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

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.

Multimetric Index to Evaluate Water Quality in Lagoons: A Biological and Geomorphological Approach

In recent years, Multimetric Indices (MMIs) have received a lot of attention thanks to their ability to develop integrative evaluations of water quality, particularly in lagoons. In this article, we propose a new MMI for determining the water quality in lagoons. The proposed index is composed of biotic and abiotic indicators, in particular macroinvertebrates, macrophytes and morphological indicators. The proposed index is based on a geometric representation of a phenomenon associated with an ecological system, the ecosystem elements are mapped as vertices of a network and the relationship between them is represented by the corresponding edges. We classify the status of water bodies, from very low to very high using the ecological quality ratio. We compare our index with different different indices that measure water quality, such as General Biotic Index (JP(G)), Macrophyte Index for River (MIR) and Shannon diversity index (H’) and validate our index with Pearson’s correlation coefficient. A strong correlation with the JP(G) and MIR indices (R2 = 0.8605 and R2=0.7661, respectively) is obtained. Although the proposed index is composed of other indices, the independence of the proposed index with respect to its component indices is proven and the structure of the geometric model associated to the proposed network is studied. A close relationship between the measure called medium articulation and the geometric model associated with the proposed index is highlighted, which allows to determine the missing relationships in the network using structural analysis. The proposed index presents a more comprehensive measure than most indices currently used and has the advantage in the scalability, since other existing indicators can be integrated into our model.

Assessment of the ecological condition of the Western Bug river basin according to the macrophyte index for rivers (MIR)

Introduction. To restore and preserve the optimal ecological status of the Western Bug river basin, it is necessary to adhere to the strategic principles of environmental management, and since the river is transboundary and tributary basins are located in Ukraine and Poland, it is important to determine the ecological status of small rivers. In the territory of the Volyn region, the rivers-tributaries Luha and Studyanka are most affected by anthropogenic impact. An ecological assessment of water quality based on the condition of macrophytes is given, as macrophytes llow to determine the degree of surface water degradation, first of all, in terms of their trophic status. The purpose of article. The purpose of article aims to assess the ecological status of the rivers of the Western Bug river basin using bioindication methods and determination of the Macrophyte Index for Rivers (MIR). Methods. Research methods are expeditionary, methods of mathematical statistics end bioindication methods and determination of the Macrophyte Index for Rivers (MIR). Results. To determine the ecological status of the rivers of the Western Bug basin and to conduct research, three test sites with a length of at least 100 m were laid on two tributaries of the first order - the rivers Luha and Studyanka. To determine the MIR (Macrophyte Index for Rivers) in the test riverbed areas, 42 indicator species of macrophytes were selected, of which 1 species belongs to the division Polipodiophyta and Equisetophyta, 40 species to the division Magnoliophyta, of which 15 belong to the class Magnoliopsida, and 25 belong to the class Liliopsida. According to the classification of the MIR indicator, to determine the ecological status, the rivers Luha and Studyanka belong to lowland watercourses, with the type of macrophytes - M-VIII (organic rivers). As a result of the calculated Macrophyte Index for Rivers (MIR), it was established (Table 4) that the water quality in the Luha river in test site 1 (Zavydiv village) has a good ecological status, MIR is 39,0; and test site 2 (Volodymyr-Volynskyi city) has a satisfactory or moderate ecological status, MIR is 31,56; in the river Studyanka, the test site 3 (Ustyluh town) has a satisfactory or moderate ecological condition, MIR is 28,31. Conclusions. According to the ecological status of rivers determined by the Macrophyte Index for Rivers (MIR), it is established that the waters of the Luha and Studyanka rivers have a satisfactory or moderate ecological condition. This suggests that the research conducted on test sites and calculations of the Macrophyte Index for Rivers (MIR) are identical and fully reflect the ecological status of the rivers Luha and Studyanka determined by hydrochemical parameters, which allows the use of this research algorithm for other rivers in the Western Bug river basin and is promising during research on other rivers of Ukraine.

