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

• Published in: Frontiers in Marine Science
• Main Authors: Yang, Yuling, Li, Wei, Li, Yahe, Xu, Nianjun
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2024
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.3389/fmars.2024.1453569; https://www.frontiersin.org/articles/10.3389/fmars.2024.1453569/full

To investigate the effects of ocean acidification (OA) and nitrogen limitation on macroalgae growth and photophysiological responses, Gracilariopsis lemaneiformis was cultured under two main conditions: ambient (Low CO 2 , LC, 390 μatm) and CO 2 enriched (High CO 2 , HC, 1000 μatm), with low (LN, 7 μmol L -1 ) and high (HN, 56 μmol L -1 ) nitrate. High CO 2 levels decreased growth under both LN and HN treatments. HC reduced Chl a , carotenoids, phycoerythrin (PE), and phycocyanin (PC) under HN conditions, while only Chl a decreased under LN conditions. NO 3 - uptake rate was restricted under LN compared to HN, while HC enhanced it under HN. Net photosynthetic O 2 evolution rates did not differ between CO 2 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 2 , showed significant effects on the relative electron transport rate (rETR max ), light use efficiency (α) and saturation light intensity (I k ) that with lowered rETR max and α under LN culture. Our results indicate that OA may negatively affect Gracilariopsis lemaneiformis growth and alter its photophysiological performance under different nutrient conditions.