Trophic linkages between periphyton and grazing macroinvertebrates in rivers with different levels of catchment development

Stable isotope signatures (δ¹³C and δ¹⁵N) were used to compare trophic linkages between epilithic periphyton and three families of macroinvertebrates (Baetidae, Leptophlebiidae and Gripopterygidae) in riffles of two rivers with developed catchments (including agriculture, urbanization, impoundment and flow regulation) and two with undeveloped catchments (native forest with no major impoundments) in the Murrumbidgee River system, New South Wales, Australia. Periphyton had much higher average δ¹⁵N values and lower average C:N ratios in the developed rivers than in the undeveloped rivers, probably because of the combined effects of nutrient enrichment, upstream impoundment and alteration of riparian vegetation. The invertebrates were generally slightly depleted in ¹³C and ¹⁵N relative to expected values if they were assimilating whole periphyton alone, which suggests that they were assimilating periphyton components selectively or also consuming other foods. The match in isotope signatures between periphyton and invertebrates was only slightly weaker in the developed than in the undeveloped rivers, suggesting that development did not greatly disrupt trophic linkages between periphyton and these invertebrates. Handling editor: M. Power     

Rapid assessment of rivers using macroinvertebrates: the role of experience, and comparisons with quantitative methods

We assessed rapid biological assessment (RBA) of macroinvertebrate communities in comparison with quantitative sampling at 18 pairs of river sites in south-eastern Australia. One member of each pair served as a reference site and the other was affected by mild to moderate human disturbance from a point or diffuse source (fish farm effluents, small municipal sewage discharges, a dam, agriculture and grazing). Samples were taken from riffles, stream edges and rocks in pools, mostly using hand nets (RBA) and Hess samplers (quantitative). Macroinvertebrates in RBA samples were always subsampled by live-picking by eye on site for 30 min. Comparisons were made between novice operators (university undergraduates) and experienced river biologists in the application of RBA, including sample identification. Quantitative samples were collected only by experienced river biologists, preserved and picked under stereomicroscopes in the laboratory, either in their entirety or after mechanical subsampling. Specimens were identified to family level for both methods. Novices recorded slightly fewer families than experts and misidentified some specimens, and expert data for the same site and habitat were on average more consistent than novice data. Nevertheless, Procrustes analysis of ordinations showed that differences between RBA and quantitative data did not depend on the type of RBA operator. And regardless of the operator, RBA data were better than quantitative data at discriminating between reference and disturbed sites for all three habitat types. We conclude that this type of RBA is sensitive and cost-effective, and we recommend improvements to inter-operator consistency.     

Development of diatom-based tools for assessing stream water quality in south-eastern Australia: assessment of environmental transfer functions

Models were developed of relationships among water quality, geospatial and species-level diatom data for 465 samples collected from stream sites across south-eastern Australia. Transfer functions were derived from weighted averaging and artificial neural network approaches. Analysis of spatial variations in species assemblages was used to divide the sites into two groups according to site elevation. The strongest predictive models for the upland group associated diatom assemblages with conductivity, longitude, altitude, and to a lesser extent pH, NO _x and TKN. The strongest predictors for the lowland group were longitude and conductivity, but artificial neural network models performed well for NO _x and temperature. The importance of the geospatial variables suggests that there may be a capacity to develop diatom sub-regions within which robust models for other water quality variables important to management can be generated. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users. Handling editor: R. Norriss     

Biological traits predict shifts in geographical ranges of freshwater invertebrates during climatic warming and drying

