PAM Chlorophyll a Fluorometry for Monitoring Health of Corals along the Coast of Qatar

Abstract

Abstract The Arabian Gulf is shallow, sub-tropical, and semi-enclosed, all factors that promote considerable variations in water quality properties. A one and half year study was conducted to evaluate the effectiveness of PAM (Pulse Amplitude Modulation) chlorophyll a fluorometry in monitoring the health of coral reefs. The objectives were: (i) to evaluate the efficacy of PAM chlorophyll fluorometry as a means of assessing sub-lethal stress in corals; (ii) to calibrate and validate this technique for future monitoring applications; (iii) to collect field data to correlate detected changes in stress status to changes in the magnitude of environmental factors that are known to affect these organisms. The study consisted of five field surveys covering seasonal variations. PAM fluorometry measurements were completed with detailed visual assessments of the health status of the corals. While the visual signs of stress were difficult to quantify, the PAM fluorescence data provided a better objective and quantitative measure of stress at the time of the surveys than those afforded by traditional visual observations. The reduced photosynthetic efficiency indicated by the PAM, without clear visual signs of impairment in coral structure, was generally followed by necrosis of parts of the colonies; this was visually verified in subsequent campaigns. Moreover, corals experienced severe bleaching during summer 2010 and PAM fluorometry data allowed a detailed analysis of the process including recovery. This study demonstrated that PAM fluorometry can improve efforts for monitoring coral health and protecting coral reef communities in the Qatar and Gulf environment by providing objective data on the photosynthetic performances and the state of stress of these organisms.