The rural Windermere catchment, English Lake District, UK comprises 11 upland and lowland lakes which feed into Windermere, England’s largest lake. Palaeolimnological algal records, alongside long-term climate and catchment land use monitoring data from all basins in the catchment were used to quantify the relative importance of regional and local-scale drivers of algal community change. Like many temperate lakes, Mann-Kendall trends showed increased concentrations of total algal production and cyanobacteria accompanied by declines in C/N ratios across the Windermere catchment over the last few centuries. Regression tree analyses suggest that nutrient enrichment has an overarching effect, with temperature playing a secondary role. Synchrony and breakpoint analyses suggested that local forcings led to catchment-wide asynchrony of algal communities after the 1950s. In the lowlands (<100 m.a.s.l), 20th century wastewater treatment installation explained the greatest changes in the algal communities, overriding agricultural intensification, but at sites without point sources, correlations to variables that indirectly explain sewage expansion such as resident catchment human populations were apparent. In contrast, algal community change in upland lakes was more responsive to atmospheric pollutants which caused acidification in the late 19th and early 20th century, alongside climatic variables notably temperature. Evidence for upland atmospheric nitrogen deposition in the 20th century was suggested by decreasing stable δ15Norg isotope values, concurrent with increased concentrations of Chlorophyll a (from all algae) but no clear response was found in algal compositional changes. Higher algal community change occurred in lakes with longer residence times overlaying sedimentary geologies typically in the lowlands. However, algal community change was also high in lowland lakes with lower residence times that had point sources, suggesting centennial-scale fertilisation had reduced the ability of local lake characteristics to attenuate environmental change. This work demonstrates that lakes within a few kilometres of one another respond uniquely to environmental change depending on physical characteristics and landscape position. Management measures should focus on reducing nutrients from waste water effluent and develop local stewardship programmes to increase environmental awareness in the region.

River networks act as a link between components of the terrestrial landscape, such as soils and groundwater, with the atmosphere and oceans, and are now believed to contribute significantly to global budgets of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The idea of rivers being an inert conduit for carbon and nitrogen to reach the coast has been challenged recently, with considerable processing of carbon and nitrogen occurring in both the water column and bed sediments in the various aquatic components that make up a river network, including lakes, streams, rivers and estuaries. Although understanding of the cycling of carbon and nitrogen has improved markedly in the last 20 years, there is still much uncertainty regarding the production and emission of greenhouse gases (GHGs) linked to this processing across river catchments and few studies have quantified GHG fluxes from source to sea. Therefore this study aimed to a) understand the spatial and temporal saturations and fluxes of GHGs from both the freshwater River Tay catchment (Scotland) and the River Tay estuary, and b) understand what controls the production of GHGs within both a freshwater lake and across multiple sites in the freshwater river using laboratory incubations of sediment. Hotspots of in-stream production and emission were evident both in the freshwater catchment and the estuary, with significant temporal and spatial variability in saturation and emission (density) for CH4, CO2 and N2O. CH4 emission densities, across the freshwater river sites, ranged from 1720 to 15500 μg C m-2 d-1 with a freshwater catchment wide mean of 4640 μg C m-2 d-1, and in general decreased from upland to lowland sites along the main river stem, with notable peaks of emission in a lowland tributary and at the outflow of a lowland loch. This corresponds well with the main drivers of spatial variability which include allochthonous inputs from gas rich soil waters and in-situ production in fine grained organic rich sediments. CH4 production was observed to be higher in the lowland tributaries (R. Isla 4500 μg C m-2 d- 1) compared to main-stem river sites both in the lowland river (129 μg C m-2 d-1) and upland river which displayed an uptake of CH4 (-1210 μg C m-2 d-1). The main driver of spatial variability in CH4 production rates was the quality of the sediment, as production was higher in fine grained sediments rich in carbon compared to sand and gravels with a low carbon content. CH4 production also varied seasonally, with temperature and seasonal variation in sediment quality as the predominant driving factors. CO2 emission densities across the freshwater catchment