The photosynthetic and respiratory rates and tolerances of benthic algae from a mangrove and salt marsh estuary: A comparative study

Abstract

Net photosynthetic and respiratory rates were studied for four species of estuarine algae dominant in a mangrove and a salt marsh on the west coast of Florida with relation to light, temperature, salinity, and periods of desiccation. Bostrychia bindert (intertidal) and Gracilaria verrucosa (subtidal) were common to both sites: Cladophora repens (intertidal) and Acanthophora spicifera (subtidal) were included from the mangrove community while Catenella repens (intertidal) and Spyridia filamentosa (subtidal) were included from the salt marsh community. Quantitative analysis of chlorophyll a showed higher levels in the salt marsh algae as compared to algae from the mangrove community. Net photosynthetic and respiratory rates were similar for both intertidal species from each site. The intertidal species showed broad tolerances to salinity with positive photosynthetic responses even when held for 3 days in distilled water. All intertidal species had high rates of photosynthesis after periods of desiccation of 4, 8 or 16 h day −1 for 3 days and these rates were evident in specimens monitored in the air as well as submerged. Peak rates of photosynthesis for all 8 species occurred under 1·12 × 10 4 μW cm −2 white light, at 30–36 °C and in 20–30%. The subtidal algae from the mangrove community ( Acanthophora and Gracilaria) had 5- to 10-fold increases in photosynthetic rates over the subtidal species from the salt marsh community ( Spyridia and Gracilaria). The physiological tolerances of the algae to site and location in salt marsh and mangrove estuaries along the west coast of Florida are discussed.