Oral Presentation Australian Society for Limnology Congress 2013

Climatic thresholds: the influence of increasing sediment temperature on aquatic biota (#119)

Daryl Nielsen 1 2 , Elke Jasper 3 , Nathan Ning 2 , Susan Lawler 3
  1. Land & Water, CSIRO, WODONGA, VIC, Australia
  2. The Murray-Darling Freshwater Research Centre, Wodonga, Victoria, Australia
  3. Environmental Management and Ecology, , La Trobe University, Wodonga, Victoria, Australia

Under the influence of climate change, dormant seeds of wetland plants and eggs of microfauna may be subjected to temperatures that may affect their viability while the wetland is in its “dry” phase.  To test the hypothesis that dormant seeds and eggs are resilient to increasing temperature, we exposed wetland sediment to a range of temperatures up to 150oC and assessed the richness and abundance of communities that developed when the sediment was inundated.  Both aquatic plants and microfauna emerged from the seed bank at temperatures lower than 50°C but few taxa emerged at higher temperatures. The nature of the response differed between the two groups. The numbers of microfauna emerging decreased abruptly once temperatures exceeded 50° C. In comparison, the abundance of aquatic plants began to decline once temperatures exceeded 30°C, suggesting that aquatic plant communities are more sensitive to temperature increases. These results suggest that changes to soil temperature during the dry phase of wetlands may play an important role in influencing wetland aquatic plant and microfauna communities. Soil temperatures in the proximity of 50° C are already known to occur during summer in parts of south-eastern Australia.  Such temperatures are likely to become more common under current climate change predictions, which may threaten the abundance and diversity of wetland microfauna and aquatic plant communities