Microbiology

UT Faculty Join New $6.5 Million Grant to Study Climate Links Between Algal Blooms and Human Health

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UT Faculty Join New $6.5 Million Grant to Study Climate Links Between Algal Blooms and Human Health

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Faculty in the University of Tennessee Department of Microbiology are part of a new $6.5 million, five-year federal grant to establish a virtual center for the study of links between climate change, harmful algal blooms, and human health.

Increased precipitation, more powerful storms, and warming Great Lakes waters all encourage the proliferation of harmful algal blooms composed of cyanobacteria, also known as blue-green algae. These microorganisms can produce toxins harmful to humans, pets, and wildlife.

Though the pea-green summer blooms in western Lake Erie are the best-known in the region, cyanobacterial harmful algal blooms, or cHABs, now occur in all five Great Lakes and in fresh waters around the US. These blooms can increase water-treatment costs for local governments and harm vital summer economies in communities that enjoying fishing, swimming, and boating. In the Knoxville area earlier this year, a cHAB of Planktothrix rubescens (“pink algae”) in Meads Quarry at Ijams Nature Center closed swimming and other activity for a month.

Student researchers collect water samples from a cyanobacterial harmful algal bloom in western Lake Erie as part of a project to study the effect of environmental conditions on toxin production by cyanobacteria. Photo by McKenzie Powers

“The University of Tennessee has a 25-plus year history of contributing to research on the security of our water supplies with respect to harmful algal blooms, with the Great Lakes being a major focus,” noted Steven Wilhelm, the Kenneth and Blaire Mossman Professor of Microbiology and one of the project’s leaders.

The UT team, including Wilhelm and David Talmy, assistant professor in the Department of Microbiology, will focus on the effects of a changing climate and identify new players in the biological problems the lake is having. To understand the drivers of toxic algal bloom events, they previously collaborated with researchers in Michigan and Berlin, Germany, on the development of mathematical models that predict toxin production by cells, and how some of the proposed abatement methods may have unintended consequences.

Understanding best abatement practices and projecting the long-term effects of a changing climate—as well as the disruptive storms that go with it—are a major goal of this research. Participants will work across four collective projects to enable an assessment of the human health risks of cHAB toxins. These complementary projects seek to determine how climate change affects cHABs and how cHABs impact human health.

This virtual center was founded at Bowling Green State University in 2018 with funding from the National Institutes of Health and the National Science Foundation. Following the retirement of founding director Professor George Bullerjahn at BGSU, the center’s administrative home moved to Ann Arbor with renewed funding from the two federal agencies under the directorship of University of Michigan (UM) Professor Gregory Dick.

The center maintains core projects as it evolves to pursue new directions informed by more than 70 research papers published in peer-reviewed scientific journals by center-funded scientists since 2018. In addition, center-funded researchers will develop new technologies for advanced monitoring and forecasting of cyanobacterial harmful algal blooms in collaboration with colleagues at NOAA’s Great Lakes Environmental Research laboratory and the U-M-based Cooperative Institute for Great Lakes Research.

“The threat to water resources in the Great Lakes—which hold about 95% of the surface fresh water in the US and support a multibillion-dollar blue economy—is real,” said Dick. “But despite these serious threats, key scientific questions surrounding the climate drivers and health impacts of cHABs remain unresolved. Our knowledge is not yet sufficient to predict how a changing climate will impact cHAB distributions, community composition, or toxicity.” 

Studies will combine observation, experiment, and modeling in areas of lake science, climatology, microbiology, and biomedical science. A community engagement core led by The Ohio State University (OSU) will communicate findings to relevant communities and stakeholders.

In addition to UT, UM and OSU, partners include more than 28 faculty researchers and dozens of students at Bowling Green State University, the University of Toledo, Wayne State University, Michigan State University, University of North Carolina, James Madison University, the State University of New York, and the University of Windsor in Canada.

By Randall Brown

Zepernick Investigates How Freshwater Diatoms Stay in the Light

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Zepernick Investigates How Freshwater Diatoms Stay in the Light

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Spring weather brings welcome conditions for flowers and plant life to bloom across the land. The right mixture of temperature, moisture, and light helps keep the green world vibrant.

Underwater plant life generally responds to similar environmental encouragements, but a curious discovery in Lake Erie circa 2012 led microbiologists to study an unseasonal display of winter abundance. Blooms of diatoms—microscopic, photosynthetic algae—were alive and well beneath (and within) the lake’s ice cover.

“Some of the main winter-spring diatom bloom formers, like Aulacoseira islandica, have a symbiotic relationship with heterotrophic bacteria capable of forming tiny ice crystals, which over time causes the diatom filaments to become buoyant—just as ice cubes float in your favorite beverage,” said Brittany Zepernick, a post-doctoral researcher and SEC Emerging Scholar in UT’s Department of Microbiology.

