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Study Suggests Connection between Invasive Species and Changing Climate Conditions - Drought, decreased freshwater inflow among conditions listed

July 2011

Aquatic zooplankton (pronounced zoh-ah-plank-ton) is a term you likely last heard in a high school science class. For aquatic scientists who study the ecosystem of the Delta, however, the tiny invertebrates are considered a critical part of the aquatic food chain.

Numerous studies have shown a strong relationship between fish survival and the production of their food supply. This makes zooplankton a true bellwether in determining the health of the Delta.

In fact, a recent research project focused on the Bay-Delta estuary, using extensive zooplankton records in the region, suggests there is a connection between significant changes in climate, water management, and the invasion of new plants and animals.

Monika Winder, a researcher at UC Davis, concludes that invasive species, or species that do not occur naturally in an area, tend to become established in extreme conditions in the Delta. These species can outcompete native species – which the Delta Plan and other efforts are attempting to protect – during times of drought and decreased flows.

Changes in climate

Delta Stewardship Council Lead Scientist Cliff Dahm reported the findings of Winder’s study to the Council during June’s Council meeting. These findings have been published in the scientific journal Ecology Letters.

“The aquatic zooplankton have gone through significant invasions by non-native species over the last 30 years,” Dahm said. “Many of the species now that are in the system are not native to the system.”

Winder, a former CALFED Science Fellow and recent recipient of grant funding from the Delta Science Program, studied seven specific types of non-native zooplankton. Her results seem to indicate that each established itself during periods of high stress related to drought and intensified by water management.

“There certainly appears to be a synergy between drought and flow alteration in the establishment of non-native zooplankton species,” Dahm said.

As the Council seeks to balance the coequal goals of providing a more reliable water supply for California and protecting, restoring and enhancing the Delta ecosystem, it has and will continue to consider the best available science, like Winder’s research, to create the Delta Plan.

To view an abstract of Winder’s research, click here.
To view the most recent staff draft of the Delta Plan, click here.

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)