Aim To test the ability of biological traits to predict climate‐related changes in geographical ranges of running‐water invertebrates. Location The Australian state of New South Wales and the Australian Capital Territory. Methods I analysed data from 8928 biomonitoring samples collected during a 16‐year period of generally rising air temperatures and declining precipitation. I used quantile regression to test for expansions and contractions on the climatically cooler, warmer, drier and wetter edges of the ranges of 120 invertebrate taxa, and correlated these shifts with the traits of thermophily (degree of preference for high versus low temperature) and rheophily (preference for flowing versus still water). Results The most commonly inferred range shifts were cool‐edge expansion plus warm‐edge contraction (71 taxa) and wet‐edge expansion plus dry‐edge contraction (71), but contractions from both cool and warm extremes (36) and from both dry and wet extremes (28) were also frequent. High‐temperature preference was associated with cool‐edge expansion and low‐temperature preference with wet‐edge expansion and contraction from all other extremes. A preference for flow was associated with wet‐edge expansion and dry‐edge contraction. Main conclusions Trait analysis has potential for predicting which species will expand their ranges and which will contract, but needs to be coupled with assessment of how the landscape provides each species with opportunities to track or avoid climate change. Improved quantification of climatically relevant traits and integration of trait analysis with species distribution modelling are likely to be beneficial.     

Responses of the Fructose-1,6-bisphosphatase and Glutamate Dehydrogenase Activities of Alfalfa to Boron,Gypsum, and Limestone Amendments of Soil

Plants cultivated on acid soils that contain toxic levels of Al³⁺ usually produce low yields. A multi-factorial treatment of gypsum (G), boron (B), and limestone (Lm) was applied to such soil in order to determine the biochemical basis of the best management plan for ameliorating the soil acidity for sustainable growth of alfalfa. The alfalfa shoots were subjected to analysis for hexose, protein, nucleotide, and chlorophyll (Chl) contents, fructose 1,6-bisphosphatase (FBPase) activity, and the RNA synthetic activity of glutamate dehydrogenase (GDH). Hexose and protein contents of control alfalfa without B and G, but with Lm (672 g m^–2) amendment were 0.87 and 38.30 g, respectively, per kg shoot. Increasing the G doses at fixed moderate doses of 0.15 and 0.30 g m^–2 B decreased the FBPase activity by 53 and 31 %, respectively. However, increasing the B doses at higher fixed G (1 kg m^–2= G_1.0) increased the FBPase activity by 91 % thus indicating that G₁ optimized the saccharide metabolism by neutralizing the soil acidity. In the absence of B, increasing the G doses also maximized the hexose and Chl contents, but minimized the nucleotide amount. In the absence of G, increasing the B doses maximized the RNA synthetic activity of GDH, but lowered the hexose and Chl contents as well as the FBPase activity without affecting the protein contents, thereby permitting the selection of B (0.45 g m^–2) with Lm as the best amendment for the sustainable growth of alfalfa. Treatment with 0.45 g B and 0.5 kg G (= G_0.5) induced the strongest B-Ca antagonism by maximizing the hexose and Chl contents but severely suppressing the FBPase activity and the RNA synthetic activity of GDH. Therefore, the coordinate optimization of saccharide metabolism through the G-dependent neutralization of soil acidity, and of RNA metabolism through the B-dependent detoxification of Al³⁺ are the biochemical options for the mitigation of the adverse effects of soil acidity for the optimization of sustainable alfalfa production.     

A shocking result—Electric fences protect western saw-shelled turtle (Myuchelys bellii) nests from depredation by foxes

Introduced red foxes (Vulpes vulpes) are a major predator of freshwater turtle nests in Australia. We evaluated the effectiveness of electric fences, in combination with individual nest protection, for shielding western saw-shelled turtle (Myuchelys bellii: Chelidae) nests from predation by foxes. We compared the numbers of raided and intact turtle nests found in paired fenced treatment and unfenced control areas of streambank. We also individually protected all intact nests found in both area types with wire mesh or a steel cage. The total numbers of nests found in treatment and control areas did not significantly differ from parity, but significantly more intact nests were found in treatment areas and significantly more raided nests in control areas. The fences were occasionally damaged by livestock, wildlife and flooding, rendering them inoperative for varying periods of time until repair. However, foxes raided nests inside the fences on only two occasions, despite these breaks in functionality. Our study demonstrates that electric fences can provide an effective method of protecting entire nesting areas from depredation by foxes.