Particle export during a bloom of Emiliania huxleyi in the North-West European continental margin

Abstract

Coccolithophores, the dominant pelagic calcifiers in the oceans, play a key role in the marine carbon cycle through calcification, primary production and carbon export, the main drivers of the biological CO 2 pump. In May 2002 a cruise was conducted on the outer shelf of the North-West European continental margin, from the north Bay of Biscay to the Celtic Sea (47.0°-50.5°N, 5.0°-11.0°W), an area where massive blooms of Emiliania huxleyi are observed annually. Biogeochemical variables including primary production, calcification, partial pressure of CO 2 (pCO 2 ), chlorophyll-a (Chl-a), particle load, particulate organic and inorganic carbon (POC, PIC) and 234 Th, were measured in surface waters to assess particle dynamic and carbon export in relation to the development of a coccolithophore bloom. We observed a marked northward decrease in Chl-a concentration and calcification rates: the bloom exhibited lower values and may be less well developed in the Goban Spur area. The export fluxes of POC and PIC from the top 80 m, determined using the ratios of POC and PIC to 234 Th of particles, ranged from 81 to 323 mg C m − 2 d − 1 and from 30 to 84 mg C m − 2 d − 1 , respectively. The highest fluxes were observed in waters presenting a well-developed coccolithophore bloom, as shown by high reflectance of surface waters. This experiment confirms that the occurrence of coccolithophores promotes efficient export of organic and inorganic carbon on the North-West European margin.

The multiple fates of sinking particles in the North Atlantic Ocean

“…These low rain ratios were driven by the large PIC fluxes at the two stations (at 50 m, 109 ± 16.3 and, 1 week later, 42 ± 6.1 mg C m À2 d À1 ). The rain ratios we documented at these two stations are among the lowest recorded for the North Atlantic and were consistent with patterns of export measured in quasi-Lagrangian mode during previous coccolithophore blooms [Foster and Shimmield, 2002;Schmidt et al, 2013]. By comparison, the higher rain ratios we observed at the two stations on the western edge of the basin (16.6 and 13.4 for QL-1 and QL-2, respectively, at 50 m) were consistent with export from a diatom bloom observed at an earlier time of year in the eastern North Atlantic [Martin et al, 2011].…”

Expression profiling of host and virus during a coccolithophore bloom provides insights into the role of viral infection in promoting carbon export

“…With estimated density lower than 0.85 g cm −3 TEP is considered to contribute to particle ascending velocity, and not to sinking [56]. Nevertheless, TEP was suggested to be important factor promoting the high carbon export rate measured during E. huxleyi blooms [57,58]. E. huxleyi cells are decorated by biogenic minerals (CaCO 3 in the coccoliths) that could contribute the missing ballast for the initiation of sinking [59][60][61].…”

Ocean warming modulates the effects of acidification on Emiliania huxleyi calcification and sinking

“…c,d) might also lower the sinking rate of aggregates by decreasing their overall density (Biermann and Engel ) and thus, altering export rates. The latter effect might be of particular importance in bloom events, because if on average, the contribution of E. huxleyi to phytoplankton POC is small and has little effect on the PIC/POC of the rain ratio, but in a bloom, this contribution becomes more significant and it might considerably affect the sinking of aggregates (Schmidt et al ). Hence, in a warmer and high CO 2 ocean individual coccolithophore cells might sink faster, while aggregates including substantial amounts of coccolithophores might sink slower.…”