Estimating the Importance of Aquatic Primary Productivity for Phosphorus Retention in Florida Everglades Mesocosms

Abstract

Constructed wetlands are being utilized to mitigate the impact that excess phosphorus in surface water has on the natural state of the Florida Everglades. This study investigates the role of aquatic metabolism in the retention of phosphorus in wetlands and how it varies with plant community. Eighteen 6-m2 mesocosms receiving inflows with relatively low phosphorus concentrations were planted with one of five wetland plant communities or left to natural colonization. In 2012, the mesocosms left to naturally colonize had significantly higher aquatic gross primary production (GPP) at 7.0 g O2 m−2 d−1 than all other communities. Mesocosms planted with Nymphaea odorata and those planted with a mix of Najas guadalupensis and Chara sp. had significantly higher GPP (5.5 and 5.9 g O2 m−2 d−1, respectively) than those with Typha domingensis, Eleocharis cellulosa, and Cladium jamaicense (1.7, 2.3, and 1.5 g O2 m−2 d−1, respectively). Rates of phosphorus cycling due to aquatic metabolism were estimated to range from 2.5 g P m−2 yr−1 in both the Cladium and Eleocharis communities to 7.7 g P m−2 yr−1in the naturally colonized mesocosms. These results provide evidence that wetland plant communities without high-biomass emergent macrophytes may perform best in the retention of phosphorus in low inflow concentration conditions.