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When designing and implementing agri-environmental policies to reduce nutrient loss, action programmes may falsely address areas where the nutrient issue from agricultural activity is not currently important and is not likely to become so in the future (a false positive), or may fail to address areas where the agricultural nutrient issue is currently important or may likely become so in the future (a false negative). Based on a case study of the Louros watershed in Greece, this work identifies database and modelling sources of false positives and negatives and proposes a decision making process aimed at minimizing the possibility of committing such errors. The baseline is well simulated and shows that the Louro's watershed falls behind a Good Environmental Status, at least marginally. Simulated mitigation measures show that the river's status can be upgraded to "Good", at least as concerns nitrates and ammonium. Simulated climate change does not seem to exert an important positive or negative effect. Land use changes forecasting considerably less cultivated area have a significant effect on Total Phosphorous but not on nitrates or ammonium concentrations. The non-linearity between nutrient disposition (inputs) and nutrient concentration in downstream water bodies (output) and the many factors that affect the nutrient disposition-transportation-concentration chain, highlights the importance of simulating the effects of mitigation actions and of future climate and land use changes before adopting and establishing agri-environmental measures.

Based on near-surface temperature measurements conducted at high temporal resolution in 16 Scottish lochs in 2001, a strong seasonal cycle was observed in the magnitude of the diel surface temperature range (DSTR). The influence of 5 site-specific potential predictor variables including altitude, latitude, longitude, lake surface area, and maximum lake depth on the timing of the start and end of a statistically significant DSTR was investigated. The DSTR is important because it is expected to have implications for many processes that affect biogeochemical cycling in lakes, including the rates of metabolic processes. The timing of the start of a statistically significant DSTR in spring showed a strong dependence on altitude, a much weaker dependence on latitude, but no dependence on any other predictor variable tested. The timing of the end of a statistically significant DSTR in autumn showed no dependence on any of the predictor variables tested. Because the start of a statistically significant DSTR is dependent on altitude but its end is not, its duration is also dependent on altitude. Because the start of a significant DSTR is related to the onset of thermal stratification, the results suggest that the altitude of a lake will affect the timing of the onset of thermal stratification and its duration.

The consequences of human impacts on aquatic ecosystem activities have been far reaching. Multiple stresses affect aquatic ecosystems globally. These can adversely affect physical, chemical and ecological water status, causing change in species composition, ecosystem structure and function and biodiversity. These impacts and the capacity for managing them are further compounded by the complex nature of the interactions between stresses. In this article the focus is on the threats posed by non-native invasive species. It considers the nature of this threat and options for management, highlighting examples of invasive freshwater species in the United Kingdom. The relationship between climate change and invasive species impacts is then examined. The article is based on a keynote presentation delivered at the Marine Invasive Species: Management of ballast water and other vectors. Key lessons derived from managing freshwater ecosystems under threat of invasive species are highlighted in terms of their relevance and potential application to other systems such as those in coastal and marine areas.

The European Water Framework Directive aims to improve ecological status within river basins. This requires knowledge of responses of aquatic assemblages to recovery processes that occur after measures have been taken to reduce major stressors. A systematic literature review comparatively assesses recovery measures across the four major water categories. The main drivers of degradation stem primarily from human population growth and increases in land use and water use changes. These drivers and pressures are the same in all four water categories: rivers, lakes, transitional and coastal waters. Few studies provide evidence of how ecological knowledge might enhance restoration success. Other major bottlenecks are the lack of data, effects mostly occur only in short-term and at local scale, the organism group(s) selected to assess recovery does not always provide the most appropriate response, the time lags of recovery are highly variable, and most restoration projects incorporate restoration of abiotic conditions and do not include abiotic extremes and biological processes. Restoration ecology is just emerging as a field in aquatic ecology and is a site, time and organism group-specific activity. It is therefore difficult to generalise. Despite the many studies only few provide evidence of how ecological knowledge might enhance restoration success.

Natural or human-induced water-level fluctuations influence the structure and function of shallow lakes, especially in semi-arid to arid climate regions. In order to reliably interpret the effect of water-level changes from sedimentary remains in the absence of historical data, it is crucial to understand the variation in sedimentary proxies in relation to water level measurements. Here, we took advantage of existing water surface elevation data on three large shallow lakes in Turkey to elucidate the impact of lake-level changes on benthic-pelagic primary production over the last 50-100 years. Sub-fossil cladocerans, diatoms, plant remains and pigments were investigated as biological variables; X-ray fluorescence (XRF) and loss on ignition (LOI) analyses were conducted as geochemical-physical variables on a set of Pb-210 and Cs-137 dated cores. Dating of the cores were robust, with the exception of uncertainties in Lake Marmara littoral core due to low unsupported 210Pb activities and high counting errors. Results indicated that Lake Marmara was dominated by benthic species throughout the sediment record, while Lakes Beysehir and Uluabat shifted from a littoral-dominated system to one with increased pelagic species abundance. In all cores there was a stronger response to longer-term (decadal) and pronounced water-level changes than to short-term (annual-biennial) and subtle changes. It was also noted that degree of alteration in proxies differed between lakes, through time and among pelagic-littoral areas, likely emphasising differences in depositional environments and/or resolution of sampling and effects of other stressors such as eutrophication. Our results highlight lake-specific changes associated with water-level fluctuations, difficulties of conducting studies at required resolution in lakes with rather mixed sediment records and complexity of palaeolimnological studies covering recent periods where multiple drivers are in force. They further emphasise the need to include instrumental records when interpreting effects of recent water-level changes from sediment core data in large shallow lakes. (C) 2016 Elsevier B.V. All rights reserved.

