorus means more algae and plant growth in freshwater ecosystems. But not necessarily. Stevenson says one good example of this is in the Florida Everglades where phosphorus concentrations increased and tightly-woven mats of algae disappeared. Perhaps surprisingly, Stevenson says some of the diatom species in those Florida mats are the same as those in the Torch Lake algae he’s studied. That includes a specie found in the Torch Lake mats when they’re at their thickest in late summer. Much of Stevenson’s research has focused on Torch Lake.
If phosphorus is down why is GBA increasing: Stevenson says it could be Quagga and Zebra mussels removing phosphorus from the water column as they pull in and filter out particles. It could be atmospheric nitrogen depositing in the water after decades of heavy nitrogen fertilizer use around the globe. That deposition could be changing variables like the lake’s growing conditions, the ratio of phosphorus, and the composition of different algal species. In other words, it could be a combination of factors or something else entirely. ESLA hopes to tap into the continuing research. Stay tuned for updates.