Understanding the Great Lakes’ Smallest Organisms
Author: Shaun McGillis, Research & Graduate Studies
Posted: January 24, 2019
CyanobacteriaThe Great Lakes—Ontario, Erie, Huron, Superior, and Michigan, contain 18% of the world’s surface freshwater, forming the most extensive freshwater system on the planet. In the U.S. and Canada, more than 35 million people rely on these lakes for drinking water, energy, jobs, recreation, and more. The lakes support multibillion-dollar fishery and tourism industries and are home to thousands of species of fish and wildlife.

Considering the scale of the Great Lakes, it might be difficult to imagine that microscopic organisms play a vital role in maintaining their ecology. Nevertheless, a group of bacteria called cyanobacteria support the lakes by contributing as much as 50% of primary productivity of bio-accessible carbon in certain areas.

Cyanobacteria are found in the oceans and on land, as well as in streams, rivers, and lakes. A milliliter of water can contain as many as 100,000 of the microorganisms. In fact, cyanobacteria are the most abundant photosynthetic cells on Earth. They acquire energy from the sun through photosynthesis and perform essential ecosystem services by converting nutrients extracted from the environment into biomass. In the great lakes where there is limited terrestrial input of carbon, cyanobacteria are at the foundation of the food chain.

And, yet, there is much we still don’t know about populations of cyanobacteria in the Great Lakes. How many distinct population groups inhabit the lakes? Where do various groups reside or overlap? How are their physical traits linked to genetics? And how are their genes affected by their environments?

Portland State research assistant professor Anne Thompson is a marine microbial ecologist who studies cyanobacteria—their genetic diversity, interactions with the environment, and contributions to global processes. Thompson partnered with University of Chicago researchers Maureen Coleman and Jacob Waldbauer to study cyanobacteria in the Great Lakes. The cyanobacteria the team will study are unicellular free-living cells and are distinct from cyanobacterial types that cause toxic blooms in some freshwater systems. The team’s work is funded by a $700,000 NSF grant and will advance knowledge of the lakes’ microbial food web by providing a picture of the genetic diversity of cyanobacteria in the lakes’ ecosystem.

“We call cyanobacteria primary producers,” Thompson said. “They provide usable carbon sources in the ecosystem by taking carbon dioxide from the atmosphere and fixing it in biomass. So, they’re really the base of the food chain. In the lab, we look at their genetic diversity to try to understand how that connects to their function in the ecosystem. We also study their abundance, distribution, and physical characteristics and how those factors relate to genetic diversity and their environment.”

Building on years of data collected by Coleman, the team will gather new samples of cyanobacteria from lakes Michigan and Superior during the spring and summer seasons. Researchers at the University of Chicago will analyze the genetic diversity and gene and protein expression of the sampled cyanobacteria at different locations, depths, and temperatures to gain a better understanding of their distribution at different times and places, and under different environmental conditions. Here at Portland State, Thompson and her team will use a technique called flow cytometry to detect and measure the physical and chemical properties of populations to determine if physical characteristics overlap with genetic diversity and environmental factors that influence gene expression.

According to Thompson, the team’s research will provide a foundation for understanding the diversity of understudied cyanobacteria populations within the Great Lakes system. Building upon that foundation, later researchers will be able to ask essential questions such as how climate change may affect organisms critical to the health of the lakes and the ecosystem services they provide.