Understanding the Impacts of Climate Change on Delta Smelt

Project Number
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Education, Training and Public Information

Climate change is expected to change both water temperature and salinity regimes in the San Francisco Estuary-Delta. This project examines potential consequences of climate change to the endangered delta smelt at multiple biological scales. In the project’s first year, laboratory experiments were conducted to determine the species’ thermal and salinity tolerances and physiological responses to warm and salty waters. Interestingly, delta smelt had lower temperature tolerance with age, and were able to survive across a broad range of salinities. The Fellow has developed a microarray for the delta smelt’s “transcriptome,” the small percent of the genome that is involved in making proteins. This lab-on-a-chip was then used to document normal levels of gene expression and how they change as water temperatures and salinities approach tolerance thresholds. Results indicate that coordinated expression changes in a large number of genes serve to respond to salinity and temperature stress, and that delta smelt experience sublethal stress well below their tolerance limits. 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 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. This research has been published in Conservation Physiology (Komoroske et al., 2014), and the Fellow is now collaborating with the U.S. Geological Survey to understand what this means for delta smelt future habitat suitability in the Delta under different climate change scenarios. Overall, the Fellow’s work will shed light on how, or whether, climate change might alter fish habitat quality and in this way help managers prioritize conservation strategies.

Research mentor: Nann A. Fangue, Wildlife, Fish and Conservation Biology, UC Davis

Community mentor: Gonzalo Castillo, U.S. Fish & Wildlife Service