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AbstractMicroplastics have been detected in lake environments globally, including in remote regions. Agricultural and populated areas are known to congregate several inputs and release pathways for microplastic. This study investigated microplastic (50–5000 µm) contamination in five Danish freshwater lakes with catchments dominated by arable land use. The concentrations in sediments (n = 3/site) and the zebra mussel, Dreissena polymorpha (n = 30/site), were calculated and compared with catchment characteristics and environmental parameters. Microplastic concentrations in sediment were relatively low (average 0.028 ± 0.017 items/g dry weight sediment) whilst only a single microplastic was found in the mussels (average 0.067 ± 0.249 items/10 individual). Hence, no relationship between the number of observed microplastics in sediment and mussels could be identified, nor could a relationship between concentration in sediment and environmental parameters. As all lakes studied received their water from moderate to heavily anthropogenically impacted catchments, it was expected that they would be sinks for microplastic with high bioavailability. Based on the results of the present study, D. polymorpha were found to not be contaminated by microplastics in the five study lakes. Thus, our results suggest that these mussels do not interact with microplastics at low concentrations. We speculate that the results on sediment and biota could be explained by several factors related to regional differences in plastic use, species characteristics, sampling size, and the fact that finding no microplastic is not always reported in the scientific literature. Thus, the paper provides insight into the dynamics between the catchment, lake, and biota in systems with low microplastic concentration.

Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss. Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlying mechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment in Iceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across a stream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in this system, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmest streams. A five-month mark-recapture study revealed that population abundance, biomass, growth rate, and production of trout all increased with stream temperature. We identified two mechanisms that contributed to these responses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the food web and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the warmer streams. We found little evidence to support a third potential mechanism: that external subsidies would play a more important role in the diet of trout with increasing stream temperature. Resource availability was also amplified through the trophic levels with warming, as predicted by metabolic theory in nutrient-replete systems. These results highlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledge of warming impacts on natural communities and ecosystem functioning. ; The authors are supported by grants awarded by NERC (NE/L011840/1 and NE/ I009280/2), the Royal Society (RG140601), the British Ecological Society (4009-4884), the Fisheries Society of the British Isles, the Grand Challenges in Ecosystems and the Environment initiative at Imperial College London, the Scottish Government Rural and Environment Science and ...

Global warming is widely predicted to reduce the biomass production of top predators, or even result in species loss.Several exceptions to this expectation have been identified, however, and it is vital that we understand the underlyingmechanisms if we are to improve our ability to predict future trends. Here, we used a natural warming experiment inIceland and quantitative theoretical predictions to investigate the success of brown trout as top predators across astream temperature gradient (4–25 °C). Brown trout are at the northern limit of their geographic distribution in thissystem, with ambient stream temperatures below their optimum for maximal growth, and above it in the warmeststreams. A five-month mark-recapture study revealed that population abundance, biomass, growth rate, and produc-tion of trout all increased with stream temperature. We identified two mechanisms that contributed to theseresponses: (1) trout became more selective in their diet as stream temperature increased, feeding higher in the foodweb and increasing in trophic position; and (2) trophic transfer through the food web was more efficient in the war-mer streams. We found little evidence to support a third potential mechanism: that external subsidies would play amore important role in the diet of trout with increasing stream temperature. Resource availability was also amplifiedthrough the trophic levels with warming, as predicted by metabolic theory in nutrient-replete systems. These resultshighlight circumstances in which top predators can thrive in warmer environments and contribute to our knowledgeof warming impacts on natural communities and ecosystem functioning. ; The authors are supported by grants awarded by NERC (NE/L011840/1 and NE/I009280/2), the Royal Society (RG140601), the British Ecological Society (4009-4884), the Fisheries Society of the British Isles, the Grand Challenges in Ecosystems and the Environment initiative at Imperial College London, the Scottish Government Rural and Environment Science and Analytical Services (RESAS), the Salmonid Fisheries Management Fund in Reykjavik, and Assistantship and Research Funds from the University of Iceland (GMG2006, GMG2007). ; Peer Reviewed ; Ritrýnt tímarit

Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process underlying these patterns, although environmental filtering was also evident in highly glacierized basins. These findings indicate that predictable mechanisms govern river invertebrate community responses to decreasing glacier cover globally. ; This work was funded by the following organisations: The UK Natural Environment Research Council grants and studentships GR9/2913, NE/E003729/1, NE/E004539/1, NE/E004148/1, 20 NE/G523963/1, NER/S/A/2003/11192, and NE/L002574/1; the European Union Environment and Climate Programme Arctic and Alpine Stream Ecosystem Research (AASER) project (ENV-CT95-0164); EU-FP7 Assessing Climate impacts on the Quality and quantity of WAter (ACQWA) project (212250); Icelandic Research Council (954890095, 954890096); University of Iceland Research Fund (GMG96, GMG97, GMG98), Wyoming Center for Environmental Hydrology and Geophysics-National Science Foundation (1208909); USA-Wyoming NASA Space Grant Faculty Research Initiation (#NNX10A095H); USA-NSF Wyoming Epscor; Nationalpark Hohe Tauern, Austria; the Royal Society (International Outgoing Grant 2006/R4); the Leverhulme Trust; the Universities of Leeds, Birmingham, Iceland and Innsbruck; European Centre for Arctic Environmental Research (ARCFAC): a Research Infrastructures Action of the European Community FP6 (026129-2008- 72); the Stelvio National Park (2000-2001); the Autonomous Province of Trento (HIGHEST project, 2001-2004, del. PAT n. 1060/2001; VETTA project, 2003-2006, del. PAT n. 3402/2002); MUSE-Museo delle Scienze. We are grateful to Russell Taylor and Mike Winterbourn at the University of Canterbury, NZ, who helped to collect NZ invertebrate data and assisted with identification, and to Hakon Adalsteinsson who contributed to data collection in Iceland. Many other people, too numerous to mention, assisted with fieldwork at all of the study locations. The European Science Foundation sponsored an exploratory ┘ラヴニゲエラヮ WミデキデノWS さGノ;IキWヴ-fed rivers, hydroecology and climate change: current knowledge and future network of monitoring sites (GLAC-HYDROECO-NETぶざ デエ;デ ┘;ゲ エWノS キミ Birmingham, UK in September of 2013 where some of the ideas in this paper were first discussed ; Peer Reviewed