Effect of spatial variation on salinity tolerance of macroinvertebrates in Eastern Australia and implications for ecosystem protection trigger values

Salinisation of freshwater has been identified as a serious environmental issue in Australia and around the world. Protective concentrations (trigger values) for salinity can be used to manage salinity impacts, though require locally relevant salinity tolerance information. 72-h acute salinity tolerance values were determined for 102 macroinvertebrates collected from 11 locations in four biologically distinct freshwater bio-regions in Northeast Australia and compared with sensitivities observed in Southeast Australia. The salinity tolerance of individual taxa was consistent across Northeast Australia and between Northeast and Southeast Australia. However, two distinct communities were identified in Northeast Australia using distributions of the acute tolerance values and a calculated index of salinity sensitivity. Salinity trigger values should therefore be representative of local or regionally relevant communities and may be adequately calculated using sensitivity values from throughout Eastern Australia. The results presented provide a basis for assessing salinity risk and determining trigger values for salinity in freshwater ecosystems at local and regional scales in Eastern Australia.     

Factors affecting river health and its assessment over broad geographic ranges: the Western Australian experience

AusRivAS is an Australia-wide program that measures river condition using predictive models to compare the macroinvertebrate families occurring at a river site with those expected if the site were in natural condition. Results of assessment of 685 sites across all major rivers in Western Australia are presented. Most rivers were in relatively natural condition in the northern half of the state where the human population is low and pastoralism is the major land use. In the south, where the human population is higher and agriculture is more intensive, rivers were mostly more disturbed. AusRivAS assessment produced some erroneous results in rivers of the south-west cropping zone because of the lack of appropriate reference site groups and biased distribution of sampling sites. Collecting low numbers of animals from many forested streams, because of low stream productivity and samples that were difficult to sort, also affected assessments. Overall, however, AusRivAs assessment identified catchment processes that were inimical to river health. These processes included salinisation, high nutrient and organic loads, erosion and loss of riparian vegetation. River regulation, channel modification and fire were also associated with river degradation. As is the case with other assessment methods, one-off sampling at individual sites using AusRivAS may be misleading. Seasonal drought, in particular, may make it difficult to relate conditions at the time of sampling to longer-term river health. AusRivAS has shown river condition in Western Australia is not markedly different from other parts of Australia which, as a whole, lacks the substantial segments of severely degraded river systems reported in England.     

High salinisation risks in a typical semi-arid river network in northern China

The objective of this study was to investigate the salinisation characteristics of a semi-arid river network in northern China and highlight the influencing factors and risks. The Ziya River Basin, a typical semi-arid river network located in the North China Plain, is studied herein. Overlying water, surface sediment and riparian soil samples were collected in July and December of 2014 in the Ziya River Basin. The results showed that the average concentrations of salt content in the overlying water and surface sediment of 10 rivers in the Ziya River Basin were 1105.64 and 2159.35?mg/L, respectively. High level of salinisation was found in most rivers not only in overlying water, but also in surface sediment. The impact of the salinisation of overlying water on riparian soil diminished with distance away from the shore and had no impact beyond 15 m from the shore. Heavy pollution can contribute greatly to the salinisation of the water column and can cause significant impacts on river sediment and riparian soil. Salinisation in the overlying water affects the sediment and riparian soil, and reveals that the high risk of salinisation in the Ziya River Basin has been underestimated.