1,721,081 research outputs found
Dataset: membrane thickness, membrane quotient, membrane porosity and membrane permeability of eggs of 5 populations of Atlantic salmon
No full textData contains information on membrane thickness, membrane quotient, membrane porosity and membrane permeability of eggs of 5 populations of Atlantic salmon. Additional data is presented on oxygen requirements derived from the application of the mass transfer theory.
Document contains data relating to below linked thesis and paper entitled: "Variation in egg structure among five populations of Atlantic salmon (Salmo salar) influences their survival in low oxygen conditions" to be published in the journal Royal Society Open Science.
Information on method of data collection and calculation is available at: https://eprints.soton.ac.uk/id/eprint/413854 </span
The influence of geomorphology on large wood dynamics in a low gradient headwater stream
Full text linkUnderstanding large wood dynamics is critical for a range of disciplines including flood risk management, ecology and geomorphology. Despite the importance of wood in rivers, our understanding of the mobility of large wood remains limited. In this study individual pieces of large wood were tagged and surveyed over a 32 month period within a third and fourth order lowland forest river. Individual pieces of wood were found to be highly mobile, with 75% of pieces moving during the survey period, and a maximum transport distance of 5.6 km. Multivariate analyses of data from this study and two other published studies identified dimensionless wood length as the important factor in explaining likelihood of movement. A length threshold of 2.5 channel widths is identified for near functional immobility, with few pieces above this size moving. In addition, for this study, wood type, branching complexity, location and dimensionless wood diameter were found to be important in determining mobility only for sinuous reaches with readily inundated floodplains. Where logjams persist over multiple years they were shown to be reworked, with component pieces being transported away and replaced by newly trapped pieces. The findings of this study have implications for river management and restoration. The high mobility observed in this study demonstrates that only very large pieces of wood of length greater than 2.5 channel widths should be considered functionally immobile. For pieces of wood of length less than the channel width the possibility of high rates of mobility and long transport distances should be anticipated
Carbon storage in river and floodplain systems: A review of evidence to update and inform policy development for riverine nature based solutions
Full text linkThe threat of climate change is increasingly motivating goals that seek to achieve net zero emissions in the next few decades (Rutter and Sasse, 2022). In the UK, net zero is a statutory requirement that must be met by 2050 (Gregg et al., 2021). An important element of this strategy is determining how nature can contribute to achieving Net zero – largely via carbon sequestration and storage (Gregg et al., 2021). The degradation of many natural systems has impacted natural carbon stores and so the role of nature-based solutions is increasingly being implemented with the beneficial aims of both increasing biodiversity as well as supporting climate change mitigation (Gregg et al., 2021). Decomposition and combustion of organic material releases CO2 to the atmosphere, while accumulation of biomass and soil organic carbon (SOC) sequesters CO2 (Hoffmann 2021). Wetlands such as peatlands, swamps, marshes, estuaries and floodplains provide optimal conditions for the sequestration and long-term storage of carbon although the precise timing of storage will depend on erosional (turnover) time of the specific habitat/system. Low oxygen concentrations support anaerobic conditions that reduce decomposition, whilst overbank sedimentation buries organic matter protecting it from further decomposition. On floodplains, the high clay content of deposits provide sites for chemical bonding with organic matter further reducing loss of carbon through decomposition and gaseous emission (Hoffman 2021). Research to date all points towards a substantial role for rivers and floodplains in the global carbon cycle (Whol and Knox 2022, Hoffman, 2021). An increasingly expanding literature consistently demonstrates that riparian ecosystems and floodplains can store a significantly larger amount of carbon per area compared to surrounding land (Suftin et al., 2016; Whol and Knox 2022). Floodplains cover 0.5–1% of the global land area but have been suggested to account for a range of 0.5–8% of global SOC storage. River networks contain significant portions of terrestrial C with greatest retention occurring in floodplain riparian ecosystems D’Elia et al (2017). Although, there is a large range of estimated values of OC in watersheds (0.5 to 1.5 Pg (Aufdenkampe et al., 2011) and 0.9 Pg (Regnier et al., 2013)), some estimates in mountainous headwater streams in the USA, indicate that riparian areas including floodplains may store about 25% of the total OC while occupying less than 1% of watershed area (Wohl et al., 2012). Sutfin et al., (2016) reported 22% of carbon entering headwater streams is unaccounted for after quantifying delivery to oceans or losses to outgassing as carbon dioxide (CO2), suggesting there is a substantial reservoir of carbon in riparian systems derived from sediment deposition. The role of rivers in carbon sequestration has often been interpreted as a conduit between terrestrial and marine carbon stores (Gregg et al., 2021). Carbon can be stored in the floodplain in many forms including above ground vegetation (Dyabla et al., 2019), and soil (Wohl et al., 2017), as well as within the river channel as large, drowned wood and vegetation (Hinshaw & Wohl, 2021). Much of the evidence remains focussed on above ground biomass and the first metre of soil (D’Elia et al., 2017). However, it is argued in Young et al., (2019) that recent carbon accumulation rates in surface peat can be