Effects of local land-use on riparian vegetation, water quality, and the functional organization of macroinvertebrate assemblages

Teasing out the Effects of Natural Stressors at Chemically Contaminated Sites

Aquatic ecosystems are often impacted by a multitude of stressors, many of which are introduced by a combination of anthropogenic activities such as agricultural development, urbanization, damming, and industrial discharge. Determining the primary stressors responsible for ecological impairments at a site can be complex and challenging; however, it is crucial for making informed management decisions. Improper diagnosis of an impaired system can lead to misguided attempts at remediation, which can be both time consuming and costly. We focused on the development, implementation, and evaluation of methodologies that, in combination, allowed us to identify the primary stressors. These included a four-phase, weight-of-evidence (WOE) assessment including in situ Toxicity Identification and Evaluation (iTIE) testing, physicochemical and macrobenthos characterization, reciprocal sediment transplants, and laboratory and in situ toxicity testing. The contaminants of concern (COCs) at the site were elevated levels of ammonia, chloride, pH, and total dissolved solids in groundwater upwellings into a high-quality waterway. Reciprocal transplants of site sediments and nearby reference sediments and traditional benthic sampling showed impaired benthic indices and multiple stations around a contaminated industrial settling basin. Impaired stations had elevated COCs in groundwaters but exhibited a steep vertical concentration gradient, with concentrations decreasing near the sediment-surface water interface. We describe Phase 4 of the study, which focused on teasing out the role of dissolved oxygen sags in benthic macroinvertebrate responses. Extensive submerged and emergent macrophytes, algae, and cyanobacteria co-occurred at the impaired sites and increased throughout the summer. Laboratory testing suggested that ammonia and pH were possibly toxic at the sites, based on groundwater concentrations. The in situ toxicity testing, however, showed toxicity occurring even at stations with low levels of COCs concurrently with large diurnal fluxes in dissolved oxygen (DO). A final phase using a type of iTIE approach utilized limnocorrals with and without aeration and with in situ toxicity measures using Hyalella azteca. The Phase 4 assessment revealed that low DO levels were primarily responsible for impaired benthic communities, and COC upwellings were diluted at the sediment-water interface to nontoxic levels. These findings will allow for improved management decisions for more efficient and effective restoration activities. Environ Toxicol Chem 2024;43:1524-1536. © 2024 SETAC.

Riparian woody plant communities in the Romanian Carpathians: Species diversity and community structure of Salix and Hippophaë communities

Riparian woody plant communities, including shrubs and trees, are essential for maintaining biodiversity, protecting against floods, reducing erosion, and transporting nutrients. However, these habitats are greatly threatened by human activities, particularly agricultural land acquisition, and the introduction of invasive species. This study examined species diversity and interspecific association in riparian woody plant communities along rivers in the Romanian Carpathians. The study focused on communities of Salix purpurea, S. alba, and Hippophaë rhamnoides in mountain regions, with varying sampling efforts at different sites for each species. A total of 174 plant species were found, predominantly herbaceous (77.9%), followed by trees (11.6%) and shrubs (10.5%). While S. alba and S. purpurea communities show high species richness and abundance, S. alba has slightly higher diversity (H' ≈ 2.23, SD = 0.28) than S. purpurea (H' ≈ 1.69, SD = 0.42). Contrarily, significant differences exist between H. rhamnoides and S. alba communities in species richness (p = .007) and Shannon diversity (p = .004). PCA analysis elaborated on distinct distribution patterns of plant associations within habitats S. purpurea community, H. rhamnoides community, and S. alba community. Four invasive species (Oenothera biennis L. and Oxalis stricta L. in S. alba communities, Reynoutria sachalinensis Nakai in both S. purpurea and H. rhamnoides communities, and Erigeron canadensis L. in H. rhamnoides communities) were identified, as requiring conservation efforts. Hemicryptophytes dominate species richness, while microphanerophytes and megaphanerophytes significantly contribute to plant abundance. H. rhamnoides formed Hippophaë rhamnoides dunes (2160) Natura 2000 habitat, while S. alba created galleries within the 92A0 Salix alba and Populus alba habitat. In conclusion, the findings from this study highlight the importance of preserving riparian habitats because their value goes beyond local or regional considerations and extends to the global scale due to their unique characteristics.

