The status of research into the effects of dryland salinity on aquatic ecosystems: a discussion paper arising from a salinity workshop in Albury, New South Wales, on 13 December 1999

"September 2000".

Project Number: Cooperative Research Centre for Freshwater Ecology Salinity Workshop - M/03/5127.

MDFRC item.

24 pages.

The Cooperative Research Centre for Freshwater Ecology (CRCFE) sponsored a one-day workshop at the Murray-Darling Freshwater Research Centre, Albury, on 13 December 1999, bringing together water resource managers and researchers to explore research requirements in the face of increased salinisation. The workshop was prompted by three recent reassessments of the salinity issue, by PMSEIC (1998), MDBC (1999), and CSIRO (Walker et al. 1999), and by the fact that the new CRCFE, in its first year of operation, is ideally situated to develop innovative research responses to emerging management problems. The three reports highlight the rapidly increasing influence of dryland salinity (as distinct from groundwater and drainage inputs) in the salinisation of aquatic systems. It results in salt inputs well upstream of irrigation influences, in streams previously unaffected by salinity. It also results in floodplain wetlands being inundated by water of higher base-level concentration of salt which in turn leads to accelerated salinisation from the seasonal cycle of filling and evaporation. Neither of these two issues has been addressed by research. The workshop identified other knowledge gaps during an examination of past and current research, especially the lack of information about sub-lethal effects of salinity and their influence on ecosystem structure and functions over time. During the workshop discussions, the following research areas requiring early response were recognised: prediction of the effects of salinity on the (sensitive) biota of low-order streams, including their biodiversity and ecological function; assessment of the ecological effects of increased salinity and increased rates of salinisation on floodplain wetland systems, particularly ephemeral systems; clarification of the sublethal effects of salinity that, through changes to reproduction, recruitment, or metabolic processes, may modify ecosystem function in affected rivers and wetlands. The workshop pinpointed six areas of research (below) that would address these issues in the short, medium or long term; areas 1, 2, 4 and 5 are of higher priority than areas 3 and 6. Short to medium term In the short to medium term, research should aim: 1. to develop and evaluate a database from existing data sets for sites for which there exist both salinity data (including EC) and biological data. This database would maximise the value of resources already invested in collection of background data, and provide a basis for developing testable hypotheses to link salinity with biological responses. 2. to survey a wide range of wetland types and rivers across a broad geographic area to assess their current condition in terms of salinity and biological integrity. This type of study should assist in establishing general relationships between salinity and biological integrity, and in identifying possible future reference sites. Medium to long term In the medium to long term, research should: 3. investigate the relationships between salinity and the survival, growth and recruitment of biota, and between salinity and ecological processes in aquatic ecosystems; 4. use field experiments to assess the response of upland stream and lowland floodplain ecosystems to increasing salinity. In lowland floodplain ecosystems, emphasis should be given to exploring the use of drought-resistant flora and fauna in sediments of ephemeral systems as generalisable indicators of response to stress in these systems. Long-term or ongoing research Long-term or ongoing research should: 5. establish experimental site(s) for medium-scale controlled experiments linking salinity and ecosystem structure and processes, in laboratory and field studies; 6. identify key taxa on which to focus future research and assessment. The recommendations from this workshop are being incorporated into project D3 within Program D (Water Quality and Ecological Assessment) of the overall research portfolio of the CRCFE. Salt in freshwater environments A review of dryland salinity was presented at the workshop. The review briefly describes salinity and the causes and results of salinisation of rivers, billabongs and wetlands, focusing on eastern Australia. It outlines aspects of the disposal of saline water from salinised areas. Finally, having mentioned potential effects of salt water on freshwater biota, it summarises what is known of the effects of salinity on aquatic ecosystems.