These ‘diatom ice cubes’ float to the Lake Erie ice cover and embed within it, putting them in position to absorb the light needed to perform photosynthesis throughout the winter months. It was good news for diatoms, which are a vital component of the cumulative ecosystem in lakes and oceans across the globe

This curious adaptation is threatened, though, as warming global temperatures have led to widespread ice decline across the Great Lakes, leaving Lake Erie in a nearly ice-free state in several recent winters and leaving diatoms stuck in murky, light-deprived waters. In these new “climatically uncharted waters,” the adaptations that benefitted these winter diatoms for so long suddenly ceased to serve them.

So, what’s a diatom to do? Zepernick and colleagues turned to the shores of Lake Erie to investigate the evolving situation. With the help of the US and Canadian Coast Guard, they sampled the ice-covered (in 2019) and ice-free (in 2020) winter waters of Lake Erie to learn how diatoms were responding to changing environmental conditions. They recently published their work in the ISME Journal—Multidisciplinary Journal of Microbial Ecology.

Two main diatom genera dominate the winter blooms: Aulacoseira islandica and Stephanodiscus spp.

“The abundance of Stephanodiscus spp. was approximately 70 percent lower in the ice-free water column of 2020 compared to the ice-covered water column of 2019,” said Zepernick. “Likewise, the abundance of Aulacoseira islandica was around 50 percent lower in the ice-free water column compared to the ice-covered water column.”

Ice floating on the surface of Lake Erie
Diatoms adapted to embed in Lake Erie’s ice cover—can they adapt to stay afloat without ice?

With ice cover across the Great Lakes at record lows—from around 80 percent covered in ice in 2018 and 2019 to just 8 percent covered in 2023—researchers expect this trend will continue in future winters. 

The next step is studying how this impacts Lake Erie, which joins the other Laurentian Great Lakes of the US and Canada to cumulatively contain approximately 20 percent of the globe’s fresh water.

“Despite the critical importance of this system, we didn’t know diatom blooms even formed in the winter-spring months until around 2012,” said Zepernick. “Many researchers have referred to the winter water column as a ‘New Frontier’ or a ‘black box.’ What we do know is that diatoms are critically important to regional lake ecosystems and global climate.”

Diatoms make up an estimated 20 percent of global carbon sequestration and oxygen production, play an enhanced role in global biogeochemical cycles, and represent a critical component of the aquatic ecosystem in freshwater systems.

“Hence, the large-scale changes already underway to the winter-spring diatom communities in Lake Erie and other lakes across the globe will result in large-scale biological and biogeochemical change,” said Zepernick.

The light at the end of the icy tunnel could rely on the diatoms’ potential to adapt. Zepernick’s recent work indicates they could possibly form clusters with adhesive proteins called fasciclins to “raft” to the surface of the muddy waters via “underwater waves” produced by wind, convection, and underwater currents.

Another adaptation Zepernick hinted at was that diatoms could increase their use of proton-pumping rhodopins (PPRs)—light harvesting, retinal-containing proteins that could serve as an alternative to classical photosynthesis. She is currently attempting to isolate freshwater diatoms from Lake Erie samples that possess PPRs to create a model freshwater diatom-PPR system for further study. Her findings could offer clues to the diatoms’ next move in a rapidly changing climate.

“PPRs are a hot topic within marine literature, yet we know very little about how these mechanisms apply to freshwater systems and taxa,” she said. “I am interested in elucidating the benefits PPRs may confer to both freshwater and marine diatoms across a variety of emerging—and future—climatic stressors.”

UT Ranks in Top 10 for Cyanobacterial Bloom Research

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UT Ranks in Top 10 for Cyanobacterial Bloom Research

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The University of Tennessee is ranked seventh in the scientific front of ecology and environmental sciences for cyanobacterial bloom research, according to the sixth annual Research Fronts report, “Phosphorus loads and pollution and health risk of cyanobacterial bloom.”

The Research Fronts report identifies the hottest emerging specialty areas in scientific research. Fronts are formed when several highly cited papers are frequently cited together, showing a common theme of research. Identifying and tracking these fronts provide advantages for publishers, research administrators, policy makers, and others who support and advance the research field.

The amount of core research papers published from an institution determines ranking within a research field. UT published four core papers out of the total 38 included in the report.

Cyanobacterial blooms occur when large amounts of wastewater containing phosphorus and nitrogen enter a body of water from industrial, agricultural, or residential areas, turning the water blue or green from an increase in algae. Toxins released by the blooms can result in ecological fallout, endangering the health and safety of the water, aquatic plants, and animals.

Core papers in the field of cyanobacterial bloom research focused on four main aspects: the impact of nutrient loads on the blooms; diversity, growth, metabolism, genetics, and toxin production of different cyanobacteria species; health-risks associated with cyanobacteria toxins; and control strategies for controlling blooms in specific areas.

Steven Wilhelm, the Kenneth and Blair Mossman Professor of Microbiology, is a key researcher at UT for cyanobacterial blooms. Wilhelm’s lab uses biomolecular tools such as DNA and RNA sequencing, metabolomics, and others to study cyanobacteria, viruses, bacteria, and algae.