. Juvenile salmonid populations in a temperate river system track synoptic trends in climate. Global Change Biology, Wiley, 2010, 16 (12) Widespread decline among Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) over recent decades have been linked to pollution, exploitation and catchment modification, but climate change is increasingly implicated. We used long-term, geographically extensive data from the Welsh River Wye, formerly a major salmon river, to examine whether climatically-mediated effects on juveniles (> 0+) might contribute to population change.Populations of Atlantic salmon and brown trout fell across the Wye catchment respectively by 50% and 67% between 1985 and 2004, but could not be explained by pollution because water quality improved during this time.Stream temperatures, estimated from calibrations against weekly air temperature at 8 sites, increased by 0.5-0.7 °C in summer and 0.7-1.0 °C in winter, with larger tributaries warming more than shaded headwaters. Rates of winter warming were slightly greater after accounting for the effect of the North Atlantic Oscillation (1.1-1.4 °C). However, warming through time was smaller than measured variations among tributaries, and alone was insufficient to explain variations in salmonid density. Instead, population variations were best explained in multi-level mixed models by a synoptic variate representing a trend towards hotter, drier summers, implying interactions between climate warming, varying discharge and fluctuatations in both brown trout and salmon. geographically extensive data from the Welsh River Wye, formerly a major salmon river, 17 to examine whether climatically-mediated effects on juveniles (> 0+) might contribute to 18 population change. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 for the UK suggest that altered summer flow and increasing summer temperatures could 36 exacerbate losses further in these species, and we advocate management actions that 37 combine reduced abstraction with enhanced riparian shading. 38 39

Invertebrate biotic indices are used widely to assess river quality. However, because reduced values can have many potential causes, general biotic indices have limited value in diagnosing reasons for impairment. Here, we investigate whether simple combinations of biotic indices can improve diagnostic capability.In the catchment of the Welsh River Wye, invertebrates varied significantly among groups of 55 streams in taxonomic composition and in index scores representing acidification (AWIC), mild eutrophication/organic pollution (BMWP/ASPT), and flow (LIFE). Although sites impacted by different forms of pollution tended to have reduced BMWP scores, acidified and enriched sites became distinguishable from each other, and from unimpaired streams, when classified on a combination of these indices. Combined indices also differentiated among competing explanations for trends in biological quality through time by revealing how increasing BMWP at some sites reflected local reductions in eutrophication.These data illustrate how simple univariate indices, calibrated to respond to specific pressures, have bio-diagnostic capability when used together even in a relatively unpolluted catchment such at the Wye. In this Special Area of Conservation, they identified specific management needs in different locations-respectively to mitigate acidification in upland base-poor tributaries and to reduce diffuse nutrients in the lower catchment. We advocate (i) the development of more pressure-specific indices, for example to detect morphological modification, sedimentation and metal impacts; and (ii) further exploration of combined indices from one or more groups of organisms (e.g., diatoms and invertebrates) to increase bio-diagnostic capability in river monitoring.

BackgroundMacroinvertebrates such as non-biting midges (Chironomidae: Diptera) are important components of freshwater ecosystems. However, they are often neglected in biodiversity and conservation research because invertebrate species richness is difficult and expensive to quantify with traditional methods. We here demonstrate that Next Generation Sequencing barcodes (“NGS barcodes”) can provide relief because they allow for fast and large-scale species-level sorting of large samples at low cost.ResultsWe used NGS barcoding to investigate the midge fauna of Singapore’s swamp forest remnant (Nee Soon Swamp Forest). Based on > 14.000 barcoded specimens, we find that the swamp forest maintains an exceptionally rich fauna composed of an observed number of 289 species (estimated 336 species) in a very small area (90 ha). We furthermore barcoded the chironomids from three surrounding reservoirs that are located in close proximity. Although the swamp forest remnant is much smaller than the combined size of the freshwater reservoirs in the study (90 ha vs. > 450 ha), the latter only contains 33 (estimated 61) species. We show that the resistance of the swamp forest species assemblage is high because only 8 of the 314 species are shared despite the close proximity. Moreover, shared species are not very abundant (3% of all specimens). A redundancy analysis revealed that ~ 21% of the compositional variance of midge communities within the swamp forest was explained by a range of variables with conductivity, stream order, stream width, temperature, latitude (flow direction), and year being significant factors influencing community structure. An LME analysis demonstrates that the total species richness decreased with increasing conductivity.ConclusionOur study demonstrates that midge diversity of a swamp forest can be so high that it questions global species diversity estimates for Chironomidae, which are an important component of many freshwater ecosystems. We furthermore demonstrate that small and natural habitat remnants can have high species turnover and can be very resistant to the invasion of species from neighboring reservoirs. Lastly, the study shows how NGS barcodes can be used to integrate specimen- and species-rich invertebrate taxa in biodiversity and conservation research.Electronic supplementary materialThe online version of this article (10.1186/s12983-018-0276-7) contains supplementary material, which is available to authorized users.

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ABSTRACT. The Nee Soon stream drainage in the Central Catchment Nature Reserve is virtually the last remaining fragment of primary freshwater swamp forest in Singapore. The forest type has been poorly studied in the Southeast Asia. The hydrology, water quality, as well as aquatic flora and fauna all have great theoretical and practical significance. The ecology and management of the Nee Soon freshwater swamp forest are reviewed, with remarks on their national, regional and global contexts. This review sets the scene for a three-year integrated conservation and management study completed in 2016.