Disentangling the Effects of Multiple Stressors on Large Rivers Using Benthic Invertebrates—A Study of Southeastern European Large Rivers with Implications for Management

Gorazd Urbanič,Vesna Petkovska,Zlatko Mihaljević,Maja Pavlin Urbanič

doi:10.3390/w12030621

Gorazd Urbanič, Vesna Petkovska + Show 2 more

Open Access

https://doi.org/10.3390/w12030621

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Journal: Water	Publication Date: Feb 25, 2020
Citations: 12	License type: CC BY 4.0

Affiliation: Ljubljana University Medical Centre, University of Zagreb

Abstract

Predicting anthropogenic actions resulting in undesirable changes in aquatic systems is crucial for the development of effective and sustainable water management strategies. Due to the co-occurrence of stressors and a lack of appropriate data, the effects on large rivers are difficult to elucidate. To overcome this problem, we developed a partial canonical correspondence analyses (pCCA) model using 292 benthic invertebrate taxa from 104 sites that incorporated the effects of three stressors groups: hydromorphology, land use, and water quality. The data covered an environmental gradient from near-natural to heavily altered sites in five large rivers in Southeastern Europe. Prior to developing the multi-stressor model, we assessed the importance of natural characteristics on individual stressor groups. Stressors proved to be the dominant factors in shaping benthic invertebrate assemblages. The pCCA among stressor-groups showed that unique effects dominated over joint effects. Thus, benthic invertebrate assemblages were suitable for disentangling the specific effect of each of the three stressor groups. While the effects of hydromorphology were dominant, both water quality and land use effects were nearly equally important. Quantifying the specific effects of hydromorphological alterations, water quality, and land use will allow water managers to better understand how large rivers have changed and to better define expectations for ecosystem conditions in the future.

Highlights

It is recognised that large rivers are economically important, but they provide various ecosystem services and require sustainable management
We examined the unique and joint effects of natural factors and major stressors on the invertebrate fauna of Southeastern European large rivers using the data along the entire environmental gradient from near-natural sites up to heavily altered sites
Strong positive correlations were observed among hydrological variables and among indices (HLM, hydromorphological modification index (HMM), hydromorphological quality and modification index (HQM))

Summary

Introduction

It is recognised that large rivers are economically important, but they provide various ecosystem services and require sustainable management. Directive [1] requires the identification of significant anthropogenic pressures and the assessment of their impacts on water bodies. We need to correctly predict human activities that create unacceptable impacts on large rivers. While the sources of stress in large rivers are numerous [2,3], little is known about the prevalence, spatial patterns, interactions with the natural environment and co-occurrence of stressors and their effects [4]. The effects of multiple stressors are difficult to predict. Water 2020, 12, 621 due to the complexity of the interactions among stressors [5,6]. The effects of the individual stressor may be masked by the presence of other stressors

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