Recent trends in stream macroinvertebrates: warm-adapted and pesticide-tolerant taxa increase in richness

Recently, a plethora of studies reporting insect declines has been published. Even though the common theme is decreasing insect richness, positive trends have also been documented. Here, we analysed nationwide, systematic monitoring data on aquatic insect richness collected at 438 sites in Switzerland from 2010 to 2019. In addition to taxonomic richness, we grouped taxa in accordance with their ecological preferences and functional traits to gain a better understanding of trends and possible underlying mechanisms. We found that in general, richness of aquatic insects remained stable or increased with time. Warm-adapted taxa, common feeding guilds and pesticide-tolerant taxa showed increasing patterns while cold-adapted, rarer feeding guilds and pesticide-sensitive taxa displayed stable trends. Both climate and land-use-related factors were the most important explanatory variables for the patterns of aquatic insect richness. Although our data cover the last decade only, our results suggest that recent developments in insect richness are context-dependent and affect functional groups differently. However, longer investigations and a good understanding of the baseline are important to reveal if the increase in temperature- and pesticide-tolerant species will lead to a decrease in specialized species and a homogenization of biotic communities in the long term

FORUM: Ecological networks: the missing links in biomonitoring science.

Monitoring anthropogenic impacts is essential for managing and conserving ecosystems, yet current biomonitoring approaches lack the tools required to deal with the effects of stressors on species and their interactions in complex natural systems.Ecological networks (trophic or mutualistic) can offer new insights into ecosystem degradation, adding value to current taxonomically constrained schemes. We highlight some examples to show how new network approaches can be used to interpret ecological responses.Synthesis and applications. Augmenting routine biomonitoring data with interaction data derived from the literature, complemented with ground-truthed data from direct observations where feasible, allows us to begin to characterise large numbers of ecological networks across environmental gradients. This process can be accelerated by adopting emerging technologies and novel analytical approaches, enabling biomonitoring to move beyond simple pass/fail schemes and to address the many ecological responses that can only be understood from a network-based perspective

Linking human impacts to community processes in terrestrial and freshwater ecosystems

Human impacts such as habitat loss, climate change and biological invasions are radically altering biodiversity, with greater effects projected into the future. Evidence suggests human impacts may differ substantially between terrestrial and freshwater ecosystems, but the reasons for these differences are poorly understood. We propose an integrative approach to explain these differences by linking impacts to four fundamental processes that structure communities: dispersal, speciation, species-level selection and ecological drift. Our goal is to provide process-based insights into why human impacts, and responses to impacts, may differ across ecosystem types using a mechanistic, eco-evolutionary comparative framework. To enable these insights, we review and synthesise (i) how the four processes influence diversity and dynamics in terrestrial versus freshwater communities, specifically whether the relative importance of each process differs among ecosystems, and (ii) the pathways by which human impacts can produce divergent responses across ecosystems, due to differences in the strength of processes among ecosystems we identify. Finally, we highlight research gaps and next steps, and discuss how this approach can provide new insights for conservation. By focusing on the processes that shape diversity in communities, we aim to mechanistically link human impacts to ongoing and future changes in ecosystems

Linking human impacts to community processes in terrestrial and freshwater ecosystems.

Human impacts such as habitat loss, climate change and biological invasions are radically altering biodiversity, with greater effects projected into the future. Evidence suggests human impacts may differ substantially between terrestrial and freshwater ecosystems, but the reasons for these differences are poorly understood. We propose an integrative approach to explain these differences by linking impacts to four fundamental processes that structure communities: dispersal, speciation, species-level selection and ecological drift. Our goal is to provide process-based insights into why human impacts, and responses to impacts, may differ across ecosystem types using a mechanistic, eco-evolutionary comparative framework. To enable these insights, we review and synthesise (i) how the four processes influence diversity and dynamics in terrestrial versus freshwater communities, specifically whether the relative importance of each process differs among ecosystems, and (ii) the pathways by which human impacts can produce divergent responses across ecosystems, due to differences in the strength of processes among ecosystems we identify. Finally, we highlight research gaps and next steps, and discuss how this approach can provide new insights for conservation. By focusing on the processes that shape diversity in communities, we aim to mechanistically link human impacts to ongoing and future changes in ecosystems

