Seasonal photosynthetic and respiratory responses of the intertidal red alga, Bostrychia binderi Harvey (Rhodophyta, Ceramiales) from a mangrove swamp and a salt marsh

The red alga Bostrychia binderi was collected from the bases of the black rush Juncus roemerianus in a salt marsh and from the pneumatophores of the black mangrove, Avicennia germinans in a mangrove swamp on the west coast of Florida. Chlorophyll a levels although similar for the two populations were 5–10% higher for salt marsh Bostrychia during September–December, and 5% lower in January than for mangrove Bostrychia. Photosynthesis was light saturated at 6300 μW/cm2/sec of white light for Bostrychia from both tidal marshes and photoinhibition did not occur at intensities up to 14 000 μW/cm2/sec of white light. Peak rates of photosynthesis for both populations occurred between 24 and 36°C and in salinities of 10‰. Maximum photosynthetic rates for light, temperature and salinity occurred in the summer months. Bostrychia (as found in a salt marsh and a mangrove swamp) displays high photosynthetic activity and broad tolerance to physical factors.