Efficient sampling methodologies for lake littoral invertebrates in compliance with the European Water Framework Directive

Lake shores are characterised by a high natural variability, which is increasingly threatened by a multitude of anthropogenic disturbances including morphological alterations to the littoral zone. The European Water Framework Directive (EU WFD) calls for the assessment of lake ecological status by monitoring biological quality elements including benthic macroinvertebrates. To identify cost- and time-efficient sampling strategies for routine lake monitoring, we sampled littoral invertebrates in 32 lakes located in different geographical regions in Europe. We compared the efficiency of two sampling methodologies, defined as habitat-specific and pooled composite sampling protocols. Benthic samples were collected from unmodified and morphologically altered shorelines. Variability within macroinvertebrate communities did not differ significantly between sampling protocols across alteration types, lake types and geographical regions. Community composition showed no significant differences between field composite samples and artificially generated composite samples, and correlation coefficients between macroinvertebrate metrics calculated with both methods and a predefined morphological stressor index were similar. We conclude that proportional composite sampling represents a time- and cost-efficient method for routine lake monitoring as requested under the EU WFD, and may be applied across various European geographical regions.     

Wetland plant communities of turloughs in southeast Galway/north Clare,Ireland in relation to environmental factors

Turloughs are seasonal wetlands in Ireland and are priority habitats under the EU Habitats Directive. A number of previously described turlough plant communities were surveyed and, using objective floristic analysis, nine communities identified. Within these nine communities, there was gradation from one community to the next. Overall, there was a broad division between sedge-dominated and grass/forb-dominated communities that is recognised by other authors. The variants in these communities differ, however, between the various authors indicating that there may be gradation from one community to the next in relation to subtle differences in environmental variables. A number of environmental variables that may affect these communities were investigated and depth of deposits over bedrock, soil moisture, date of emptying of the turlough, and water phosphorus and nitrogen were found to correlate with the turlough plant communities in this study.     

Conservation implications of grazing practices on the plant and dipteran communities of a turlough in Co. Mayo,Ireland

Turloughs, which are classified as priority habitats under the European Habitats Directive, are seasonally flooded depressions found almost exclusively in Ireland. In 2001, three adjacent fields with different stocking densities were selected and plant/dipteran communities within the same vegetation zone of each field (site) were investigated using quadrats and sweep netting, respectively. There was a significant positive relationship between Diptera morphospecies richness/Diptera abundance and mean vegetation height (P < 0.001). However, no significant relationship between Diptera morphospecies richness and plant species richness was found. Median Diptera morphospecies richness per sweep was lower at the site with the highest stocking density (17) than at the other two sites (22 and 31, respectively). Total species richness of Sciomyzidae was greater at the least grazed site (7) than at the more heavily grazed sites (2 and 1, respectively). The results suggest that an evaluation of turlough management practices based on plant communities alone is not sufficient and that at least some areas within the turlough basin remain ungrazed on a rotational basis to ensure maximum diversity of Diptera.     

Developing a classifier for the Habitats Directive grassland types in Denmark using species lists for prediction

Abstract. This paper describes the use of supervised methods for the classification of vegetation. The difference between supervised classification and clustering is outlined, with reference to their current use in vegetation science. In the paper we describe the classification of Danish grasslands according to the Habitats Directive of the European Union, and demonstrate how a supervised classification can be used to achieve a standardized and statistical interpretation within a local flora. We thereby offer a statistical solution to the legal problem of protection of certain selected habitat types. The Habitats Directive protects three types of Danish grassland habitats, whereas two remaining types fall outside protection. A classification model is developed, using available Danish grassland data, for the discrimination of these five types based on their species composition. This new Habitats Directive classification is compared to a previously published unsupervised classification of Danish grassland vegetation. An indicator species analysis is used to find significant indicator species for the three protected habitat types in Denmark, and these are compared to the characteristic species mentioned in the interpretation manual of the Habitats Directive. Eventually, we discuss the pros and cons of supervised and unsupervised classification and conclude that supervised methods deserve more attention in vegetation science.     

