Water quality, vegetation, and management of stormwater ponds draining three distinct urban land uses in central Florida

Stormwater ponds are prevalent engineered water features that are designed to mitigate the effects of urban land use on downstream water bodies. These systems contribute significantly to the total area of aquatic ecosystems in some urban watersheds, making them important integrative features for examining human impacts on water ecosystem services. We investigated the distribution of stormwater ponds in relation to different land uses and examined dissolved nutrients in pond water, pond vegetation, and pond management practices in stormwater ponds receiving runoff from distinct urban lands uses in a rapidly developing suburban watershed of Orlando, FL, USA. Stormwater ponds represented 40.2% of the total area of non-forested freshwater systems in the watershed and were dominated by ponds situated in residential (43.7%), followed by roadways (14.7%), and institutional (2.3%) land uses. We randomly selected 8 ponds receiving runoff from each of these three lands uses, using schools to represent the institutional land use, and expressways to represent roadways, and sampled them monthly from May-Sept. 2015 for nutrient and physical characteristics and assessed their general cover of emergent and submerged vegetation. Total nitrogen (TN) concentrations differed significantly between expressway and school ponds, with expressway ponds having TN concentrations 51.7% higher than schools. Both total phosphorus (TP) and TN varied differently through time in the different lands uses and concentrations of most dissolved nutrients separated out from pond vegetative cover in a principal component analysis. Ponds with higher TN and chlorophyll a (chla) concentrations had lower water clarity. Management intensity for removal of aquatic vegetation and algae was lower in school ponds than in expressway and residential ponds, and school ponds contained the highest abundance and diversity of vegetation. Different urban land uses had varying impacts on water quality, and more intense chemical use to control vegetation and algae was related to greater nutrient and chla concentrations and lower water clarity. Our results indicate that there are important differences in nutrient concentration in stormwater ponds in the different land uses that may be related both to differences in surface runoff, and in management practices use to control overgrowth of vegetation and algae.