Burthe, Sarah J.; Henrys, Peter A; Mackay, Eleanor B.; Spears, Bryan M.; Campbell, Ronald; Carvalho, Laurence; Dudley, Bernard; Gunn, Iain D.M.; Johns, David G.; Maberly, Stephen C.; May, Linda; Newell, Mark A.; Wanless, Sarah; Winfield, Ian J.; Thackeray, Stephen J.; Daunt, Francis. 2016. Do early warning indicators consistently predict nonlinear change in longterm ecological data? Journal of Applied Ecology, 53 (3). 666-676. 10.1111/1365-2664.12519

Summary Anthropogenic pressures, including climate change, are causing nonlinear changes in ecosystems globally. The development of reliable early warning indicators (EWIs) to predict these changes is vital for the adaptive management of ecosystems and the protection of biodiversity, natural capital and ecosystem services. Increased variance and autocorrelation are potential early warning indicators and can be readily estimated from ecological time series. Here, we undertook a comprehensive test of the consistency between early warning indicators and nonlinear abundance change across species, trophic levels and ecosystem types. We tested whether long‐term abundance time series of 55 taxa (126 data sets) across multiple trophic levels in marine and freshwater ecosystems showed (i) significant nonlinear change in abundance ‘turning points’ and (ii) significant increases in variance and autocorrelation (‘early warning indicators’). For each data set, we then quantified the prevalence of three cases: true positives (early warning indicators and associated turning point), false negatives (turning point but no associated early warning indicators) and false positives (early warning indicators but no turning point). True positives were rare, representing only 9% (16 of 170) of cases using variance, and 13% (19 of 152) of cases using autocorrelation. False positives were more prevalent than false negatives (53% vs. 38% for variance; 47% vs. 40% for autocorrelation). False results were found in every decade and across all trophic levels and ecosystems. Time series that contained true positives were uncommon (8% for variance; 6% for autocorrelation), with all but one time series also containing false classifications. Coherence between the types of early warning indicators was generally low with 43% of time series categorized differently based on variance compared to autocorrelation. Synthesis and applications. Conservation management requires effective early warnings of ecosystem change using readily available data, and variance and autocorrelation in abundance data have been suggested as candidates. However, our study shows that they consistently fail to predict nonlinear change. For early warning indicators to be effective tools for preventative management of ecosystem change, we recommend that multivariate approaches of a suite of potential indicators are adopted, incorporating analyses of anthropogenic drivers and process‐based understanding.

The spatial and seasonal dynamics of surface water fluxes of the greenhouse gases (GHG) CO2, CH4, and N2O were quantified in the Tay estuary, Scotland, on seven sampling occasions every 3 months during 2009/2010. This estuary is a relatively pristine river-dominated macrotidal estuary system of a type that is sparsely represented in global GHG flux studies. Significant spatial and temporal variability in GHG fluxes were measured, with similar spatial dynamics to that of other European estuaries. Greatest temporal and spatial variability in gas saturations were found for CH4, which was higher in the summer, with peaks in saturation occurring in the freshwater upper estuary and sharply decreasing in the midestuary mixing zone. Concentrations of CO4 and N2O were also generally higher in the upper to middle estuary in summer, although seasonality was less pronounced. Estimated air-sea fluxes also displayed significant spatial and temporal variability. Total annual CO2 emissions were greatest in the middle estuary zone (13.8 x 10(6) kg C yr(-1)), and lowest in the upper estuary (1.52 x 10(6) kg C yr(-1)). Seasonally, the highest CO2 emissions integrated across the estuary were in spring and autumn, with the lowest in winter. Total annual CH4 emissions were also highest in the middle estuary (0.05 x 10(6) kg C yr(-1)) and lowest in the upper estuary (0.01 x 10(6) kg C yr(-1)), whereas total N2O emissions, whilst highest in the middle estuary (2344 kg N yr(-1)), were lowest in the outer estuary (-435 kg N yr(-1)). Emissions of CH4 and N2O were substantially higher in the summer than any other season and lowest emissions were found in winter. The estimated annual exchange of both CO2 and N2O is substantially lower than those reported in other European macrotidal estuaries. (C) 2014 Elsevier Ltd. All rights reserved.

