Increased surface seawater pCO2 in the eastern Bering Sea shelf: An effect of blooms of coccolithophorid Emiliania huxleyi?

Abstract

Increased surface seawater pCO2 observed in the eastern Bering Sea shelf (long 168°W–160°W; lat 54°N–68°N) were examined in relation to blooms of the coccolithophorid Emiliania huxleyi, using data obtained from R/V Mirai cruises once or twice annually (August–October 1998–2002). A principal component analysis demonstrated that there are two spatial scales of pCO2 variability associated with E. huxleyi blooms. One is a small‐scale variation (∼0.2° in latitude), which shows a decrease of pCO2 by 18 μatm relative to surrounding waters. The other is a large‐scale variation (∼10.0° in latitude), with spatial gradient in pCO2 of up to 250 μatm. Detailed analyses show that the large‐scale variation is associated with diatom blooms, while the small‐scale variation is associated with coccolithophorid blooms with a calcification:photosynthesis = 1.0, and thus that seawater pCO2 is affected by the composition of marine ecosystems and its response to climate variability. SST rise also contributed to increased pCO2.