San Francisco Bay - Ecology

Ecology

Despite its urban and industrial character, San Francisco Bay and the Sacramento-San Joaquin Delta remain perhaps California's most important ecological habitats. California's Dungeness crab, California halibut, and Pacific salmon fisheries rely on the bay as a nursery. The few remaining salt marshes now represent most of California's remaining salt marsh, supporting a number of endangered species and providing key ecosystem services such as filtering pollutants and sediments from the rivers. San Francisco Bay is recognized for protection by the California Bays and Estuaries Policy.

Most famously, the bay is a key link in the Pacific Flyway. Millions of waterfowl annually use the bay shallows as a refuge. Two endangered species of birds are found here: the California least tern and the California clapper rail. Exposed bay muds provide important feeding areas for shorebirds, but underlying layers of bay mud pose geological hazards for structures near many parts of the bay perimeter. San Francisco Bay provided the nation's first wildlife refuge, Oakland's artificial Lake Merritt, constructed in the 1860s, and America's first urban National Wildlife Refuge, the Don Edwards San Francisco Bay National Wildlife Refuge (SFBNWR) in 1972. The Bay is also plagued by non-native species.

Salt produced from San Francisco Bay is produced in salt evaporation ponds and is shipped throughout the Western United States to bakeries, canneries, fisheries, cheese makers and other food industries and used to de-ice winter highways, clean kidney dialysis machines, for animal nutrition, and in many industries.

Low-salinity salt ponds mirror the ecosystem of the bay, with fish and fish-eating birds in abundance. Mid-salinity ponds support dense populations of brine shrimp, which provide a rich food source for millions of shorebirds. Only salt-tolerant micro-algae survive in the high salinity ponds, and impart a deep red color to these ponds from the pigment within the algae protoplasm.

The seasonal range of water temperature in the Bay is from about 8 °C (46 °F) to about 23 °C (73 °F).

Industrial, mining, and other uses of mercury have resulted in a widespread distribution in the bay, with uptake in the bay's phytoplankton and contamination of its sportfish.In January 1971, two Standard Oil tankers collided in the bay, creating an 800,000 gallon oil spill disaster, which spurred environmental protection of the bay. In November 2007, a ship named COSCO Busan collided with the San Francisco – Oakland Bay Bridge and spilled over 58,000 gallons of bunker fuel, creating the largest oil spill in the region since 1996.

At times, San Francisco Bay is covered in fog.

For the first time in 65 years, Pacific Harbor Porpoise (Phocoena phocoena) returned to the Bay in 2009. Golden Gate Cetacean Research, a non-profit organization focused on research on cetaceans, has developed a photo-identification database enabling the scientists to identify specific porpoise individuals and is trying to ascertain whether a healthier bay has brought their return. Pacific harbor porpoise range from Point Conception, California to Alaska and across to the Kamchatka Peninsula and Japan. Recent genetic studies show that there is a local stock from San Francisco to the Russian River and that eastern Pacific coastal populations rarely migrate far, unlike western Atlantic Harbor porpoise.