The Macrophyte Index for Rivers (MIR) as an Advantageous Approach to Running Water Assessment in Local Geographical Conditions

The Macrophyte Index for Rivers (MIR) was developed in 2007, and it was one of the first biological methods developed in Poland under the requirements of the Water Framework Directive to assess the ecological status of running waters. It is based on the quantitative and qualitative evaluation of 153 indicator taxa. The aim of this study was to evaluate the ability of the MIR method to detect trophic degradation in rivers and to compare its efficiency with other macrophyte metrics. Our investigation was based on 100 sites, representing a very clear gradient from near oligotrophic to eutrophic conditions. The results showed that macrophytes can be distinguished in terms of their ecological requirements for nutrient concentration in water, and this can be used to develop an effective system of freshwater assessment. The MIR was shown to be the indicator most strongly correlated with various forms of nutrients, and it was demonstrated that calibration of the macrophyte method to local biogeographical conditions resulted in greater effectiveness of the assessment method.

Impact of hydromorphological pressures on the macrophytes bioindicators of the ecological water quality in Mediterranean rivers

One of the important tools to evaluate the ecological quality of surface water is the Macrophytes indices based on the bioindication capacity of aquatic plants. In Mediterranean rivers (France, Spain, and Portugal), the development of some macrophytes indices like l’Indice Biologique Macrophytes Rivières (IBMR), the biological metric score (BMS), as well as the Fluvial Macrophyte Index (IMF) are founded on the determination of the indicator values of the floristic reference lists. The aim of this study was to test the impact of the eco-Mediterranean differences (from one country to another) on the indicator taxa by comparing the indicator values of the Euro‐ Mediterranean macrophyte indices. With this in mind, we explore the possibility of the introduction of the Euro‐Mediterranean macrophytes-based indices in Morocco (i.e. the hydrological basin of Sebou (HBS)) as a part of a preliminary attempt to develop the first Afro-Mediterranean macrophyte index. We confirm that the ecological amplitude and species optima vary between Mediterranean ecoregions, and indicator taxa differ between countries: There are medium to small correlations between Mediterranean indices: IBMR/BMS (p = 0.000, R2 = 0.57), IMF/BMS (p = 0.000, R2 = 0.34), and IBMR/IMF (p = 0.000, R2 = 0.30). Five species exhibit major differences in indicator values: Zannichelliapalustris and Potamogetonpectinatus have more eutrophic indicator values in France (IBMR) than in Spain (IMF). Potamogetonnodosus, Amblystegiumriparium and Lycopuseuropaeus have broader ecological amplitudes in Portugal (BMS) than in France (IBMR) and in Spain (IMF), where it is restricted to eutrophic conditions. Furthermore, the three indicator systems include different indicator-taxon numbers. The comparison of the HBS elaborated list with the Euro‐Mediterranean indices revealed the low level of common taxa approximately 6.76% of all indicator species used in the French index (IBMR), 10.48% in the Portuguese index (IMF) and 12.38% in the Spanish index (BMS). These results show the inadequacy of the trophic indices approach with the HBS conditions and thus the need for the development of an index based on biotic indices approach.

How many indicator species are required to assess the ecological status of a river?

The presented research focused on macrophytes, which constitute a primary element in the assessment of the ecological status of surface waters following the guidelines of the Water Framework Directive. In Poland, such assessments are conducted using the Macrophyte Index for Rivers (MIR). The objective of this study was to characterize macrophyte species in rivers in terms of their information value in the assessment of the ecological status of rivers. The macrophyte survey was carried out at 100 river sites in the lowland area of Poland. Botanical data were used to verify the completeness of samples (the number of taxa). In the presented research, the information provided by each species was controlled. Entropy was used as the main part of information analysis. This analysis showed that the adoption of a standard approach in the studies of river macrophytes is likely to provide sample underestimation (with missing species). This may potentially lead to incorrect determination of MIR and thus result in a wrong environmental decision. On this basis, a sample completeness criterion was developed. Using this criterion, the average value of information for macrophyte species in medium-sized lowland rivers is suffcient to be considered representative.

