Effects of Salinity and Flow on Macroinverterbrates in SA

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This week’s featured research article has just been published in Ecological Indicators by EPA and SARDI researchers and examines effects of salinity and flow interactions on macroinvertebrate traits in temporary streams in South Australia.  Increasing salinity in freshwater ecosystems is globally widespread, especially, in arid and semi-arid regions, and can co-occur with flow intermittency, particularly in temporary streams. Both these stressors are known to affect macroinvertebrate traits individually, but their interactive effects have not been previously considered. There are inconsistencies reported in the literature regarding the response of particular traits to flow or salinity, and the researchers hypothesized that interactive effects between these two stressors may underlie inconsistencies in the literature. They used multivariate and univariate approaches to investigate the effects of salinity and flow interactions on macroinvertebrate traits using 13 years of data sampled across multiple sites in South Australia. The interactions seemed to be driven by the differential response of different taxa with the same trait category being abundant in different parts of the interaction plot. The findings suggest that, in addition to differences in methodological and analytical approaches, interactions may also underlie inconsistencies in trait responses to flow and salinity. The researchers state that to foster the operative use of traits to resolve the effects of multiple stressors on ecosystems, there is the need for a better mechanistic understanding of how specific stressors (e.g. flow and salinity) act as trait filters, potentially through the use of experiments, to ensure that each of the stressors is strong enough to produce clear trait responses. The researchers conclude that the study has demonstrated congruence across studies regarding how particular traits respond to flow intermittency and gradients of salinity, thus generally, some conclusions can be drawn regarding these responses. They suggest that hydrological alteration to ground water-fed streams may be associated with salinity increases and its influence on trait composition. The paper can be downloaded here (or email jennie.fluin@sa.gov.au for a copy).