How Do We Quantify Climate Change in Kelp Forest Ecosystems?

Dr. Kristy Kroeker (Center) and Members of Her Lab. Photo Courtesy of Dr. Kristy Kroeker.

Dr. Kristy Kroeker researches ecological effects of climate change, ocean acidification, and deoxygenation in marine communities and ecosystems. In the face of global ecological change, Kroeker is asking the questions that will determine how we approach restoration in high stress and dynamic marine environments. Last Friday, Oct. 29 during one of the Biology Department’s weekly seminars, Kroeker posed the question: “How do we realistically think about global change when multiple things are changing and not only is it affecting just one individual, but affecting all quite differently?” 

Kroeker’s journey to science was very much a west coast story, but by no means a straight approach. After receiving her bachelors at the University of California, Santa Cruz, Kroeker shifted her focus towards science communication and education. “I was really driven by wanting to make a contribution more broadly,” Kroeker said. After working for outdoor educational program Outward Bound and then teaching middle school science in north Portland, Kroeker received her Ph.D. at Stanford University and postdoc at the University of California, Davis. She then returned to the University of California, Santa Cruz where she now works as an associate professor in ecology and evolutionary biology. Reflecting back on her career path, Kroeker said that she would not have changed any of it. “All of those experiences were super influential and have shaped the way I do my science and the way that I teach in the classroom.” 

Kroeker’s drive to contribute broadly by investing in community systems is apparent in the way she conducts her research. At the beginning of her presentation, Kroeker shared the lens that guides her as she models the broad effects of climate change on individual species and ecosystems: Ecological Leverage Points. This model predicts that key species interactions on the individual level that are sensitive to abiotic changes, such as changes in ocean acidification and warming temperatures, can amount to larger changes at the level of marine communities or ecosystems. Kroeker uses this model to quantify how increasingly warmer, less oxygenated, and more acidic ocean environments on the west coast of the United States will impact the demand versus intake of individual species and the consumption versus production of ecosystems. 

Kroeker and her team have used a variety of techniques to predict how future conditions will affect crucial ecosystem interactions, but many of the indicators that have successfully produced the most robust and relevant data actually already existed in the ocean itself. One such tool came in the deceptive host of a pink and long-lived coralline alga called Clathromorphum Neresostratum.

Coating the floor of the once vibrant kelp forest ecosystems off the coast of the Aleutian Archipelago in Alaska, this pink alga became of interest to Kroeker and her team. Because the alga is so long-lived and grows “very much like trees” adding new layers of growth each year, it has allowed Kroeker to work with the alga the same way scientists have used carbon dating and tree rings to obtain data on terrestrial temperature fluctuations.   

While this is only one example of the innovative techniques Kroeker shared in her talk, it illustrates how in a dynamic and multi-stress environment, the best way to understand how ecological interactions will shift as a result of ocean global change may exist within the systems themselves. The implications of this research do not simply inform Kroeker’s ongoing projects, but present a harsh reality about what is going on in the oceans right now.  

“It is one of the first times that we have actually shown that this is happening now. That it is not happening in the future, or predicting to happen in the future, but currently in the North Pacific, changes in ocean temperature, and likely acidification, is leading to the deterioration of this ecosystem,” said Kroeker.

Through working with students, policy makers, and managers, Kroeker’s research both informs future scientific strategies to quantify an increasingly shifting and stressed ecosystem and disseminates that information to a public that has the power to make serious change. Readers interested in learning more about Kroeker’s research can email Kristy Gonyer of the Reed College biology department for recordings of the seminars and more information about upcoming speakers.

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