Oral Presentation Society for Freshwater Science 2026 Annual Meeting

Urbanization restructures but does not consistently reduce freshwater pond biodiversity (135310)

Julia Portmann 1 , David Skelly 1
  1. Yale University, Hamden, CT, United States

Urbanization is a significant and increasing driver of landscape change. It has been linked to habitat fragmentation and degradation, particularly in freshwater systems. Small, seasonal ponds are a particular system of interest; they support high biodiversity but are often overlooked. Many studies focus on vertebrates and plants in lentic systems, but macroinvertebrates are an essential and abundant component of every pond. We monitored macroinvertebrate predator communities annually in thirty-two ponds spanning an urban gradient in northeastern USA (New Haven County, CT) from 2019 to 2024. We quantified ‘urbanicity’—how urban the setting is in which a given pond is located—using a PCA of land cover, night time lights, and road density, measured pond surface area, water depth, water temperature, pH, conductivity, and canopy cover. We did not find clear patterns of reduced biodiversity due to urbanization, although we did detect shifts in community composition. Rather, pH, water temperature, and canopy cover were the most important predictors for overall macroinvertebrate richness and diversity. At the order level, we found that Hemiptera abundance increased with urbanicity, Trichoptera abundance declined with urbanicity, and Odonata and Coleoptera abundances were not predicted by urbanicity. At the genus/family level, only three taxa were predicted by urbanicity: Aeshna presence was negatively predicted while Corixidae and Anax presence were positively predicted. Across a robust dataset, we found minimal evidence that urbanization reduces lentic macroinvertebrate biodiversity, but that it instead shifts community composition. Urban ponds are important habitat for native biodiversity and our results suggest that loss of urban ponds is a greater threat than the conditions within or surrounding them.