International audience; Land use effects are considered among the main stressors on freshwater biodiversity, with up to 80% of land in Europe under intensive use. Here, we address the impact of arable and urban landscapes on taxon richness, Shannon–Wiener diversity, taxon rareness and taxonomic distinctness of eleven organ- ism groups encompassing vertebrates, invertebrates and plants, occurring in five freshwater ecosystem types across Europe: rivers, floodplains, lakes, ponds and groundwater. In addition, nine geo-climatic descriptors (e.g. latitude, longitude, precipitation) were used to disentangle land use effects from those of natural drivers of biodiversity. Using a variance partitioning scheme based on boosted regression trees and generalised linear regression modelling, we sought: (i) to partition the unique, shared and unex- plained variation in the metrics explained by both groups of descriptor variables, (ii) to quantify the contribution of each descriptor variable to biodiversity variation in the most parsimonious regression model and (iii) to identify interactions of land use and natural descriptors. The variation in biodiver- sity uniquely described by land use was consistently low across both ecosystem types and organism groups. In contrast, geo-climatic descriptors uniquely, and jointly with land use, explained significantly more variance in all 39 biodiversity metrics tested. Regression models revealed significant interactions between geo-climatic descriptors and land use for a third of the models, with interactions accounting for up to 17% of the model’s deviance. However, no consistent patterns were observed related to the type of biodiversity metric and organism group considered. Subdividing data according to the strongest geo-climatic gradient in each dataset aimed to reduce the strength of natural descriptors relative to land use. Although data sub-setting can highlight land use effects on freshwater biodiversity, sub-setting our data often failed to produce stronger land use effects. There was no increase in spatial congruence in the subsets, suggesting that the observed land use effects were not dependent on the spatial extent of the subsets. Our results confirm significant joint effects of, and interactions between, land use and natural environmental descriptors on freshwater biodiversity, across ecosystem types and organism groups. This has implications for biodiversity monitoring. First, the combined analysis of anthropogenic and natural descriptors is a prerequisite for the analysis of human threats to biodiversity. Second, geo-climatically, but not necessarily geographically more homogeneous datasets can help unmask the role of anthropogenic descriptors. And third, whole community-based biodiversity metrics (including taxon richness) are not ideal indicators of anthropogenic effects on biodiversity at broad scales.

Peer-reviewed. Copyright: © 2016 Woolway et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.PLoS ONE 11(3): e0152466. doi:10.1371/journal.pone.0152466, Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored., This project was funded by OTT Hydrometry Ltd and a University College London impact award awarded to RIW and is part of the Natural Environment Research Council (NERC) Sensor Network project United Kingdom Lake Ecological Observatory Network (UKLEON;NE/I007407/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Diatom species distributions on remote islands are influenced by both habitat quality and location. In this study diatom distributions and water quality were explored in the Falkland Islands archipelago with reference to island floras elsewhere, using 28 freshwater sites (small ponds, shallow lowland lakes, upland tarns and several streams). Site water chemistries varied from strongly acid to circum-neutral and from low to high conductivity and water-colour. Dissolved ions co-varied with conductivity and varied strongly between sites and ion ratios indicated a strong influence of sea-salt deposition. Canonical Correspondence Analysis of the diatom and environmental data revealed three groups of sites, (1) high water-colour and low pH, (2) low conductivity and low water-colour, and (3) high conductivity and higher pH. Diatom species frequency abundances were most strongly influenced by water conductivity and pH. Diatom assemblages were composed of both cosmopolitan and regionally endemic Subantarctic speci...

This paper reports on the conclusions of a workshop dedicated to science and data gaps in EU-funded projects relevant to water resources and water management, where over 25 EU projects were represented. Institutional and financial obstacles to data access for use in modeling exercises were identified, and gaps in scientific knowledge that contribute to uncertainty were highlighted. The paper identifies a number of sectors where these gaps often represent crucial barriers to successful research outcomes, and suggests ways and means of alleviating some of these difficulties. One approach could be through the implementation of policies aimed at ensuring free and unrestricted access to data, especially those generated by the numerous research projects that focus on issues of water availability, quality and management. Another complementary initiative could be the setting up of a centralized ‘‘clearinghouse'' for data exchange between scientists, end-users and policymakers. It is hoped that, if implemented, some of the recommendations formulated in the present paper may help pave the way for a more rapid and efficient production of research results that are of importance for policy guidance at the local, national and supra-national (EU) levels.

