Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes

Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO<sub>2</sub> depletion in surface waters. Cyanobacteria and other groups of phytopla...

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Main Authors: A. M. Morales-Williams, A. D. Wanamaker Jr., J. A. Downing
Format: Article
Language:English
Published: Copernicus Publications 2017-06-01
Series:Biogeosciences
Online Access:http://www.biogeosciences.net/14/2865/2017/bg-14-2865-2017.pdf
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author A. M. Morales-Williams
A. M. Morales-Williams
A. M. Morales-Williams
A. D. Wanamaker Jr.
J. A. Downing
J. A. Downing
author_facet A. M. Morales-Williams
A. M. Morales-Williams
A. M. Morales-Williams
A. D. Wanamaker Jr.
J. A. Downing
J. A. Downing
author_sort A. M. Morales-Williams
collection DOAJ
description Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO<sub>2</sub> depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO<sub>3</sub><sup>−</sup>) across their cell membrane when CO<sub>2</sub> concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO<sub>2</sub> depletion, we measured the <i>δ</i><sup>13</sup>C signatures of dissolved inorganic carbon (<i>δ</i><sup>13</sup>C<sub>DIC</sub>) and phytoplankton particulate organic carbon (<i>δ</i><sup>13</sup>C<sub>phyto</sub>) in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass–balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO<sub>2</sub> stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton <i>δ</i><sup>13</sup>C signatures as well as a significant nonlinear negative relationship between water column <i>ρ</i>CO<sub>2</sub> and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO<sub>2</sub> or HCO<sub>3</sub><sup>−</sup> during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO<sub>2</sub> drops below atmospheric equilibrium. Our results indicate that active HCO<sub>3</sub><sup>−</sup> uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO<sub>2</sub> is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.
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spelling doaj.art-00b7d5aee24b406ba61e3efb1e374b912022-12-21T20:30:10ZengCopernicus PublicationsBiogeosciences1726-41701726-41892017-06-01142865287510.5194/bg-14-2865-2017Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakesA. M. Morales-Williams0A. M. Morales-Williams1A. M. Morales-Williams2A. D. Wanamaker Jr.3J. A. Downing4J. A. Downing5Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011, USADepartment of Ecology, Evolution, and Behavior, University of Minnesota Twin Cities, 1475 Gortner Ave., Saint Paul, MN 55108, USARubenstein School of Environment and Natural Resources, University of Vermont, 81 Carrigan Drive, Burlington, VT 05405, USADepartment of Geological and Atmospheric Science, Iowa State University, 253 Science Hall, Ames, IA 50011, USADepartment of Ecology, Evolution, and Organismal Biology, Iowa State University, 251 Bessey Hall, Ames, IA 50011, USAMinnesota Sea Grant, University of Minnesota Duluth, 141 Chester Park, 31 West College St., Duluth, MN 55812, USAPhytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO<sub>2</sub> depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO<sub>3</sub><sup>−</sup>) across their cell membrane when CO<sub>2</sub> concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO<sub>2</sub> depletion, we measured the <i>δ</i><sup>13</sup>C signatures of dissolved inorganic carbon (<i>δ</i><sup>13</sup>C<sub>DIC</sub>) and phytoplankton particulate organic carbon (<i>δ</i><sup>13</sup>C<sub>phyto</sub>) in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass–balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO<sub>2</sub> stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton <i>δ</i><sup>13</sup>C signatures as well as a significant nonlinear negative relationship between water column <i>ρ</i>CO<sub>2</sub> and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO<sub>2</sub> or HCO<sub>3</sub><sup>−</sup> during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO<sub>2</sub> drops below atmospheric equilibrium. Our results indicate that active HCO<sub>3</sub><sup>−</sup> uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO<sub>2</sub> is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.http://www.biogeosciences.net/14/2865/2017/bg-14-2865-2017.pdf
spellingShingle A. M. Morales-Williams
A. M. Morales-Williams
A. M. Morales-Williams
A. D. Wanamaker Jr.
J. A. Downing
J. A. Downing
Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
Biogeosciences
title Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
title_full Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
title_fullStr Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
title_full_unstemmed Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
title_short Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes
title_sort cyanobacterial carbon concentrating mechanisms facilitate sustained co sub 2 sub depletion in eutrophic lakes
url http://www.biogeosciences.net/14/2865/2017/bg-14-2865-2017.pdf
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