Clams as CO2 generators: The Potamocorbula amurensis example in San Francisco Bay
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<p>Respiration and calcium carbonate production by the invasive Asian clam, Potamocorbula amurensis, were calculated to assess
their importance as CO2 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/CaCO3 conversion factor, averaged 221 (6184) g CaCO3 m22
yr21 . Net calcium carbonate production by this exotic bivalve releases CO2 at a mean rate of 18 (617) g C m22 yr21 . Respiration
by P. amurensis, estimated from secondary production, releases additional CO2 at a mean rate of 37 (634) g C m22 yr21 . Therefore,
total net CO2 production by P. amurensis averages 55 (651) g C m22 yr21 in an estuarine domain where net primary production
consumes only 20 g inorganic C m22 yr21 . CO2 production by P. amurensis in northern San Francisco Bay is an underestimate
of the total CO2 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 CO2 production rate in
the worlds estuaries of 1 3 1014 g C yr21 , which suggests that calcified benthic organisms in estuaries generate CO2 equal
in magnitude to the CO2 emissions from the worlds lakes or from planetary volcanism (the net source is determined by the highly
variable rate of CO2 consumption by carbonate dissolution). This biogenic CO2 source is increasing because of the continuing
global translocation of mollusks and their successful colonization of new habitats.</p>
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Title Clams as CO2 generators: The Potamocorbula amurensis example in San Francisco Bay