Lakes across the world are suffering from anthropogenically induced nutrient enrichment problems and many attempts are being made to improve their water quality and ecosystem function. Most metrics that are being used to monitor recovery are based on relationships that have been established across a range of lakes. These may not respond quickly to in-lake changes in water quality when nutrient management strategies are put in place. This paper uses data routinely collected from Loch Leven, UK, to examine the immediate and longer-term responses of the rotifer community to a 60% reduction in phosphorus input from the catchment in the early 1990s. We conclude that changes in rotifer abundance and relative species composition are sensitive indicators of lake-specific changes in water quality, responding more quickly than more widely used metrics, such as total phosphorus and chlorophyll a concentrations. However, like all indicators of change, such indices must be used with care in situations where rotifer populations are subject to multiple stressors.

The European Water Framework Directive adopted in 2000, despite being prescriptive, has stimulated the development of a diverse array of biological assessment methods in Europe. The multitude of indicators currently used in biomonitoring lacks consistency and thus constrains the comparability of assessments at an international scale. Therefore, there is an argument to define and validate metrics with more universal application that can be applied EU-wide. We explored two metrics based on macrophyte taxonomic composition, the empirically based Intercalibration Common Metric for lake macrophytes (ICMLM) and the expert-based Ellenberg Index (EI), for their ability to detect eutrophication in different types of European lowland lakes. Data from 1474 unique lake-years from 11 countries were used to explore relationships between these metrics and the seasonal mean concentration of total phosphorus (TP) using linear regression.ICMLM gave a linear and relatively strong (R = 0.72, p < 0.0001) response over the entire spectrum of TP concentrations, whereas EI performed best in lakes with the TP concentrations up to 250 mu g L-1 (R = 0.64, p < 0.0001) and was largely insensitive to higher phosphorus concentrations. Both metrics performed better in Nordic lakes than in the Central-Baltic ones. The responses of both metrics to TP were not modified or only very weakly modified by altitude, lake size and mean depth but were significantly affected by alkalinity. The ICMLM-TP relationship was stronger in lakes with water alkalinity > 0.2 meq L-1 and significantly weaker in less buffered lakes. EI performed better in lakes with alkalinity <1.0 meq L-1, whereas in high alkalinity lakes the response was significantly weaker. In all the lakes and in lakes from all the size, depth and alkalinity types, ICMLM was more strongly correlated with TP than EI and was proportionally less sensitive to alkalinity.We also tested the effect of including helophytes on the metric response to eutrophication pressure by comparing the strength of the relationships to TP of the Ellenberg Index calculated firstly using only hydrophyte taxa (EI'(HYDR)) and secondly using all macrophyte taxa including both hydrophytes and emergent vegetation (EI'(TOT)). The differences in metric performance in all the lakes and all the size, depth and alkalinity types, except for the Nordic lakes, were non-significant. Thus, including helophytes generally did not significantly improve the strength of the EI-TP relationships. (C) 2014 Elsevier Ltd. All rights reserved.

A special issue of the scientific journal Hydrobiologia was published this week, bringing together some of the research from the EU’s WISER project which looked at improving methods to assess the ecological status and recovery of water bodies in Europe. The Centre for Ecology & Hydrology (CEH) was one of 25 European research institutions from 19 countries involved in the three-year project, and Dr Laurence Carvalho, a freshwater ecologist at CEH, is a guest editor on the new special issue. The issue brings together 31 papers, with ten featuring authors from CEH. They look at topics covering new biological metrics for assessing the ecological status of lakes, including phytoplankton, macrophytes and fish; uncertainties in these assessments in relation to the amount of sampling effort; recovery processes in rivers, lakes and coastal waters and the processes and opportunities with managing large environmental datasets. Dr Carvalho said, This special issue synthesises a great deal of new ecological understanding of how freshwater and coastal organisms respond to pressures in our environment and how we now use this science to monitor the health of European waters. This work is enabling the limited resources available for restoring freshwaters to be more effectively targeted, for the benefit of biodiversity and for all the important services that we gain from freshwaters, a cleaner water supply and a healthier environment for recreation. The WISER project, established to support the implementation of the Water Framework Directive, was coordinated by the University of Duisberg-Essen and concluded in 2012. Key findings, reports, databases, software and other deliverables can be found on the WISER website. http://www.ceh.ac.uk/news/news_archive/WISER-methods-water-bodies-special-issue_2013_10.html

Phytoplankton constitutes a diverse array of short-lived organisms which derive their nutrients from the water column of lakes. These features make this community the most direct and earliest indicator of the impacts of changing nutrient conditions on lake ecosystems. It also makes them particularly suitable for measuring the success of restoration measures following reductions in nutrient loads. This paper integrates a large volume of work on a number of measures, or metrics, developed for using phytoplankton to assess the ecological status of European lakes, as required for the Water Framework Directive. It assesses the indicator strength of these metrics, specifically in relation to representing the impacts of eutrophication. It also examines how these measures vary naturally at different locations within a lake, as well as between lakes, and how much variability is associated with different replicate samples, different months within a year and between years. On the basis of this analysis, three of the strongest metrics (chlorophyll-a, phytoplankton trophic index (PTI), and cyanobacterial biovolume) are recommended for use as robust measures for assessing the ecological quality of lakes in relation to nutrient-enrichment pressures and a minimum recommended sampling frequency is provided for these three metrics.

