Inorganic Carbon Acquisition by Aquatic Primary Producers

Physiological control on carbon isotope fractionation in marine phytoplankton

“…No internal membrane systems with localized CAs associated to C fixation as present in diatoms have been recognized in haptophytes and dinoflagellates (Rokitta et al, 2022). In fact, some dinoflagellate species even lack the pyrenoid compartment, where RubisCO is located in most eukaryotic algae (Ratti et al, 2007).…”

“…The CCMs have evolved over time as a response to declining atmospheric CO 2 concentrations to ensure effective carboxylation in the vicinity of RubisCO in oxygenated waters (Giordano et al, 2005). Phytoplankton CCMs comprise a variety of physiological adaptations, and include active uptake of CO 2 and HCO − 3 , the use of carbonic anhydrase (CA) to accelerate the interconversion between CO 2 and HCO − 3 , and ways to minimize the CO 2 efflux from the cell (Badger et al, 1998;Reinfelder, 2011;Rokitta et al, 2022). These processes can strongly influence 13 C fractionation patterns of phytoplankton (Sharkey and Berry, 1985).…”

Abrupt and acclimation responses to changing temperature elicit divergent physiological effects in the diatom Phaeodactylum tricornutum

“…By contrast, and rely to a large extent on the biochemical rate of involved electron transport chains, which are strongly controlled by membrane fluidity (Maksimov et al ., 2017), and are therefore highly temperature‐dependent, more strongly than enzymatic processes (Los et al ., 2013). Also, the less pronounced inhibition of may be explained by the increased carboxylation affinity of RubisCO with declining temperatures (Hall & Keys, 1983; Rokitta et al ., 2022), and the concomitantly increased CO 2 : O 2 ratio in colder seawater (Jordan & Ogren, 1981; Zeebe & Wolf‐Gladrow, 2001), which may further compensate the thermodynamic decrease of enzyme‐catalyzed reaction rates.…”

Higher temperature, increased CO2, and changing nutrient ratios alter the carbon metabolism and induce oxidative stress in a cosmopolitan diatom

“…We observed a higher photosynthetic rate at 21°C than at 18°C, which may originate from a thermal enhancement of electron flow in photosynthetic light reaction, and/or from an enhanced activity of the CO 2 fixing enzyme RuBisCo under higher temperatures (Table 2; Ras et al 2013). In addition to warming, elevated p CO 2 further increased photosynthetic activity, likely as a result of higher C availability, which may enable a reallocation of energy, possibly due to lower demand for the carbon concentration mechanism activity (Young et al 2015; Rokitta et al 2022). Light‐harvesting pigments (Chl a , fucoxanthin) were not affected by any of the drivers, indicating that the light‐harvesting portion of the antenna complex was not affected by temperature, p CO 2 , or dissolved nutrient ratios.…”

“…However, other studies have shown that responses of phytoplankton to increasing oceanic p CO 2 may be complex (Beardall and Raven 2004; Taucher et al 2015; Alvarez‐Fernandez et al 2018), and the consequences for photosynthesis and wider phytoplankton ecophysiology remain to be clarified. Studies have found different effects of warming and ocean acidification on various physiological processes related to carbon metabolism in phytoplankton, including increase in photosynthesis and respiration rates (Wu et al 2010; Goldman et al 2017), higher DOC production (Engel et al 2010), and downregulation of carbon‐concentrating mechanisms (Thangaraj and Sun 2021; Rokitta et al 2022). Environmental ratios of dissolved inorganic N : P influence cellular quotas of POC, photosynthetic and growth rate in phytoplankton (Rasdi and Qin 2014; Li and Sun 2016), as well as DOC exudation (Obernosterer and Herndl 1995).…”