A fish-based index for the assessment of the ecological quality of temperate lakes

A fish – based index for the assessment of the ecological quality of natural temperate lakes was developed, in accordance to the requirements of the Water Framework Directive (WFD) 2000/60/EC. As a case study, 11 natural lakes located at northern and western Greece were selected. Fish surveys were conducted during mid summer to mid autumn in 2010, 2011 and 2012 using Nordic gillnets and electrofishing. Environmental parameters and anthropogenic pressures were assessed for each lake. Fish species richness, abundance, trophic, reproductive and habitat functional guilds were used for extracting a set of 107 metrics, meeting the requirements of the WFD. All metrics were initially tested as candidates for the index development. A stepwise linear regression of each metric against environmental parameters (lake area, altitude, maximum depth, alkalinity) and anthropogenic pressures (drainage area covered by non-natural land uses – NNLC, water total phosphorus concentrations – TP, Lake Habitat Modification Score – LHMS) was initially conducted for ensuring pressure-response relationships. Reference conditions for each lake were estimated by the hindcasting procedure and the ecological quality for each lake was expressed as the ecological quality ratio (EQR) by a value ranging from 0 (poor quality) to 1 (excellent quality). Two fish fauna metrics, the relative numerical abundance of introduced species (Introduced_a) and the relative biomass of omnivorous species (OMNI_b) were finally extracted as the most significant, responding to LHMS and TP, respectively. The final index was expressed as the mean values of the EQRs of these two metrics. The multimetric fish index presented herein could serve as a tool for assessing the ecological quality of natural lakes at broad geographical scale and generally, in the Mediterranean temperate lakes with similar hydromorphological characteristics.     

Reference conditions and WFD compliant class boundaries for phytoplankton biomass and chlorophyll-a in Alpine lakes

The intercalibration (IC) exercise is a key element in the implementation of the Water Framework Directive (WFD) in Europe. Its focus lies on the harmonization of national classification methods to guarantee a common understanding of ‘Good Ecological Status’ in surface waters. This article defines reference conditions and sets class boundaries for deep (mean depth >15 m, IC lake type L-AL3) and moderately deep (mean depth 3–15 m, IC lake type L-AL4) Alpine lakes >0.5 km². Data were collated from each of the five EU member states included in the Alpine Geographical Intercalibration Group (Alpine GIG: Austria, France, Germany, Italy and Slovenia). Hydro-morphological, chemical and biological data from 161 sites (sampling stations) in 144 Alpine lakes over a period of seven decades were collated in a database. Based on a set of reference criteria, 18 L-AL3 and 13 L-AL4 reference sites were selected. Reference conditions were defined using a combined approach, based on historical, paleolimnological and monitoring data in conjunction with trophic modelling and expert judgement. Reference values and class boundaries were set for annual mean total biomass (biovolume), and then derived for annual mean chlorophyll-a using a regression between the two parameters. In order to allow for geographical differences within the Alpine GIG and to facilitate the inclusion of the broadly defined common IC types and national lake types, ranges were defined for each reference value. Range of reference values are 0.2–0.3 mg l^?1 (L-AL3) and 0.5–0.7 mg l^?1 (L-AL4) for total biovolume and 1.5–1.9 μg l^?1 (L-AL3) and 2.7–3.3 μg l^?1 (L-AL4) for chlorophyll-a. Depending on lake type and variable, the ecological quality ratios (EQR) for setting the class boundaries lie between 0.60 and 0.75 for the high/good class boundary and between 0.25 and 0.41 for the good/moderate class boundary. The response of sensitive phytoplankton taxa along a nutrient gradient and the occurrence of ‘undesirable conditions and secondary effects’ as defined in the WFD was used to validate the class boundary values, which are thus considered to be compliant with the requirements of the WFD.     

