Oxygenic photosynthesis can be measured easily using O₂ or CO₂ gas exchange, oxygen electrodes, Winkler titration, ¹⁴CO₂-fixation and by PAM (pulse amplitude modulation) fluorometry. PAM estimates the photosynthetic electron transport rate (ETR) by measuring the variable fluorescence of chlorophyll (Chl) a (> 695 nm) induced by absorption of blue or red light. Anoxygenic photosynthetic bacteria (APB) do not use water as an electron source and are typically photoheterotrophic rather than photoautotrophic and so ¹⁴CO₂ fixation is a misleading estimate of photosynthetic electron transport in APB photosynthesis. In vivo bacteriochlorophyll a (BChl a) absorbs blue light similar to Chl a but its characteristic longer-wavelength absorption is in the infrared and fluorescence is at > 800 nm. Blue light-induced PAM fluorescence can be used to measure the ETR in purple non-sulphur anoxygenic photobacteria and purple sulphur photobacteria because their RC-2 type BChl a complexes fluoresce similarly to PSII but at longer wavelengths than Chl a. Conventional PAM fluorometers using blue light cannot readily distinguish between oxygenic and RC-2 type anoxygenic photosynthesis because they use a simple > 700 nm highpass filter in front of the detector diode. We modified one fluorometer to use a 695–750-nm bandpass filter to measure Chl a fluorescence from PS-II, representing oxygenic photosynthesis. Similarly, we modified another fluorometer to use a highpass filter (> 830 nm) to measure BChl a fluorescence, representing anoxygenic photosynthesis. However, the fluorescence bands of Chl a and BChl a were found to be too wide to unambiguously distinguish between oxygenic and anoxygenic photosynthesis purely by fluorometry. Treatment with the specific PS-II inhibitor DCMU (Diuron) did enable discrimination of the two types of photosynthesis in a mixture of oxygenic and anoxygenic organisms. Ecological niches made up of both oxygenic and anoxygenic organisms such as microbial mats and hypereutrophic environments such as sewage ponds, wastewater ponds and prawn farm ponds are much more common than often realized. Anoxygenic photosynthesis in such systems is significant yet largely unquantified.

生氧光合作用可以很容易地使用了O来测量₂或CO ₂气体交换，氧电极，温克勒滴定法，¹⁴ CO ₂ -fixation和由PAM（p ulse一个mplitude米odulation）荧光。PAM通过测量由蓝光或红光吸收引起的叶绿素（Ch1）a（> 695 nm）的可变荧光来估算光合电子传输速率（ETR）。产氧光合细菌（APB）不使用水作为电子源，通常是光异养性的，而不是光合自养性的，因此¹⁴ CO ₂固定是APB光合作用中光合电子传输的误导性估计。体内细菌叶绿素一个（BCHL一）吸收蓝光类似于叶绿素一个，但其特性较长波长吸收是在红外线和荧光是在> 800纳米。蓝色光诱导荧光PAM可以被用于测量在紫色非硫不产氧发光细菌和紫色硫发光细菌的ETR，因为它们的RC-2型BCHL一个复合物类似地发出荧光到PSII但比叶绿素更长的波长一。传统的使用蓝光的PAM荧光计无法轻松地区分含氧光合作用和RC-2型无氧光合作用，因为它们在检测器二极管的前面使用了一个简单的> 700 nm高通滤波器。我们修改了一个荧光计，使用695-750 nm带通滤光片来测量Chl a从PS-II发出的荧光，这代表了氧的光合作用。类似地，我们修改另一个荧光计使用了高通滤波器（> 830纳米）来测量的Bchl一个荧光，表示不产氧光合作用。但是，Chl a和BChl a的荧光带被发现太宽以至于不能通过荧光法明确地区分含氧和无氧光合作用。用特定的PS-II抑制剂DCMU（Diuron）处理确实能够区分含氧和无氧生物混合物中的两种光合作用。由含氧和无氧生物（如微生物垫）和营养过高的环境（如污水池，废水池和对虾养殖场）组成的生态位比通常实现的更为普遍。在这样的系统中，产氧的光合作用很重要，但基本上没有被量化。