Coastal lagoons, while providing crucial habitat for a wide range of biodiversity, are often under intense urbanisation pressures resulting in their degradation. Insectivorous bats utilise these highly productive ecosystems and are directly impacted by their decline in quality. We compared bat activity and richness with prey biomass across a gradient of lagoon quality in coastal lagoons of Greater Sydney to determine the extent to which bats and their prey were impacted by lagoon degradation. Next, we honed in on the mechanisms behind insectivorous bats’ decline in degraded lagoons by examining food web structure (using analysis of δ13C and δ15N stable isotopes) and heavy metal contamination of lagoon sediment, invertebrates and bat tissue. Insectivorous bat communities were found to comprise of more species and be more active at undisturbed lagoons. Australia’s only trawling bat, Myotis macropus, was absent from all low quality lagoons. Heavy metal contamination of coastal lagoons is a significant source of degradation. Analysis of heavy metal concentrations in sediments, invertebrates and insectivorous bats confirmed that these contaminants were present at degraded lagoons and were operating within the trophic structures of these habitats. While trophic structure structure did not differ significantly with lagoon quality, M. macropus showed a small shift towards more δ13C enriched diets in low quality lagoons, potentially indicating avoidance of contaminated aquatic prey resources. The present study demonstrates that while coastal lagoons support a rich bat community, ongoing development of these habitats is likely to negatively impact on insectivorous bat species. Degradation has led to a disruption of food webs at coastal lagoons likely as a result of past contamination events rather than current contamination level.
Level 5 East Biological Sciences South (E26)
UNSW, Kensington 2052