Epiphytes of aquatic vegetation harbor unique microbiomes that are important for P and N cycling in stormwater treatment areas of the Everglades
The Everglades stormwater treatment areas (STAs) are constructed wetlands that reduce total phosphorus (TP) being discharged into Everglades National Park. Microbial communities of the STAs are important in reducing surface water TP, however, little is known about their biological mechanisms related to phosphorus (P) and nitrogen (N) cycling. For this study we compared the microbial, algal, and functional gene composition in surface water, floc (the unconsolidated uppermost sediment layer), and epiphytes associated with submerged aquatic vegetation (SAV, Chara sp.) and emergent aquatic vegetation (EAV, Typha sp.) within STA-3/4. Algae (organisms containing chlorophyll a that are not true plants) were visually identified through microscopic analysis, and microbial communities and functional genes were identified with metagenome sequencing. We found that surface water, floc, and epiphytes all had unique microbial and algal community composition and likely play different roles in N and P cycling. Surface water samples likely play a minor role in N and P cycling, while both floc and epiphytes have similar N metabolism functions. The epiphytes had higher algal biomass and higher abundance of organic P metabolism genes compared to surface water and floc; epiphytes may play an important role in P cycling compared to other sample types. Differences in phosphonate metabolism genes between SAV and EAV suggested these microbial communities may have distinct different roles in P metabolism in the STAs. Understanding these compositional and functional potential differences between microbial niches of the STAs helps better inform the management of these treatment wetlands to remove TP from surface waters.