A Delicate Balance

I did research this summer on riparian zones at Point Reyes with Saint Mary’s biology Professor Michael Marchetti and the Carlson Lab at UC Berkeley.

A riparian zone is an interface between land and water and can be dry part of the year and wet at other times. At Point Reyes there’s a section of riparian stream where steelhead trout are threatened. The longterm objective of the study is to give park rangers and the state Department of Fish & Wildlife the information they need to care for the threatened fish species in the area. 

To find out what’s going on with the trout, we graphed the food web in the system—who’s eating whom—using carbon and isotope dating.  The food we eat has a nitrogen and carbon signature. When you metabolize food, you internalize or excrete nitrogen isotopes and carbon. So, I collected tissue samples—invertebrate samples on shore and in the streams and fin clip samples from the trout—so we could use these nitrogen and carbon signatures to graph the food map of the system. It’s a really cool, easy way to get information that will be important in helping the steelhead trout.

We’re also trying to understand the role and importance of these fragmented systems. Even though there’s a huge die-out during the dry season, and it isn’t necessarily beautiful to look at, it has a functional role in the ecosystem. If the water table drops too much, there will be no pools during the dry season. And you have to have them during the dry season—a fragile point in the life cycle of the trout—for anything to survive. This information is meaningful to regulating water control and irrigation upstream to make sure there is water available for living systems downstream.

- Eliot Jackson '13
When environmental studies student Eliot Jackson ’13 was little, if her parents couldn’t find her, they would listen for running water or go find the dirt where she likely was playing—always trying to figure out how things work.