Microscopic examination of photoautotrophic and phosphatase-producing organisms in phosphorus-limited Everglades periphyton mats

Using a fluorescent-labeled enzyme substrate, we examined the location of in situ phosphatase activity in a periphyton mat and explored the potential associations of phosphatase-producing organisms (PPO) and cyanobacteria within these mats. Our results indicate that most PPOs are concentrated in the lower section of the mat, and the phosphatase activity appears to be associated with heterotrophic organisms that are in close proximity to chlorophyll-containing cyanobacteria. The lack of observed phosphatase by larger photosynthetic cells and the close association of these cells with PPOs indicate a possible interaction whereby PPOs obtain photosynthetically fixed carbon from cyanobacteria and, in turn, provide inorganic phosphorus (P) and other compounds to the cyanobacteria. We believe these results may represent additional evidence for algal-bacterial symbiosis in aquatic systems and, in particular, the P-limited cyanobacterial mat communities