Calcification and latitudinal distribution of extant coccolithophores across the Drake Passage during late austral summer 2016
<p>Coccolithophores are globally distributed microscopic marine algae that exert a major influence on the global carbon cycle through calcification and primary productivity. There is recent interest in coccolithophore polar communities; however field observations regarding their biogeographic...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-09-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/16/3679/2019/bg-16-3679-2019.pdf |
| Summary: | <p>Coccolithophores are globally distributed microscopic marine algae that
exert a major influence on the global carbon cycle through calcification and
primary productivity. There is recent interest in coccolithophore polar
communities; however field observations regarding their biogeographic
distribution are scarce for the Southern Ocean (SO). This study documents the
latitudinal, as well as in depth, variability in the coccolithophore
assemblage composition and the coccolith mass variation in the ecologically
dominant <i>Emiliania huxleyi</i> across the Drake Passage. Ninety-six water samples were taken
between 10 and 150 m water depth from 18 stations during <i>POLARSTERN</i>
Expedition PS97 (February–April 2016). A minimum of 200 coccospheres per
sample were identified in the scanning electron microscope, and coccolith mass
was estimated with light microscopy. We find that coccolithophore abundance,
diversity and maximum depth habitat decrease southwards, marking different
oceanographic fronts as ecological boundaries. We characterize three zones:
(1) the Chilean margin, where <i>E. huxleyi</i> type A (normal and overcalcified) and type R
are present; (2) the Subantarctic Zone (SAZ), where <i>E. huxleyi</i> reaches maximum values
of <span class="inline-formula">212.5×10<sup>3</sup></span> cells L<span class="inline-formula"><sup>−1</sup></span> and types B/C, C and O are dominant; and (3) the Polar
Front Zone (PFZ), where <i>E. huxleyi</i> types B/C and C dominate. We link the decreasing
trend in <i>E. huxleyi </i>coccolith mass to the poleward latitudinal succession from the type A
to the type B group. Remarkably, we find that coccolith mass is strongly
anticorrelated to total alkalinity, total <span class="inline-formula">CO<sub>2</sub></span>, the bicarbonate ion and pH.
We speculate that low temperatures are a greater limiting factor than
carbonate chemistry in the Southern Ocean. However, further in situ
oceanographic data are needed to verify the proposed relationships. We
hypothesize that assemblage composition and calcification modes of <i>E. huxleyi</i> in the
Drake Passage will be strongly influenced by the ongoing climate change.</p> |
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| ISSN: | 1726-4170 1726-4189 |