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Abstract Substrate composition has been widely recognised as a primary variable shaping lotic macroinvertebrate communities at the habitat unit level. However, fundamental understanding of how communities inhabiting mineralogical habitats (i.e., gravel, sand and silt) are structured across differing rivers is lacking. Moreover, research largely focusses on gravel beds and fine sediment in general (

Abstract Despite lotic systems demonstrating high levels of seasonal and spatial variability, most research and biomonitoring practices do not consider seasonality when interpreting results and are typically focused at the meso‐scale (combined pool/riffle samples) rather than considering habitat patch dynamics. We therefore sought to determine if the sampling season (spring, summer and autumn) influenced observed macroinvertebrate biodiversity, structure and function at the habitat unit scale (determined by substrate composition), and if this in turn influenced the assessment of fine sediment (sand and silt) pressures. We found that biodiversity supported at the habitat level was not seasonally consistent with the contribution of nestedness and turnover in structuring communities varying seasonally. Habitat differences in community composition were evident for taxonomic communities regardless of the season but were not seasonally consistent for functional communities, and, notably, season explained a greater amount of variance in functional community composition than the habitat unit. Macroinvertebrate biodiversity supported by silt habitats demonstrated strong seasonal differences and communities were functionally comparable to sand habitats in spring and to gravel habitats in autumn. Sand communities were impoverished compared to other habitats regardless of the season. Silt habitats demonstrated a strong increase in Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa and functional richness from spring into autumn, while vegetation habitats displayed a peak in EPT abundance in summer. Only silt and sand habitats demonstrated temporal variability in functional evenness suggesting that these habitats are different in terms of their resource partitioning and productivity over time compared to other habitats. Gravel and vegetation habitats appeared to be more stable over time with functional richness and evenness remaining consistent. To accurately evaluate the influence of fine sediment on lotic ecosystems, it is imperative that routine biomonitoring and scientific research discriminate between sand and silt fractions, given they support different biodiversity, particularly during summer and autumn months.

Abstract Biological invasions remain one of the most pressing threats to biodiversity globally, with unprecedented rates of establishment that are unlikely to abate in the future. As such the occurrence of multiple interacting invasive non‐native species (INNS) is becoming more common. Despite this, much of the research on the interaction of multiple INNS is conducted within laboratory settings, with field studies remaining rare or being conducted as one‐off sampling. There is therefore a deficit of knowledge pertaining to the natural population trajectories of multiple INNS and the wider ecological implications for the structure and function of the native communities. Here we present multiple years of data collected from a reservoir in the United Kingdom, which has undergone invasion by three congener non‐native amphipods. We initially observed the coexistence of Dikerogammarus haemobaphes with Crangonyx pseudogracilis under habitat segregation in the reservoir. However, the following year saw complete displacement of C. pseudogracilis and reduced abundances of D. haemobaphes once the more competitive Dikerogammarus villosus established abundant populations in the reservoir. D. villosus exhibited strong effects for the structure and function of the wider macroinvertebrate community composition in addition to driving reductions in taxa and functional richness. Gastropoda taxa appeared to be unaffected by the invasion dynamics. Significant increases in functional divergence (and less so functional dispersion) values were also observed following D. villosus establishment, with this response metric possibly representing an important tool in detecting stress from biological invasions that we urge scientists to test more extensively. In contrast to D. villosus, D. haemobaphes implications for the wider ecological community appeared to be limited. Importantly, we observed evidence to suggest the presence of boom–bust cycles with the explosion of D. villosus leading to a dramatic drop in their abundances the following year. We believe that the wider ecological implications of their abundant populations were so great that resources were not sufficient within the reservoir to support their abundant populations, leading to the observed population collapses. We call for further studies that investigate the population trajectories and wider ecological implications of multiple non‐native species in field settings to further our limited knowledge base.

Abstract Ponds are among the most biodiverse and ecologically important freshwater habitats globally and may provide a significant opportunity to mitigate anthropogenic pressures and reverse the decline of aquatic biodiversity. Ponds also provide important contributions to society through the provision of ecosystem services. Despite the ecological and societal importance of ponds, freshwater research, policy, and conservation have historically focused on larger water bodies, with significant gaps remaining in our understanding and conservation of pond ecosystems. In May 2019, pond researchers and practitioners participated in a workshop to tackle several pond ecology, conservation, and management issues. Nine research themes and 30 research questions were identified during and following the workshop to address knowledge gaps around: (1) pond habitat definition; (2) global and long‐term data availability; (3) anthropogenic stressors; (4) aquatic–terrestrial interactions; (5) succession and disturbance; (6) freshwater connectivity; (7) pond monitoring and technological advances; (8) socio‐economic factors; and (9) conservation, management, and policy. Key areas for the future inclusion of ponds in environmental and conservation policy were also discussed. Addressing gaps in our fundamental understanding of pond ecosystems will facilitate more effective research‐led conservation and management of pondscapes, their inclusion in environmental policy, support the sustainability of ecosystem services, and help address many of the global threats driving the decline in freshwater biodiversity.

Abstract River regulation globally has reduced the riverine connectivity (longitudinal, lateral and vertically) with significant consequences for their abiotic and biotic components. To restore the ecological integrity of regulated rivers, artificial floods are increasingly being employed in large‐scale flow restoration efforts. Despite considerable recognition regarding the ecological and geomorphological effects of artificial floods on benthic habitats, understanding the implications for the hyporheic zone is essentially absent. This void in our management knowledge base is considerable given that one of the most widely associated consequences of flow regulation is excessive deposition of fine sediment (sedimentation; particles