title: Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13C Fractionation in Marine Dinoflagellates.
abstract: Along with increasing oceanic CO2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated pCO2 in combination with light or nitrogen-limitation on 13C fractionation (εp) in four dinoflagellate species. We cultured Gonyaulax spinifera and Protoceratium reticulatum in dilute batches under low-light ('LL') and high-light ('HL') conditions, and grew Alexandrium fundyense and Scrippsiella trochoidea in nitrogen-limited continuous cultures ('LN') and nitrogen-replete batches ('HN'). The observed CO2-dependency of εp remained unaffected by the availability of light for both G. spinifera and P. reticulatum, though at HL εp was consistently lower by about 2.7‰ over the tested CO2 range for P. reticulatum. This may reflect increased uptake of (13C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO2-dependency of εp disappeared under LN conditions in both A. fundyense and S. trochoidea. The generally higher εp under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO2-dependent εp under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO2-proxy. Our results however demonstrate that light- and nitrogen-limitation also affect εp, thereby illustrating the need to carefully consider prevailing environmental conditions.
authors.affiliation: Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands.|Marine Biogeosciences, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Mirja
authors.initials: M
authors.lastname: Hoins
authors.affiliation: Marine Biogeosciences, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Eberlein
authors.affiliation: Marine Biogeosciences, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Christian H
authors.initials: CH
authors.lastname: Groβmann
authors.affiliation: Marine Biogeosciences, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Karen
authors.initials: K
authors.lastname: Brandenburg
authors.affiliation: Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands.|Geology Department, Royal Netherlands Institute for Sea Research (NIOZ), Den Hoorn (Texel), The Netherlands.
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: Reichart
authors.affiliation: Marine Biogeosciences, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Rost
authors.affiliation: Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Appy
authors.initials: A
authors.lastname: Sluijs
authors.affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Dedmer B
authors.initials: DB
authors.lastname: Van de Waal
mesh_terms: D000143:Acids / Q000737:chemistry*; D002247:Carbon Isotopes / Q000032:analysis*; D004141:Dinoflagellida / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008027:Light; D008386:Marine Biology; D009584:Nitrogen / Q000737:chemistry*; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*
chemical_list: D000143:Acids; D002247:Carbon Isotopes; D009584:Nitrogen