Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Desiccation tolerance of river and floodplain mussels in Australia’s Murray-Darling Basin  (#167)

Daniel Wright 1 , Jason Thiem 1 , Elka Blackman 1 , Alan Lymbery 2 , Stephen Beatty 2 , Samantha Davis 3
  1. DPI fisheries, Narrandera, NEW SOUTH WALES, Australia
  2. Centre for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch University, Murdoch, WA, Australia
  3. Department of Primary Industries, Freshwater environment, Dubbo, NSW, Australia
  1. Freshwater mussels provide a range of ecosystem services but are globally imperilled. Mass die-offs, reduced species richness and local extinctions of freshwater mussels have resulted from river drying events which often co-occur with high ambient temperatures. These events are predicted to increase in occurrence and severity under the influence of climate change. We studied the desiccation tolerance of two freshwater mussel species (Alathyria jacksoni and Velesunio ambiguus) in Australia’s Murray-Darling Basin across a range of upper temperatures to better understand the potential impact of drying events and climate change on these species. 
  2. During laboratory trials, freshwater mussels buried in sediment were exposed to 29, 32, 35, 38 and 41°C, simulating drying events during drought conditions at these temperatures. Lethal temperatures and lethal times at which 50% mortality occurred were used to infer species-specific tolerances.
  3. The lethal time for 50% of mussels to reach mortality was significantly shorter for A. jacksoni (14 days) than V. ambiguus (58 days) in the drying sediment conditions at 29°C but did not differ markedly at higher temperatures. Over short-term exposures to drying, the lethal temperatures that 50% of mussels could survive were similar between species, ranging from 39-40°C at 1 day to 29-31°C at 10 days. 
  4. We confirm freshwater mussel tolerance to desiccation is highly temperature dependant. Our results suggest that the species-specific difference in desiccation tolerance between A. jacksoni and V. ambiguus diminishes as their upper thermal limit is approached. Thus, even the more desiccation-tolerant V. ambiguus may be at increasing risk from drying events of greater magnitude and severity.
  5. Management interventions aimed at reducing sediment temperatures, such as providing shade via riparian vegetation and maintaining and optimising the timing of environmental flows, could help alleviate the impact of drying events and climate change on these species and freshwater mussel populations in general.