Diversity and distribution of Phytophthora species across different types of riparian vegetation in Italy with the description of Phytophthora heteromorpha sp. nov

Riparian formations encompass a diverse suite of transitional zones between terrestrial and aquatic ecosystems. During the last decades, these formations have been impacted by several emerging diseases. The first outbreaks were detected on alder formations, but have progressively also been observed on other plant species such as Betula pubescens, Nerium oleander, Populus alba, Salix alpina, Salix purpurea and Tamarix gallica. Declining plants showed a plethora of symptoms (leaf spot, shoot blight, bleeding cankers and root rot) indicative of Phytophthora infections. Since there is little information about the aetiology of these pathosystems, from November 2019 to March 2023, an in-depth study was conducted in 46 riparian ecosystems spanning from the Mediterranean to Alpine regions. Overall, 744 symptomatic samples (stem bleeding cankers and root with rhizosphere) from 27 host species were collected for Phytophthora isolation. Based on morphology and DNA sequence data, 20 known Phytophthora species belonging to seven phylogenetic clades have been identified: P. plurivora (202 isolates), P. gonapodyides (156), P. pseudosyringae (84), P. lacustris (57), P. acerina (31), P. idaei (30), P. alpina (20), P. pseudocryptogea (19), P. cambivora (13), P. pseudotsugae (13), P. cactorum (9), P. honggalleglyana (6), P. pseudogregata (6), P. debattistii (4), P. multivora (4), P. cinnamomi (3), P. bilorbang (2) P. crassamura (2), P. ilicis (2) and P. inundata (2). In addition, 26 isolates of a new putative species obtained from Alnus incana and Pinus sylvestris are described here as Phytophthora heteromorpha sp. nov. The new species proved to be pathogenic on grey alder causing symptoms congruent with field observations. This study represents the most comprehensive investigation on the Phytophthora species associated with declining riparian vegetation in Italy and highlights that the polyphagous pathogen P. plurivora represents a growing threat to Mediterranean, temperate and alpine ecosystems.

Different responses of taxonomic and functional trait structure of benthic macroinvertebrate assemblages to eutrophication in a large Chinese freshwater lake

Functional trait measures have the potential to represent local habitat conditions and are considered promising tools for biomonitoring and bioassessment programs. Macroinvertebrates are an ecologically significant group in freshwater ecosystems and possess a range of functional traits which are employed to assess ecological quality. Nevertheless, the relationships between macroinvertebrate functional structure and anthropogenic disturbances remain poorly understood. In this study, we conducted a comparison of how functional trait-based and taxonomy-based composition of macroinvertebrate assemblages responded to eutrophication in Lake Taihu, a typical large eutrophic freshwater lake in China. Specifically, we examined both the taxonomy-based and trait-based compositions of benthic macroinvertebrates varied along the eutrophication gradient. Eutrophication was associated with remarkable decreases in the abundance of gastropod taxa and increases in Oligochaeta and Chironomidae. Ten categories belonging to six traits were significantly different among three site groups. The eutrophic and transition sites showed higher abundance of Size2, burrowers, and integument-respiration organisms than macrophytic sites, whereas abundance of Size1, conical-shaped, sprawlers, scrapers, and lung-respiration were higher in macrophytic sites. Both taxonomic (36.8%) and functional compositions (39.8%) of macroinvertebrate assemblages were influenced by the same variables: CODMn and transparency. Our study showed that macroinvertebrate trait-based approaches can be considered a useful supplement to traditional taxonomic approach for biomonitoring programs in freshwater lakes.

Aquatic insects for monitoring the health status of riverine potholes: A case study in Chalakudy river basin, Kerala, India

Potholes are microhabitats in riverine ecosystems that substantially contribute to the unique regional faunal diversity and community composition. Investigations on the ecological status of potholes in riverine habitats are very scanty. The present work is of utmost importance, particularly as a pioneering study to evaluate the health status of riverine potholes using aquatic insects as potential biological indicators. Samples of water and aquatic insects were collected and analyzed during the pre-monsoon season from February 2022 to May 2022 in the potholes at Athirappilly and the Ezhattumugham regions of the Chalakudy river basin. The present study identified 208 individuals represented by 15 families in the potholes at Athirappilly, whereas 94 individuals belong to 10 families at Ezhattumugham. The computation of water quality parameters and benthic metrics revealed a significant variation between the stations. Spearman correlation analysis revealed that the water temperature, electrical conductivity, dissolved oxygen concentration, and biochemical oxygen demand were influencing the distribution of aquatic insects in the potholes. Families such as Perlidae, Ephemeridae, Baetidae, Stenopsychidae, and Hydropsychidae (sensitive families) reported from the well-oxygenated potholes at Athirappilly, where the water temperature and biochemical oxygen demand were minimum. The significantly high percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and a low family biotic index value indicate good health condition of the potholes at Athirappilly. In contrast, the low percentage composition of Ephemeroptera, Plecoptera, and Trichoptera taxa and high family biotic index values, with the abundance of tolerant families (Micronectidae, Caenidae, and Chironomidae), reflect the impact of organic pollution at Ezhattumugham.

