The Photosynthetic Capacity of the Phytoplankton in the Waters of a Coral Reef

Abstract

Phytoplankton are relatively scarce in surface waters in a region of the Great Barrier Reef near Lizard Island. The phytoplankton sampled have a high rate of photosynthetic efficiency (1.2 millimoles CO₂ fixed per milligram chlorophyll a per hour), although between 30 and 50% of the total carbon fixed may be excreted in soluble form. The rate of photosynthetic CO₂ fixation into the particulate fraction is sensitive to varying levels of oxygen, suggesting the existence of a photorespiratory mechanism, a factor which might significantly influence the photosynthetic productivity of the algae in these tropical waters.