The relative availability of inorganic carbon and inorganic nitrogen influences the response of the dinoflagellate Protoceratium reticulatum to elevated CO₂

Abstract

This work originates from three facts: (i) changes in CO availability influence metabolic processes in algal cells; (ii) Spatial and temporal variations of nitrogen availability cause repercussions on phytoplankton physiology; (iii) Growth and cell composition are dependent on the stoichiometry of nutritional resources. In this study, we assess whether the impact of rising pCO is influenced by N availability, through the impact that it would have on the C/N stoichiometry, in conditions of N sufficiency. Our experiments used the dinoflagellate Protoceratium reticulatum, which we cultured under three CO regimes (400, 1,000, and 5,000 ppmv, pH of 8.1) and either variable (the NO concentration was always 2.5 mmol · L ) or constant (NO concentration varied to maintain the same C /NO ratio at all pCO ) C /NO ratio. Regardless of N availability, cells had higher specific growth rates, but lower cell dry weight and C and N quotas, at elevated CO . The carbohydrate pool size and the C/N was unaltered in all treatments. The lipid content only decreased at high pCO at constant C /NO ratio. In the variable C /NO conditions, the relative abundance of Rubisco (and other proteins) also changed; this did not occur at constant C /NO . Thus, the biomass quality of P. reticulatum for grazers was affected by the C /NO ratio in the environment and not only by the pCO , both with respect to the size of the main organic pools and the composition of the expressed proteome.

Ecophysiological changes and spore formation: two strategies in response to low‐temperature and high‐light stress in Klebsormidium cf. flaccidum (Klebsormidiophyceae, Streptophyta)1

“…, Pierangelini et al. ). Nevertheless, there are some exceptions within Klebsormidiophyceae; e.g., in Klebsormidium crenulatum the ETR started to decrease slightly at PFDs higher than 500 μmol photons · m −2 · s −1 (Karsten and Holzinger ).…”

Impacts of Seagrass on Benthic Microalgae and Phytoplankton Communities in an Experimentally Warmed Coral Reef Mesocosm

“…Since the benthic microalgal and phytoplankton communities consist of hundreds to thousands of species (Cahoon, 1999;Tew et al, 2017b), it may be more pragmatic to instead monitor cumulative effects of OA on the system, rather than at a species by species level. At the community level, OA can enhance phytoplankton growth (McCarthy et al, 2012;Pierangelini et al, 2016), alter assemblages (Tortell et al, 2002;Ziveri et al, 2014), and negatively affect certain diatom species (Gao et al, 2012;Torstensson et al, 2012), and we found higher abundances of benthic microalgae in the seagrass mesocosms, particularly upon raising the temperature to 28 • C. Although it is tempting to speculate that this could be due to seagrass sequestering of CO 2 , the carbonate system was actually similar between seagrass and control mesocosms. Instead, only nitrate levels differed significantly.…”

The Enzymology of Ocean Global Change

“…1,000 ppm pCO 2 (Pierangelini et al 2017). Expression of genes involved in nitrate uptake and assimilation pathways is upregulated under low-pH, high-pCO 2 conditions in both the diatom Chaetoceros muelleri (Liang et al 2020) and the chlorophyte Coccomyxa subellipsoidea (Peng et al 2016).…”