14 páginas, 3 figuras, 2 tablas., 1. A survey of c. 350 remote high altitude and high latitude lakes from 12 different mountain regions across Europe was undertaken to explore ecosystem variability, climate forcing, environmental conditions and pollution threats at a scale not previously attempted. 2. Lakes were sampled for a range of contemporary and sub-fossil organisms including planktonic crustaceans, rotifers, littoral invertebrates, chironomids, diatoms and cladocerans. Survey and cartographic data were used to determine environmental characteristics at each site. Organic pollutants and trace metal concentrations were measured in the lake sediment. 3. A number of separate studies were undertaken which examined the environmental characteristics of the surveyed lakes (climate forcing and chemical composition), distribution of biota relative to local, regional and biogeographical factors and pollution threats (acidification, heavy metals and persistent organic pollutants) to these sensitive ecosystems. 4. There is a strong regional element to the way that environmental factors combine (including climate and pollution threats) and the biota responds in mountain lakes across Europe. From a management perspective it is clear that lake classification and the development of useful typologies and assessments of reference conditions should be undertaken at regional rather than pan-European scales. 5. There are some common features across lake districts related to the timing of industrialisation, but the studies carried out on metals, organic pollutants and nitrate deposition indicate that each lake district has distinct pollution threats. Climate warming already affects most of the lake districts and there are considerable uncertainties as to how this will modify conditions in remote European mountain systems. 6. The lake district concept goes beyond a geographical construct and merits further theoretical and experimental development as an ecological concept., Financial support from the EU projects EUROLIMPACS (GOCE-CT-2003-505540) and EMERGE (EVK1- CT-1999-00032) is acknowledged.

P> A survey of c. 350 remote high altitude and high latitude lakes from 11 different mountain regions was undertaken to explore species distribution across Europe at a scale not previously attempted.Lakes were sampled for planktonic crustaceans, rotifers, littoral invertebrates and sub-fossil chironomids, diatoms and cladocerans. Each lake was characterised in terms of water chemistry, morphology, catchment attributes and geographical location.Separate twinspan analyses were undertaken on diatom, chironomid, planktonic crustacean, littoral invertebrate and cladoceran (chydorids only) data to classify sites according to taxonomic composition. For most datasets there was a spatial component to the classification with distinct geographical groups emerging - Norway and Scotland, Finland and Central/Eastern Europe.Constrained ordination methods were employed to examine how species responded to a range of environmental factors, which were aggregated into a series of component groups - proximal environment (the chemical, trophic and physical attributes of the lake), catchment characteristics and geographical location. Several key environmental gradients were identified, which explained significant levels of the variance across several of the biological groups including dissolved organic carbon (chironomids, planktonic crustaceans), temperature (chironomids and littoral invertebrates), chloride/sea-salt (littoral invertebrates, diatoms and rotifers), lake morphology (all groups), calcium/pH (diatoms), nitrate (chydorids, littoral invertebrates, rotifers and planktonic crustaceans) and fish (littoral invertebrates). In some cases these statistical relationships are likely to represent direct ecological constraints and, in others, it is probable that the environmental variable is acting as a surrogate for some other attribute or process.Variance partitioning was undertaken to quantify how much of the variation in each biological group could be uniquely attributed to variables representing the proximal environment, catchment characteristics and geographical location. For most groups the location of the lake tends to explain the greatest variation in species composition across the Lake Districts. The proximal environment was also important but, with the exception of diatoms, secondary to location. Therefore, a strong geographical signal emerged from the analyses. Three distinct limno-regions were identified; Nordic (Scotland and Norway), Sub-Arctic (Northern Finland) and Alpine (Pyrenees, the Alps and Eastern Europe ranges).Our results have implications for the development of regionalisation schemes based on biological responses to environmental gradients; (i) lake 'types' based on environmental factors cannot be extrapolated throughout Europe, even within the relatively narrow gradients found in remote mountain lakes, (ii) biotic response to large-scale variations in environmental conditions, such as those that could be expected with climate change, is likely to vary according to regions because of the biogeographical differences among them.

SUMMARY 1. We carried out a coordinated survey of mountain lakes covering the main ranges across Europe (including Greenland), sampling 379 lakes above the local tree line in 2000. The objectives were to identify the main sources of chemical variability in mountain lakes, define a chemical classification of lakes, and develop tools to extrapolate our results to regional lake populations through an empirical regionalisation or upscaling of chemical properties. 2. We investigated the main causes of chemical variability using factor analysis (FA) and empirical relationships between chemistry and several environmental variables. Weathering, sea salt inputs, atmospheric deposition of N and S, and biological activity in soils of the catchment were identified as the major drivers of lake chemistry. 3. We tested discriminant analysis (DA) to predict the lake chemistry. It was possible to use the lithology of the catchments to predict the range of Ca 2+ and SO4 2) into which a lake of unknown chemistry will decrease. Lakes with lower SO4 2) concentrations have little geologically derived S, and better reflect the variations in atmospheric S loading. The influence of marine aerosols on lakewater chemistry could also be predicted from the minimum distance to the sea and altitude of the lakes. 4. The most remarkable result of FA was to reveal a factor correlated to DOC (positively) and NO3 ) (negatively). This inverse relationship might be the result either of independent processes active in the catchment soils and acting in an opposite sense, or a direct interaction, e.g. limitation of denitrification by DOC availability. Such a relationship has

