Open AccessSaturating light and not increased carbon dioxide under ocean acidification drives photosynthesis and growth in Ulva rigida (Chlorophyta)
Author(s) -
Rautenberger Ralf,
Fernández Pamela A.,
Strittmatter Martina,
Heesch Svenja,
Cornwall Christopher E.,
Hurd Catriona L.,
Roleda Michael Y.
Publication year - 2015
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.1382
Subject(s) - photosynthesis , chlorophyta , total inorganic carbon , carbon dioxide , ocean acidification , environmental chemistry , isotopes of carbon , mixotroph , algae , carbon fibers , botany , dissolved organic carbon , chemistry , biology , seawater , ecology , total organic carbon , heterotroph , genetics , materials science , composite number , bacteria , composite material
Abstract Carbon physiology of a genetically identified Ulva rigida was investigated under different CO 2(aq) and light levels. The study was designed to answer whether (1) light or exogenous inorganic carbon (Ci) pool is driving growth; and (2) elevated CO 2(aq) concentration under ocean acidification ( OA ) will downregulate CA ext ‐mediated HCO 3 − dehydration and alter the stable carbon isotope ( δ 13 C) signatures toward more CO 2 use to support higher growth rate. At pH T 9.0 where CO 2(aq) is <1 μ mol L −1 , inhibition of the known HCO 3 − use mechanisms, that is, direct HCO 3 − uptake through the AE port and CA ext ‐mediated HCO 3 − dehydration decreased net photosynthesis ( NPS ) by only 56–83%, leaving the carbon uptake mechanism for the remaining 17–44% of the NPS unaccounted. An in silico search for carbon‐concentrating mechanism elements in expressed sequence tag libraries of Ulva found putative light‐dependent HCO 3 − transporters to which the remaining NPS can be attributed. The shift in δ 13 C signatures from –22‰ toward –10‰ under saturating light but not under elevated CO 2(aq) suggest preference and substantial HCO 3 − use to support photosynthesis and growth. U. rigida is Ci saturated, and growth was primarily controlled by light. Therefore, increased levels of CO 2(aq) predicted for the future will not, in isolation, stimulate Ulva blooms.