Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 16
Biogeosciences, 13, 4843-4861, 2016
https://doi.org/10.5194/bg-13-4843-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 4843-4861, 2016
https://doi.org/10.5194/bg-13-4843-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Aug 2016

Research article | 29 Aug 2016

Coccolithophore responses to environmental variability in the South China Sea: species composition and calcite content

Xiaobo Jin1, Chuanlian Liu1, Alex J. Poulton2, Minhan Dai3, and Xianghui Guo3 Xiaobo Jin et al.
  • 1State Key Laboratory of Marine Geology, Tongji University, 200092 Shanghai, China
  • 2Ocean Biogeochemistry and Ecosystems, National Oceanography Centre, Southampton, SO14 3ZH, UK
  • 3State Key Laboratory of Marine Environmental Science, Xiamen University, 361005 Xiamen, China

Abstract. Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths) and the relative cellular levels of photosynthesis and calcification rates. All three of these factors vary between coccolithophore species and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (SCS) during summer 2014 in order to examine how environmental variability influenced species composition and cellular levels of calcite content. Average coccolithophore abundance and their calcite concentration in the water column were 11.82 cellsmL−1 and 1508.3pg CmL−1, respectively, during the cruise. Water samples can be divided into three floral groups according to their distinct coccolithophore communities. The vertical structure of the coccolithophore community in the water column was controlled by the trophic conditions, which were regulated by mesoscale eddies across the SCS basin. The evaluation of coccolithophore-based calcite in the surface ocean also showed that three key species in the SCS (Emiliania huxleyi, Gephyrocapsa oceanica, Florisphaera profunda) and other larger, numerically rare species made almost equal contributions to total coccolith-based calcite in the water column. For Emiliania huxleyi biometry measurements, coccolith size positively correlated with nutrients (nitrate, phosphate), and it is suggested that coccolith length is influenced by light and nutrients through the regulation of growth rates. Larger-sized coccoliths were also linked statistically to low pH and calcite saturation states; however, it is not a simple cause and effect relationship, as carbonate chemistry was strongly co-correlated with the other key environmental factors (nutrients, light).

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The vertical structure of the coccolithophore community in the water column was controlled by trophic conditions, which were regulated by mesoscale eddies across the South China Sea basin. Three key species (Emiliania huxleyi, Gephyrocapsa oceanica, Florisphaera profunda) contributed roughly half of the surface ocean coccolith-calcite concentrations. E. huxleyi coccolith length is influenced by light and nutrients through the regulation of growth rates.
The vertical structure of the coccolithophore community in the water column was controlled by...
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