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The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt

The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt
The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt
The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region, provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Water samples for phytoplankton enumeration were collected from the upper 30 m during two cruises, the first to the South Atlantic sector (Jan–Feb 2011; 60 °W–15 °E and 36–60 °S) and the second in the South Indian sector (Feb–Mar 2012; 40–120 °E and 36–60 °S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Sub-Tropical, Polar, and Sub-Antarctic Fronts. The influence of environmental parameters, such as sea-surface temperature (SST), salinity, carbonate chemistry (i.e., pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macro-nutrients (i.e., nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB, was assessed statistically. Nanophytoplankton (cells 2–20 μm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, the coccolithophore Emiliania huxleyi and the diatoms Fragilariopsis nana, F. pseudonana and Pseudonitzschia sp. were the most dominant and widely distributed species. A combination of SST, macro-nutrient concentrations and pCO2 were the best statistical descriptors of biogeographic variability of biomineralizing species composition between stations. Emiliania huxleyi occurred in the silicic acid-depleted waters between the Sub-Antarctic Front and the Polar Front, indicating a favorable environment for this coccolithophore in the GCB after spring diatom blooms remove silicic acid to limiting levels. After full consideration of variability in carbonate chemistry and temperature on the distribution of nanoplankton in the GCB, we find that temperature remains the dominant driver of biogeography in a large proportion of the modern Southern Ocean.
1726-4170
4905–4925
Smith, Helen E. K.
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Poulton, Alex J.
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Garley, Rebecca
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Hopkins, Jason
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Lubelczyk, Laura C.
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Drapeau, Dave T.
d37d0b57-1a63-44c7-b937-68d2f51f2f4b
Rauschenberg, Sara
cb420d73-e9a1-4319-a119-7b8cecda0dec
Twining, Ben S.
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Bates, Nicholas R.
2eb8c60d-41a7-4018-95e7-c02a9e4eb347
Balch, William M.
18270567-fc45-4bc9-bd82-253d473e9564
Smith, Helen E. K.
e9ebdc59-6964-49b5-a2cd-b76d58ab77e1
Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Garley, Rebecca
e745b465-9c9b-4b85-995b-a3d4e5af8fd0
Hopkins, Jason
1da01369-84a8-4c55-8577-ed6c37a07037
Lubelczyk, Laura C.
bf238cfa-0ac4-4b43-a443-22d954ef22d6
Drapeau, Dave T.
d37d0b57-1a63-44c7-b937-68d2f51f2f4b
Rauschenberg, Sara
cb420d73-e9a1-4319-a119-7b8cecda0dec
Twining, Ben S.
2e32b216-7b95-47cf-bf6f-eecf0272c162
Bates, Nicholas R.
2eb8c60d-41a7-4018-95e7-c02a9e4eb347
Balch, William M.
18270567-fc45-4bc9-bd82-253d473e9564

Smith, Helen E. K., Poulton, Alex J., Garley, Rebecca, Hopkins, Jason, Lubelczyk, Laura C., Drapeau, Dave T., Rauschenberg, Sara, Twining, Ben S., Bates, Nicholas R. and Balch, William M. (2017) The influence of environmental variability on the biogeography of coccolithophores and diatoms in the Great Calcite Belt. Biogeosciences, 14, 4905–4925. (doi:10.5194/bg-14-4905-2017).

Record type: Article

Abstract

The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region, provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Water samples for phytoplankton enumeration were collected from the upper 30 m during two cruises, the first to the South Atlantic sector (Jan–Feb 2011; 60 °W–15 °E and 36–60 °S) and the second in the South Indian sector (Feb–Mar 2012; 40–120 °E and 36–60 °S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Sub-Tropical, Polar, and Sub-Antarctic Fronts. The influence of environmental parameters, such as sea-surface temperature (SST), salinity, carbonate chemistry (i.e., pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macro-nutrients (i.e., nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB, was assessed statistically. Nanophytoplankton (cells 2–20 μm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, the coccolithophore Emiliania huxleyi and the diatoms Fragilariopsis nana, F. pseudonana and Pseudonitzschia sp. were the most dominant and widely distributed species. A combination of SST, macro-nutrient concentrations and pCO2 were the best statistical descriptors of biogeographic variability of biomineralizing species composition between stations. Emiliania huxleyi occurred in the silicic acid-depleted waters between the Sub-Antarctic Front and the Polar Front, indicating a favorable environment for this coccolithophore in the GCB after spring diatom blooms remove silicic acid to limiting levels. After full consideration of variability in carbonate chemistry and temperature on the distribution of nanoplankton in the GCB, we find that temperature remains the dominant driver of biogeography in a large proportion of the modern Southern Ocean.

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e-pub ahead of print date: 13 April 2017
Published date: 7 November 2017
Organisations: Ocean and Earth Science, Marine Biogeochemistry, Ocean Biochemistry & Ecosystems, National Oceanography Centre

Identifiers

Local EPrints ID: 407946
URI: https://eprints.soton.ac.uk/id/eprint/407946
ISSN: 1726-4170
PURE UUID: 0b95be34-cfd4-4137-b041-2e3cbbff41d5

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Date deposited: 05 May 2017 01:02
Last modified: 02 Dec 2019 19:08

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Contributors

Author: Helen E. K. Smith
Author: Alex J. Poulton
Author: Rebecca Garley
Author: Jason Hopkins
Author: Laura C. Lubelczyk
Author: Dave T. Drapeau
Author: Sara Rauschenberg
Author: Ben S. Twining
Author: Nicholas R. Bates
Author: William M. Balch

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