misinterpreted in relation to carbon storage. It suggests that surface/topsoil peat measurements do not account for the future ability to be decomposed/lost in comparison to deeper long-term stores. This suggests that although there may be peat/organic matter present in topsoil this may not necessarily translate into long term carbon sequestration. A need for deeper sediment cores and paleoenvironmental analysis to present the natural state of UK rivers is identified across the literature (D’Elia et al., 2017; Quine et al., 2022), however, is not yet widely implemented, although the current Natural England led project to develop a national peat map is aiming to rectify this omission. The quantification of carbon stored in floodplains and the potential for restoration to increase this remains poorly understood (Hinshaw & Wohl, 2021; Hofmann 2021). To be able to quantify carbon storage it requires understanding how much is buried (storage quantity), over what timescales (storage period) and what processes are associated with carbon burial and storage. These factors are addressed in this report to better understand carbon storage in UK floodplains and whether current restoration is effective at increasing this. <br/
Does variation in egg structure among five populations of Atlantic salmon (Salmo salar) influence their survival in low oxygen conditions?
No full textOxygen supply to the salmonid egg surface can be limited by external factors such as sedimentation and groundwater upwelling, while the egg membrane itself can impede diffusion from the egg surface to the embryo. Therefore, the structure of egg membranes could affect the rate at which embryos obtain oxygen from their surroundings. Published field data indicate that oxygen stress experienced by salmonid eggs can vary widely among populations. Therefore, if membrane architecture influences diffusion rate to the embryo, selection for more permeable membranes could occur in oxygen-stressed environments. Using electron microscopy, the membrane structure of eggs obtained from five UK Atlantic salmon (Salmo salar) populations is described. Membrane thickness, porosity and permeability to dissolved oxygen varied among populations. Furthermore, comparison of membranes of eggs that survived laboratory controlled low-oxygen conditions compared to those that died suggested that ova with less permeable membranes were more susceptible to hypoxia-induced mortality. In addition, membrane porosity was lower than previously reported indicating that oxygen requirements during incubation have been underestimated, so models such as the mass transfer theory that predict incubation success could currently overestimate ova survival. Variation in egg membrane structure influences low oxygen tolerance of Atlantic salmon embryos and could represent adaptation to low oxygen stress. Consequently, stock enhancement techniques such as supportive breeding that relieve incubation stress could erode structural adaptations
Incorporating hydromorphology in strategic approaches to managing flows for salmonids
No full textWhilst flow is often seen simplistically as a measurable and manageable variable in rivers, the habitatvalue of flow is delivered by interactions with channel morphology and substrate. The resulting hydromorphologyimpacts on all salmonid life stages; its proper understanding requires integration between the sciences ofhydrology/hydraulics, geomorphology and freshwater ecology, but this integration is scarce. This study describesthose features of river channel morphology and dynamics that are most relevant to hydromorphological status,describes progress in field assessment and outlines practical progress in calibrating in-channel habitat condition asan aid to setting flows. However, the incorporation of the true spatial and temporal variability of hydromorphologyawaits further refinement of survey techniques and the long-awaited interdisciplinary research on causalprocess links. Meanwhile, amongst the geomorphological tools available to those setting environmental flows arefluvial audits, the definition and mapping of meso-scale biotopes and the use of realistic river typologies for thelocal application of general flow rules
Estimating the contribution of in-stream cattle faeces deposits to nutrient loading in an English Chalk stream
No full textNumerous studies have shown that the addition of faecal matter from livestock to aquatic ecosystems can have a detrimental effect upon water quality. English Chalk streams, as groundwater-dominated rivers of high ecological importance, are particularly susceptible to nutrient loading from cattle faeces. Naturally low concentrations of nitrogen, phosphorus and potassium in such rivers increase their vulnerability to external perturbation from organic matter inputs. Despite this, the amount of faeces directly contributed by livestock such as cattle to a river system is rarely quantified.To provide an assessment of nutrient loading due to cattle, a study combining observational data of animal behaviour with faecal analysis was undertaken in an English Chalk stream. Results show that cattle faeces was 89.4% water, containing 0.79% nitrogen, 0.43% phosphorous and 0.43% potassium by wet mass. It was estimated that a herd of 33 cattle deposited over 8 tonnes of faeces into a 770 m river reach over a seven-month period in 2010. This loading is estimated to have increased in-stream nitrogen, phosphorus and potassium concentrations in the reach by 0.0036 mg l−1, 0.002 mg l−1 and 0.002 mg l−1 respectively; a small proportion of the overall nutrient content of the river. Moreover, it has been demonstrated that by combining behavioural data with faecal data it is possible to estimate the likely nutrient loading due solely to direct inputs from cattle faeces. With sufficient data, calculations such as those employed in this study can be used to provide accurate estimates of the nutrient loading due to livestock in watercourses
Alevin Details and Hatch Timing
No full textData on post hatch Atlantic salmon biometrics: Fork length; Mass; Body mass and number of caudal fin rays.