Mountain regions are cold environments that are hostile to human occupation and widely regarded as places where the air is clean, water is pure and ecosystems are pristine. Yet many mountain regions, especially in Europe, are far from pristine. In the 1980s, research showed that mountain lakes were especially vulnerable to acid deposition and sediment core studies at many sites demonstrated that some mountain lakes had become acidified over the course of the last century. Since then, studies of the water chemistry, biology and history of lakes across the different European mountain regions have increased our understanding of the processes within these systems, their ecological condition and the threats facing them. These studies have demonstrated that: i) gradients of sulphur, nitrogen, metals and persistent organic pollutant deposition occur from relatively uncontaminated regions in Spain and Central Norway to regions of heavy pollution loading in central and eastern Europe;ii) nitrate and sulphate concentrations in lake water reflect the gradients in atmospheric deposition;iii) concentrations of mercury, lead and cadmium in fish tissue show marked regional differences;iv) the spatial pattern of organochlorine concentrations in fish and in sediments follow the pattern for other pollutants, although there is also good evidence for the selective cold trapping of some compounds both at high latitudes and at high altitudes;v) fish suffer physiological stress in mountain lake-water of low ionic strength;vi) climate change over the last century is likely to have induced significant changes in lake ice-cover and water column stratification and mixing in some regions and these have in turn influenced the structure and productivity of biological communities; This paper provides a review of the research undertaken on European mountain lakes over the past 30 years. In particular, it highlights the stresses faced by these vulnerable systems and the effects these have had, continue to have, and are likely to have on mountain lake ecosystems in future.

It is now accepted that some human-induced climate change is unavoidable. Potential impacts on water supply have received much attention, but relatively little is known about the concomitant changes in water quality. Projected changes in air temperature and rainfall could affect river flows and, hence, the mobility and dilution of contaminants. Increased water temperatures will affect chemical reaction kinetics and, combined with deteriorations in quality, freshwater ecological status. With increased flows there will be changes in stream power and, hence, sediment loads with the potential to alter the morphology of rivers and the transfer of sediments to lakes, thereby impacting freshwater habitats in both lake and stream systems. This paper reviews such impacts through the lens of UK surface water quality. Widely accepted climate change scenarios suggest more frequent droughts in summer, as well as flash-flooding, leading to uncontrolled discharges from urban areas to receiving water courses and estuaries. Invasion by alien species is highly likely, as is migration of species within the UK adapting to changing temperatures and flow regimes. Lower flows, reduced velocities and, hence, higher water residence times in rivers and lakes will enhance the potential for toxic algal blooms and reduce dissolved oxygen levels. Upland streams could experience increased dissolved organic carbon and colour levels, requiring action at water treatment plants to prevent toxic by-products entering public water supplies. Storms that terminate drought periods will flush nutrients from urban and rural areas or generate acid pulses in acidified upland catchments. Policy responses to climate change, such as the growth of bio-fuels or emission controls, will further impact freshwater quality.

Climate change is expected to modify rainfall, temperature and catchment hydrological responses across the world, and adapting to these water-related changes is a pressing challenge. This paper reviews the impact of anthropogenic climate change on water in the UK and looks at projections of future change. The natural variability of the UK climate makes change hard to detect; only historical increases in air temperature can be attributed to anthropogenic climate forcing, but over the last 50 years more winter rainfall has been falling in intense events. Future changes in rainfall and evapotranspiration could lead to changed flow regimes and impacts on water quality, aquatic ecosystems and water availability. Summer flows may decrease on average, but floods may become larger and more frequent. River and lake water quality may decline as a result of higher water temperatures, lower river flows and increased algal blooms in summer, and because of higher flows in the winter. In communicating this important work, researchers should pay particular attention to explaining confidence and uncertainty clearly. Much of the relevant research is either global or highly localized: decision-makers would benefit from more studies that address water and climate change at a spatial and temporal scale appropriate for the decisions they make.

After more than a decade of implementation by water managers in all river basins across Europe, the Water Framework Directive (WFD) has now reached a maturity age. However, some significant gaps still remain in the way WFD is implemented, and there is now a need for water managers and scientist to communicate better in order to find scientific solutions to these gaps. To do so, a Science-Policy Interface (SPI) activity was launched in 2010 led by Directorate General (DG) Research and Onema (the French national agency for water and aquatic ecosystems), providing an interactive forum to connect scientists and WFD end-users. One major aim of the SPI activity was to establish a list of most crucial research and development needs for enhancing WFD implementation. The purpose of the present study is to make the synthesis of the proposals made regarding ecological status, for which 10 priority issues were raised. For lakes, temporary streams as well as transitional and coastal waters, WFD implementation still strongly suffer from the lack of WFD-compliant bioassessment methods. For rivers, special attention should now be paid to the ecological impacts of hydromorphological alterations on biological communities, notably those affecting river continuity and riparian covering. Spatial extrapolation tools are needed in order to evaluate ecological status for water bodies not directly surveyed. The need for more functional bioassessment tools as complements to usual WFD-compliant tools, and to clearly connect good ecological state, biodiversity and ecosystem services when implementing WFD have also been identified as crucial issues., JRC.H.1-Water Resources

