Growth, photosynthetic and nutrition characteristics of Pyropia haitanensis in response to the effects of increased CO2 and chloramphenicol

Pyropia haitanensis was cultured under two CO2 (410 (LC), 1000 (HC) mu L L-1) concentrations and six chloramphenicol (CAP)-methanol solutions (0, 0+methanol, 10, 50, 100, 250 mu g mL(-1)) to investigate the effects of elevated CO2 and CAP on its growth, photosynthesis and biochemical characteristics. HC had no obvious effects on the growth rate (RGR) with CAP in the range of 10 to 100 mu g mL(-1), but the decrease of RGR by HC was statistically significant with the CAP dosage at 250 mu g mL(-1). HC had no significant effect on net photosynthetic rates (P-n) in the present of CAP (10-250 mu g mL(-1)). CAP greatly reduced net photosynthesis as well as the maximal photochemical yield (F-v/F-m) and photosynthetic efficiency (alpha(ETR)). In contrast, the maximum relative electron transport rates (rETR(m)) were almost constant with the CAP dosage from 10 to 100 mu g mL(-1). HC significantly increased the energy fluxes (per RC) for absorption (ABS/RC), trapping (TRo/RC) and transport fluxes (ETo/RC) with the dosage of CAP at 250 mu g mL(-1). Principal component analysis (PCA) indicated that CAP was positively correlated with the synthesis of free amino acids (FAA), contents of umami-, sweet- and essential AA were significantly enhanced with the interaction of HC and higher CAP dosage at 100 mu g mL(-1), which led to the variation of flavor in algae. Furthermore, phycobiliproteins and soluble protein (SP) contents were remarkably reduced by CAP. Contents of chlorophyll a (Chl a), carotenoids (Car), soluble carbohydrates (SC) and C/N ratios were almost unchanged among treatments. The study indicates that future ocean acidification has no obvious effects on the biomass productivity of P. haitanensis, maintained steady photosynthetic activities with the CAP (within 100 mu g mL(-1)) and induces better flavor. The data obtained have important theoretical relevance for in-depth understanding of algal responses to global changes and oceanic contamination.