Relating environmental pressures to littoral biological water quality indicators in Western Balkan lakes: Can we fill the largest gaps?

Vera Biberdžić,Jelena Rakočević,Suzana Patceva,Biljana Budzakoska Gjoreska,Tatjana Loshkoska,Marina Talevska,Ivana Živić,Zamira Dana,Pavle Đurašković,Vjola Braho,Elizabeta Veljanoska-Sarafiloska,Tor Erik Eriksen,Danijela Vidaković,Susanne C Schneider,Lirika Kupe,Konstantin Zdraveski,Katarina Jovanović,Aleksandra Marković,Jelena Krizmanić,Dag Øystein Hjermann ,Katarina Stojanović,Joanna Lynn Kemp,Alma Imeri,Sonja Trajanovska,Sasho Trajanovski,Magdalena Cara,Jan E Vermaat

doi:10.1016/j.scitotenv.2021.150160

Abstract

Along six transects in each of six lakes across the Western Balkans, we collected data for three groups of littoral biological water quality indicators: epilithic diatoms, macrophytes, and benthic invertebrates. We assessed the relationships between them and three environmental pressures: nutrient load (eutrophication), hydro-morphological alteration of the shoreline, and water level variation, separating the effect of individual lakes and continuous explanatory variables. Lake water total phosphorus concentration (TP) showed substantial variation but was not related to any of the tested biological indicators, nor to any of the tested pressures. We suggest that this may be due to feedback processes such as P removal in the lake littoral zone. Instead, we found that a gradient in surrounding land-use towards increasing urbanization, and a land-use-based estimate of P run-off, served as a better descriptor of eutrophication. Overall, eutrophication and water level fluctuation were most important for explaining variation in the assessed indicators, whereas shoreline hydro-morphological alteration was less important. Diatom indicators were most responsive to all three pressures, whereas macrophyte biomass and species number responded only to water level fluctuation. The Trophic Diatom Index for Lakes (TDIL) was negatively related to urbanization and wave exposure. This indicates that it is a suitable indicator for pressures related to urbanization, although a confounding effect of wave exposure is possible. Invertebrate abundance responded strongly to eutrophication, but the indicator based on taxonomic composition (Average Score Per Taxon) did not. Our results suggest that our metrics can be applied in Western Balkan lakes, despite the high number of endemic species present in some of these lakes. We argue that local water management should focus on abating the causes of eutrophication and water level fluctuation, whilst preserving sufficient lengths of undeveloped shoreline to ensure good water quality in the long run.

Highlights

IntroductionThe implementation of the Water Framework Directive across the European Union is a major effort to harmonize and improve water quality assessment (a.o. Birk et al, 2012, Poikane et al, 2014). Poikane et al (2015) reported that both data and methodological harmonization efforts from eastern continental Europe and the Mediterranean are few, and that, in particular, overall assessments of combined pressures are lacking. Poikane et al (2015) suggested that for the Mediterranean this may be partly related to the small absolute number of lakes present, their unique character and often small size
Our results suggest that our metrics can be applied in Western Balkan lakes, despite the high number of endemic species present in some of these lakes
We identified a priori the following three pressures as being potentially important (Poikane et al, 2014; Pilotto et al, 2015) and often independent (Johnson et al, 2018), being caused by different underlying societal drivers: increased nutrient-load leading to eutrophication, hydromorphological change in the littoral zone due the construction of hard or sandy shores, and hydrological changes leading to altered seasonal water level fluctuation and wave erosion regimes

Summary

Introduction

The implementation of the Water Framework Directive across the European Union is a major effort to harmonize and improve water quality assessment (a.o. Birk et al, 2012, Poikane et al, 2014). Poikane et al (2015) reported that both data and methodological harmonization efforts from eastern continental Europe and the Mediterranean are few, and that, in particular, overall assessments of combined pressures are lacking. Poikane et al (2015) suggested that for the Mediterranean this may be partly related to the small absolute number of lakes present, their unique character and often small size. The implementation of the Water Framework Directive across the European Union is a major effort to harmonize and improve water quality assessment Poikane et al (2015) reported that both data and methodological harmonization efforts from eastern continental Europe and the Mediterranean are few, and that, in particular, overall assessments of combined pressures are lacking. Our consortium collected a multi-indicator data set from the littoral zones of six lakes in the Western Balkans, a region adjacent to the Mediterranean and eastern continental Europe. We used methods that are broadly consistent with the methodological requirements for these specific indicators as set out in the European Water Framework Directive (Schneider et al, 2020a).

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Discussion

Conclusion