Adaptation, phenology and disturbance of macroinvertebrates in temporary water bodies

The temporal transition of species dominance following disturbances is strongly influenced by taxon life histories. In temporary water bodies, seasonal progression can be rapid. The community response of aquatic littoral invertebrate communities to disturbance was measured across four temporary water bodies (turloughs) representing a hydroperiod gradient in the karst landscape of western Ireland. Three distinct turlough wet-phases were identified based on macroinvertebrate taxon richness and community composition: filling, aquatic and drying phase. Invertebrates able to recolonise the turlough environment quickly upon flooding from refugia (e.g. sink-holes or little puddles) or resting stages within the turlough basin demonstrated highest proportion in abundances during the initial filling phase. Over time, the number of actively dispersing invertebrates, generally occupying turloughs only for a part of their life-cycle, increased. Hydroperiod had a significant effect on macroinvertebrate taxon richness, with short hydroperiods supporting low faunal diversity. Influence of hydrological disturbance generally decreased with progression of the annual wet phase, indicated by a decrease in taxon richness variation and an increase of biodiversity with time. Our study highlights the importance of life-cycle strategies of species for the occurrence of fairly predictable and periodically occurring seasonal patterns, and emphasizes the importance of ecological disturbances for colonisation cycles.     

Ability of invertebrate indices to assess ecological condition on intertidal rocky shores

The implementation of directives such as the European Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) has promoted the development of several tools and methods for assessing the ecological health of marine ecosystems. Within the scope of the WFD and in terms of rocky shores, several multimetric tools were developed based on the macroalgae biological quality element (BQE), in addition to those based on macroinvertebrates.The WFD requires member states to assess each BQE separately. The present work aimed to test the ability of ecological indices to distinguish sites within anthropogenic disturbance gradients caused by organic enrichment, using macroinvertebrate communities on intertidal rocky shores. Owing to the lack of more specific indices (for rocky shore), indices based on abundance, diversity and/or taxonomic composition were selected from several widely used indices in ecological studies and/or developed for soft-bottom macroinvertebrate communities.Present findings reveal several indices based on diversity and/or taxonomic composition able to distinguish sites within the disturbance gradients, showing increasing quality from the site nearest the source of organic enrichment to that farthest from it, especially indices calculated using biomass data, and in the summer season. Such results open good perspectives for the use of intertidal macroinvertebrate communities from rocky shores, and also help add the perspective of this biological quality element in the ecological quality assessment of coastal waters.     

Upland habitat conservation in Scotland: a review of progress and some proposals for action

Summary

The uplands cover around 70% of Scotland's land surface. Many of the extensive and well-developed habitats are internationally distinctive in their floristics. Almost 250 Sites of Special Scientific Interest are designated primarily for upland habitat interests, and there are 23 upland National Nature Reserves. The EC Habitats Directive lists 23 ‘natural habitat’ types found in the Scottish uplands. More than 70 potential Special Areas of Conservation, proposed for designation under the Directive, have been identified by Scottish Natural Heritage. The UK Biodiversity Action Plan has statements for five principal upland habitats, and costed action plans are being developed for each of these. The impact of man, since the 1940s, points to heavy grazing pressure, poor burning practices and acidic deposition as the major influences on habitat change. Actions are discussed for the conservation of key upland habitats in five biogeographical zones. A distinction is made between the need to restore habitats to areas from which they have been lost and the enhancement or rehabilitation of existing areas of the habitat. Examples are given of suggested criteria for ‘favourable condition’ under the EC Habitats Directive. More generally, examples are given of some desired changes in habitat composition for improved conservation.     

A review of dystrophic lake and pool habitat in Europe: An Irish perspective

Freshwater lakes and pools contained within peatlands are unique habitats that support rare and specialised species. Despite this, these ecosystems have been overlooked in conservation and management practices. One of these habitats, ‘3160 Natural dystrophic lakes and ponds’, is protected under the European Union (EU) Habitats Directive with a concerning proportion of these habitats having an “unfavourable-bad” or an “unfavourable-inadequate” conservation status across Europe. Our current understanding of the key physico-chemical and ecological features of this habitat is inadequate which is hindering the implementation of effective conservation measures. This review summarises the current knowledge of this protected lake habitat as defined under the EU Habitats Directive. With a focus on Ireland, we demonstrate how the current monitoring and assessment methods used to characterise and assess the structure and function and conservation status of this habitat, which relies largely on the use of macrophyte community composition and surrogate physico-chemical data collected under the EU Water Framework Directive, is ineffective. We propose the incorporation of further or alternative ecological metrics including, but not limited to, algae and macroinvertebrates which are needed to improve our understanding of the structure and function of this priority lake habitat. In addition, application of such data via ecological metrics would allow for the quantification of biodiversity and species rarity metrics which would aid in identifying sites of conservation importance.     

