A new paradigm for biomonitoring: an example building on the Danish Stream Plant Index

Effects of anthropogenic pollution and hydrological variation on macroinvertebrates in Mediterranean rivers: A case-study in the upper Tagus river basin (Spain)

Seasonal hydrological variation and chemical pollution represent two main drivers of freshwater biodiversity change in Mediterranean rivers. We investigated to what extent low flow conditions can modify the effects of chemical pollution on macroinvertebrate communities. To that purpose, we selected twelve sampling sites in the upper Tagus river basin (central Spain) having different sources of chemical pollution and levels of seasonal hydrological variation. The sites were classified as natural (high flow variation, low chemical impact), agricultural (high flow variation, high agricultural chemical inputs) and urban (limited flow variation, high urban chemical inputs). In these sites, we measured daily water discharge, nutrients, and contaminant concentrations, and we sampled benthic macroinvertebrates, in spring, summer and autumn. Significant differences related to toxic pressure and nutrient concentrations were observed between the three groups of sites. Seasonal patterns were found for some water quality parameters (e.g. nitrites, ammonia, suspended solids, metal toxicity), particularly in agricultural sites. Taxonomic and functional richness were slightly lower in the polluted sites (agricultural and urban), particularly during low flow periods (summer and early autumn). Functional diversity was significantly lower in sites with seasonal flow variation (agricultural sites) as compared to the more constant ones (urban sites). The frequency of traits such as large size, asexual reproduction, aquatic passive dispersion and the production of cocoons increased in response to pollution during low flow periods. This study shows that the impacts of anthropogenic chemical pollution on taxonomic and functional characteristics of macroinvertebrate communities seem to be larger during low flow periods. Therefore, further studies and monitoring campaigns assessing the effects of chemical pollution within these periods are recommended.

Implementation of the Water Framework Directive: Lessons Learned and Future Perspectives for an Ecologically Meaningful Classification Based on Phytoplankton of the Status of Greek Lakes, Mediterranean Region

The enactment of the Water Framework Directive (WFD) initiated scientific efforts to develop reliable methods for comparing prevailing lake conditions against reference (or nonimpaired) states, using the state of a set biological elements. Drawing a distinction between impaired and natural conditions can be a challenging exercise. Another important aspect is to ensure that water quality assessment is comparable among the different Member States. In this context, the present paper offers a constructive critique of the practices followed during the WFD implementation in Greece by pinpointing methodological weaknesses and knowledge gaps that undermine our ability to classify the ecological quality of Greek lakes. One of the pillars of WDF is a valid lake typology that sets ecological standards transcending geographic regions and national boundaries. The national typology of Greek lakes has failed to take into account essential components. WFD compliance assessments based on the descriptions of phytoplankton communities are oversimplified and as such should be revisited. Exclusion of most chroococcal species from the analysis of cyanobacteria biovolume in Greek lakes/reservoirs and most reservoirs in Spain, Portugal, and Cyprus is not consistent with the distribution of those taxa in lakes. Similarly, the total biovolume reference values and the indices used in classification schemes reflect misunderstandings of WFD core principles. This hampers the comparability of ecological status across Europe and leads to quality standards that are too relaxed to provide an efficient target for the protection of Greek/transboundary lakes such as the ancient Lake Megali Prespa.

The future of European water management: Demonstration of a new WFD compliant framework to support sustainable management under multiple stress

The Water Framework Directive (WFD), which is the most comprehensive instrument of EU water policy, is more relevant than ever. Sixty percent of Europe's surface water bodies still fail to achieve good ecological status and a multitude of new stressors continue to emerge. A sustained and wholehearted water management effort is therefore of highest priority. Here, we present a new biological assessment approach specifically designed to safeguard sustainable water management under multiple stress. The framework contains three independent elements: 1) an ecological assessment system based on community abundance and composition to quantify ecological status; 2) a diagnostic tool to identify cause(s) of ecological degradation; 3) a management platform to guide the choice of relevant mitigation measures for improvement of the ecological status. The proposed framework is fully compliant with the WFD and currently applied in the assessment of aquatic plant communities in Danish streams. Importantly, the approach presented is not restricted to specific taxonomic groups or ecosystem types but is an example of how a simple approach can bring the conceptual idea of the WFD - that community characteristics in unimpacted, type-specific water bodies should be the backbone in ecological assessments - into practice.

Diagnosing the causes of river deterioration using stressor-specific metrics

More often than not, rivers are impacted by multiple stressors simultaneously affecting water quality, ecological flow, habitat diversity and ultimately lotic biodiversity. Identifying individual stressors as specific causes of deterioration can help inform water managers about stressor hierarchy and appropriate management options. Here, we investigate whether biological metrics from bioassessment schemes hold diagnostic capabilities to distinguish between the impact of individual stressors. We hypothesise that stressor-specific responses occur, when individual stressors show independent 'modes of action' (i.e. the specific stress-induced changes of environmental factors that modify the ecological niches of the species constituting the biological community). The stress receptors comprised three aquatic organism groups (macrophytes, benthic invertebrates, fish) represented by 437 biological metrics relevant in aquatic bioassessment. The stressor groups under investigation were physico-chemical, hydromorphological and hydrological stress. The data originated from official monitoring programmes with 769 sampling sites located at three broad river types in Western and Central Germany. Linear and non-linear variance partitioning was performed separately for each river type, with the non-linear analysis using a combination of boosted regression tree modeling and variance partitioning. We considered metrics to be potentially stressor-specific, if the corresponding models were explained predominantly by one stressor group. The linear analyses revealed 16 metrics that met our criteria. Subsequent non-linear modeling resulted in two genuinely stressor-specific metrics, both based on invertebrate data: The Index of Biocoenotic Region (specifically indicating hydromorphological stress) and the Relative abundance of alien invertebrate species (specifically indicating physico-chemical stress). We conclude that stressor-specific metrics can be empirically derived based on available monitoring data, and thus help support decision making in environmental management. However, their applicability is restricted to specific regions (e.g. river basin districts) reflecting the case-specific circumstance to which these metrics are conditioned.

Hydrological and environmental variables outperform spatial factors in structuring species, trait composition, and beta diversity of pelagic algae

There has been increasing interest in algae-based bioassessment, particularly, trait-based approaches are increasingly suggested. However, the main drivers, especially the contribution of hydrological variables, of species composition, trait composition, and beta diversity of algae communities are less studied. To link species and trait composition to multiple factors (i.e., hydrological variables, local environmental variables, and spatial factors) that potentially control species occurrence/abundance and to determine their relative roles in shaping species composition, trait composition, and beta diversities of pelagic algae communities, samples were collected from a German lowland catchment, where a well-proven ecohydrological modeling enabled to predict long-term discharges at each sampling site. Both trait and species composition showed significant correlations with hydrological, environmental, and spatial variables, and variation partitioning revealed that the hydrological and local environmental variables outperformed spatial variables. A higher variation of trait composition (57.0%) than species composition (37.5%) could be explained by abiotic factors. Mantel tests showed that both species and trait-based beta diversities were mostly related to hydrological and environmental heterogeneity with hydrological contributing more than environmental variables, while purely spatial impact was less important. Our findings revealed the relative importance of hydrological variables in shaping pelagic algae community and their spatial patterns of beta diversities, emphasizing the need to include hydrological variables in long-term biomonitoring campaigns and biodiversity conservation or restoration. A key implication for biodiversity conservation was that maintaining the instream flow regime and keeping various habitats among rivers are of vital importance. However, further investigations at multispatial and temporal scales are greatly needed.