Is all salinity the same? I. The effect of ionic compositions on the salinity tolerance of five species of freshwater invertebrates

Salts of marine origin, predominantly consisting of Na+ and Cl- ions, are dominant in most Australian inland saline waters. The proportions of other ions, Ca2+, Mg2+, SO42-, HCO3- and CO32-, in the water may influence salinity tolerance of freshwater organisms and thus the effect of increasing salinity may vary with difference in ionic proportions. We exposed freshwater invertebrates to different concentrations of four ionic compositions and compared them with commercial sea salt ( Ocean Nature). They were: synthetic Ocean Nature (ONS) and three saline water types (ONS but without: SO42-, HCO3- and CO32- (S1); Ca2+, HCO3- and CO32- (S2); and Ca2+ and Mg2+ (S3)), which are considered to be the predominant saline water types in south-eastern Australia and the Western Australian wheatbelt. The 96-h LC50 values for the five media were determined for six invertebrate species and sub-lethal responses were observed for two species. There were no differences between responses of invertebrates to various ionic compositions in acute toxicity tests. However, in prolonged sub-lethal tests, animals reacted differently to the various ionic compositions. The greatest effect was observed in water types lacking Ca, for which plausible physiological mechanisms exist. Variation in ionic proportions should be taken into account when considering sub-lethal effects of salinity on freshwater invertebrates

Relative salinity tolerance of freshwater macroinvertebrates from the south-east Eastern Cape, South Africa compared with the Barwon Catchment, Victoria, Australia

Salinity is rising in many southern African and Australian rivers with unknown effects on aquatic organisms. The extent of spatial variation, at any scale, in salt tolerances of aquatic organisms is unknown, so whether data from one location is applicable elsewhere is also unknown. The acute tolerances (72-h median lethal concentration (LC50)) to sea salt of 49 macroinvertebrate taxa from the south-east Eastern Cape (SEEC), South Africa were compared with those of 57 species from the Barwon Catchment, Victoria, Australia. The mean LC50 values from both locations were similar (Barwon: 31 and SEEC: 32 mS cm(-1)) and less abundant (rare) taxa tended to be more tolerant than more abundant (common) taxa. There was, however, a greater range of LC50 values (5.5-76 mS cm(-1)) in the Barwon Catchment than in the SEEC (11-47 mS cm(-1)). The species sensitivity distribution (SSD) for SEEC taxa was bimodal whereas the Barwon Catchment's SSD had a single peak. With few exceptions, members of an order had similar tolerances in both locations. The differences in SSD between locations were related to crustacean, odonate and non-arthropod relative richness. Although it is not ideal to extrapolate SSDs from one location to another, it may be reasonable to assume similar salinity tolerances among related taxa

Energetics as a lens to understanding aquatic insect's responses to changing temperature, dissolved oxygen and salinity regimes

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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. Crown Copyrigh

Looking beneath the surface: using hydrogeology and traits to explain flow variability effects on stream macroinvertebrates

Flow variability drives important instream ecohydrological processes. Nonetheless, generalizations about ecological responses to flow variability are elusive and complicated by interacting factors. Hydrogeological controls on groundwater inputs into streams are often an overlooked factor that may interact with flow variability and influence instream ecology. Flow effects on ecology are also complicated by flora and fauna trait diversity, which makes some organisms more sensitive to flow variability than others. To improve understanding regarding the effects of flow variability on instream communities, we utilized a long-term 17-year data set of macroinvertebrate communities from eight sites on the Upper Murrumbidgee River catchment, south eastern Australia. Hydrogeological mapping provided a proxy of groundwater influence on instream ecology. Generalized linear mixed models were used to test hydrogeology (i.e. groundwater influence) and flow variability effects on selected taxa and trait groups. Trait groups tested were those with drought-resistant life stages, no drought-resistant life stages and those with poor dispersal traits. Non-drought resistant and poor dispersing taxa responded to hydrogeology and stream flow variables, while taxa with drought-resistant traits did not. Poor dispersing taxa displayed the strongest positive response to interactions between high mean flow and hydrogeological conditions that facilitate groundwater inputs. While the importance of flow variability is widely recognized, the combined role of hydrogeology and trait groups on macroinvertebrate responses has not been widely considered thus far. This study demonstrates that the consideration of hydrogeology and faunal traits can help improve the understanding of macroinvertebrate population and community responses to flow regime variability. Copyright © 2016 John Wiley & Sons, Ltd

Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive

Similar recovery time of microbial functions from fungicide stress across biogeographical regions

Abstract Determining whether the structural and functional stress responses of communities are similar across space and time is paramount for forecasting and extrapolating the consequences of anthropogenic pressures on ecosystems and their services. Stream ecosystems are under high anthropogenic pressure; however, studies have only examined the response of stream communities across large scales over multiple generations. We studied the responses of leaf-associated microbial communities in streams within three European biogeographical regions to chemical stress in a microcosm experiment with multiple cycles of fungicide pollution and resource colonisation. Fungal community composition and the ecosystem function leaf decomposition were measured as response variables. Microbial leaf decomposition showed similar recovery times under environmental levels of fungicide exposure across regions. Initially, the decomposition declined (between 19 and 53%) under fungicide stress and recovered to control levels during the third cycle of pollution and colonisation. Although community composition and its stress response varied between regions, this suggests similar functional community adaptation towards fungicide stress over time. Genetic, epigenetic and physiological adaptations, as well as species turnover, may have contributed to community adaptation but further studies are required to determine if and to which extent these mechanisms are operating. Overall, our findings provide the first evidence of a similar functional response of microbial leaf decomposition to chemical stress across space and time

Effects of salinity on leaf breakdown: dryland salinity versus salinity from a coalmine

Salinization of freshwater ecosystems as a result of human activities represents a global threat for ecosystems’ integrity. Whether different sources of salinity with their differing ionic compositions lead to variable effects in ecosystem functioning is unknown. Therefore, the present study assessed the impact of dryland- (50\ua0μS/cm to 11,000\ua0μS/cm) and coalmine-induced (100\ua0μS/cm to 2400\ua0μS/cm) salinization on the leaf litter breakdown, with focus on microorganisms as main decomposer, in two catchments in New South Wales, Australia. The breakdown of Eucalyptus camaldulensis leaves decreased with increasing salinity by up to a factor of three. Coalmine salinity, which is characterised by a higher share of bicarbonates, had a slightly but consistently higher breakdown rate at a given salinity relative to dryland salinity, which is characterised by ionic proportions similar to sea water. Complementary laboratory experiments supported the stimulatory impact of sodium bicarbonates on leaf breakdown when compared to sodium chloride or artificial sea salt. Furthermore, microbial inoculum from a high salinity site (11,000\ua0μS/cm) yielded lower leaf breakdown at lower salinity relative to inoculum from a low salinity site (50\ua0μS/cm). Conversely, inoculum from the high salinity site was less sensitive towards increasing salinity levels relative to inoculum from the low salinity site. The effects of the different inoculum were the same regardless of salt source (sodium bicarbonate, sodium chloride and artificial sea salt). Finally, the microorganism-mediated leaf litter breakdown was most efficient at intermediate salinity levels (≈500\ua0μS/cm). The present study thus points to severe implications of increasing salinity intensities on the ecosystem function of leaf litter breakdown, while the underlying processes need further scrutiny