Seed dormancy,after-ripening and light requirements of four annual Asteraceae in south-western Australia

A dissected-leaved form of Ranunculus repens L. occurs in the temporary limestone lakes (turloughs) across the west of Ireland. Turloughs fill with groundwater for up to 8 months of the year. Under experimental conditions, these turlough populations demonstrated a higher rate of aerial and submerged photosynthesis than populations of the more typical broad-leaved ruderal form. The turlough populations also had higher rates of stomatal conductance and exhibited a higher stomatal index on the upper leaf surface and a lower index on the lower leaf surface than the ruderal populations. Neither population could utilize bicarbonate to any great extent, with rates of photosynthesis under submerged conditions being only 5 % of aerial rates. Respiration under submerged conditions was significantly higher in the turlough populations than in ruderal populations, and it is hypothesized that the more dissected leaf shape of the turlough population may have a thinner boundary layer and thus enhance gas exchange in submerged conditions.     

How much is enough? Adequate sample size for littoral macroinvertebrates in lowland lakes

Littoral macroinvertebrates are increasingly used for assessing the ecological status of lakes according to the EU Water Framework Directive. This requires harmonised sampling methods, but information on the appropriate spatial scale of the sampling as well as on the adequate sample sizes are mostly lacking. In this study, we compared the spatial variability of littoral (<1.2 m water depth) macroinvertebrate community composition within habitats and within sites to test whether habitat-specific sampling can reduce their spatial variability. Furthermore, we determined the sample size necessary to obtain maximum species richness for a given habitat type. Spatial variability of macroinvertebrate community composition was significantly lower within habitats than within sampling sites, except for communities of coarse woody debris. Species–area curves revealed that a sample size of 1 m² per habitat was not sufficient to obtain the maximum species richness due to the dominance of rare species, which suggests that compilation of taxon inventories may require more exhaustive sampling with sampling sizes substantially larger than 1 m². Separate analysis for species assigned to incidence classes showed that a mean area of 0.63 m² per habitat is sufficient to record all species with frequent and medium incidences, and 76% of the rare species. We conclude that habitat-specific sampling is an effective way to reduce the inherent spatial variability of littoral macroinvertebrate communities and that a sample size of 0.63 m² per habitat is sufficient to represent their dominant and subdominant elements. The application of this adequate sample size to other lake types than large oligotrophic lakes has to be exercised with caution, in particular if community composition and richness patterns differ. However, our results are based on data from lakes that represent the typical lake type found throughout the Central Baltic ecoregion ensuring its wider applicability in this ecoregion.     

Importance of scalar and riparian habitat effects for assessment of ecological status using littoral diatoms

The classification of waterbodies under the Water Framework Directive is dependent on the ability of monitoring programmes to reflect habitat quality using biotic elements including benthic diatom communities. This study investigated the influence of specific riparian habitats, of mixed woodland, grassland and lake artificial structures such as jetties and slipways, on benthic diatom assemblages in nine lakes across gradients of total phosphorus, alkalinity and in the presence or absence of Dreissena polymorpha. The heterogeneity of the benthic diatom assemblages at riparian and lake scale was assessed by taking three replicates per site category per lake, following standard European Union protocols. Canonical correspondence analysis (CCA) and mixed effect modelling was used to investigate the main environmental controls on assemblage structure. Non-metric Multidimensional Scaling (NMDS) was used to examine patterns in assemblage structure. No single environmental gradient was found to control benthic diatom composition, with differences among assemblages influenced both by riparian habitat type within lakes and interaction of multiple environment gradients, including presence of D. polymorpha. Greater control was exerted on community structure at the lake than local riparian scale. The influence of scalar factors on diatom assemblages increased with increasing scale. We recommend that for effective monitoring and assessment of ecological status, standard sampling protocols should include localised littoral habitats with individual samples pooled across riparian habitat types, thereby accounting for both multiple environmental and spatial controls on community structure.     