Summary 1 Anthropogenic nitrogen (N) deposition may have several impacts on upland moorland ecosystems, including changes in vegetation composition, eutrophication and surface water acidification through nitrate leaching, but few studies linking N deposition to key biogeochemical processes have been published. 2 A stable isotope tracer (15N) was used to determine the fate of inorganic N inputs to four moorland catchments across gradients of N deposition and leaching, through 2-weekly additions to experimental plots on major soil types over 1 year. 3 An apparent decline in total 15N recovery from soils and vegetation as the proportion of leached N deposition increased was not significant at the P = 0·05 level, but a significant relationship was found for recovery in mosses and lichens. 4 Vegetation retained 31–68% of 15N inputs, and 15N recovery increased significantly (P = 0·01) with biomass for all compartments except woody shrubs. Mosses and lichens showed far greater 15N recovery per unit biomass than grasses or ericaceous shrubs. There was no significant variation in the proportion of 15N recovered in higher plants across the N deposition gradient (24–29%). In contrast, the proportion recovered in mosses and lichens declined from 44% to 2% as deposition increased, mirroring a decline in their biomass and showing a highly significant inverse relationship (P = 0·01) with nitrate leaching. 5 The proportion of 15N recovered in litter plus surface soils (33–39%) was remarkably constant across the deposition gradient for a variety of soil types. However, significantly declining recovery per unit biomass in litter (P

Previous research has established clear relationshipsbetween the chemical composition of surface waters andthe nature of their contributing catchments. Theserelationships are particularly strong when broadenvironmental gradients are considered. However, forfreshwaters at higher altitudes, some of the catchmentprocesses that mediate chemical composition are lessinfluential than those at lower altitudes. The waterchemistry of 85 upland lochs in Scotland, U.K. is examinedto assess differences in chemical composition along arelatively short altitude gradient. Principal componentsanalysis identifies the main gradients of variationwithin the dataset. A series of digital datasets is usedto characterise the catchments according to a range ofattributes including soils and landcover. Multivariatestatistical analysis is undertaken to examine the extentto which the catchment attributes can explain variationin surface water chemistry in upland systems. Theseempirical relationships may be used in the development ofregionalisation procedures, which will allow upscaling ofknowledge from individual sites to regions.

In this special issue we present papers based on data from the UK's Acid Waters Monitoring Network (UK AWMN) and other UK acid waters. The AWMN was set up in 1988. It was designed to monitor the chemical and biological response of acidified surface waters in the UK to the planned reduction in the emission of acidic sulphur and nitrogen gases as required by the UNECE Convention on Long Range Transboundary Air Pollution. Most papers in the volume are concerned with the changes that have taken place at the 22 AWMN sites during 20 years of monitoring from 1988 to 2008. They show that significant changes in deposition chemistry, in water chemistry and, to a lesser extent, in biology have taken place, consistent with a recovery from acidification. However, when compared with pre-acidification conditions inferred from lake sediment records, the extent of biological recovery so far is shown to be quite limited. The volume also contains papers on other aspects of surface water acidification in the UK. They include evidence for persistent highly acidic conditions of streams in the North York Moors, data from Scotland showing how afforestation is modifying recovery from acidification and the results of chemical speciation modelling in explaining the relationship between acidification and macroinvertebrate species richness at AWMN and other sites in the UK. The final papers are concerned with projections for the future and the extent to which acidified sites will continue to improve. They conclude that recovery will continue albeit slowly during this century but that other pressures principally from climate and land-use change are likely to alter the recovery pathways towards novel ecological endpoints potentially quite different from past baselines.

Climate change is expected to profoundly affect both temperature and net precipitation, with implications for lake water level. We describe the design of a harmonized, simultaneous, cross- European mesocosm experiment to elucidate the effects of climate change on community structure, functioning, and metabolism in shallow lakes at low and high nutrient levels with contrasting depths (1 and 2 m). We used cylindrical (D = 1.2 m) tanks that were either 1.2 or 2.2 m high, each having a 10-cm sediment layer. We inoculated the mesocosms with a mixed sample of sediment and plankton from lakes with contrasting nutrient concentrations and added macrophytes and planktivorous fish. Sediment was pre-equilibrated to the required experimental nutrient concentration. During the experiment the water level decreased with increasing temperature (up to 90 cm in the Mediterranean mesocosms) while conductivity increased. The average chlorophyll a concentration increased with temperature in the deep mesocosms but was more variable in the shallow mesocosms. Macrophyte

In the UK the “critical loads” approach has been used to derive maps based on the 10km x 10km national grid. However, this grid based approach is inappropriate for catchment scale management and these maps cannot be used for “stock at risk” assessments of the number of water bodies or lengths of streams in a given area that may be vulnerable to acidification. Critical loads are determined across two large river catchments in England (The Duddon) and Wales (The Glaslyn). High resolution, digital datasets are used to characterise the attributes of each subcatchment in terms of land cover, soil, geology, topography and topology. Empirical models used to examine the relationship between these attributes and critical loads indicate that the former can be used to account for significant variation in the latter. However, these relationships can vary from catchment to catchment. Thus, although this approach provides the potential for identifying sensitive surface waters on a catchment wide basis, it is likely that models will need to be parameterised on a catchment specific basis.

