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Production of dissolved organic carbon by Arctic plankton communities: Responses to elevated carbon dioxide and the availability of light and nutrients

Production of dissolved organic carbon by Arctic plankton communities: Responses to elevated carbon dioxide and the availability of light and nutrients
Production of dissolved organic carbon by Arctic plankton communities: Responses to elevated carbon dioxide and the availability of light and nutrients

The extracellular release of dissolved organic carbon (DOC) by phytoplankton is a potentially important source of labile organic carbon for bacterioplankton in pelagic ecosystems. In the context of increasing seawater partial pressure of CO2 (pCO2), via the oceanic absorption of elevated atmospheric CO2 (ocean acidification), several previous studies have reported increases to the relative amount of carbon fixed into particulates, via primary production (PP), and dissolved phases (DOC). During the summer of 2012 we measured DOC production by phytoplankton communities in the Nordic seas of the Arctic Ocean (Greenland, Norwegian and Barents Sea) from both in situ sampling and during three bioassay experiments where pCO2 levels (targets ~550 µatm, ~750 µatm, ~1000 µatm) were elevated relative to ambient conditions. Measurements of DOC production and PP came from 24 h incubations and therefore represent net DOC production rates, where an unknown portion of the DOC released has potentially been utilised by heterotrophic organisms. Production of DOC (net pDOC) by in situ communities varied from 0.09 to 0.64 mmol C m?3 d?1 (average 0.25 mmol C m?3 d?1), with comparative rates in two of the experimental bioassays (0.04–1.23 mmol C m?3 d?1) and increasing dramatically in the third (up to 5.88 mmol C m?3 d?1). When expressed as a fraction of total carbon fixation (i.e., PP plus pDOC), percentage extracellular release (PER) was 14% on average (range 2–46%) for in situ measurements, with PER in the three bioassays having a very similar range (2–50%). A marked increase in pDOC (and PER) was only observed in one of the bioassays where nutrient levels (nitrate, silicic acid) dropped dramatically relative to starting (ambient) concentrations; no pCO2 treatment effect on pDOC (or PER) was evident across the three experiments. Examination of in situ net pDOC (and PER) found significant correlations with decreasing silicic acid and increasing euphotic zone depth, indicating that nutrient and light availability were strong drivers of the partitioning of primary production between particulate and dissolved phases. Furthermore, the third bioassay experiment had relatively high levels of diatom biomass as well as a strong response to nitrate and silicic acid depletion, and we suggest that nutrient starved or light limited diatom communities may be strong producers of DOC in Arctic ecosystems.
Dissolved organic carbon, Arctic Ocean, Ocean acidification, Phytoplankton, Bacteria, Diatoms
0967-0645
60-74
Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Daniels, Chris J.
aec2572b-e302-4f8e-ab7a-86b8bdf1c155
Esposito, Mario
ec7184a9-d60e-4255-a8ea-5636d960d5df
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Mitchell, Elaine
9054ff5a-aba9-4305-b9ac-a37bf05c7fb8
Ribas-Ribas, Mariana
85a1f816-cfbd-4a9d-83ff-28611827edcd
Russell, Benjamin C.
a6630e2a-c871-40c2-a80f-e230b1d86be8
Stinchcombe, Mark C.
433dd398-15f7-4730-9f1e-992d65bec70b
Tynan, Eithne
dfed4bbd-ea2a-4ff9-81f5-de2af563943b
Richier, Sophie
5f9dc2da-8e13-49d6-8d71-cdbb2c38342c
Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Daniels, Chris J.
aec2572b-e302-4f8e-ab7a-86b8bdf1c155
Esposito, Mario
ec7184a9-d60e-4255-a8ea-5636d960d5df
Humphreys, Matthew P.
40cb219a-c2dd-4581-94d0-52fb1c992498
Mitchell, Elaine
9054ff5a-aba9-4305-b9ac-a37bf05c7fb8
Ribas-Ribas, Mariana
85a1f816-cfbd-4a9d-83ff-28611827edcd
Russell, Benjamin C.
a6630e2a-c871-40c2-a80f-e230b1d86be8
Stinchcombe, Mark C.
433dd398-15f7-4730-9f1e-992d65bec70b
Tynan, Eithne
dfed4bbd-ea2a-4ff9-81f5-de2af563943b
Richier, Sophie
5f9dc2da-8e13-49d6-8d71-cdbb2c38342c