The release of zinc and lead from mine tailings

Mining and processing of metal ores are important causes of soil and groundwater contamination in many regions worldwide. Metal contaminations are a serious risk for the environment and human health. The assessment of metal contaminations in the soil is therefore an important task. nA common approach to assess the environmental risk emanating from inorganic contaminations to soil and groundwater is the use of batch or column leaching tests. In this regard, the suitability of leaching tests is a controversial issue. In the first part of this work the applicability and comparability of common leaching tests in the scope of groundwater risk assessment of inorganic contamination is reviewed and critically discussed. Soil water sampling methods (the suction cup method and centrifugation) are addressed as an alternative to leaching tests. Reasons for limitations of the comparability of leaching test results are exposed and recommendations are given for the expedient application of leaching tests for groundwater risk assessment. Leaching tests are usually carried out in open contact with the atmosphere disregarding possible changes of redox conditions. This can affect the original metal speciation and distribution, particularly when anoxic samples are investigated. The influence of sample storage on leaching test results of sulfide bearing anoxic material from a former flotation dump is investigated in a long-term study. Since the oxidation of the sulfide-bearing samples leads to a significant overestimation of metal release, a feasible modification for the conduction of common leaching tests for anoxic material is proposed, where oxidation is prevented efficiently. A comparison of leaching test results to soil water analyzes have shown that the modified saturation soil extraction (SSE) is found to be the only of the tested leaching procedures, which can be recommended for the assessment of current soil water concentrations at anoxic sites if direct investigation of the soil water is impossible due to technical reasons. The vertical distribution and speciation of Zn and Pb in the flotation residues as well as metal concentrations in soil water and plants were investigated to evaluate the environmental risk arising from this site due to the release of metals. The variations in pH and inorganic C content show an acidification of the topsoil with pH values down to 5.5 in the soil and a soil water pH of 6 in 1 m depth. This is due to the oxidation of sulfides and depletion in carbonates. In the anoxic subsoil pH conditions are still neutral and soil water collected with suction cups is in equilibrium with carbonate minerals. Results from extended x-ray absorption fine-structure (EXAFS) spectroscopy confirm that Zn is mainly bound in sphalerite in the subsoil and weathering reactions lead to a redistribution of Zn in the topsoil. A loss of 35% Zn and S from the topsoil compared to the parent material with 10 g/kg Zn has been observed. 13% of total Zn in the topsoil can be regarded as mobile or easily mobilizable according to sequential chemical extractions (SCE). Zn concentrations of 10 mg/L were found in the soil water, where pH is acidic. Electron supply and the buffer capacity of the soil were identified as main factors controlling Zn mobility and release to the groundwater. Variable Pb concentrations up to 30 µg/L were observed in the soil water. In contrast to Zn, Pb is enriched in the mobile fraction of the oxidized topsoil by a factor of 2 compared to the subsoil with 2 g/kg Pb. 80% of the cation exchange capacity in the topsoil is occupied by Pb. Therefore, plant uptake and bioavailability are of major concern. If the site is not prevented from proceeding acidification in the future, a significant release of Zn, S, and Pb to the groundwater has to be expected. Results from this study show that the assessment of metal release especially from sulfide bearing anoxic material requires an extensive comprehension of leaching mechanisms on the one hand and on weathering processes, which influence the speciation and the mobility of metals, on the other hand. Processes, which may change redox and pH conditions in the future, have to be addressed to enable sound decisions for soil and groundwater protection and remediation.Der Abbau und die Verarbeitung von Metallerzen sind eine häufige Ursache für Boden- und Grundwasserkontaminationen in vielen Regionen der Welt. Schwermetallkontaminationen sind eine ernstzunehmende Gefahr für Mensch und Umwelt. Daher ist die Erkundung und Beurteilung von Schwermetallkontaminationen in Böden eine wichtige Herausforderung. Ein häufiges Verfahren für die Abschätzung