Validation of diatoms as proxies for phytobenthos when assessing ecological status in lakes

Research to develop tools to assess the ecological status of phytobenthos, as required in Annex V of the European Union Water Framework Directive, has focussed largely on diatoms. Diatoms are often the most abundant and diverse group of algae within the phytobenthos and have been used widely for other monitoring purposes. However, there is little empirical justification for the use of diatoms as proxies for the wider phytobenthos. In this paper, we re-examine an existing dataset compiled largely from littoral samples from standing waters in the English Lake District and compared transfer functions for total phosphorus, dissolved inorganic carbon, conductivity and calcium concentration generated from diatoms and non-diatoms separately and together. The results show that transfer functions generated from diatoms alone are as powerful as transfer functions generated from diatoms and non-diatoms combined, while transfer functions generated from non-diatoms alone are less effective. These results provide support for the use of diatoms as proxies for phytobenthos when ecological status is being assessed. Handling editor: J. Saros     

An approach to intercalibrate ecological classification tools using fish in transitional water of the North East Atlantic

A simple procedure to harmonise and intercalibrate eight national methods classifying the ecological status using fish in transitional waters of the North East Atlantic is described. These methods were initially intercalibrated and a new method recently developed was added to this exercise. A common human pressure index pre-classified the status of each water body in an independent way. Ecological class boundaries values were established according to the level of anthropogenic pressure using regression analyses. A simulated dataset was used to assess the level of agreement between the fish classification methods. Fleiss’ multi-rater kappa analysis indicated that boundary harmonisation was achieved; all classifications fell within one class of each other and class agreement between methods exceeded 70%. The use of a pressure index to establish boundary thresholds provides a practical method of defining and harmonizing the quality classes associated with human pressures, as required by the European Water Framework Directive.     

Submerged macrophyte vegetation and the European Water Framework Directive: assessment of status and trends in shallow,alkaline lakes in the Netherlands

The submerged macrophyte vegetation of lakes created after enclosing former estuaries, situated in the central and south-western part of the Netherlands, has been monitored annually from 1992 onwards. Between 1992 and 2004, pronounced changes in overall cover and species composition of the submerged vegetation have occurred, resulting from changes of water quality and morphology in the lakes. In most cases vegetation cover and species diversity increased or remained stable, with the exception of two lakes in the southwest part of the country. Abundance and species composition were assessed according to the requirements of the EU Water Framework Directive, using the assessment procedure proposed to assess macrophytes in natural water bodies in the Netherlands. The assessment procedure included calculation of the ‘ecological quality ratio’ (EQR) for each of eleven water bodies in each of 13 years, based on transect monitoring data. The EQR indicating Good Ecological Status for Macrophytes was achieved in only three of the lakes. The consequences of hydromorphological modifications, and measures necessary to achieve the desired condition are discussed. Nutrient concentrations should be reduced further, while additional management measures are necessary to improve conditions for macrophytes.     

Assessment metrics for littoral seagrass under the European Water Framework Directive; outcomes of UK intercalibration with the Netherlands

Under the Water Framework Directive (WFD) taxonomic composition, presence of disturbance sensitive species, abundance and cover are stated attributes for monitoring the status of marine angiosperms; a biological quality element required for assessment of environmental condition. Member States (MS) are required to devise metrics for assessing these attributes to establish ecological status of water bodies. Furthermore the Directive requires intercalibration of metrics and data between MSs. Seagrass are the only truly marine angiosperms. The proposed suites of UK and Dutch metrics for assessing the specified seagrass attributes are described and comparisons made. UK and Dutch metrics are intercalibrated through testing against each nationality’s seagrass data. Strong agreement is established in the outcomes of the two suites of tools; >83%. Differences in outcomes are usually due to lack of availability of raw data. Importantly, where outcomes differ they still fall on the same side of the Good/Moderate boundary. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users Handling editor: K. Martens An erratum to this article is available at .     

A method for prioritizing the reestablishment of river continuity in Austrian rivers

River continuity is one of the hydro-morphological elements supporting the classification of the ecological status of rivers. In order to achieve good ecological status in the continuity of rivers, the impacts of anthropogenic activities must be limited to the extent that some fish age classes may be missing and there may only be slight changes in species composition and abundance from the type specific community. The main goal of the project is to list priorities for removing obstruction to migration within 12 years to reestablish river continuity so as to allow undisturbed migration of aquatic organisms. The ecological status of the river, the cost–benefit ratio of the proposed restoration and the distance between obstructions are analysed. More than 200 obstructions in about 170 km of river were evaluated. A 1st ranking of the parameter “extension of undisturbed river length” shows significant alterations in comparison with the 2nd and 3rd ranking, where the river length is weighted over the parameters “ecological status” of the river reach and the “cost–benefit ratio” of the measure. The ecological status is classified by comparing the present versus the potential natural morphological conditions (Leitbild). The cost–benefit ratio takes into account the increase of the fish species composition and the cost of the measures in relation to local circumstances of available property and height of the drop. Examples of obstructions in the Pinka R. move back in the priority list to a maximum of −9 places and forwards to a maximum of +8 places. As a result the list of obstructions by priority for removal to be removed first at the top is analysed. The financial policy and a schedule for removal for the period 2003–2015 are based upon the results of the priority list. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. L. Welcomme & G. Marmulla Hydropower, Flood Control and Water Abstraction: Implications for Fish and Fisheries     