Testing the European stream typology of the Water Framework Directive for macroinvertebrates

In the EU Water Framework Directive (WFD) a typological framework is defined for assessing the ecological quality of water bodies in the future. The conditions in the Directive impose a strong demand for `new' assessment systems. During the AQEM project an assessment system was developed for European streams using macroinvertebrates. The aim of this study was to test if the typology suggested in the WFD is useful for developing an assessment system for macroinvertebrates in streams. In total 889 streams of 29 stream types were sampled in eight countries all over the major geographical gradients in Europe. These stream types fit the WFD typological demands and fit to the major European geographic regions (ecoregions). The sites included gradients from reference conditions (for the definition see Nijboer et al., 2004) to sites with bad ecological quality. Despite standardisation there were large differences between the participating countries concerning the number of taxa, the number of specimens and the taxonomic resolution. The data, including macroinvertebrates and environmental variables were analysed by using Canonical Correspondence Analysis (CCA). The observed macroinvertebrate distribution largely supported the WFD typological criteria. This means that the major macroinvertebrate distribution patterns in European streams follow climatological and geomorphological conditions and are well distinguished in terms of stream types. Furthermore, it was shown that large scale factors affected the macroinvertebrate distribution even on a very fine scale. Most explanatory variables seemed to be scale independent. Even at a fine scale major factors concerning geology, geomorphology and hydrology added to the species occurrences. Within stream types morphology together with physico-chemistry best explained the macroinvertebrates distribution. In conclusion, the WFD typology is useful for an assessment system for streams using macroinvertebrates. The large scale factors were indeed the variables that explained most of the variation in species composition. But as these factors even strongly act at the scale of stream types, a further refinement is most probably necessary to disentangle typological actors from water quality ones.     

Eulittoral macroinvertebrate communities of lowland lakes: discrimination among trophic states

1. Nutrient inputs from urban and agricultural land use often result in shifts in species composition of pelagic and profundal invertebrate communities. Here, we test if nutrient enrichment affects the composition of eulittoral macroinvertebrate communities, and, if so, if macroinvertebrate communities of five different habitat types reflect differences in trophic state. 2. Macroinvertebrate community composition of 36 lakes was significantly correlated with total phosphorus (TP) concentration, the proportion of coarse woody debris (CWD) and root habitats and the proportion of grassland. 3. However, macroinvertebrate communities of five major habitat types from eight lakes were more dissimilar among habitats than among trophic states. Community composition of reed and stone habitats was significantly correlated with wind exposure but not TP concentration, while macroinvertebrate composition of sand habitats was related to TP concentration and coarse sediments. In CWD and root habitats, both TP concentration and a predominance of invasive species covaried, which made it difficult to relate the observed compositional differences to either trophic state or to the effects of competition between native and invasive species. 4. Trophic state influenced the composition of eulittoral macroinvertebrate communities but to a lesser extent than has been previously reported for profundal habitats. Moreover, the effects of trophic state were nested within habitat type and were partially superseded by biotic interactions and small‐scaled habitat complexity. Although eulittoral macroinvertebrate communities were not strong indicators of the trophic state of lowland lakes, they may be used to assess other anthropogenic impacts on lakeshores.     

The effect of habitat-specific sampling on biological assessment of water quality using a predictive model

