Research about Northern San Francisco Bay

USGS2010

Selenium concentrations and stable isotopic compositions of carbon and nitrogen in the benthic clam Corbula amurensis from northern San Francisco Bay, California: May 1995–February 2010

The clam-based food webs of San Francisco Bay, California efficiently bioaccumlate selenium and thus provide pathways for exposure to predators important to the estuary. This study documents changes in monthly selenium concentrations for the clam Corbula amurensis , a keystone species of the estuary, at five locations in northern San Francisco Bay from 1995 through 2010. Samples were collected from designated U.S. Geological Survey stations and prepared and analyzed by U.S. Geological Survey methods. Stable isotopes of carbon and nitrogen in soft tissues of clams also were measured as an indicator of sources of selenium for the clams. These monitoring data indicate that clam selenium concentrations ranged from a low of 2 to a high of 22 micrograms per gram dry weight with strong spatial and seasonal variation over the period of study.

California↗

USGS2003

Clams as CO2 generators: The Potamocorbula amurensis example in San Francisco Bay

Respiration and calcium carbonate production by the invasive Asian clam, Potamocorbula amurensis , were calculated to assess their importance as CO 2 sources in northern San Francisco Bay. Production, calculated using monthly population density and size structure measured at three sites over 7 yr and a shell length/CaCO 3 conversion factor, averaged 221(±184)g CaCO 3 m −2 yr −1 . Net calcium carbonate production by this exotic bivalve releases CO 2 at a mean rate of 18(±17)g C m −2 yr −1 . Respiration by P. amurensis , estimated from secondary production, releases additional CO 2 at a mean rate of 37(±34)g C m −2 yr −1 . Therefore, total net CO 2 production by P. amurensis averages 55(±51)g C m −2 yr −1 in an estuarine domain where net primary production consumes only 20g inorganic C m −2 yr −1 . CO 2 production by P. amurensis in northern San Francisco Bay is an underestimate of the total CO 2 supply from the calcified zoobenthic communities of San Francisco Bay, and results from other studies have suggested that this rate is not unusual for temperate estuaries. Global extrapolation yields a gross CO 2 production rate in the world's estuaries of 1x10 14 g C yr −1 , which suggests that calcified benthic organisms in estuaries generate CO 2 equal in magnitude to the CO 2 emissions from the world's lakes or from planetary volcanism (the net source is determined by the highly variable rate of CO 2 consumption by carbonate dissolution). This biogenic CO 2 source is increasing because of the continuing global translocation of mollusks and their successful colonization of new habitats.

California↗