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Heme b quotas are low in Southern Ocean phytoplankton

Heme b quotas are low in Southern Ocean phytoplankton
Heme b quotas are low in Southern Ocean phytoplankton
Heme is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of heme b in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate heme b (pmol l-1) observed at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (<6 µm in diameter) had heme b quotas <1 µmol mol-1 carbon, the lowest yet reported for marine phytoplankton. Heme b was also depleted in these species with respect to chlorophyll a. We calculated the amount of carbon accumulated per mole of heme b per second in our cultures (heme growth efficiency, HGE) and found that small Southern Ocean species can maintain growth rates, even while heme b content is reduced. Small Southern Ocean phytoplankton can thus produce more particulate carbon than larger Southern Ocean or small coastal species at equivalent iron concentrations. Combining primary productivity and heme b concentrations reported for the open ocean, we found that HGE in natural populations was within the range of our laboratory culture results. HGE was also observed to be higher at open ocean stations characterized by low iron concentrations. Our results suggest that low heme b quotas do not necessarily result in reduced growth and that marine phytoplankton can optimize iron use by manipulating the intracellular hemoprotein pool.
Iron, Phaeocystis sp., Diatoms, Haptophyte, Limitation, Coastal phytoplankton, Nutrients
29-40
Gledhill, Martha
da795c1e-1489-4d40-9df1-fc6bde54382d
Gerringa, Loes J.A.
0675b739-d214-4bf0-a923-398557683fcf
Laan, Patrick
384f06ba-d5e7-4d64-b4a0-a2ebb3f6e04b
Timmermans, Klaas R.
c175279e-c314-4a39-b9e7-b06b4ffeedec
Gledhill, Martha
da795c1e-1489-4d40-9df1-fc6bde54382d
Gerringa, Loes J.A.
0675b739-d214-4bf0-a923-398557683fcf
Laan, Patrick
384f06ba-d5e7-4d64-b4a0-a2ebb3f6e04b
Timmermans, Klaas R.
c175279e-c314-4a39-b9e7-b06b4ffeedec

Gledhill, Martha, Gerringa, Loes J.A., Laan, Patrick and Timmermans, Klaas R. (2015) Heme b quotas are low in Southern Ocean phytoplankton. Marine Ecology Progress Series, 532, 29-40. (doi:10.3354/meps11345).

Record type: Article

Abstract

Heme is the iron-containing prosthetic group of hemoproteins, and is thus required for photosynthesis, respiration and nitrate reduction in marine phytoplankton. Here we report concentrations of heme b in Southern Ocean phytoplankton and contrast our findings with those in coastal species. The concentration of particulate heme b (pmol l-1) observed at the end of the exponential growth phase was related to the concentration of dissolved iron in the culture media. Small Southern Ocean phytoplankton species (<6 µm in diameter) had heme b quotas <1 µmol mol-1 carbon, the lowest yet reported for marine phytoplankton. Heme b was also depleted in these species with respect to chlorophyll a. We calculated the amount of carbon accumulated per mole of heme b per second in our cultures (heme growth efficiency, HGE) and found that small Southern Ocean species can maintain growth rates, even while heme b content is reduced. Small Southern Ocean phytoplankton can thus produce more particulate carbon than larger Southern Ocean or small coastal species at equivalent iron concentrations. Combining primary productivity and heme b concentrations reported for the open ocean, we found that HGE in natural populations was within the range of our laboratory culture results. HGE was also observed to be higher at open ocean stations characterized by low iron concentrations. Our results suggest that low heme b quotas do not necessarily result in reduced growth and that marine phytoplankton can optimize iron use by manipulating the intracellular hemoprotein pool.

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Published date: 2015
Keywords: Iron, Phaeocystis sp., Diatoms, Haptophyte, Limitation, Coastal phytoplankton, Nutrients
Organisations: Ocean and Earth Science

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Local EPrints ID: 380840
URI: http://eprints.soton.ac.uk/id/eprint/380840
PURE UUID: 24cff558-aa5f-458d-a61f-236b11cfff10

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Date deposited: 24 Aug 2015 14:31
Last modified: 08 Jan 2022 12:25

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Contributors

Author: Martha Gledhill
Author: Loes J.A. Gerringa
Author: Patrick Laan
Author: Klaas R. Timmermans

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