Uncovering the mysteries of cyanobacteria in inland lakes

Rebecca North grew up on the shores of the Bay of Quinte in Belleville Ontario, a picturesque location off the coast of Lake Ontario. Known as the ‘heart of the sea and the river’ it has reputation for sailing, walleye fishing, and harmful algal blooms or HABs. “I grew up swimming in the Bay as a kid. Now, people don’t even let their dogs near it,” notes North when she talks about her hometown. For North, growing up on the water instilled in her not only a love for water, but also a fascination with phytoplankton.

“There is a lot of conflicting research on what causes harmful algal blooms. We have seen an increase in blooms in recent years – both in times and in places. And we know nutrients have an impact,” notes North. “But what if nutrients aren’t the full story? What other factors come into play? Do climate change, rising temperatures and light have a role to play in bloom development?”

This is one of the fundamental research questions her lab is focusing on. Past research has shown that cyanobacteria like warm temperatures and high nutrients. While the occurrence of blooms in lakes that are surrounded by agricultural lands in the hot summer months are common, North’s lab and others are finding blooms under ice and in areas without high nutrient levels – for example in the boundary waters of Northern Minnesota and Lake Superior.

This has led North and her colleagues to investigate if changes in water temperature due to climate change, or if changes in light are impacting bloom production and persistence. “Cyanobacteria have little balloons that allow them to go to areas that have more light, so it is possible that cyanobacteria are outcompeting other phytoplankton for the limited light available under ice,” notes North.

Another fundamental research question fueling her work is what causes phytoplankton – including cyanobacteria – to release toxins? Research shows that toxin levels are not linearly related to the telltale sign of a bloom – green water. According to North, water can look clear and still have high levels of cyanotoxins.

“You can see the cyanobacteria present in the lake that do produce toxins, but just because they are there does not mean they are actively producing toxins. We don’t yet know why they produce toxins and what factors make them turn toxins on and off.”

With so much still unknown when it comes to harmful algal bloom research, North and her collaborators are working with citizen scientists and students to help gather data and examine these important questions. North helps run the Reservoir Observer Student Scientists or ROSS program at the University of Missouri. The program engages high school students in water quality monitoring in their local lakes and reservoirs while also teaching the next generation of scientists and decision makers about the impacts of water quality on their community. High school classes participate in a limnology curriculum, learn first-hand how to conduct water sampling, and conduct weekly water monitoring on a local water body year-round.

Currently, students in Columbia, Missouri and Waterville, Minnesota are collecting weekly water samples during the school year as a part of the program. Those samples are then sent back to North’s lab where they are used to help understand what factors correlate with bloom and toxin occurrence. The ROSS program, which recently received a NIFA SPECA grant, is helping to empower high school students to pay attention to the water quality in their local lakes and, by engaging them in analyzing their own water samples, it is introducing them to limnology as a future field of study.

North is also a mentor for the Watershed Management Research and Outreach Internship Program, and in summer 2023 will be welcoming another undergraduate to her team who will help mentor the ROSS students.

“The watershed intern helps train the ROSS students; it is a great opportunity for near to peer learning. In addition to collecting samples themselves, the intern also works with the high school students, so we have ongoing monitoring in the fall and spring,” notes North. “I have seen the impact of exposure to limnology at a young age – in fact I am an example of that. Hopefully, by continuing that tradition we are ensuring that we have a strong group of scientists following us to help continue to uncover the answers to research questions.”

Rebecca North, University of Missouri

Rebecca North is an Assistant Professor of Water Quality in the College of Agriculture, Food and Natural Resources. Her research is focused on addressing the question: What controls phytoplankton biomass of inland waters? North’s team focuses on the effects of multiple stressors on nutrient cycling, bioavailability, and primary production in Missouri water bodies with particular attention to the source and timing of nutrient loading and the response of the receiving water body. Ecosystem stressors include, but are not limited to: climate change, landscape modification (i.e., agricultural, urban, and industrial applications), eutrophication, and invasive species (i.e., zebra mussels). North’s research is conceptually driven and applies field, lab, and quantitative approaches to studying issues in watershed and lake management on a year-round basis.