ranged from 517 to 2550 mg C m-2 d-1 with a catchment mean flux density of 1500 mg C m-2 d-1. Flux densities on the whole increased along the main river stem from upland sites to lowland sites, with higher fluxes in lowland tributaries. Seasonally, CO2 flux density was highest in late summer and autumn and lowest in winter at most sites, highlighting the importance in seasonal environmental controls such as temperature, light, and substrate availability. Production rates in the sediment increased from upland to lowland sites with highest production rates evident in the lowland tributaries, and in autumn sediment samples. N2O emission density also showed considerable spatial and seasonal variation across the catchment with flux densities ranging from 176 to 1850 μg N m-2 d-1 with a mean flux of 780 μg N m-2 d-1. Mean fluxes were highest in the lowland tributaries and lowest in the upland river with sediment experiments finding similar spatial variation in N2O production. On the whole, in-stream N2O production and emission across the freshwater catchment was driven by increases in nutrient concentration (NO3 -, NH4 +) which in turn was related to the proportion of agricultural landuse. The saturation and emission of GHGs also varied substantially both spatially and temporally in the River Tay estuary, with a mean emission density of 2790 μg CH4-C m-2 d-1, 990 mg CO2-C m-2 d-1 and 162 μg N2O-N m-2 d-1. The spatial variability of GHG concentrations and emission densities in the estuary were predominantly controlled by the balance between lateral inputs (from tidal flushing of surrounding intertidal areas), in-situ microbial production/consumption (both in the water column and bed sediments) and physical mixing/loss processes. Although emission densities of CH4, CO2 and N2O appear low compared to the freshwater river, this is because the estuary is emitting large quantities of gas in the middle and outer estuary, for example net annual emission of N2O increased from 84.7 kg N2O-N yr-1 in the upper freshwater section of the estuary to 888 kg N2O-N yr-1 in the middle estuary section, then decreased to 309 kg N2O-N yr-1 in the saltwater lower estuary. Overall, this study has shown that both dissolved and aerial fluxes of GHGs vary markedly both spatially and temporal from source to sea in a temperate river catchment, with hotspots of in-stream production and emission across the river catchment. The catchment (river, lake and estuary) was a smaller source of CO2, CH4 and N2O emission (total emission and by area) compared to other highly polluted aquatic systems both in the UK and globally.

The presence of human pharmaceuticals in the environment has raised concerns regarding their potential adverse effects on non-target aquatic organisms. Pharmaceuticals are designed to target specific molecular pathways in humans in order to produce known pharmacological and physiological responses, before toxicological effects are seen. The “Read-Across Hypothesis” stipulates that pharmaceuticals can produce similar biological effects in fish, as in humans, if the molecular target is conserved, and the internal (blood plasma) concentrations are similar. The read-across hypothesis was tested using ibuprofen, a non-steroidal anti-inflammatory drug, and the model fish test species, the fathead minnow (Pimephales promelas), to determine if ibuprofen can cause similar target-mediated effects in teleost fish and humans, at comparable blood plasma concentrations. Fathead minnows were exposed, using continuous flow-through systems, for ≤96 hours to a range of ibuprofen water concentrations (100, 270, 370 and 500 µg/L) to determine if plasma concentrations similar to human therapeutic plasma concentrations (HTPCs, or Cmax) could be established in fish blood plasma. The mode of action of ibuprofen was used to identify relevant endpoints (i.e. cyclooxygenase (COX) enzyme) in order to examine target-mediated effects following drug exposure. The water and plasma ibuprofen concentrations were determined using LC-MS/MS. The measured ibuprofen plasma concentrations in individual fish were linked to target-mediated effects on COX gene expression, COX enzyme activity and prostaglandin E2 (PGE2) synthesis (products of COX activity), which were quantified using molecular (QPCR) and biochemical (colourimetric and enzyme immunoassay) assays, and linked with the Cmax of ibuprofen. It was demonstrated that in fish with a mean ibuprofen plasma concentration 1.8-fold below the Cmax, PGE2 concentrations (the most robust endpoint) was significantly inhibited following ibuprofen exposure. However, in fish exposed to an ibuprofen concentration closer to (2 to 3-fold above) environmentally relevant water concentrations (i.e. 9 µg/L), when the mean plasma concentration was 224-fold below the Cmax, fish did not respond to ibuprofen exposure. This study provides qualitative and quantitative evidence for the applicability of the “read-across hypothesis”, and highlights its potential utility for prioritising pharmaceuticals for environmental risk assessment.