des Gefährdungspotenzials von anorganischen Kontaminationen für Boden und Grundwasser ist der Einsatz von Elutionsverfahren (Schüttel- und Säulenversuche). Die Eignung von Elutionsverfahren für die Beurteilung von Sickerwasserkonzentrationen ist umstritten. Im ersten Teil dieser Arbeit wird die Anwendbarkeit und Vergleichbarkeit von Elutionsverfahren im Rahmen der Sickerwasserprognose von anorganischen Kontaminationen kritisch diskutiert und bewertet. Als praktikable Alternative zu den Elutionsverfahren werden Verfahren für die Beprobung von Sickerwasser (Saugkerzen und Zentrifugation) dargestellt. Empfehlungen für den sinnvollen Einsatz von Elutionsverfahren im Rahmen der Sickerwasserprognose werden gegeben. Elutionsverfahren werden normalerweise in offenem Kontakt zur Atmosphäre durchgeführt, ohne die Redox-Bedingungen zu berücksichtigen. Vor allem bei ursprünglich anoxischen Proben kann dies zu einer Veränderung der Schwermetall Speziierung und Verteilung führen. An sulfidhaltigem Material aus einer ehemaligen Flotationshalde wurde der Einfluss der Probenlagerung auf die Ergebnisse von Elutionsverfahren in einer Langzeitstudie untersucht. Da die Oxidation der sulfidhaltigen Proben zu einer erheblichen Überschätzung der Schwermetallfreisetzung führt, wird eine einfach durchzuführende Modifikation der Elutionsverfahren vorgeschlagen, bei der eine Oxidation der Proben verhindert werden kann. Ein Vergleich von Ergebnissen aus Elutionsverfahren mit Sickerwasseranalysen hat ergeben, dass der modifizierte Bodensättigungsextrakt als einziges der getesteten Elutionsverfahren für die Abschätzung der aktuellen Sickerwasserkonzentrationen an anoxischen Standorten empfohlen werden kann für die Fälle, in denen das Sickerwasser aus technischen Gründen nicht direkt beprobt werden kann. Um das Gefährdungspotenzial der ehemaligen Flotationshalde durch die Freisetzung von Schwermetallen abschätzen zu können, wurde die vertikale Verteilung und Speziierung von Zn und Pb in den Flotationsrückständen sowie die Schwermetallkonzentration in Sickerwasser und Pflanzen untersucht. Die pH-Werte und Kohlenstoffgehalte zeigen eine Versauerung des Oberbodens mit Boden-pH-Werten bis 5,5. Dies ist auf die Oxidation von Sulfiden und einer Abreicherung von Karbonaten zurückzuführen. Im anoxischen Unterboden sind die pH-Bedingungen neutral und das Sickerwasser aus den Saugkerzen befindet sich im Gleichgewicht mit Karbonaten. Ergebnisse aus Untersuchungen mittels "Extended X-Ray Absorption Fine Structure" (EXAFS) Spektroskopie an der Zn K-Kante bestätigen, dass Zn im Unterboden hauptsächlich als Sphalerit vorliegt und Verwitterungsreaktionen im Oberboden zu einer Umverteilung in andere Zn Spezies führen. 35% des Zn und S wurden aus dem Oberboden bereits ausgetragen, bezogen auf das Ursprungsmaterial mit 10 g/kg Zn. 13% des Zn im Oberboden können als mobil bzw. leicht mobilisierbar angesehen werden, wie Sequentielle Chemische Extraktionen (SCE) gezeigt haben. Im schwach sauren Sickerwasser in 1 m Tiefe wurden Zn Konzentrationen von ca. 10 mg/L festgestellt. Die Zufuhr von Elektronen und die Pufferkapazität des Bodens wurden als wichtigste Steuerparameter für die Zn Mobilität und Freisetzung ins Grundwasser identifiziert. Variierende Pb Konzentrationen von bis zu 30 µg/L wurden im Sickerwasser beobachtet. Im Gegensatz zu Zn wird Pb im oxidierten Oberboden mit einem Faktor von 2 angereichert, verglichen mit dem Unterboden mit Pb Gehalten von ca. 2 g/kg. 80% der Kationenaustauschkapazität des Oberbodens ist mit Pb belegt. Daher sind die Fragen der Pflanzenaufnahme und Bioverfügbarkeit von vorrangiger Bedeutung. Falls der Standort in Zukunft nicht vor voranschreitender Versauerung geschützt wird, ist mit einem signifikanten Austrag von Zn, S und Pb ins Grundwasser zu rechnen. Die Ergebnisse dieser Studie zeigen, dass die Beurteilung der Freisetzung von Schwermetallen, vor allem bei sulfidhaltigem anoxischen Material, ein umfassendes Verständnis sowohl der Freisetzungsprozesse als auch der Verwitterungsprozesse, die die Mobilität der Schwermetalle beeinflussen, erfordert. Prozesse, die die Redox- und pH-Bedingungen in der Zukunft verändern können, müssen berücksichtigt werden, um angemessene Entscheidungen für den Boden- und Grundwasserschutz und für die Sanierung treffen zu können

Appendix A. Tables with model parameters, factors for current and temperature tolerance, substrate/microhabitat and water quality classes, saprobic conditions, and estimation of environmental inputs.

Tables with model parameters, factors for current and temperature tolerance, substrate/microhabitat and water quality classes, saprobic conditions, and estimation of environmental inputs