Quantum Efficiency and Photosynthetic Production of a Temperate Turf Algal Community

Abstract

A preliminary investigation of the production and photosynthetic efficiency of a temperate, sub-tidal, turf algal community using in situ measurements of photosynthesis and respiration is reported. Results indicated that temperate turfs have high biomass specific productivity, but are less productive on an areal basis than either the surrounding macro-algal community or their tropical counterparts. Net 24 h production ranges between 12 and 78 mmol O₂ m^-2 d^-1 (corresponding to a carbon fixation rate of 0.1–0.9 g C m^-2 d^-1). Inefficient use of the available substrata, due to the early successional nature of these communities, is considered to be the cause of this low productivity. A quantum efficiency of 0.034 µmol O₂ µmol photons^-1 and a sub-saturating light itensity of 134–210 µmol photons m^-2 s^-1 indicate that photosynthetic saturation was easily achieved and suggests that self-shading in the turf community was not significant.