Incidence and Thermal Biology of an Invasive Cladoceran, Daphnia lumholtzi

Abstract

Nearly every wetland and aquatic ecosystem in the U.S. is being impacted by non-indigenous species (NIS). Among these, the Southeast Atlantic-Gulf region has the greatest number of aquatic species introductions. In addition to documenting introductions and assessing their impacts, it is important to summarize the traits that characterize successful invaders. One NIS that is generating increasing interest is the subtropical zooplankton Daphnia lumholtzi, which has spread to aquatic systems throughout the US. Many studies have documented the success of D. lumholtzi in reservoirs and lakes, where high thermal tolerance allows it to exploit a vacant thermal niche. However, to date there has been limited characterization of its establishment in estuarine environments. The Alabama River delta offers a unique opportunity to investigate D. lumholtzi distribution compared to native species, as well as how thermal factors may affect its invasive potential in this ecosystem. We collected monthly zooplankton samples from 8 sites across the Alabama River delta system over a two-year period, which confirmed that D. lumholtzi has established a population in the estuary and is most often found during warmer summer months. We are currently conducting studies to determine how thermal factors affect its survival and life history characteristics in the estuary.