Changes of photosynthetic performances in mature thalli of the red alga Gelidium amansii (Gelidiaceae) exposed to different salinities

Abstract

ABSTRACTPhotosynthetic parameters, including net O2 evolution, pigment content and fast chlorophyll a (Chl a) fluorescence kinetics, were studied in mature thalli of Gelidium amansii, a marine agar-producing red seaweed, exposed to different salinities (0–35 psu) for 10 days. The results showed that the net O2 evolution at 25–32 psu was unchanged, but significantly decreased at either lower or higher salinities. Hypo-saline (15 psu and below) and hyper-saline (35 psu) conditions induced significant losses of Chl a, carotenoids and phycobiliproteins, which correlated with the decrease in the absorption flux per cross-section of fronds (ABS/CSo). Polyphasic fluorescence transients revealed that salinities at 10 and 35 psu both caused multiple effects on photosynthetic electron transport. Algae exposed to low salinity at 10 psu showed extensive damage to the donor side of the oxygen-evolving complex (OEC), reaction centre and acceptor side of PSII. Data on net O2 evolution showed that 35 psu salinity was more destructive than 10 psu, with the absence of marked osmotic injury to the OEC. The results of this study indicate the possibility of G. amansii cultivation in estuarine waters with 20–32 psu salinity.