The study aimed to disentangle the climate–hydrology–ecology chain of processes at large spatial and temporal scales. River ecology was considered in terms of some of the main controls of physical habitat (environmental flows, hydraulics, and water temperature). The research included four complementing studies investigating associations between: (1) climate (atmospheric circulation and regional climate) and river flows; (2) river flows and river hydraulics; (3) regional climate and river water temperature; (4) regional climate and environmental flows. The first three studies focused on current conditions, had a national (mainland UK, or England and Wales) geographical scope and a seasonal temporal scale, and used only near-natural sites. In each study, the main drivers were identified, as well as the rivers or regions most/least sensitive. UK-focussed findings were then put into the wider context of future climate- and human-induced river flow change at the pan-European scale: a novel method to assess ecological risk due to flow alteration was developed and applied to flow scenarios for the 2050s. The role of basin properties in modifying those associations was also assessed. Two key aspects emerged: (i) importance of seasonal patterns; and (ii) strong basin property patterns. The study addressed the lack of studies with extensive geographical coverage, high site density, and long periods of records. Spatial patterns could only be found for studies involving climate and flow (historical or future projections); for hydraulics and temperature, spatial patterns were related to basin properties. For all studies, a small set of basin properties were found to have a significant influence: elevation, permeability (except for hydraulics), size (hydraulics and temperature only).

The arrival of a non-native species to has the potential to shape native communities by influencing ecological interactions such as predation, foraging, competition and disease transfer. A designation of invasive is applied to an introduced non-native species that has the potential to threaten the continued wellbeing of a native species, pose a risk to human health or negatively impact the economy. The European bullhead (Cottus perifretum) is a freshwater benthic-dwelling fish that is native to England but considered invasive in Scotland. The species was first reported in Scotland in the 1950's and thriving populations are now established in the waters of the Clyde, Forth and Tweed catchments. Bullhead presence is thought to negatively impact native stone loach (Barbatula barbatula) and brown trout (Salmo trutta) parr, due to shared preferences for habitat and prey resources. They are also thought to prey upon the eggs of native Atlantic salmon (Salmo salar) and brown trout, two species that are of high commercial value in Scotland. In other areas of introduction, bullheads have been found to increase parasite infection rates in native fishes. The species therefore has the capacity to incite competition and alter parasite/host interactions in areas of introduction, to the potential detriment of native fauna and the Scottish economy. The European bullhead has been the subject of considerable taxonomic scrutiny in recent years, resulting in its reclassification as a species complex. What was once considered a single species with a distribution encompassing Europe, Russia, Asia and Scandinavia, has been shown to consist of at least 15 distinct species. Genetic examination of bullheads from England confirmed the presence of Cottus perifretum, not Cottus gobio as traditionally listed in all UK literature and legislation. Native English bullhead is currently protected under Annex II of the European Commission Habitats Directive 92/43/EEC, based on the historic assumption that the species present is C. gobio. Analysis of the taxonomic identity of Scottish bullheads has remained outstanding. In this study the invasive status of bullhead was explored by examining feeding and parasitological interactions between bullheads and native freshwater communities in south-east Scotland. An assessment of the feeding preferences of native brown trout and stone loach in the presence and absence of bullheads tested competition for prey resources. Parasitological interactions were investigated by examining the shared parasite fauna of bullheads and native fish and invertebrate species. Bullheads from the Clyde and Forth catchments were analysed to provide a molecular and morphological description of this introduced species. Phylogenetic analysis of COX1 sequences obtained from Scottish bullheads, and a pair-wise distance calculation based on a Kimura 2-parameter model, showed that samples clustered in a distinct clade with English C. perifretum. Significant intraspecific variation was reported in all morphological features examined, but pooled data also