Analysis of phytoplankton data from about 1,500 lakes in 20 European countries has revealed that two-thirds of the species that dominate lakes during the summer are dominant right across Europe. Using Canonical Correspondence Analyses, we have examined how both habitat conditions within lakes and environmental factors over broad geographical scales explained the distribution of the 151 most common summer dominant species. The distributions of these species were best explained by water colour and latitude, although alkalinity and total phosphorus also appeared to be important explanatory factors. Contrary to our original hypothesis, summer water temperatures had a negligible impact on the distribution of dominants, although, due to the restricted summer season we examined, only a limited temperature gradient was present in the dataset. Cryptophytes occurred more frequently among dominants in Northern Europe whereas cyanobacteria and dinophytes dominated more in Central and Southern Europe. Our analyses suggest that besides nutrient concentrations, other water chemistry variables, such as alkalinity and the content of humic substances, have at least as important a role in determining the distribution of the dominant phytoplankton species in European lakes.

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTGeo-Engineering in Lakes—A Call for ConsensusBryan M. Spears*†, Bernard Dudley†, Kasper Reitzel‡, and Emil Rydin§View Author Information† Centre for Ecology and Hydrology in Edinburgh, Penicuik, Midlothian, Scotland, UK EH26 0QB‡ Institute of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark§ Erken Laboratory, Department of Ecology and Genetics, Uppsala University, Norrtälje, Sweden*E-mail: [email protected]Cite this: Environ. Sci. Technol. 2013, 47, 9, 3953–3954Publication Date (Web):April 24, 2013Publication History Published online24 April 2013Published inissue 7 May 2013https://doi.org/10.1021/es401363wCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2050Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-AlertsSUBJECTS:Water treatment Get e-Alerts

The implementation of the Water Framework Directive has required intense research in applied aquatic ecology in Europe, and thus created challenges for data management in international research projects. In the project Waterbodies in Europe: Integrative Systems to assess Ecological status and Recovery (WISER), biological and environmental data from rivers, lakes, transitional and coastal waters in 26 European countries were collated. More than one million records of biological observations were stored in the project's central database, representing phytoplankton, macrophytes, macroalgae, angiosperms, phytobenthos, invertebrates and fish. The central database includes new data from the WISER field campaign in lakes and transitional/coastal waters during 2009–2010 (more than 6,000 biological samples from 58 waterbodies in 14 countries). The purpose of this paper is to provide an overview of the data collated within WISER, in order to facilitate future re-use of these data by other scientists. More specifically, the objectives are to (1) describe the data management in WISER, (2) describe the structure and content of the WISER central database and (3) share experiences and give recommendations for data management in large ecological research projects.

In ecological sciences, the role of metadata (i.e. key information about a dataset) to make existing datasets visible and discoverable has become increasingly important. Within the EU-funded WISER project (Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery), we designed a metadatabase to allow scientists to find the optimal data for their analyses. An online questionnaire helped to collect metadata from the data providers and an online query tool http://www.wiser.eu/results/metadatabase/) facilitated data evaluation. The WISER metadatabase currently holds information on 114 datasets (22 river, 71 lake, 1 general freshwater and 20 coastal/transitional datasets), which also can be accessed by external scientists. We evaluate if generally used metadata standards (e.g. Darwin Core, ISO 19115, CSDGM, EML) are suitable for such specific purposes as WISER and suggest at least the linkage with standard metadata fields. Furthermore, we discuss whether the simple metadata documentation is enough for others to reuse a dataset andwhy there is still reluctance to publish both metadata and primary research data (i.e. time and financial constraints, misuse of data, abandoning intellectual property rights). We emphasise that metadata publication has major advantages as it makes datasets detectable by other scientists and generally makes a scientist's work more visible.

