Combined Effects of Ocean Acidification and Light or Nitrogen Availabilities on 13 C Fractionation in Marine Dinoflagellates

• Published in: PLOS ONE
• Main Authors: Hoins, Mirja, Eberlein, Tim, Groβmann, Christian H., Brandenburg, Karen, Reichart, Gert-Jan, Rost, Björn, Sluijs, Appy, Van de Waal, Dedmer B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: international; Ocean acidification
• Online Access: https://pure.knaw.nl/portal/en/publications/06046baf-89c9-4f36-a6e6-7070acc255b8; https://doi.org/10.1371/journal.pone.0154370; https://hdl.handle.net/20.500.11755/06046baf-89c9-4f36-a6e6-7070acc255b8; https://pure.knaw.nl/ws/files/1900798/6089_Hoins.PDF

Along with increasing oceanic CO 2 concentrations, enhanced stratification constrains phytoplankton to shallower upper mixed layers with altered light regimes and nutrient concentrations. Here, we investigate the effects of elevated p CO 2 in combination with light or nitrogen-limitation on 13 C fractionation (ε p ) 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 CO 2 -dependency of ε p remained unaffected by the availability of light for both G . spinifera and P . reticulatum , though at HL ε p was consistently lower by about 2.7‰ over the tested CO 2 range for P . reticulatum . This may reflect increased uptake of ( 13 C-enriched) bicarbonate fueled by increased ATP production under HL conditions. The observed CO 2 -dependency of ε p disappeared under LN conditions in both A . fundyense and S . trochoidea . The generally higher ε p under LN may be associated with lower organic carbon production rates and/or higher ATP:NADPH ratios. CO 2 -dependent ε p under non-limiting conditions has been observed in several dinoflagellate species, showing potential for a new CO 2 -proxy. Our results however demonstrate that light- and nitrogen-limitation also affect ε p , thereby illustrating the need to carefully consider prevailing environmental conditions.