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Article

Responses of Freshwater Diatoms and Macrophytes Rely on the Stressor Gradient Length across the River Systems

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URBANZERO Institute for holistic environmental management, Ltd., Selo pri Mirni 17, 8233 Mirna, Slovenia
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Institute for Water of the Republic of Slovenia, Einspielerjeva ulica 6, 1000 Ljubljana, Slovenia
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Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
*
Authors to whom correspondence should be addressed.
Academic Editor: Stefano Amalfitano
Water 2021, 13(13), 1814; https://doi.org/10.3390/w13131814
Received: 10 May 2021 / Revised: 26 June 2021 / Accepted: 27 June 2021 / Published: 30 June 2021
(This article belongs to the Special Issue Large Rivers: Ecology and Management in a Changing World)
Phytobenthic diatoms and macrophyte communities respond differently to stressors in aquatic environments. For the assessment of the ecological status of rivers in Slovenia, we use several indices, including the River Macrophyte Index (RMI) and Trophic index (TI) based on macrophyte and phytobenthic diatoms communities, respectively. In the present study, we examined the relationships between nutrient variables and values of RMI and TI using varied stressor gradient lengths. We also aimed to explain the variability of macrophyte and diatom communities with different stressors, namely nutrients and land cover variables and their combinations. The relationships of RMI and TI with nutrient variables varied significantly and were affected by the length of the stressor gradient. We obtained a stronger relationship between the RMI and total phosphorous at an approximately <0.3-mg/L annual mean value, while, for the relationships with the TI, the values were significant at bigger gradient lengths. The greatest share of variability in the macrophyte and diatom community was explained by the combination of land use and nutrient variables and the lowest share by phosphorus and nitrogen variables. When we applied a composite stressor gradient, it explained a similar share of the variability of both macrophyte and diatom communities (up to 26%). A principal component analysis (PCA) based on land use and nutrient stressor gradient revealed that the relationship between RMI EQR and PCA1 that represents intensive agriculture depends on the length of the gradient. The relationship was stronger for shorter gradients at lower values and decreased as the gradient extended towards higher values. Both tested assessment methods showed that macrophyte communities are more sensitive to shorter stressor gradients of lower values, whereas diatom communities are more sensitive to longer stressor gradient and higher values of the stressor. View Full-Text
Keywords: diatoms; macrophytes; river; trophic condition; indices; nutrients; land use variables; composite gradient diatoms; macrophytes; river; trophic condition; indices; nutrients; land use variables; composite gradient
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MDPI and ACS Style

Urbanič, G.; Debeljak, B.; Kuhar, U.; Germ, M.; Gaberščik, A. Responses of Freshwater Diatoms and Macrophytes Rely on the Stressor Gradient Length across the River Systems. Water 2021, 13, 1814. https://doi.org/10.3390/w13131814

AMA Style

Urbanič G, Debeljak B, Kuhar U, Germ M, Gaberščik A. Responses of Freshwater Diatoms and Macrophytes Rely on the Stressor Gradient Length across the River Systems. Water. 2021; 13(13):1814. https://doi.org/10.3390/w13131814

Chicago/Turabian Style

Urbanič, Gorazd, Barbara Debeljak, Urška Kuhar, Mateja Germ, and Alenka Gaberščik. 2021. "Responses of Freshwater Diatoms and Macrophytes Rely on the Stressor Gradient Length across the River Systems" Water 13, no. 13: 1814. https://doi.org/10.3390/w13131814

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