The effect of irradiance and temperature on the photosynthesis of an agarophyte, Gelidiella acerosa (Gelidiales, Rhodophyta), from Krabi, Thailand

摘要

The effect of irradiance and temperature on the photosynthesis of an agarophyte from Thailand, Gelidiella acerosa (Gelidiales, Rhodophyta), was determined using dissolved oxygen sensors and pulse-amplitude modulated fluorometry (PAM). A model of the net photosynthesis-irradiance (P-E) curve at 28 A degrees C revealed that the saturation and compensation irradiances were 83 (95 % Bayesian credible interval (BCI), 52-128) mu mol photons m(-2) s(-1) and 37 (BCI, 29-45) mu mol photons m(-2) s(-1), respectively. Gross photosynthesis and dark respiration were also determined over a range of temperatures (16-40 A degrees C), revealing that the gross photosynthetic rate was highest at 18.4 (BCI, 15.9-20.8) mg O-2 g(ww) (-1) min(-1) at 29.2 (BCI, 26.8-32.1) A degrees C. Dark respiration rate could be fitted to a second-order polynomial regression (P 0.01) over the range of the experimental temperatures, and the magnitudes of the rates ranged from 0.49 to 0.93 mg O-2 g(ww) (-1) min(-1) A degrees C-1. The highest value of the maximum effective quantum yield (I broken vertical bar(PSII) at 0 mu mol photons m(-2) s(-1)) occurred at 27.7 (BCI, 26.5-28.9) A degrees C and was 0.57 (BCI, 0.55-0.58), and the values of I broken vertical bar(PSII) decreased above and below 27.7 A degrees C. Although this species is considered to be well-adapted to the current seawater temperatures of the region, the results of the experiments also suggest that they are likely close to the limiting temperature conditions.