A method of decomposing the variation in the acid neutralizing capacity (ANC) of surface waters in Scotland is described. Using national datasets, a series of variables relating to 703 catchments across Scotland is divided into three components representing (i) land cover, (ii) soil and (iii) atmospheric deposition/altitude. Redundancy analysis (RDA) and (partial) redundancy analysis are used to quantify the amount of variation in ANC uniquely attributable to each of these components, independent of the effects of the others. The variation accounted for by covarying combinations of these components is also determined. Approximately 55% of the total variation in ANC across the 703 sites is explained by the variables representing catchment characteristics and atmospheric deposition. Of this, 8.5%, 2.4% and 6.9% are uniquely attributable to the land cover, soil and deposition/altitude components, respectively. A further 38% of ANC variation is associated with the covariation between components, with 18% accounted for by the combination of all three. Approximately 45% of the variation in ANC remains unexplained. The results reflect the integrated nature of catchment processes and demonstrate, for these data, that it is a combination of land cover, soil and deposition and altitude factors which most explain variation in freshwater ANC level. The approach offers a tool with which to assess the sensitivity of surface waters to acid deposition at a regional scale and provides a way of identifying regional differences in catchment response to acid loading.

Maps of freshwater critical loads are used toguide emission strategies for sulphur and nitrogen bothnationally and internationally. Water chemistry data arerequired to calculate critical loads and the production ofnational maps therefore relies on the existence of extensivechemistry datasets. However, the data required to calculatecritical loads are not readily available for all sites. Thisarticle explores how empirical statistical models mightpotentially be used to predict critical loads using nationallyavailable datasets representing a range of catchmentcharacteristics. Initially a global regression model forexplaining freshwater critical load variation across a broadspectrum of catchment types (from lowland agricultural tomountain lakes) throughout mainland Britain is described. Whenattention is focused on more specific catchment types (i.e.upland and non-arable) it is shown that the global model hasless explanatory power. A regionalisation of Great Britain(based on 100 km grid squares) shows that the global modelcannot necessarily be applied successfully within a narrowerregional context. Separate analyses were undertaken on each ofthe regional subsets using backward selection regression. Thevariables emerging as significant predictors variedsubstantially across the regions, as did the explanatory powerof the models. This was also the case when the analysis wasconfined to upland and non-arable catchments. This approachcould be developed so that critical loads assessments can bemade for populations of standing waters rather than simplythose for which water chemistry is available.

Current applications of the critical loads concept are geared primarily toward targeting emission control strategies at a national and international level. Maps of critical loads for freshwaters have been produced in grid form based on water samples of representative sites within each grid square. However, the water chemistry data required to calculate freshwater critical loads are not always readily available at a national level and maps are therefore limited to catchments where such data exist. This paper describes the development of an approach that uses nationally available secondary data to predict freshwater critical loads for catchments lacking the appropriate water chemistry information. An empirical statistical model is calibrated using data from 78 catchments throughout Scotland. Water chemistry for each catchment has been determined. Each catchment is characterized according to a number of attributes. Redundancy analysis of these data shows clear relationships between catchment attributes and the critical load derived from the water chemistry. The key variables that explain most of the variation in critical load relate to soil, geology and land use within the catchment. Using these variables as predictors in a regression analysis, the critical load can be predicted across a broad gradient of sensitivity (R2adj=0.81). The predictive power of the model was maintained when different combinations of explanatory variables were used. This accords the approach a degree of flexibility in that model parameterization can be geared toward availability of secondary data. There are limitations with the model as presently calibrated. However, the approach offers considerable scope for environmental managers to undertake national inventories of catchment sensitivity and specific assessments of individual catchments.

This article considers the interactions between climate change and other drivers of change including hydromorphological modification, acid deposition, contamination by toxic substances using evidence from laboratory experiments, field experiments, and modeling. This article evaluates these processes in relation to extreme events, seasonal changes, in ecosystems, trends over the decades, mitigation strategies, and ecosystem recovery. Aspects of hydrophysical, hydrochemical, and ecological change can be used as early indicators of climate change in aquatic ecosystems and it addresses implications for the future climate change for freshwater ecosystems management at the catchment scale Keywords: climate change; freshwater; acidifcation; restoration; pollutants

Earth’s climate is changing, and by the end of the 21st century in Europe, average temperatures are likely to have risen by at least 2 °C, and more likely 4 °C, with associated effects on patterns of precipitation and the frequency of extreme weather events. Attention among policy-makers is divided about how to minimise the change, how to mitigate its effects, how to maintain the natural resources on which societies depend and how to adapt human societies to the changes. Natural systems are still seen, through a long tradition of conservation management that is largely species-based, as amenable to adaptive management, and biodiversity, mostly perceived as the richness of plant and vertebrate communities, often forms a focus for planning. We argue that prediction of particular species changes will be possible only in a minority of cases but that prediction of trends in general structure and operation of four generic freshwater ecosystems (erosive rivers, depositional floodplain rivers, shallow lakes and deep lakes) in three broad zones of Europe (Mediterranean, Central and Arctic- Boreal) is practicable. Maintenance and rehabilitation of ecological structures and operations will inevitably and incidentally embrace restoration of appropriate levels of species biodiversity. Using expert judgement, based on an extensive literature, we have outlined, primarily for lay policy makers, the pristine features of these systems, their states under current human impacts, how these states are likely to alter with a warming of 2 °C to 4 °C and what might be done to mitigate this. We have avoided technical terms in the interests of communication, and although we have included full referencing as in academic papers, we have eliminated degrees of detail that could confuse broad policy-making

