The Effects of Copper Pollution on Fouling Assemblage Diversity: A Tropical-Temperate Comparison

BACKGROUND: The invasion of habitats by non-indigenous species (NIS) occurs at a global scale and can generate significant ecological, evolutionary, economic and social consequences. Estuarine and coastal ecosystems are particularly vulnerable to pollution from numerous sources due to years of human-induced degradation and shipping. Pollution is considered as a class of disturbance with anthropogenic roots and recent studies have concluded that high frequencies of disturbance may facilitate invasions by increasing the availability of resources. METHODOLOGY/PRINCIPAL FINDINGS: To examine the effects of heavy metal pollution as disturbance in shaping patterns of exotic versus native diversity in marine fouling communities we exposed fouling communities to different concentrations of copper in one temperate (Virginia) and one tropical (Panama) region. Diversity was categorized as total, native and non-indigenous and we also incorporated taxonomic and functional richness. Our findings indicate that total fouling diversity decreased with increasing copper pollution, whether taxonomic or functional diversity is considered. Both native and non-indigenous richness decreased with increasing copper concentrations at the tropical site whereas at the temperate site, non-indigenous richness was too low to detect any effect. CONCLUSIONS/SIGNIFICANCE: Non-indigenous richness decreased with increasing metal concentrations, contradicting previous investigations that evaluate the influence of heavy metal pollution on diversity and invasibility of fouling assemblages. These results provide first insights on how the invasive species pool in a certain region may play a key role in the disturbance vs. non-indigenous diversity relationship

Rapid turnover in site occupancy of a pond-breeding frog demonstrates the need for landscape-level management

Habitat loss and habitat isolation have contributed to declines in the green and golden bell frog (Litoria aurea) over much of its former range in south-eastern Australia. Understanding the parameters critical for the persistence of extant populations is required to halt further declines. We assessed waterbody occupancy in a local network of potential L. aurea breeding habitats on Kooragang Island, Australia, by conducting surveys over two years (2000 and 2001) at 30 waterbodies, and using site-occupancy models. The probability that a waterbody was used by L. aurea in 2000 increased with increasing waterbody area, and decreasing distance to the nearest waterbody where L. aurea was detected and where reproductive recruitment was observed. Large waterbodies where high numbers of L. aurea were detected in 2000 were more likely to be used in 2001. The probability that a waterbody used in 2000 was not used in 2001 (i.e., turnover) decreased with increasing waterbody area and increasing numbers of L. aurea detected at the site in 2000. Our results demonstrate the potential for frog abundance, immigration, and recruitment to reduce local turnover. We recommend that conservation strategies for extant populations of L. aurea protect mosaics of wetland habitat and maintain connectivity among waterbodies