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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2017-112
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-2017-112
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Submitted as: research article 16 May 2017

Submitted as: research article | 16 May 2017

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Living coccolithophores from the eastern equatorial Indian Ocean during the spring intermonsoon: Indicators of hydrography

Jun Sun1,2,3, Haijiao Liu1,2,3, Xiaodong Zhang2,3, Cuixia Zhang2,3, and Shuqun Song4 Jun Sun et al.
  • 1Institute of Marine Science and Technology, Shandong University, 27 Shanda Nan Road, Jinan 250110, PR China
  • 2Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin 300457, PR China
  • 3College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin 300457, PR China
  • 4CASKey Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China

Abstract. We studied the biodiversity of autotrophic calcareous coccolithophore assemblages at 30 locations in the eastern equatorial Indian Ocean (EEIO) (80°–94° E, 6° N–5° S) and evaluated the importance of regional hydrology. We found 25 taxa of coccospheres and 17 taxa of coccoliths. The coccolithophore community was dominated by Gephyrocapsa oceanica, Emiliania huxleyi, Florisphaera profunda, Umbilicosphaera sibogae, and Helicosphaera carteri. The abundance of coccoliths and coccospheres ranged from 0.192×103 to 161.709×103 coccoliths l−1 and 0.192×103 to 68.365×103 cells l−1, averaged at 22.658×103 coccoliths l−1 and 9.386×103 cells l−1, respectively. Biogenic PIC, POC, and rain ratio mean values were 0.498 μgC l−1, 1.047 μgC l−1, and 0.990 respectively. High abundances of both coccoliths and coccospheres in the surface ocean layer occurred north of the equator. Vertically, the great majority of coccoliths and coccospheres were concentrated in water less than 75 m deep. The ratios between the number of coccospheres and free coccoliths across four transects indicated a pattern that varied among different oceanographic settings. The H’ and J values of coccospheres were similar compared with those of coccoliths. Abundant coccolithophores along the equator) mainly occurred west of 90° E, which was in accordance with the presence of Wyrtki jets (WJs). F. profunda was not found in surface water, indicating a stratified and stable water system. U. irregularis dominated in the equatorial zone, suggesting oligotrophic water conditions. Coccosphere distribution was explained by environmental variables, indicated by multi-dimensional scaling (MDS) ordination in response variables and principal components analysis (PCA) ordination in explanatory variables. Coccolithophore distribution was related to temperature, salinity, density and chlorophyll a.

Jun Sun et al.
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Jun Sun et al.
Jun Sun et al.
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Short summary
The coccolithophore abundance in this study was relatively low, resulting from the weak winds and minimal nutrient upwelling compared to previous studies that were conducted during the monsoon seasons. During the spring intermonsoon period, no significant oceanic circulation occurred in the EEIO except for WJs. We inferred that, in the study area, different coccolithophore species had specific environmental preferences. Thus, coccolithophore species are good indicators of oceanographic changes.
The coccolithophore abundance in this study was relatively low, resulting from the weak winds...
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