Oxygenic and anoxygenic photosynthesis in a sewage pond

Leachate sewage ponds at Phuket Integrated Waste Management (Phuket, Thailand) are typical hypereutrophic red-water ponds found at sewage treatment plants and piggery, feedlot and poultry waste ponds with mixed communities of anoxygenic purple photosynthetic bacteria (PPB) (Bacteriochlorophyll a) and Chlorella-type green algae (Chl a + b). In vivo integrating sphere spectrometer scans (Model AE PPB, Eopt = 386 ± 15 μmol quanta m−2 s−1, ETRmax = 316 ± 7.3 μmol e− g−1 BChl a s−1 but in a mixture of Chlorella and PPB only the oxygenic photosynthesis could be detected. In sewage pond samples, PAM rapid light curves in the presence and absence of DCMU allowed separate estimates of oxygen and anoxygenic photosynthesis to be made only if the Chl a content was very low (Chl a ≈ 0.26 μg mL−1; BChl a ≈ 1.4 μg mL−1). If substantial amounts of Chl a were present, fluorescence from PSII overwhelmed the signal from RC-2 of PPB, preventing the detection of anoxygenic photosynthesis. New PAM technology to measure Chl a and BChl a fluorescence separately is needed.