15 páginas, 4 figuras, 4 tablas., High mountain lakes are sensitive to environmental change and the effects of air pollution and lake acidification have been recorded in many countries. The EU funded EMERGE programme included a pan-European assessment of the extent of acidification in mountain lakes located above the tree-line. A static critical loads model, the First-order Acidity Balance (FAB) model, was used to assess (1) the extent of critical load exceedance in 300 lakes in nine European lake districts and (2) the relative importance of sulphur and nitrogen deposition in contributing to acidification. The regional sensitivity of FAB to the choice of critical acid neutralising capacity (ANC: 0 or 20 meq L–1) was explored. With a critical ANC value of 0 meq L–1 only four lake districts had sites showing exceedance of critical loads; Piedmont Aquat. Sci. 67 (2005) 237–251 1015-1621/05/030237-15 DOI 10.1007/s00027-005-0742-0 © EAWAG, Dübendorf, 2005 Aquatic Sciences Ticino, the Pyrenees, the Retezat Mountains and the Tatras. When a more stringent critical ANC of 20 meq L–1 was used, all nine lake districts showed critical load exceedance in one or more lakes. For two lake districts, the Retezat Mountains of Romania and the Rila Mountains of Bulgaria, critical load exceedance is recorded here for the first time. Nitrogen is a more important agent of acidification in some areas such as the Pyrenees and Piedmont Ticino, and its relative importance is likely to increase elsewhere as pan-European measures to reduce sulphur deposition continue to take effect. Given the coarse scale deposition data used and potentially underestimated loads at high altitudes, the extent of the acidification problem may be under-represented here., This work was funded under the EU EMERGE Programme (EVK1-CT-1999-00032).

11 páginas, 5 tablas, 5 figuras., The integrated assessment models that drive atmospheric pollutant emission reduction policies within Europe, under the Convention on Long-range Transboundary Air Pollution, work at the scale of the EMEP grid (50 ¥ 50 km). Critical loads are used to link anthropogenic deposition to adverse effects for individual ecosystems within each grid cell. The critical loads have two aspects, ecosystem area and the ecosystem specific critical load. The presence of highly acid-sensitive ecosystems within these grid cells can lead to very low critical loads of acidity which provide emission targets that are difficult to achieve: these cells are known as “binding grid squares”. Since mountain lakes are highly sensitive to environmental change, their inclusion in critical loads assessments might be expected to result in lower EMEP scale critical loads. The combination of mountain lakes data with those from other ecosystems already included Aquat. Sci. 67 (2005) 252–262 1015-1621/05/030252-11 DOI 10.1007/s00027-005-0743-z © EAWAG, Dübendorf, 2005 Aquatic Sciences in the integrated modelling shows unexpected results. The average accumulated exceedance of critical loads of acidity may increase with either the presence of significant mountain lake catchment areas within grid cells or the presence of highly acidified clusters of sites. These circumstances occur in only a small number of grid cells. Furthermore, the relatively low sensitivity of mountain lakes to acidification in some regions means that their inclusion in EMEP scale models would lead to a relaxation of emission abatement requirements because of an increase in the area of ecosystems not exceeding critical loads and a decrease in AAE. Hence the potential effects of the inclusion of mountain lake critical loads of acidity in EMEP scale models vary greatly on a regional basis. The assumption that mountain lakes data could increase the incidence of “binding grid squares” is found to be unlikely., This work was funded under the EU EMERGE Programme (EVK1-CT-1999-00032).

Previous attempts to identify regions of Britain vulnerable to acidification have used sensitivity maps based on the distribution of soils, geology, and land cover across Great Britain. Additionally, a systematic survey of freshwaters undertaken as part of the U.K. critical loads mapping programme provides a regional assessment of both sensitivity (critical loads) and, in tandem with deposition data, potential impact (critical load exceedance). Both approaches, while useful for identifying regional patterns, do not enable estimates of the number of affected water bodies to be made. Recent EU legislation (e.g., The Water Framework Directive) requires member states to set water quality objectives for all water bodies. We developed a GIS-based inventory of standing water bodies in response to the need for legislation-driven assessments of the status of the U.K. lake population. This paper describes how the inventory can be used to assess the number of standing water bodies in Britain that are vulnerable to acid deposition (at current levels), building on the sensitivity mapping undertaken previously. Using this approach, approximately 31% of all standing waters in Great Britain (excluding the Shetlands and orkney) larger than 0.02 ha are identified as ‘at risk’ from acidification. Higher proportions are vulnerable in Scotland and Wales. Additionally, large numbers of standing waters in areas designated for environmental protection purposes are also vulnerable.

