Effects of ocean acidification on growth and physiology of Ulva lactuca ( Chlorophyta) in a rockpool‐scenario

• Published in: Phycological Research
• Main Authors: Olischläger, Mark, Bartsch, Inka, Gutow, Lars, Wiencke, Christian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1111/pre.12006; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fpre.12006; https://onlinelibrary.wiley.com/doi/pdf/10.1111/pre.12006

Summary Rising atmospheric CO 2 ‐concentrations will have severe consequences for a variety of biological processes. We investigated the responses of the green alga U lva lactuca ( L innaeus) to rising CO 2 ‐concentrations in a rockpool scenario. U . lactuca was cultured under aeration with air containing either preindustrial pCO 2 (280 μatm) or the pCO 2 predicted by the end of the 21st century (700 μatm) for 31 days. We addressed the following question: Will elevated CO 2 ‐concentrations affect photosynthesis (net photosynthesis, maximum relative electron transport rate ( rETR (max)), maximum quantum yield ( Fv/Fm ), pigment composition) and growth of U . lactuca in rockpools with limited water exchange? Two phases of the experiment were distinguished: In the initial phase (day 1–4) the S eawater C arbonate S ystem ( SWCS ) of the culture medium could be adjusted to the selected atmospheric pCO 2 condition by continuous aeration with target pCO 2 values. In the second phase (day 4–31) the SWCS was largely determined by the metabolism of the growing U . lactuca biomass. In the initial phase, Fv/Fm and rETR (max) were only slightly elevated at high CO 2 ‐concentrations, whereas growth was significantly enhanced. After 31 days the Chl a content of the thalli was significantly lower under future conditions and the photosynthesis of thalli grown under preindustrial conditions was not dependent on external carbonic anhydrase. Biomass increased significantly at high CO 2 ‐concentrations. At low CO 2 ‐concentrations most adult thalli disintegrated between day 14 and 21, whereas at high CO 2 ‐concentrations most thalli remained integer until day 31. Thallus disintegration at low CO 2 ‐concentrations was mirrored by a drastic decline in seawater dissolved inorganic carbon and HCO 3 − . Accordingly, the SWCS differed significantly between the treatments. Our results indicated a slight enhancement of photosynthetic performance and significantly elevated growth of U . lactuca at future CO 2 ‐concentrations. The accelerated ...