Eutrophication is the most widespread pressure impacting on lakes worldwide and, in general, its control is underpinned by the premise that algal biomass is regulated by phosphorus availability. This paper aims to demonstrate that not all lakes will conform to the underlying principle of the Chl:TP relationships using variables collected widely in lake monitoring programmes across the world (i.e. total phosphorus (TP) and chlorophyll a (Chl) concentrations). The ratio of annual mean Chl and TP concentrations in 94 lakes (2007 and 2008) was used as a measure of the efficiency with which TP is transferred into algal biomass (i.e. as an indicator of P limitation) to investigate the validity of the phosphorus reduction approach. Chl:TP ratios ranged from 0.02 to 0.84 in 2007 and from 0.03 to 0.96 in 2008. Chl and TP values were positively correlated (p < 0.05) with alkalinity, and negatively correlated with depth and surface area, in both years. In general, mean annual Chl and TP concentrations increased as alkalinity increased and depth decreased. However, Chl:TP ratio was highest in high alkalinity lakes in 2007, and moderate alkalinity lakes in 2008. Our results indicate that the use of TP water quality targets alone is insufficient to accurately manage eutrophication pressures at the lake specific scale, and that a wider range of ecological and ecosystem service evaluation targets would provide a more comprehensive assessment of management needs. The wide range of Chl:TP ratio values reported in this study suggests that, although reducing TP concentrations in lakes is undoubtedly a sensible approach to eutrophication management in many cases, TP reductions alone may not result in the expected reductions in phytoplankton biomass in all lakes.

There is an acknowledged need among stakeholders that new hydromorphological metrics are required to facilitate site remediation and for reporting at national and European levels. Pressure/ impact data were assembled from across Europe. The task was challenging, but useful information was gathered. For each major hydromorphological pressure, the physical response gradients of rivers was summarised as diagnostic diagrams. For the first time we provide evidence that metrics indicating HYMO impact could be developed from monitoring data on fish and macrophytes. For the first time we demonstrate the potential to derive metrics sensitive to fine sediment. We provide evidence that phytobenthos (diatoms), invertebrates and macrophytes have the potential to be used in combined metrics. We found that many existing macroinvertebrate metrics lack specificity and can provide false positive responses to HYMO pressure, suggesting that disentanglement of multi-stressor responses is critical to good diagnosis. There is evidence that aquatic habitats protected under the Habitats Directive will be increasingly vulnerable to hydrological pressures with the changing climate. Frequently, overlooked topics such as sediment quality and groundwater issues ought to supplement or be included in HYMO assessments due to their potential for explaining variance in biological datasets. Land-use data on a spatial scale beyond the reach scale (corridor and catchment) relates to site-specific macroinvertebrate metrics and could be a more robust way of assessing impacts.

Lake phytoplankton are adopted world-wide as a sensitive indicator of water quality. European environmental legislation, the EU Water Framework Directive (WFD), formalises this, requiring the use of phytoplankton to assess the ecological status of lakes and coastal waters. Here we provide a rigorous assessment of a number of proposed phytoplankton metrics for assessing the ecological quality of European lakes, specifically in response to nutrient enrichment, or eutrophication, the most widespread pressure affecting lakes. To be useful indicators, metrics must have a small measurement error relative to the eutrophication signal we want them to represent among lakes of different nutrient status. An understanding of variability in metric scores among different locations around a lake, or due to sampling and analytical variability can also identify how best this measurement error is minimised.To quantify metric variability, we analyse data from a multi-scale field campaign of 32 European lakes, resolving the extent to which seven phytoplankton metrics (including chlorophyll a, the most widely used metric of lake quality) vary among lakes, among sampling locations within a lake and through sample replication and processing. We also relate these metrics to environmental variables, including total phosphorus concentration as an indicator of eutrophication.For all seven metrics, 65-96% of the variance in metric scores was among lakes, much higher than variability occurring due to sampling/sample processing. Using multi-model inference, there was strong support for relationships between among-lake variation in three metrics and differences in total phosphorus concentrations. Three of the metrics were also related to mean lake depth. Variability among locations within a lake was minimal (<4%), with sub-samples and analysts accounting for much of the within-lake metric variance. This indicates that a single sampling location is representative and suggests that sub-sample replication and standardisation of analyst procedures should result in increased precision of ecological assessments based upon these metrics.For three phytoplankton metrics being used in the WFD: chlorophyll a concentration, the Phytoplankton Trophic Index (PTI) and cyanobacterial biovolume, >85% of the variance in metric scores was among-lakes and total phosphorus concentration was well supported as a predictor of this variation. Based upon this study, we can recommend that these three proposed metrics can be considered sufficiently robust for the ecological status assessment of European lakes in WFD monitoring schemes. (C) 2012 Elsevier Ltd. All rights reserved.