Big new idea introduced with the help of tiny plankton

Journal reporting science On Feb. 16, the team showed how microscopic relationships in plankton — such as between an organism’s size and nutrients — scale up to scales that potentially affect food webs.

“Using data that other researchers have measured on these organisms at the microscale, our model presents can predict what is happening at the scale of the entire ecosystem.” .

“We can now show how the lower-level principles of life feed into these higher levels based on environmental interactions and evolutionary considerations,” said Elena Leachman, a senior staff scientist in Carnegie’s Biosphere Sciences and Engineering Division. ” “Until now, people mostly considered these levels in isolation.”

The new report will enable the team and its colleagues to design new experiments to test, refine, and expand the model to other species and ecosystems. This could ultimately enable the model to inform ecosystem management strategies in different environments around the world.

Small organisms, global effects

The team is also interested in what else they can learn from their model and the plankton they study.

“We chose them as a model system for a few reasons,” said Christopher Klossmeier, an MSU Research Foundation professor at the WK Kellogg Biological Station. He is also a faculty member of the Plant Biology Department, the Integrative Biology Department and the Ecology, Evolution and Behavior, or EEB, program at MSU.

One reason is that plankton are the main research focus for the research group led by Lichtman and Klossmeier.

“They’re relatively simple organisms. If something is going to follow the rules, plankton are a good candidate,” Klossmeier said. “But they are also globally important. They are responsible for about half of the primary production on Earth and are the basis of most aquatic food webs.”

Primary producers use biochemical processes such as photosynthesis to convert the soil’s carbon and raw nutrients into compounds that are useful to the organisms themselves and their predators. This means that plankton are an important cog in the natural machinery that cycles the planet’s essential life elements, including carbon, nitrogen and oxygen.

Having a scaling model that describes plankton can thus be useful for better understanding these key processes, as well as whether and how they are changing with the planet’s climate.

The team did not include climate-related variables such as temperature in the study, but the researchers are already planning their next steps in that direction.

“The effects of global warming can alter low-level physiological processes,” Leachman said. “We can then use this framework to see how these effects reach different levels of the organization.”

Eye-popping simplicity

Wickman has not always been a plankton ecologist. His undergraduate degree was in physics, but he switched to ecology during his doctoral studies in Sweden before joining the Klossmeier-Lachmann lab in 2020.

The team said his background in physics shaped his approach to developing the model, which Leachman described as “elegant — stripping out everything but the essential processes.”

To begin with, Wickman built from basic theories describing his system of interest. Only in that case, the system was not, say, quantum mechanical particles. These were small organisms connected by a simple food web.

Within this web, phytoplankton are the primary producers and zooplankton are their predators.

“Well, grazers really,” Wickman said of zooplankton. “We don’t usually call cows grazers.”

To fully appreciate the workings of this important relationship and its global implications, researchers are breaking it down into components driven by ecology and evolution.

For example, microscopic considerations such as phytoplankton size affect its ability to compete for nutrients, which in turn affects how large cells can acquire and become food for zooplankton. What is the probability of

These microscopic factors are thus linked to macroscopic variables, including nutrient distribution and how densely or less diverse plankton populate their environment.

Over the past several decades, scientists have developed mathematics that describe individually important relationships at the microscale and macroscale. Attempts to eliminate the scales, however, have frustrated researchers, Wickman said.

This is because previous attempts to build this relationship have led to compromises. Some previous models have opted for simplicity at the expense of accuracy and realism. Others have countered this complexity with heavy computational power, making it less accessible and harder to work with.

“Our model includes real ecological and evolutionary mechanisms but is simple enough to use,” Wickman said.

The work began as pure theory, but Leachman suggested that it should be possible to test his predictions using existing data. “My eyes popped out when I saw how well the model matched the observations,” he said.

Supported by the US National Science Foundation, or NSF, the team had been working on the problem for several years and had previously published a paper that developed the ecological evolutionary modeling techniques they relied on. were

Now, the team has demonstrated the potential of their model by combining it with real-world data.

“The revelation that patterns that emerge at macroecological scales can be explained by characteristics of individual organisms at the microecological scale,” said Steve Dudgeon, program director in NSF’s Directorate for Biological Sciences.

“The study provides new avenues of research that can enhance the prediction of how ecosystems, and the relationships between the organisms in them, will change in a changing environment as they interact with ecological evolutionary dynamics.”

Because of the natural variability of biological systems, the model and its results may seem confusing to someone accustomed to the precision of physics, but Wickman sees them with enthusiasm.

“We actually got pretty good accuracy for the environment,” he said. “We may not have the same theoretical elegance as physics, but that means we have a lot more territory to explore.”