AUTHOR=Yang Yuling , Li Wei , Li Yahe , Xu Nianjun 

TITLE=Effects of ocean acidification and nitrogen limitation on the growth and photophysiological performances of marine macroalgae Gracilariopsis lemaneiformis

JOURNAL=Frontiers in Marine Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1453569

DOI=10.3389/fmars.2024.1453569

ISSN=2296-7745

ABSTRACT=<p>To investigate the effects of ocean acidification (OA) and nitrogen limitation on macroalgae growth and photophysiological responses, <italic>Gracilariopsis lemaneiformis</italic> was cultured under two main conditions: ambient (Low CO<sub>2</sub>, LC, 390 μatm) and CO<sub>2</sub> enriched (High CO<sub>2</sub>, HC, 1000 μatm), with low (LN, 7 μmol L<sup>-1</sup>) and high (HN, 56 μmol L<sup>-1</sup>) nitrate. High CO<sub>2</sub> levels decreased growth under both LN and HN treatments. HC reduced Chl <italic>a</italic>, carotenoids, phycoerythrin (PE), and phycocyanin (PC) under HN conditions, while only Chl <italic>a</italic> decreased under LN conditions. NO<sub>3</sub><sup>-</sup> uptake rate was restricted under LN compared to HN, while HC enhanced it under HN. Net photosynthetic O<sub>2</sub> evolution rates did not differ between CO<sub>2</sub> and nitrate treatments. Dark respiration rates were higher under HN, further boosted by HC. The stimulated effective quantum yield (Y(II)) corresponded to decreased non-photochemical quenching (NPQ) under HN conditions. Nitrate, not CO<sub>2</sub>, showed significant effects on the relative electron transport rate (rETR<sub>max</sub>), light use efficiency (α) and saturation light intensity (I<sub>k</sub>) that with lowered rETR<sub>max</sub> and α under LN culture. Our results indicate that OA may negatively affect <italic>Gracilariopsis lemaneiformis</italic> growth and alter its photophysiological performance under different nutrient conditions.</p>