An inventory of standing waters (freshwater lakes and lochs) was derived from ordnance Survey digital map data at a scale of 1:50 000 and represents the most comprehensive survey of its kind for Great Britain. The inventory includes 43 738 water bodies in England, Scotland, Wales and the Isle of Man and contains basic physical data such as location, surface area, perimeter and altitude. Catchment areas were computed for water bodies with a surface area larger than 1 ha from a digital terrain model (DTM) using customised routines in a geographical information system (GIS). The resulting polygons were then used to derive catchment-related information from a variety of national datasets including population density, livestock density, land cover, solid and drift geology, meteorological data, freshwater sensitivity status, acid deposition and conservation status. Using data derived from the inventory a risk-based prioritisation protocol was developed to identify standing waters at risk of harm from acidification and eutrophication. This information is required by the Environment Agency, Scottish Environmental Protection Agency and the U.K. statutory conservation bodies to co-ordinate actions and monitor change under international, European and national legislation.

Critical loads are used in international negotiations to reduce acid deposition resulting from emissions of sulphur and nitrogen compounds within Europe. For freshwater ecosystems, the First-order Acidity Balance (FAB) model is used to generate national maps of critical loads and exceedances for both sulphur (S) and nitrogen (N). In Wales, two survey datasets have been used to calculate critical loads and exceedances; one based on water bodies selected to be “mostsensitive” to acidification within a 10 km grid and the other based on a random selection of standing waters. Both datasets indicate that critical loads were exceeded in 1990 in a significant proportion of Welsh lakes and streams; 36% of sites in the grid-basea survey and 31% of sites in the random survey. However, implementation of the Gothenburg Protocol would protect all but 6% of sites in the grid-based survey and all sites in the random survey. Assessment of the relative success of the Gothenburg Protocol in protecting Welsh freshwater ecosystems therefore depends on the site selection strategy employed.

Environmental organisations in the UK have shown increasing interest in freshwater critical loads and acid sensitivity maps as a means of assessing pollution at the local and regional level. These maps can be used to identify sensitive areas when considering catchment management plans. The use of national data sets to map the sensitivity of freshwaters to acidification, highlighted the problems of relating national datasets to smaller, localised areas. The study described here investigated the use of detailed large-scale maps to predict the sensitivity of surface waters to acidification for two river catchments. Three large-scale acid sensitivity maps were produced and validated using measured freshwater critical loads. In addition, a score system relating to the buffering capacity for each soil and geology type was devised. The score value was found to have a better correlation with water chemistry and freshwater critical loads than the acid sensitivity maps. The study concluded that it was not necessary to use the largest scale data available in order to improve predictions of sensitive areas.

13 páginas, 10 figuras, 1 tabla., Baseline and historical environmental data are sparse in high-altitude regions. Diatom assemblages preserved in lake sediment records can, however, provide proxy data of past environmental and biological conditions. Sediment cores were retrieved from 209 high altitude lakes from 11 countries in Europe. Diatoms were extracted and counted from surface-sediment samples and sediments representing pre-industrial conditions. Regional changes in diatom assemblages covering at least the last c. 150 years are discussed and quantified using ordination techniques and dissimilarity indices. Distinct changes in diatom composition are identified and regional patterns highlighted, with two lake regions showing particularly large changes in diatom composition (Central Swiss Alps and the Pyrenees). Several driving Aquat. Sci. 67 (2005) 224–236 1015-1621/05/030224-13 DOI 10.1007/s00027-004-0745-2 © EAWAG, Dübendorf, 2005 Aquatic Sciences mechanisms that might have caused the changes in the diatom community are discussed. Pre-industrial and present-day lake-water pH are inferred from the diatom assemblages and their prediction accuracy compared to contemporary water-chemistry measurements for each lake. Regional pH changes are minimal with no lake region exceeding 0.27 pH units of change in the period covering the last c. 150 years. The majority of lakes studied show an increase in planktonic diatom species over the period covering the past c. 150 years. We hypothesise that changes in the ratio of planktonic to non-planktonic diatoms within the study lake-regions are related to changes in climate and to associated changes in nutrients, ice-cover and erosion caused by climate warming., This research is part of the EMERGE Framework 5 project, supported by the European Union.

The dynamic model MAGIC is used to predict the future response of surface waters to reductions in S deposition as stipulated by the recently agreed emission protocol (the 1999 Gothenburg Protocol). MAGIC was calibrated to 30 sites in the Scottish mountains with the best available soil and deposition data derived from large scale spatial datasets, and surface water chemistry from a regional loch survey conducted in October 2000. A comparison of input parameters and model responses are made at Lochnagar, a site for which detailed, high resolution spatial/temporal data exist. The model is capable of reproducing observed trends in non-marine SO4 2-, however simulated NO3 - from 1990 to 2000 is lower than the observed trends at Lochnagar due to possible hydrological controls and in-lake processes, rather than terrestrial processes. The Scottish Highlands are remote from emission sources and consequently peak deposition inputs of S in the 1980s are relatively low (33 kg S ha-1 y-1) compared to other regions in Europe. Nonetheless the amount of deposition appears sufficient to cause environmental damage in this acid sensitive region. During the 1980s, simulated Acid Neutralising Capacity (ANC) of 13% of the modelled lakes was