Coccolithophore abundance and production and their impacts on particulate inorganic carbon cycling in the western North Pacific
<p>Coccolithophores are globally distributed, calcifying phytoplankton that play an important role in the marine carbon cycle through their contribution to the carbonate pump. However, limited knowledge of their biogeography and environmental drivers hinders our ability to predict the response...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/3681/2025/bg-22-3681-2025.pdf |
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| Summary: | <p>Coccolithophores are globally distributed, calcifying phytoplankton that play an important role in the marine carbon cycle through their contribution to the carbonate pump. However, limited knowledge of their biogeography and environmental drivers hinders our ability to predict the response of the marine carbonate pump to climate change. Here, we investigated coccolithophore abundance, species composition, coccolithophore-derived calcium carbonate (CaCO<span class="inline-formula"><sub>3</sub></span> as calcite), and particulate inorganic carbon (PIC) concentrations in the upper water column of the western North Pacific Ocean. Sampling was conducted along a meridional transect spanning the oligotrophic subtropical gyre and the nutrient-rich Kuroshio–Oyashio transition region. Our results show that <i>Umbellosphaera tenuis</i> is the numerically dominant coccolithophore species in the subtropical gyre, while <i>Emiliania huxleyi</i> and <i>Syracosphaera</i> spp. dominated in the transition region. The coccolithophore community composition exhibited significant depth- and latitude-dependent variations. On average, coccolithophore calcite contributed 79 <span class="inline-formula">±</span> 27 % of the total CaCO<span class="inline-formula"><sub>3 </sub></span> standing stock in Niskin bottle samples from the euphotic zone, with a higher contribution observed in the subtropical gyre (91 <span class="inline-formula">±</span> 30 %) compared to the Kuroshio–Oyashio transition region (70 <span class="inline-formula">±</span> 24 %). This pattern was further supported by size-fractionated PIC data from in situ pump samples, with the small size fraction (1–51 <span class="inline-formula">µ</span>m) contributing 76 <span class="inline-formula">±</span> 11 % of the total PIC (<span class="inline-formula"><i>></i></span> 1 <span class="inline-formula">µ</span>m) in the subtropical gyre, compared to 67 <span class="inline-formula">±</span> 13 % in the transition region. During the sampling period, coccolithophore CaCO<span class="inline-formula"><sub>3</sub></span> production rates ranged from 0.8 to 2.1 mmol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span>, averaging 1.5 <span class="inline-formula">±</span> 0.7 mmol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span> in the subtropical gyre and 1.2 <span class="inline-formula">±</span> 0.4 mmol m<span class="inline-formula"><sup>−2</sup></span> d<span class="inline-formula"><sup>−1</sup></span> in the transition region. These findings highlight the critical role of coccolithophores in the pelagic CaCO<span class="inline-formula"><sub>3</sub></span> cycle, particularly in oligotrophic ocean waters, and emphasize the need for improved mechanistic understanding of their distribution and calcification dynamics in a changing ocean.</p> |
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| ISSN: | 1726-4170 1726-4189 |