Impacts of environmental scenarios on chlorophyll-a in the management of shallow, eutrophic lakes following biomanipulation: An application of a numerical model

Accurate prediction of species changes in lake ecosystems following biomanipulation measures is of paramount importance in view of water quality management. The temporal variation of phytoplankton biomass as chlorophyll-a and transparency as Secchi depth measurements are studied in the Lake Bleiswijkse Zoom, The Netherlands, with a comprehensive structural dynamic model. In the formulation of the biological model, phytoplankton as several species, zooplankton, detritus, planktivores and benthivores, and piscivores are considered to be major contributing state variables for the model. The primary goal of this paper is to describe the possible impacts of several environmental scenarios on chlorophyll-a biomass qualitatively as it would help lake and environmental managers and relevant authorities elucidate the processes of eutrophication and biomanipulation in a broad way. Some of the scenarios that have been studied by this model are: (1) The effect of fixed stoichiometry in terms of internal nitrogen and phosphorus that are tied up within algal cells; (2) the effects of external phosphorus limitation; (3) light limitation and external nitrogen limitation on algal growth; (4) probable consequences that have taken place within the chlorophyll-a biomass due to change in biomasses of various aquatic organisms; and (5) possible changes of chlorophyll-a biomass due to higher temperatures caused by global warming.     

Distribution and aspects of population dynamics of the zebra mussel,Dreissena polymorpha (Pallas, 1771), in the lake IJsselmeer area (The Netherlands)

Summary The distribution, settling and growth of the zebra mussel, Dreissena polymorpha Pallas, in Lake IJsselmeer and Lake Markermeer in The Netherlands were studied from 1980 to 1985. In these lakes D. polymorpha is the most important food source for wintering diving ducks. The study was part of an investigation into the carrying capacity of the lakes for these birds.     

Fish community response to the longitudinal environmental gradient in Czech deep-valley reservoirs: Implications for ecological monitoring and management

Ecological quality assessment of non-natural water bodies is, in contrast to natural systems, less developed and requires determining biological indicators that reliably reflect environmental conditions and anthropogenic pressures. This study was motivated to propose fish indicators appropriate for assessment of reservoir ecosystems in central Europe. We analysed changes in water quality, total biomass and the taxonomic, trophic and size composition of fish communities along the longitudinal axes of four elongated, deep-valley reservoirs. Due to high nutrient inputs from their catchments, the reservoirs exhibited pronounced within-system gradients in primary productivity and water transparency. Although fish communities were similar among the reservoirs and dominated by few native species, the community structure and biomass systematically changed along the longitudinal axes of the reservoirs. The biomass and proportion of planktivores/benthivores in the fish community were highest at eutrophic sites near the river inflow and declined substantially towards deep, more oligotrophic sites close to the dam. The biomass and proportion of piscivores significantly increased downstream within the reservoirs alongside improving water quality. At species level, perch Perca fluviatilis and bream Abramis brama responded most sensitively, although in opposite directions, to the longitudinal environmental gradient. The major longitudinal changes in fish community characteristics were found to be consistent between pelagic and benthic habitats. The results of this study suggest that fish communities are appropriate indicators of eutrophication and can be used for ecological quality assessment of non-natural lentic water bodies, such as reservoirs. Moreover, our results underline the necessity to consider within-system gradients in water quality and the fish community when planning sampling programmes for deep-valley reservoirs.     