Poulton, Alex J., Daniels, Chris J., Esposito, Mario, Humphreys, Matthew P., Mitchell, Elaine, Ribas-Ribas, Mariana, Russell, Benjamin C., Stinchcombe, Mark C., Tynan, Eithne and Richier, Sophie (2016) Production of dissolved organic carbon by Arctic plankton communities: Responses to elevated carbon dioxide and the availability of light and nutrients. Deep Sea Research Part II: Topical Studies in Oceanography, 127, 60-74. (doi:10.1016/j.dsr2.2016.01.002).

Record type: Article

Abstract


The extracellular release of dissolved organic carbon (DOC) by phytoplankton is a potentially important source of labile organic carbon for bacterioplankton in pelagic ecosystems. In the context of increasing seawater partial pressure of CO2 (pCO2), via the oceanic absorption of elevated atmospheric CO2 (ocean acidification), several previous studies have reported increases to the relative amount of carbon fixed into particulates, via primary production (PP), and dissolved phases (DOC). During the summer of 2012 we measured DOC production by phytoplankton communities in the Nordic seas of the Arctic Ocean (Greenland, Norwegian and Barents Sea) from both in situ sampling and during three bioassay experiments where pCO2 levels (targets ~550 µatm, ~750 µatm, ~1000 µatm) were elevated relative to ambient conditions. Measurements of DOC production and PP came from 24 h incubations and therefore represent net DOC production rates, where an unknown portion of the DOC released has potentially been utilised by heterotrophic organisms. Production of DOC (net pDOC) by in situ communities varied from 0.09 to 0.64 mmol C m?3 d?1 (average 0.25 mmol C m?3 d?1), with comparative rates in two of the experimental bioassays (0.04–1.23 mmol C m?3 d?1) and increasing dramatically in the third (up to 5.88 mmol C m?3 d?1). When expressed as a fraction of total carbon fixation (i.e., PP plus pDOC), percentage extracellular release (PER) was 14% on average (range 2–46%) for in situ measurements, with PER in the three bioassays having a very similar range (2–50%). A marked increase in pDOC (and PER) was only observed in one of the bioassays where nutrient levels (nitrate, silicic acid) dropped dramatically relative to starting (ambient) concentrations; no pCO2 treatment effect on pDOC (or PER) was evident across the three experiments. Examination of in situ net pDOC (and PER) found significant correlations with decreasing silicic acid and increasing euphotic zone depth, indicating that nutrient and light availability were strong drivers of the partitioning of primary production between particulate and dissolved phases. Furthermore, the third bioassay experiment had relatively high levels of diatom biomass as well as a strong response to nitrate and silicic acid depletion, and we suggest that nutrient starved or light limited diatom communities may be strong producers of DOC in Arctic ecosystems.

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Accepted/In Press date: 14 January 2016
Published date: May 2016
Keywords: Dissolved organic carbon, Arctic Ocean, Ocean acidification, Phytoplankton, Bacteria, Diatoms
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 388148
URI: http://eprints.soton.ac.uk/id/eprint/388148
ISSN: 0967-0645
PURE UUID: a7588cd8-e8a8-421f-959e-18904ab82374
ORCID for Matthew P. Humphreys: ORCID iD orcid.org/0000-0002-9371-7128

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Date deposited: 19 Feb 2016 10:41
Last modified: 09 Jan 2022 03:47

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Contributors

Author: Alex J. Poulton
Author: Chris J. Daniels
Author: Mario Esposito
Author: Matthew P. Humphreys ORCID iD
Author: Elaine Mitchell
Author: Mariana Ribas-Ribas
Author: Benjamin C. Russell
Author: Mark C. Stinchcombe
Author: Eithne Tynan
Author: Sophie Richier

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