Ulva is the dominant genus in the green tide events and is considered to have efficient CO2 concentrating mechanisms (CCMs). However, little is understood regarding the impacts of ocean acidification on the CCMs of Ulva and the consequences of thalli's acclimation to ocean acidification in terms of responding to environmental factors. Here, we grew a cosmopolitan green alga, Ulva linza at ambient (LC) and elevated (HC) CO2 levels and investigated the alteration of CCMs in U. linza grown at HC and its responses to the changed seawater carbon chemistry and light intensity.
Carbon physiology of a genetically identified Ulva rigida was investigated under different CO2(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 CO2(aq) concentration under ocean acidification (OA) will downregulate CAext-mediated inline image dehydration and alter the stable carbon isotope ($δ$13C) signatures toward more CO2 use to support higher growth rate.
Exposure of the toxigenic dinoflagellate Alexandrium catenella to variations in pCO2/pH, comparable to current and near-future levels observed in Southern Chilean fjords, revealed potential functional adaptation mechanisms. Under calculated conditions for pH(total scale) and pCO2 ranging from 7.73–8.66 to 69.7–721.3 $μ$atm, respectively, the Chilean strain Q09 presented an optimum growth rate and dissolved inorganic carbon (DIC) uptake at near-equilibrium pCO2/pH conditions (∼8.1).
This study investigated the impact of photon flux and elevated CO2 concentrations on growth and photosynthetic electron transport on the marine diatom Chaetoceros muelleri and looked for evidence for the presence of a CO2-concentrating mechanism (CCM). pH drift experiments clearly showed that C. muelleri has the capacity to use bicarbonate to acquire inorganic carbon through one or multiple CCMs. The final pH achieved in unbuffered cultures was not changed by light intensity, even under very low photon flux, implying a low energy demand of bicarbonate use via a CCM.