Clams as CO<sub>2</sub> generators: The <i>Potamocorbula amurensis</i> example in San Francisco Bay
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Resource Abstract:
<p>Respiration and calcium carbonate production by the invasive Asian clam, <i>Potamocorbula amurensis</i>, were calculated
to assess their importance as CO<sub>2</sub> 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<sub>3</sub> conversion factor, averaged
221( 184)g CaCO<sub>3</sub> m<sup> 2</sup>yr<sup> 1</sup>. Net calcium carbonate production by this exotic bivalve releases
CO<sub>2</sub> at a mean rate of 18( 17)g C m<sup> 2</sup>yr<sup> 1</sup>. Respiration by <i>P. amurensis</i>, estimated from
secondary production, releases additional CO<sub>2</sub> at a mean rate of 37( 34)g C m<sup> 2</sup>yr<sup> 1</sup>. Therefore,
total net CO<sub>2</sub> production by <i>P. amurensis</i> averages 55( 51)g C m<sup> 2</sup>yr<sup> 1</sup> in an estuarine
domain where net primary production consumes only 20g inorganic C m<sup> 2</sup>yr<sup> 1</sup>. CO<sub>2</sub> production
by <i>P. amurensis</i> in northern San Francisco Bay is an underestimate of the total CO<sub>2</sub> 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<sub>2</sub> production rate in the world's estuaries of 1x10<sup>14</sup>g
C yr<sup> 1</sup>, which suggests that calcified benthic organisms in estuaries generate CO<sub>2</sub> equal in magnitude
to the CO<sub>2</sub> emissions from the world's lakes or from planetary volcanism (the net source is determined by the highly
variable rate of CO<sub>2</sub> consumption by carbonate dissolution). This biogenic CO<sub>2</sub> source is increasing because
of the continuing global translocation of mollusks and their successful colonization of new habitats.</p>
Citation
Title Clams as CO<sub>2</sub> generators: The <i>Potamocorbula amurensis</i> example in San Francisco Bay