1. Detection of impairment in macroinvertebrate communities using rapid biological assessment depends on the ability to compare sites, with confidence that differences obtained result from water quality. However, collections from more than one habitat type may introduce variation that can potentially mask water quality differences among sites. Data were collected from the riffle, edge, pool-rock and macrophyte habitats at reference (minimally disturbed) and test (disturbed) stream sites throughout the Australian Capital Territory. The effect of habitat-specific sampling on predictive models for detecting impairment in macroinvertebrate communities was determined. Four models were used: riffle only, edge only, each habitat as an individual object, and all habitats sampled at a site considered as a composite sample. 2. Macroinvertebrates from individual habitats generally clustered into separate groups because collections from the same habitat at different sites were more similar than collections from different habitats within a site. Thus, in the habitats as individual objects model, the taxa predicted to occur at a test site may be an indication of habitat type rather than water quality. The outputs of the composite habitats and riffle and edge models were similar. However, the variable number of habitats included at each site in the composite model may confound the detection of biological impairment because of unequal sampling effort. The riffle and edge models were the most robust because they were less confounded by inter-habitat variation and were based on comparisons made between equivalent environmental units. 3. Comparison of observed/expected taxa ratios for test sites showed that each model could detect biological impairment, indicating considerable data redundancy was introduced by sampling several habitats. In particular, the pool-rock and macrophyte habitats contributed no information with regard to macroinvertebrate taxon occurrence or detection of biological impairment that could not be obtained from either the riffle or edge habitats within the study area.     

National and European perspectives on climate change sensitivity of the habitats directive characteristic plant species

The main goal of the Habitats Directive, a key document for European conservation, is to maintain a ‘favourable’ conservation status of selected species and habitats. In the face of near-future climatic change this goal may become difficult to achieve. Here, we evaluate the sensitivity to climate change of 84 plant species that characterise the Danish habitat types included in the Habitats Directive. A fuzzy bioclimatic envelope model, linking European and Northwest African species’ distribution data with climate, was used to predict climatically suitable areas for these species in year 2100 under two-climate change scenarios. Climate sensitivity was evaluated at both Danish and European scales to provide an explicit European perspective on the impacts predicted for Denmark. In all 69–99% of the species were predicted to become negatively affected by climate change at either scale. Application of international Red List criteria showed that 43–55% and 17–69% would become vulnerable in Denmark and Europe, respectively. Northwest African atlas data were used to improve the ecological accuracy of the future predictions. For comparison, using only European data added 0–7% to these numbers. No species were predicted to become extinct in Europe, but 4–7% could be lost from Denmark. Some species were predicted to become positively affected in Denmark, but negatively affected in Europe. In addition to nationally endangered species, this group would be an important focus for a Danish conservation strategy. A geographically differentiated Danish conservation strategy is suggested as the eastern part of Denmark was predicted to be more negatively affected than the western part. No differences in the sensitivity of the Habitats Directive habitats were found. We conclude that the conservation strategy of the Habitats Directive needs to integrate the expected shifts in species’ distributions due to climate change.     

A comparison of the European Water Framework Directive physical typology and RIVPACS-type models as alternative methods of establishing reference conditions for benthic macroinvertebrates

The EU Water Framework Directive requires European Union Member States to establish ‘type-specific biological reference conditions’ for streams and rivers. Types can be defined by using either a fixed typology (System-A), defined by ecoregions and categories of altitude, catchment area and geology, or by means of an alternative characterisation (System-B) that can use a variety of physical and chemical factors. Several European countries also have existing RIVPACS-type models that give site (rather than stream type) specific predictions of benthic macroinvertebrate communities. In this paper we compare the Water Framework Directive (WFD) System-A physical typology and three existing European multivariate RIVPACS-type models as alternative methods of establishing reference conditions. This work is carried out in Great Britain – using RIVPACS, Sweden – using SWEPAC_SRI and the Czech Republic – using PERLA. We found that in all three countries, all seasons and season combinations, and for all biotic indices tested, RIVPACS-type models were more effective (lower standard deviations of O/E ratios) than models based solely on the WFD System-A variables or null models (based on a single expectation for all sites). We also investigated the explanatory power of whole groups of WFD System-A variables and RIVPACS-type model variables, and the explanatory power of individual variables. We found that variables used in the RIVPACS-type models were often better correlates of macroinvertebrate community variation than the WFD System-A variables. We conclude that this is primarily because while the latter use very broad categories of map-derived variables, the former are based on continuous variables selected for their ecological significance.     