revealed a resemblance to the published description provided for C. perifretum. Scottish bullhead is therefore confirmed to be an introduced pocket of the native English species, which is considered under threat in some areas due to habitat modifications and population decline. Comparisons between the dietary compositions of bullheads, brown trout and stone loach showed that the prey selection of brown trout and stone loach varied in the sample locations that contained co-occuring bullheads, when compared to locations where bullheads were absent. However, no direct evidence of trophic competition between bullheads and either brown trout or stone loach was reported. An examination of parasitological interactions recovered eight parasite species from four distinct taxonomic groups in total, of which four species (Echinorhynchus truttae, Apatemon gracilis, Diplostomum volvens and Raphidascaris acus) were shared between bullheads and one or more native fishes. Echinorhynchus truttae was also shared with gammarid crustaceans. Bullhead presence was found to coincide with D. volvens infections in European minnow (Phoxinus phoxinus) and a reduced prevalence of E. truttae in brown trout. Diplostomum volvens was only reported from minnow found in sites with bullheads, strongly suggesting bullheads were responsible for introducing this parasite to native minnows. Bullheads functioned as an alternative host for E. truttae, diluting brown trout parasite loads and reducing overall infection rates in sites where bullhead and brown trout co-exist. The findings reported for both feeding preference and parasite burdens in the presence and absence of bullheads suggest that bullheads do have some effect on the ecology of native species, but these are considered minimal and unlikely to impact the long-term survival of native species. Eradication of Scottish bullhead may contradict the conservation effort that is currently in place. Given the current lack of evidence to validate bullhead's invasive qualities and the recent confirmation of its genetic lineage, revisiting the designation of the bullhead as invasive is warranted. Active eradication should be treated with caution until a significant negative impact can be proven.

Der Bericht liefert einen Überblick über die Belastung der sächsischen Böden und Gewässer mit Nährstoffen. Bilanziert wurden u. a. Phosphor-und Stickstoff- sowie Sedimenteinträge in die Gewässer. Die Abschätzungen erfolgten auf Basis des in Sachsen entwickelten Modells STOFFBILANZ. Die Betrachtungen beziehen sich auf die Zeitschnitte der Jahre 2000, 2005, 2012 sowie 2021 und 2027. Die Veröffentlichung richtet sich an Ingenieur- und Planungsbüros, Forschungs-, Lehr- und Fortbildungseinrichtungen, Umwelt- und Landwirtschaftsverbände sowie an Behörden, die im Bereich Gewässerschutz und Landwirtschaft in Sachsen tätig sind.

Climate change and the accompanying increase in global surface temperatures pose a major threat to freshwater ecosystems, especially at high latitudes where warming is predicted to be particularly rapid. To date many aspects of how rising temperatures can impact fresh waters remain unknown. Information about temperature effects on the level of communities, food webs, ecosystems is especially scarce. The few studies focusing on higher levels of organisation have used either laboratory microcosm experiments, which can lack realism or space-for-time substitution across large ranges of latitude, which can be confounded by bio-geographical effects. This study aimed to overcome these shortcomings by using a “natural experiment” in a set of 16 geothermally heated streams in the Hengill area, South-West Iceland, with water temperatures ranging from 4ºC to 49ºC (mean temperature). Data were analysed for two seasons, August 2008 and April 2009. The principal goal of this study was to assess the effects of temperature on the structure and functioning of food webs. Additionally the persistence of the community structures along the temperature gradient was examined through time (comparison of previously collected data in August 2004 and August 2008). Abundances of cold-stenotherm species decreased whereas those of eurythermal species increased with increasing temperatures leading to knock-on effects on abundances of other species. Species community overlap between streams declined as temperature difference between streams increased. The persistence of species composition through time was weakened at the extremes of the temperature gradient. Food webs showed a clear size structuring in analyses of trivariate food webs, abundance and biomass size spectra. Analysis of connectance, complexity, mean link length, mean 2-span, mean community span and slopes and intercepts of linear regressions fitted to the trivariate foods or size spectra revealed the impact of temperature change on freshwater ecosystems.