Data on hatch timings that were used to calculate Kaplan-Meier hatch rates
This dataset supports:
Bloomer, Jack et al (2016) The Effects of Oxygen Depletion due to Upwelling Groundwater on the Post-Hatch Fitness of Atlantic Salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences</span
High resolution scanning of South Pacific lake sediment: relative benefits offered by state-of-the-art micro-XRF and SEM systems
No full textA methodological evaluation for the efficient investigation of laminated core material collected from the South Pacific islands is presented that is expected to be of broad interest to the core scanning community. Efficient identification of laminae, their number, chemistry and mineralogy provide crucial information in inferring sediment accumulation rates and environmental and climate change. The material investigated was collected as part of NERC grant NE/N006674/1 - The legacy of cyclone Pam: a unique opportunity to build a long term record of cyclone activity in the western tropical Pacific (PIs David Sear, Pete Langdon and Ian Croudace). The project is part of a multi-party study involving the PIs, 3 PhD students and collaborating specialists. Analytical data obtained from measurements of a 10 cm section of resin impregnated lake sediment from Lake Te Roto (Atiu Island, Cook Islands) will be discussed. Investigation of the sediment block was made using Itrax, Bruker M4+ micro-XRF and Leo SEM systems. The benefits of using the different approaches are evaluated with the purpose of establishing a preferred approach that would be applied to detailed investigation of all or selected core material collected from two field campaigns. The analytical timeline including an efficiency budget (sample preparation, analysis) as well as the robustness and comparability of analytical outputs (textural, density and elemental variations) will be presented
Science and practice of salmonid spawning habitat remediation
No full textSalmon and trout are evocative symbols of natural river ecosystems. Despite their symbolic (and economic) importance for humans, especially in the case of anadromous salmon and trout, we have inflicted great losses in their numbers and distribution. Within Europe, the Atlantic salmon (Salmo salar) is currently extinct in four countries – Germany, Belgium, the Netherlands and Switzerland – and populations are close to extinction in another six – Spain, France, Portugal, Denmark, Finland and the Baltic states. Only Scotland, Norway, Iceland and Ireland have comparatively healthy populations, although figures suggest that even there salmon numbers are significantly depleted when compared to historical densities (WWF 2001; Youngson et al. 2002; Montgomery 2003). Within North America, current figures indicate that 84% of Atlantic salmon populations are now extinct, with the remaining populations in a critical condition (WWF 2001). In Canada, the picture is less severe, although only 8% of populations have recently been classified as healthy. Figures for Pacific salmon (Oncorhynchus spp.) indicate that populations have also declined, and 17 Pacific salmon runs are now extinct, with a further 214 runs at risk of extinction or of special concern (Nehlsen et al. 1991; Huntington et al. 1996; Shea and Mangel 2001). Alaska remains the primary natural haven in North America where one can observe Pacific salmon populations in a more or less pristine state, although even here returning salmon numbers are affected by fisheries harvest. Unfortunately, declining salmon numbers are not a recent phenomenon and historical accounts reveal a tortuous path of decline that traces human influence over riverine landscapes (Montgomery 2003). For some, the future for many salmon and trout populations can appear bleak (Lackey et al. 2006)
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