Light and Dark Respiration and Release of Organic Carbon in Marine Macrophytes of the Great Barrier Reef Region

Abstract

Respiration and organic carbon release were examined in several submersed marine macroalgae and vascular plants of the Great Barrier Reef region by use of a ¹⁴C assay. Loss of ¹⁴CO₂ and organic ¹⁴C from prelabelled plants was followed in the light and dark at low and high dissolved oxygen concentrations. While refixation of respired carbon in the light was substantial in some cases, rates of loss of CO₂ in the light were significant and suggested presence of photorespiration, particularly in Cymodocea rotundata and Halophila ovata, in which respiration in the light was enhanced by high dissolved oxygen concentration. Release of dissolved organic carbon was relatively low, and lack of enhancement by high oxygen suggested minimal involvement of glycollate excretion.