The extensive acidification of fresh waters across Europe and North America during the 20th century led to extensive and widespread loss of species, which fundamentally changed the structure of resident communities. While attempts to limit or halt acidifying emissions have been successful in reversing the chemical consequences of acidification, any corresponding biological recovery has been patchy at best. The main aim of this thesis was to investigate potential ecological constraints on this biological recovery, ranging from interactions between individuals to ecosystem-level processes, using a model stream system that has been extensively studied for over 40 years. I used a combination of long-term survey data and experiments, both in the field and the laboratory, to provide evidence that the lag in recovery of acidified aquatic communities is due to intrinsic resistance to re-colonisation by acid-sensitive species, as a result of both direct and indirect interactions between predators and prey. However, there is also evidence of recovery at an ecosystem level, with rates of microbial decomposition increasing – a key link in the transfer of energy to higher trophic levels, which could be facilitating population increases in large-bodied predators. These findings increase our understanding of the drivers which govern the structure and function of ecological networks in response to an important climatic stressor. This is especially relevant given the rapid industrialisation of countries such as India and China, which could well soon experience anthropogenic acidification on a significant scale.

Climate change can have potentially catastrophic effects upon biodiversity and food web structure and according to the fourth IPCC report, ambient temperatures will rise by between 3.0-5.0 °C over the next century, with already an average increase in global surface temperature of ~0.74°C in the past 100 years. This has known implications in ecology from individuals to ecosystems. The microbial loop consists of small organisms ranging in body size from bacteria (1-15 μm), single-celled eukaryotes (10-1000 μm) and multicellular organisms (250 – 1000 μm) that assimilate dissolved organic carbon into the “classical food web”. ! The principal goal of this thesis was to assess how rising global temperatures might impact the natural microbial assemblages in 20 mesocosms under 2 treatments – 10 warmed (in line with IPCC predictions) and 10 ambient. The abundance and body mass of 4 major microbial loop taxa (desmids, flagellates, heterotrophic protists and meiofauna) were quantified at monthly intervals over a 2-year period. Secondly, in a microcosm experiment, the population dynamics of three pure cultures of ciliates were monitored across a temperature gradient; the rate of population decline under starvation and changes in body size were quantified.! Results showed that (1) rising global temperatures alters the size spectrum in the autotrophic protists, (2) temperature interacts with temporal and spatial gradients, resulting in changes in phenology (3) these changes in phenology are observable at both the community level and the population level within the microbial assemblage of the mesocosms and (4) extinction rates and body mass reduction in experimental microcosms were faster at warmer temperatures and partially support predictions of the metabolic theory of ecology.! The implications of these findings are discussed in terms of (1) continued research into the role that small organisms play in community and ecosystem ecologyand (2) the use of these small organisms in experiments as models to inform ecological theory by scaling up from microcosms and finally, (3) I discuss future directions in freshwater microbial ecology, focusing on the increased use of molecular techniques.

