The LI-6800 is trusted by leading researchers and institutions around the world to measure carbon assimilation (A) and pulse-amplitude modulated (PAM) chlorophyll a fluorescence in terrestrial plants. With high precision CO2 and H2O gas analyzers and automated system controls, the LI-6800 is used to test novel hypotheses at the forefront of photophysiology research. The NEW 6800-18 Aquatic Chamber extends these capabilities to samples that must remain immersed in water or surrounded by humid air, enabling researchers to explore questions related to photosynthesis of algae in aquatic suspension, coral, and macrophytes.