Response of macroalgae and macroinvertebrates to anthropogenic disturbance gradients in rocky shores

The compliance of macroalgal and macroinvertebrate assemblages to anthropogenic disturbance gradients (e.g., nutrient enrichment) was investigated at intertidal rocky shores. Macroalgae and macroinvertebrates presented parallel behavior, both showing shifts in the communities’ structural variation along the gradients, in which an higher number of opportunistic species (and higher abundances) were found in more stressful sites (close to the disturbance source), in contrast to less disturbed sites (far from the disturbance source), which showed higher presence of more sensitive species (and higher abundance of several of them).The macroinvertebrate abundance and taxonomic composition, which are parameters required by the Water Framework Directive (WFD) to be included in tools for the ecological quality status assessment, responded to the disturbance gradient. Results suggest that the macroinvertebrate biological element might be considered an indicator of disturbance in intertidal rocky shores as good as the macroalgae, and therefore the development of a specific methodology based solely on benthic macroinvertebrates of rocky shores, presently a gap in the ecological quality status assessment for the WFD, seems feasible.     

Assessment of quality of three marine benthic habitat types in northern Baltic Sea

The European Union Habitats Directive (HD) obliges member states to assess the conservation status of marine habitat types but no explicit methodologies for assessing the quality of habitats have been stated in the directive or accompanying documents. In this study, a system was developed to assess the structure and functioning of three important marine habitat types in the Estonian sea area: sandbanks (HD code 1110), mudflats (1140), and reefs (1170). The assessment system includes a list of ecological criteria and favourable reference values together with procedural rules and field sampling locations. The habitat types listed in the HD are broadly defined and may encompass different communities depending upon distinct environmental gradients. By considering these environmental gradients the habitat types reefs and sandbanks were zoned and the assessment criteria and corresponding favourable reference values were defined separately for each zone. A set of several metrics like benthos indices, community variables, presence of sensitive or typical species, proportions of functional or taxonomic groups were tested as potential criteria for determining habitat quality. The most appropriate criteria were selected for incorporation into the assessment system based on ecological eligibility, suitability to local conditions, occurrence rates of benthic species, responses to disturbances, statistical properties of distribution of measured values, and practical considerations. Extensive benthos database (records from the whole Estonian sea area, 1995–2014) was used to calculate values of criteria to support the selection of criteria and to derive reference values. In order to fully take into account their crucial role in maintaining the structure and functioning of habitats, the criteria on habitat-forming species were assigned higher hierarchical order in the assessment scheme compared to other criteria. Special field works were carried out to assess the status of the three habitat types in 2015. The quality of all three monitored habitats was assessed to be in a favourable status. Additionally, the distributions of the three habitat types were mapped. To date, this is the first study in the Baltic Sea region that formulates HD compliant explicit criteria, reference values, and assessment procedures for several marine habitat types. The main challenges of the study were to derive assessment criteria and favourable reference values that are ecologically relevant and practically feasible.     

Natura 2000 habitats in Tuscany (central Italy): synthesis of main conservation features based on a comprehensive database

We analyse and report a synthesis of a long-term project leading to the creation of a database of habitats of conservation interest in Tuscany (Italy). All available floristic and vegetation literature from 1960 to date and relating to the Tuscan territory, and all terrestrial and inland water (non-marine) Habitats of European Community Interest as listed in Annex I of the EU Habitats Directive present in Tuscany have been identified and taken into account. A total of 2,691 sites were attributed to 82 different conservation interest habitat types and were geo-localised and uploaded to the database. For each habitat site, threat and pressure factors are indicated and a quick expert-based assessment made on the basis of three parameters: rarity, vulnerability and a quality estimate. For the analysis, all database information was referred to a vectorial 10 × 10 km grid. The territorial distribution of habitats is discussed with respect to: the level of information available, the numbers of reports and the habitat-type concentration. The major threats and pressures affecting these Tuscan habitats are highlighted and discussed. Vegetation dynamics proved to be the most important natural/seminatural threat. Another important threat is invasion by/competition with other organisms, mainly invasive alien species. Among anthropic threats, the management of riparian and aquatic vegetation together with water management all strongly affect many habitat types with links to wetlands. Infrastructures, particularly those connected with tourism and recreation, are an important threat factor especially in coastal areas. Some positive effects of certain anthropic pressures are also illustrated. Lastly, some actions to improve habitat knowledge, evaluation and conservation are suggested.