Artificial islands supporting migratory bird populations as potential sources of microinvertebrate dispersal

Abstract

Estuarine waters are key hotspots for the introduction and spread of invasive species. The construction of two artificial islands in the Oder Estuary (Central Europe) in 2021 created new habitats that have attracted a diverse range of species, including aquatic invertebrates and migratory birds. This study investigates the role of these islands in facilitating the dispersal of microinvertebrates and their potential contributions to local biodiversity. Zooplankton samples were collected from ponds on the islands and nearby lagoon waters, revealing significant differences in species composition. The pond on Brysna Island exhibited a higher zooplankton abundance than the pond on Śmięcka Island, likely due to variations in nutrient levels and hydrological connectivity with the lagoon. The dominance of species such as Eurytemora carolleeae and Acanthocyclops trajani suggests that these artificial habitats may facilitate the establishment of invasive or expansive taxa. The presence of Daphnia magna, rarely found in estuarine environments, highlights the unique conditions of these isolated ponds, where low fish predation supports its occurrence. Migratory birds may play a crucial role in dispersing these microinvertebrates, potentially transporting resting eggs or cysts across regions. The study suggests that these artificial islands, situated along a major bird migration route, could contribute to the spread of non-native, potentially invasive species throughout the region. These findings highlight the need to monitor artificial habitats, as they may impact regional biodiversity. Further research is required to assess the ecological effects of these islands, particularly their role in species dispersal and invasion dynamics.