Suburbanization alters small pond ecosystems: shifts in nitrogen and food web dynamics

Small ponds often survive the transition from forested to suburban land cover and provide habitat for many species, yet little is known about how suburbanization affects pond ecosystems. We surveyed 18 small ponds across a forest-to-suburban land cover gradient and compared how physical and chemical changes altered biological and ecosystem properties, such as nutrient and food web dynamics. Suburbanization decreased canopy cover, increased water temperatures, and increased periphyton chlorophyll a, but was associated with only weak increases in total nutrients. Yet, stable isotope analysis indicated that suburbanization altered nitrogen dynamics and resource use in the food web. We observed increases in delta N-15 in algae, biofilm, and frog larvae across the suburban gradient, indicative of wastewater intrusion. Suburbanization also shifted the energy and nutrient source of a dominant consumer (Rana sylvatica; = Lithobates sylvaticus) from leaf litter to algae. Overall, we identified cryptic changes to suburban pond ecosystems, highlighting that suburbanization can profoundly impact nutrients and food web resources. As residential land use increases globally, we may expect substantial shifts in nutrient dynamics and food web pathways.