Oral Presentation Freshwater Sciences 2023

The aridzone wetlands of the Paroo, western NSW: probably resilient to climate change?  (#513)

Brian Timms 1
  1. University of NSW, Sydney, NSW, Australia

Wetlands in the Paroo in outback NSW are ephemeral systems of various communities differentiated mainly by hydroperiod, turbidity and salinity. Based on 34 years of data, most support characteristic fauna when wet, varying most within according to rainfall volumes and hence filling depth, with other factors insignificant.  Of the wetland types, saline lakes (3-100 g/L) in the Paroo which receive significant intermittent stream inflows and then deflate salt during the dry periods are the most resilient. It matters little in what season they fill, the periods between fillings or the depth of filling.  But the later factor can influence community development, a two month hydroperiod producing a truncated faunal list compared to a 18 month inundation, but still the same dominant species according to their salinity tolerances. The crustacean and rotifer component still hatch from muds that have been experimentally baked to 600C, and at various hydroperiod regimes of up to 10 years. With climate change for the area predicted to experience more intense summer temperatures and greater flooding rains at longer intervals, I suggest that the saline lake fauna is already adapted to these factors and little variation above what has already been observed will be evident. However the great majority of inland salt lakes in southern and middle Australia have relatively small catchments with limited inflows and negligible dry period deflation, so that salts may accumulate over millenia thus potentially changing the fauna, again according to salinity tolerances of dominant invertebrates. The other wetland communities of the arid inland (e.g. claypans, treed and grassy swamps, samphires) may not be quite so resilient, but due to strong preadaptations are still likely to be more tolerant than freshwater wetlands in less harsh climates