The importance of validated ecological indicators for manure regulations in the Netherlands

The termination of the EU milk quota system on April 1, 2015 is leading to an increase in manure production in the Netherlands. Rather than focus on the quality of water and nature, of which at least the water quality has strongly improved during the last decades, discussions appear to center on strengthening proxy measures that are already being used and which are only remotely related to the quality issue. The quality of water and nature is determined for ground- and surface water by first measuring their N and P content and for nature areas the N deposition. When these values are higher than threshold values determined by ecologists, quality is inadequate and measures are needed. When values are lower, quality is adequate. Three basic problems need to be addressed: (i) threshold values are in practice considered to be permanent while they should be dynamic reflecting a learning process when comparing measurements of N and P values on the one hand and a simultaneous ecological characterization on the other. This requires more cooperation between soil scientists, hydrologists and ecologists. Dynamic characterization may well lead to locally different threshold values. (ii) many measurements of water quality are being made but hardly any measurements of N deposition on nature areas. Such measurements are needed to allow judgements as to the effect of agricultural practices on nature quality. (iii) The necessary further improvement in water and nature quality, as far as it is affected by agricultural practices, can only be achieved when farmers are fully committed and engaged. The current top-down regulations with a “command-and-control” character, while effective in the 1990s, cannot serve this purpose in the information age, the more so since farmers are increasingly well educated and ask too many questions that are not being answered. The suggestion is made to change the generic character of the legislation (“one size fits all”) to a system where “tailor made” management systems are designed for individual farms,considering environmental conditions in the area where the farm occurs. Researchers and farmers can work together in a joint-learning mode to develop such designs that can be recognized by certificates with a legal status. In any case, the proportionality principle needs to be considered assuring that the severity of measures taken are in balance with societal effects.     

Ecological aspects,explosive range extension and impact of a mass invader,Corophium curvispinum Sars, 1895 (Crustacea: Amphipoda), in the Lower Rhine (The Netherlands)

A few years after it invaded, the amphipod Corophium curvispinum Sars appeared to be the most numerous macroinvertebrate species in the River Rhine. From 1987 to 1991 the densities of this species on the stones of groins in the Lower Rhine at a depth of 0.5 m increased from 2 to 200000 specimens per m². In the Lower Rhine and its branches the densities of C. curvispinum increased with increasing current velocities and with increasing water depths. So far, a maximum population density of 750000 specimens per m² has been found in the Lower Rhine, which is many times the densities recorded elsewhere. Population parameters, densities and distribution of C. curvispinum were studied in the Lower Rhine and its branches, using artificial substrates and sampling stones from groins. The success of this immigrant is related to its competitive strategy, which shows several aspects of a r-strategy. In addition, the heavily eutrophicated Lower Rhine provides abundant food (phytoplankton, suspended organic matter) for this opportunistic filter-feeder. The increased salinity and water temperatures in the Lower Rhine resulting from industrial discharges have contributed to the current success of this southern species originating in brackish waters. The very high densities of C. curvispinum might have an enormous impact on the river ecosystem by changing food webs.     

Importance of secondary habitats and need for ecological management for the conservation of Diphasiastrum tristachyum (Lycopodiaceae, Pteridophyta) in the Vosges Mountains (France)

Diphasiastrum tristachyum, which is a rare Pteridophyte under national protection in France, has been discovered in several places in the Vosges Mountains during the last two decades. With its 20 currently existing populations in these mountains, it appears to be the Diphasiastrum species with the largest current distribution in the Vosges. This species mainly occurs on Vosgian sandstone substrate, in northern or northeastern exposures up to 600 m a.s.l., corresponding to the lower and middle montane levels in the Vosges Mountains. The main habitat (16 sites) are forest track borders. Only in single cases could D. tristachyum be found in other habitats such as a skiing track, a heath submitted to regular fire, an abandoned quarry and a limit of a forest plantation weeded with herbicides. All of these sites are secondary places of young anthropic origin. No really natural and primary habitats of D. tristachyum in the Vosges Mountains could be found. All localities show fragments or beginnings of heath communities belonging to the Genistion alliance. Because of the progressive succession of these communities towards forests if no human regulation occurs, D. tristachyum may have only ephemeral existence in such secondary Vosgian sites. This shows the need for a conservation and management programme which comprises measures like keeping open growing sites by the removal of invading trees, controlled pruning of dwarf shrubs and removal of the soil vegetation and the humus layer. A long-term stabilisation of the Vosgian populations of D. tristachyum may only be possible in this way.