Determining the change point for the error in the Macrophyte Index for Rivers

SummaryThe consequences of the growing demand for water include a significant deterioration in its quality and a drastic decline in biodiversity, which is a serious threat to the hydrological and biocenotic balance of freshwater ecosystems. A good indicator of aquatic environment quality is macrophytes. Studies on macrophytes are one of the primary elements in the ecological status assessment of surface waters, in accordance with the guidelines of the Water Framework Directive. In Poland, research on the ecological status of rivers with regard to macrophytes has been carried out since 2008, using the Macrophyte Index for Rivers (MIR), which takes into account the number and coverage of macrophyte taxa. An analysis of numbers of species that need to be indicated at a site for valid assessment of the ecosystem was conducted on the basis of studies on macrophytes from 2008–2013, at 60 sites in small lowland rivers with a sandy substrate, of which 20 sites were selected on the most diverse watercourses: the least clean (quality class V), moderate (quality class III), and the cleanest (quality class I). The results of the botanical studies served to assess the completeness of the samples (the number of species recorded at a site) used to evaluate the ecological status of a river. The proposed analyses enabled estimation of the approximate number of species required to determine the MIR for rivers in each quality class.

Response of vegetation to growing recreational pressure in the shallow Raczyńskie Lake

Strong human impact accelerates eutrophication which deteriorates water quality and consequently prevents recreational use. Increasing trophy and low transparency induce macrophyte rebuilding. A gradual transformation of the land use of the direct catchment area of Raczyńskie Lake from agricultural to recreational has been observed over the last 45 years. In built-up areas sewage facilities were inadequate and septic tanks did not work properly and as a consequence most wastewater was able to infiltrate through the ground into the lake. The lake ecosystem became unstable and water blooms intensified. The aim of the study was to assess the changes in the composition of the lake vegetation over the last 45 years, during which the use of the direct catchment has changed and recreational pressure increased. A reduction of the number of plant communities from 24 to 15 and the disappearance of almost all the submerged vegetation was observed. The dominant reed beds (Phragmitetum communis, Typhetum angustifoliae) were unable to provide a sufficient barrier to the flow of pollution from the catchment because of the numerous gaps made for angling piers, bathing sites, jetties, etc. The macrophyte index indicated a bad ecological status. To improve the ecological status of Raczyńskie Lake it is necessary to introduce intensive protection and restoration treatments.

An attempt to assess the ecological status of a lake based on historical and current maps of submerged vegetation

The possibility of doing a back assessment of the ecological status of a lake based on archival bathymetric maps indicating areas overgrown with rushes and aquatic vegetation was verified. This assessment was assumed to be in accordance with that performed with the official Polish macrophyte-based method for lake assessment (Ecological State Macrophyte Index, ESMI). The study was conducted on Lake Dobrąg located in the Warmian-Masurian Voivodeship (surface area - 108 ha, maximum depth - 27.9 m, mean depth - 11.6 m). It included the hydroacoustic distribution of submerged macrophytes along 85 evenly distributed belt transects (perpendicularl to the shore line), creating a bathymetric chart and maps of vegetation occurrence and identifying areas occupied by hydrophytes (Cmax) and the maximum depth of lake colonization (Z). Analogous data were read from archival bathymetric chart dating from 1964-1968. The values obtained were compared with the means (and their confidence intervals) of 83 stratified lakes in Poland in different ecological status classes. Analysis of changes indicated that the ecological status of the lake had deteriorated. In the mid-1960s, the status of the lake was less than “very good” while the current status borders between “good” and “moderate.” The results indicate that the proposed method could be useful when attempting to assess changes in ecological status using archival bathymetric charts showing areas overgrown with vegetation and the distribution of it in lakes.