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How Climate Change May Be Affecting the Delta Ecosystem

August 2014
Lisa Komoroski

Climate change is expected to increase both water temperatures and salinity in the Delta. How might this affect sensitive species? Delta Science Fellow Lisa Komoroske examined potential consequences of climate change to the endangered Delta Smelt, a flagship species in the Delta in danger of extinction.

Komoroske, a doctoral student at UC Davis who will graduate in December 2014, conducted laboratory experiments to determine the Delta Smelt’s thermal and salinity tolerances and physiological responses to warm and salty waters that might occur in the future.

She and her mentors developed a slide with DNA sequences from the smelt’s “transcriptome,” the small percent of the genetic material that is involved in making proteins. This lab-on-a-chip was used to document how the fish respond as water temperatures and salinities approach tolerance thresholds and to understand when they become stressed.

“What we do is not all that different from what happens when people go to the doctor and get blood or other tests to help assess if they are healthy, sick, or under stress,” Komoroske explained. “They are using what we call ‘biomarkers’- things that we can measure that provide information about the state of your body, how it is responding to its environment, and to know what course of action to take to get you better. These biomarkers work because of previous research on how things like your immune system function, similar conceptually to what we developed for the Delta Smelt.”

Examining different life stages of Delta Smelt and comparing their responses to water temperatures in the Delta, Komoroske and her colleagues discovered that juvenile smelt are likely to be the stage most vulnerable to the effects of climate change. This is in part because Delta Smelt often have a one-year life cycle, and the juveniles are the stage that occur in the late summer and early fall when water temperatures are highest.

“If we understand where the most sensitive stages are, we can give that information to managers at federal and state agencies making decisions about doing habitat restoration and other conservation actions, and say here’s one important place to focus your efforts,” she said.

Komoroske and her fellow researchers are now using their results to collaborate with U.S. Geological Survey climate model scientists to understand what this means for climate change predictions. “Linking the knowledge we’ve gained about Delta Smelt temperature sensitivity with what is forecasted for the Delta will really help us understand where good, stressful, or completely unsuitable habitat will likely be for Delta Smelt as well as other sensitive native fishes in the next 50-100 years.”

Although her Fellows research has ended, Komoroske recently received funding from the National Science Foundation to do an extension project with Delta Science Post-Doctoral Fellow Dr. Kenneth Jeffries, also at U.C. Davis, comparing Delta Smelt with Menidia, an invasive fish that can survive in much higher water temperatures.

“By comparing the genetic and physiological differences between the species, we can perhaps understand the adaptations that help one species thrive in conditions that are very stressful for others,” she said.

Komoroske’s research has been published in the online, open-access peer-reviewed journal, Conservation Physiology Komoroske et al., 2014. She has worked on conservation ecology projects in Louisiana, Thailand, Mexico and California, and as an avid scuba diver and hiker, hopes to continue research to understand and protect coastal and aquatic ecosystems in the future.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)