Abstract:

The coral holobiont is a complex system containing the coral polyp and its symbiotic zooxanthellae. Zooxanthellae provides an important source of energy for coral polyps through photosynthesis. The light compensation point of coral holobiont can indicate the light adaptability of coral, and it is an important photosynthetic characteristic index. However, the measurement of light compensation points of the coral holobiont was little reported. Here we reported a method for determining the light compensation point of coral holobiont. According to the theory of diffusion equilibrium, the light compensation point of coral Pocillopora damicornis was determined by using dissolved oxygen microelectrode combined with light intensity adjustable light source. Our results showed that the concentration of dissolved oxygen in coral diffusion boundary layer responded rapidly to the change of photosynthetically active radiation (PAR). The concentration of dissolved oxygen in coral diffusion boundary layer was highly correlated with the PAR，and higher correlation coefficient was achieved in the process of PAR decreasing. The light compensation point of the coral P. damicornis was 1.52 μE/m2/s, which was equivalent to those of shade-tolerant plants. A relatively low light compensation point allowed coral P. damicornis to inhabit a wider range of water depths, which expanded the habitat of coral. The dissolved oxygen microelectrode related techniques and methods had a wide application prospect in the research of coral holobiont photosynthesis.

Key words: microelectrode, Pocillopora damicornis, diffusive boundary layer, dissolved oxygen diffusive equilibrium, light compensation point