Long-term sustainable phosphorus (P) retention in a low-P stormwater wetland for Everglades restoration.

The Stormwater Treatment Areas (STAs) are large wetlands constructed for phosphorus (P) retention for Everglades restoration in south Florida (USA), and include areas of submerged aquatic vegetation (SAV) at a globally unprecedented scale (~12,000 ha). The goal of this study was to elucidate the fate of P retained in large-scale SAV wetlands, and the associated temporal trends in P removal and retention. In a well-performing, 929-ha SAV-dominated STA surface water flow-through treatment wetland, measurements of accrued soil depth and soil P storage performed every ~4-6 years revealed a steady-state longitudinal soil P enrichment profile established within the first ~4 years of flow-through operation.

Periphyton and Flocculent Materials Are Important Ecological Compartments Supporting Abundant and Diverse Mercury Methylator Assemblages in the Florida Everglades.

Mercury (Hg) methylation in the Florida Everglades is of great environmental concern because of its adverse effects on human and wildlife health through biomagnification in aquatic food webs. Periphyton and flocculant materials (floc) overlaying peat soil are important ecological compartments producing methylmercury (MeHg) in this ecosystem. These compartments retain higher concentrations of MeHg than did soil at study sites across nutrient and/or sulfate gradient(s).

Syntrophs dominate sequences associated with the mercury methylation-related gene hgcA in the water conservation areas of the Florida Everglades.

The mechanisms and rates of mercury methylation in the Florida Everglades are of great concern because of potential adverse impacts on human and wildlife health through mercury accumulation in aquatic food webs. We developed a new PCR primer set targeting hgcA, a gene encoding a corrinoid protein essential for Hg methylation across broad phylogenetic boundaries, and used this primer set to study the distribution of hgcA sequences in soils collected from three sites along a gradient in sulfate and nutrient concentrations in the northern Everglades. The sequences obtained were distributed in diverse phyla, including Proteobacteria, Chloroflexi, Firmicutes, and Methanomicrobia; however, hgcA clone libraries from all sites were dominated by sequences clustering within the order Syntrophobacterales of the Deltaproteobacteria (49 to 65% of total sequences).

Temporal and spatial patterns of internal phosphorus recycling in a South Florida (USA) stormwater treatment area.

Large constructed wetlands, known as stormwater treatment areas (STAs), have been deployed to remove phosphorus (P) in drainage waters before discharge into the Everglades in South Florida, USA. Their P removal performance depends on internal P cycling under typically hydrated, but with occasionally desiccated, conditions. We examined the spatial and temporal P removal capacity under different hydrologic conditions along a STA flow path.