Researchers chart effects of climate change on Tomales Bay

Salmon numbers are dwindling. Seals are raising fewer pups. And higher levels of carbon dioxide in the atmosphere could pose problems for the oysters of Tomales Bay — and the humans who love them — researchers said at Friday’s “State of the Bay” conference.

The once-a-decade event at the Inverness Yacht Club described the kind of changes global warming could bring to the waters of Tomales Bay — some of which are already taking place. Warmer temperatures are likely to bring more frequent “El Nino” events, driving upswells of cold ocean waters from the Pacific to the bay — and driving away the kinds of fish favored by harbor seals.

“I don’t want to join in this terrible song, but climate change experts have predicted more frequent, more intense El Ninos,” said Sarah Allen, senior scientist for the Point Reyes National Seashore. “There is less productivity for harbor seals during El Ninos.”

At the same time, the changing climate seems to be favoring California sea lions, and could eventually bring more gray whales to the bay.

About 200 people took part Friday in the first of two days devoted to the health of Tomales Bay. The event was presented by the Tomales Bay Watershed Council, whose members brought together an all-star panel of scientists and researchers from the University of California at Davis, the National Park Service, the California Department of Fish and Game and the Gulf of the Farallones National Marine Sanctuary.

Of particular concern to Friday’s presenters was the increasing acidification of bay waters, said Ann Russell, a UC Davis geologist. Higher levels of carbon dioxide in the atmosphere are being absorbed into the bay and the surrounding ocean, making the waters more acidic, Russell said.

“Not only are we increasing atmospheric carbon dioxide beyond what’s been recorded over the last 800,000 years, but it’s increasing at a rate — and this is the critical thing for us — that is unprecedented in geologic time,” Russell said.

Under those conditions, shellfish such as native Olympia oysters have to expend more energy to build their shells. Increasing levels of atmospheric carbon could eventually lead to fewer, smaller shellfish. The change could also affect predators such as salmon, which feed on a kind of native snail, Russell said.

Conditions for salmon in general — especially for the bay’s native coho salmon — have been dismal, said several researchers, many of whom voiced doubts that salmon will still be found in Lagunitas and San Geronimo creeks a decade from now. While the number of salmon nests, or redds, has increased incrementally in the past three years, there are still fewer than 500 coho salmon in Lagunitas Creek — a far cry from the hundreds of fish that swam from the creek to the ocean in previous decades.

Rob Rogers, Marin Independent JournalFull article.

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