There is little doubt that anthropogenic climate change will have long lasting, unavoidable, large scale and cross sector effects. Having a clear understanding of the scale and rate of projected future changes, and the potential impacts of those changes at multiple spatial and temporal scales, will be important to allow environmental managers the best chance of adapting to changing conditions. There are particular concerns about impacts on freshwater systems due to the coupling of direct impacts to both hydrology and ecology. Expected changes can be grouped into three functional categories: those affecting physico-chemical (broadly water quality), hydromorphological (physical structure and habitat) and biological elements of the lake system. The Lake-Landscape Context framework provides a way of approaching the sensitivity or resilience of an individual lake to change by exploring the complex and multi-layered relations between water, land and human activity. However, the exact combination of strategies and actions available to environmental managers is yet to be comprehensively documented beyond broad principles. To reach this goal, to manage our ecosystems in the most comprehensive and responsible way, we need to have a clear understanding of what and where that resource is, what the conservation priorities currently are and where threats to these priorities are likely to emerge. Therefore, the overall aim of this thesis was to develop adaptation strategies to minimise climate change impacts on the conservation interests of Scotland’s standing freshwater. This was approached through the adoption of the ESVRA conceptual framework, intended to assist policymakers and practitioners in adaptation planning. Practical actions can be guided by working through the framework’s four key stages: understanding exposure to the pressure (external drivers); considering the sensitivity and resilience of the system at multiple scales (internal functions); exploring areas of vulnerability (a measure of sensitivity plus exposure); and consideration of multiple possible responses across spatial and temporal scales. Chapter 2 explores the lake resource making use of the latest geospatial data and GIS techniques to investigate Scottish standing freshwaters in depth. 5,165 Scottish lakes exhibit an outstanding myriad of forms and sizes ranging across the country. This variety of form, density and distribution contribute to habitats of international importance for numerous species. Perhaps because of this diversity, no natural grouping of lakes were found based on simple hydromorphological categorisations. The use of landscape and wildness ‘scoring’ is a novel geographic approach, which may be an important factor in how landscapes are valued in the future. Chapter 3 investigates the direct exposure to global climate change facing Scotland. Projected changes to global climate were downscaled to illustrate impact on the UK and Scotland using both the UKCP09 and HadGEM2-ES climate models. Climate change by the 2050s will impact the UK in the range 1.1°C to 2.7°C with a clear South-East/North-West gradient. Precipitation too is projected to change in the UK in this time, with annual precipitation varying from -65 to +116 mm/yr. By incorporating the climate model data into a GIS it was possible to further interrogate the results for specific locations, with a detailed water balance model created for all 5165 lakes. This model suggests that during the summer months there will be sustained periods of water scarcity and deficit. Finally, in this chapter, a climate change spatial risk assessment was undertaken, identifying 200 lakes in the area of greatest projected change. Leading on from these findings, Chapter 4 explores the vulnerability of Scotland’s standing freshwaters. A vulnerability framework attempts to place resilience as a key part of the model, which has to date been missing from similar assessments. The expert weighted scoring mechanism highlights 851 of Scotland’s standing freshwaters, geographically spread across the country, as being highly vulnerable to projected climate changes. The results were mapped to show the vulnerability across Scotland and a display system for individual lakes proposed that allows a transparent and coherent structure that can shed light on distinct components of vulnerability, so that each can be evaluated individually, and in combination. Finally, in Chapter 5, a multipart online survey with key stakeholder experts actively involved in freshwater environmental management was produced to approach adaptation strategies and actions themselves. Over 80 adaptation actions specifically applicable to Scotland’s standing freshwaters were collated and grouped into 12 adaptation strategies. All 12 strategies were considered desirable with six strategies considered ‘Definitely feasible’, a further four considered ‘Likely feasible’. This provides a framework of potential actions that could help to reduce system sensitivity by increasing adaptive capacity or system resilience. In conclusion, while there are undoubtedly challenges ahead for Scotland’s standing freshwaters and for those who manage them, there is clear opportunity to make proactive and engaged decisions to minimise the impact of climate changes on the conservation interest of these important habitats.