No abstract

International audienceThe interface between groundwater and surface water within riverine/riparian ecosystems--the hyporheic zone (HZ)--is experiencing a rapid growth of research interest from a range of scientific disciplines, often with different perspectives. The majority of the multi-disciplinary research aims to elucidate HZ process dynamics and their importance for surface water and groundwater ecohydrology and biogeochemical cycling. This paper presents a critical inter-disciplinary review of recent advances of research centred on the HZ and highlights the current state of knowledge regarding hydrological, biogeochemical and ecohydrological process understanding. The spatial and temporal variability of surface water and groundwater exchange (hyporheic exchange flows), biogeochemical cycling and heat exchange (thermal regime) are considered in relation to both experimental measurements and modelling of these phenomena. We explore how this knowledge has helped to increase our understanding of HZ ecohydrology, and particularly its invertebrate community, the processing of organic matter, trophic cascading and ecosystem engineering by macrophytes and other organisms across a range of spatial and temporal scales. In addition to providing a detailed review of HZ functions, we present an inter-disciplinary perspective on how to advance and integrate HZ process understanding across traditional discipline boundaries. We therefore attempt to highlight knowledge gaps and research needs within the individual disciplines and demonstrate how innovations and advances in research, made within traditional subject-specific boundaries (e.g. hydrology, biochemistry and ecology), can be used to enhance inter-disciplinary scientific progress by cross-system comparisons and fostering of greater dialogue between scientific disciplines

Diseases of failed inflammation resolution are common and largely incurable. Therapeutic induction of inflammation resolution is an attractive strategy to bring about healing without increasing susceptibility to infection. However, therapeutic targeting of inflammation resolution has been hampered by a lack of understanding of the underlying molecular controls. To address this drug development challenge, we developed an in vivo screen for proresolution therapeutics in a transgenic zebrafish model. Inflammation induced by sterile tissue injury was assessed for accelerated resolution in the presence of a library of known compounds. Of the molecules with proresolution activity, tanshinone IIA, derived from a Chinese medicinal herb, potently induced inflammation resolution in vivo both by induction of neutrophil apoptosis and by promoting reverse migration of neutrophils. Tanshinone IIA blocked proinflammatory signals in vivo, and its effects are conserved in human neutrophils, supporting a potential role in treating human inflammation and providing compelling evidence of the translational potential of this screening strategy.

The application of general successional theory to stream ecosystems has not been widely addressed due to a lack of long‐term studies on stream channels at sufficiently large spatial scales. Wolf Point Creek in Glacier Bay, Alaska, a lake‐fed stream that began to emerge from under glacial ice in the mid‐1940s, offers an opportunity to address this imbalance. We examine the stream's development from 1977 to 2005, with reference to concepts of succession and community assembly. Dispersal constraints have influenced the succession, as non‐insect taxa required at least 20 years to colonize. We suggest that tolerance is a major mechanism of macroinvertebrate community assembly. Most taxa, with the exception of the cold‐tolerant first colonizers, have persisted within the community following colonization, although relative abundance has changed markedly with time. However, biotic processes do influence colonization and succession. Redd (nest) digging by spawning salmon creates disturbed patches that facilitate the persistence of some early colonizers, and riparian vegetation facilitates colonization by caddisflies and chironomids. We further suggest that both deterministic and stochastic elements influence succession and community assembly in streams. Our study highlights the importance of reestablishing riparian vegetation during stream restoration programs and of increased in‐stream habitat complexity from inputs of coarse woody debris to improve nutrient retention, particularly of salmon carcasses.

Neutrophil removal from inflammatory sites is regulated by lipid mediator signals between macrophages and neutrophils.

In May 1997, physical and biological variables were studied in 16 streams of different ages and contrasting stages of development following glacial recession in Glacier Bay National Park, southeast Alaska. The number of microcrustacean and macroinvertebrate taxa and juvenile fish abundance and diversity were significantly greater in older streams. Microcrustacean diversity was related to the amount of instream wood and percent pool habitat, while the number of macroinvertebrate taxa was related to bed stability, amount of instream wood, and percent pool habitat. The percent contribution of Ephemeroptera to stream benthic communities increased significantly with stream age and the amount of coarse benthic organic matter. Juvenile Dolly Varden (Salvelinus malma) were dominant in the younger streams, but juvenile coho salmon (Oncorhynchus kisutch) abundance was greater in older streams associated with increased pool habitat. Upstream lakes significantly influenced channel stability, percent Chironomidae, total macroinvertebrate and meiofaunal abundance, and percent fish cover. Stable isotope analyses indicated nitrogen enrichment from marine sources in macroinvertebrates and juvenile fish in older streams with established salmon runs. The findings are encapsulated in a conceptual summary of stream development that proposes stream assemblages to be determined by direct interactions with the terrestrial, marine, and lake ecosystems.

The headwaters of karst rivers experience 10 considerable hydrological variability, including 11 spates and streambed drying. Extreme summer 12 flooding on the River Lathkill (Derbyshire, UK) 13 provided the opportunity to examine the invertebrate 14 community response to unseasonal spate flows, flow. 15 recession and, at temporary sites, streambed drying. 16 Invertebrates were sampled at sites with differing 17 flow permanence regimes during and after the spates. 18 Following streambed drying at temporary sites, AlElectronic supplementary material The online version of A2 this article

Zebrafish are a unique model for pharmacological manipulation of physiological processes such as inflammation; they are small and permeable to many small molecular compounds, and being transparent, they permit the visualization and quantitation of the inflammatory response by observation of transgenically labeled inflammatory cell populations. Using a transgenic line specifically labeling neutrophils in vivo (mpx:GFP), we studied the effects of a range of pharmacological agents on the resolution of inflammation in vivo. These agents were selected for their ability to modulate neutrophil function and lifespan in human neutrophils in vitro. Agents delaying neutrophil apoptosis (LPS, dbcAMP, and several caspase inhibitors) all lead to a delay in resolution of neutrophilic inflammation. Reciprocally, pyocyanin and roscovitine (inducers of neutrophil apoptosis) lead to reduced neutrophil numbers. The occurrence of apoptosis was observed by time-lapse analysis and confirmed by dual staining for neutrophil-specific mpx activity (TSA staining) and an apoptotic marker (TUNEL). During inflammation, macrophages follow neutrophils into the inflamed site, and TUNEL/TSA dual-positive material can be demonstrated within macrophages, consistent with their uptake of apoptotic neutrophils. This model has several advantages over mammalian models and lends itself to the study of pharmaceutical agents modulating inflammation.