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CABA Seminar Explores Lower Food Web Dynamics

March 2014

One of the state's coequal goals is the restoration and enhancement of the Delta ecosystem. Just restoring or creating habitat, however, may not produce the desired results, especially in the creation of improved food sources for fish.

“If we invest in large-scale restoration activities in the Delta by turning existing properties into marsh, food productivity may or may not increase enough to support fish in open water, so we’d better find out,” said Garrett Liles, an environmental scientist in the Delta Stewardship Council’s (Council) Delta Science Program.

That question became part of a collaborative day-long seminar sponsored by the Delta Science Program and the U.C. Davis Center for Aquatic Biology and Aquaculture or CABA. The seminar, entitled “Lower Food Web Dynamics in California’s Bay-Delta Ecosystem,” was held February 18 on the Davis campus. A webcast of the six-hour event can be found here.

The discussion was spurred by various ecosystem restoration plans being proposed for the Delta to halt or reverse the decline of the lower food web production of organisms such as phytoplankton and in turn provide a more robust habitat for all creatures up the aquatic food chain. Some scientists, however, wonder if other elements, such as the invasive Asian clams, might defeat the purpose.

The Delta Science Program and CABA felt more discussion was necessary to provide decision-makers and other stakeholders with the best available science and an adaptive management plan, as outlined in the Council’s Delta Plan, that would reduce the guesswork when choosing an appropriate restoration plan.

“Will a particular proposed restoration plan benefit the system, provide no benefit to the system, or actually degrade the system? Those are the questions that still need to be answered,” said Liles. “This seminar provided the targets we should aim for to alleviate the uncertainty.”

In all, six doctoral speakers - five from the U.S. and one from France -, each having a critical understanding of the factors at play in the Delta’s food web, offered background information on a wide variety of Delta ecosystem topics including water flows, naturally occurring nutrients, and the various invasive species. Their individual Power Presentations are available here. The discussion points were chosen because of how they might or might not be affected by the various restoration plans being proposed.

As each speaker finished talking, a secondary panel of six experts from state, federal, and private organizations, with direct knowledge of the restoration plans, then affirmed or challenged the speaker’s conclusions. Members of the audience were also allowed to address the speakers.

“This was not just an exercise to have another seminar,” said Liles. “Our goal was to determine what we know and what we don’t know scientifically – and then to come up with some non-binding opinions on what our next objectives should be when studying the dynamics of the lower pelagic food webs and subsequently how to promote resilient aquatic ecosystems in the Delta.”

The answers to some of the those questions will make their way into a scientifically peer-reviewed, third-party issue paper that will assist decision-makers and other stakeholders when choosing the restoration component that will best suit the Delta ecosystem. That paper will be published in the Council-sponsored San Francisco Estuary and Watershed Science online journal.

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)