Zooplankton communities and their responses to fish presence and urban cover across garden and other urban ponds

Abstract

As cities expand globally, the ratio of artificial to natural freshwater habitats is increasing. While public urban ponds have been the subject of an increasing number of biodiversity studies, the biota of garden ponds in private residential gardens, particularly their zooplankton communities, remain largely unknown. We tested whether smaller, privately managed garden ponds can support zooplankton communities comparable to larger urban ponds and contribute to urban aquatic biodiversity. We also assessed how garden and urban ponds respond to urbanization and fish presence in terms of density, diversity, and community composition. Garden ponds hosted lower local and regional diversity compared to urban ponds, particularly for Cladocera and Copepoda, and were more strongly dominated by Rotifera. Even so, more than half of all zooplankton species were shared between the two pond types, with unique species in each. Urbanization increased rotifer and reduced microcrustacean density in urban ponds, while garden pond communities were largely unaffected, likely due to their smaller species pool and buffering by the surrounding private greenery. We found that urbanization had no significant impact on species richness for either pond type. Among local environmental variables, fish presence played an important role in shaping zooplankton communities in both urban and garden ponds. Our study provides the first systematic study of garden pond zooplankton and highlights the complementary roles of urban and garden ponds in maintaining aquatic biodiversity within urban landscapes.