Heavy ionic pollution disrupts assemblages of algae, macroinvertebrates and riparian vegetation

Urban streams display consistent ecological symptoms that commonly express degraded biological, physical, and chemical conditions: the urban stream syndrome (USS). Changes linked to the USS result in consistent declines in the abundance and richness of algae, invertebrates, and riparian vegetation. In this paper, we assessed the impacts of extreme ionic pollution from an industrial effluent in an urban stream. We studied the community composition of benthic algae and benthic invertebrates and the indicator traits of riparian vegetation. The dominant pool of benthic algae, benthic invertebrates and riparian species were considered as euryece. However, ionic pollution impacted these three biotic compartments' communities, disrupting these tolerant species assemblages. Indeed, after the effluent, we observed the higher occurrence of conductivity-tolerant benthic taxa, like Nitzschia palea or Potamopyrgus antipodarum and plant species reflecting nitrogen and salt contents in soils. Providing insights into organisms' responses and resistance to heavy ionic pollution, this study sheds light on how industrial environmental perturbations could alter the ecology of freshwater aquatic biodiversity and riparian vegetation.

Evidence of biological recovery from gross pollution in English and Welsh rivers over three decades

Uncertainty around the changing ecological status of European rivers reflects an evolving array of anthropogenic stressors, including climate change. Although previous studies have revealed some recovery from historical pollution in the 1990s and early-2000s, there are contrasting trends among pollutants across Europe and recovery may have stalled or been reversed. To provide more contemporary evidence on trends and status, here we investigate changes in English and Welsh river macroinvertebrate communities over almost 30 years (1991-2019) using a network of nearly 4000 survey locations. Analysis comprised: i) trends in taxonomic and functional richness, community composition and ecological traits, ii) gains, losses and turnover of taxa, and the overall homogeneity of macroinvertebrate communities nationally, and iii) an exploration of how temporal trends varied with catchment characteristics. Taxonomic richness increased, primarily in the 1990s, whilst a shift towards pollution-sensitive taxa continued throughout the study period, accompanied by a growing prevalence in traits such as preferences for fast-flowing conditions, coarser substrata, and 'shredding' or 'scraping' feeding strategies. Changes consistent with improvement occurred in both urbanised and agricultural catchments, but were more pronounced in urban rivers as they gained pollution sensitive taxa that were otherwise more prevalent in rural rivers. Overall, these results indicate continuing biological recovery from organic pollution, consistent with national scale trends in water quality. Results reemphasise the importance of looking at multiple facets of diversity, with periods of near-constant richness disguising changes in taxonomic and functional composition. Whilst this national-scale picture is broadly positive, we highlight the need to investigate more local variations or pollutants that depart from this aggregate picture.

Spatial variation in the community structure and response of benthic macroinvertebrates to multiple environmental factors in mountain rivers

Exploring the response between benthic community changes and environmental variables has significance for restoring the health of river ecosystems. However, little is known of the impact on communities of interactions between multiple environmental factors, and frequent changes in the flow of mountain rivers are different from those in the flow of plain river networks, which also impact differently the benthic community. Thus, there is a need for research on the response of benthic communities to environmental changes in mountain rivers under flow regulation. In this study, we collected samples from the Jiangshan River in the dry season (November 2021) and the wet season (July 2022) to investigate the aquatic ecology and benthic macroinvertebrate communities in the watershed. Multi-dimension analyses were used to analyze the spatial variation in the community structure and response of benthic macroinvertebrates to multiple environmental factors. In addition, the explanatory power of the interaction between multiple factors on the spatial variation of communities, and the distribution characteristics of benthic community and their causes were investigated. The results showed that herbivores are the most abundant forms in the benthic community of mountain rivers. The structure of benthic community in Jiangshan River was significantly affected by water quality and substrate, whereas the overall community structure was affected by river flow conditions. Furthermore, nitrite nitrogen and ammonium nitrogen were the key environmental factors impacting the spatial heterogeneity of communities during the dry and wet season, respectively. Meanwhile, the interaction between these environmental factors showed a synergistic effect, enhancing the influence of these environmental factors on community structure. Thus, controlling urban and agricultural pollution and releasing ecological flow would be effective strategies to improve benthic biodiversity. Our study showed that using the interaction of environmental factors was a suitable way to evaluate the association between environmental variables and variation in benthic macroinvertebrate community structure in river ecosystems.

The impact of land use on stream macroinvertebrates: a bibliometric analysis for 2010-2021

Changes in stream biodiversity are now mainly driven by land-use development. However, a literature review on the impact of land use on stream macroinvertebrates is lacking, especially a scientometric review. Here, we bibliometrically analyzed the literature on land use and stream macroinvertebrates that were published in 2010-2021 and listed in the Web of Science database. We found that the impact of land use on stream macroinvertebrates had been increasingly studied and that these studies were distributed across the globe and had multi-national collaborations. Through co-citation analysis and high-frequency keyword analysis, we found that land use and some environmental factors, especially water quality and habitat, affected macroinvertebrate community biodiversity, biotic integrity, and patterns. Macroinvertebrate traits, analytical methods or models, evaluation index development, and riparian vegetation were the research hotspots. Using historical direct citation network analysis, we also found that the analytical methods in this field and the macroinvertebrate evaluation index had clear development trends from 2010 to 2021. Our findings can help researchers quickly grasp the background of the impact of land use on stream macroinvertebrates and inform future research.

Insights from the Niger Delta Region, Nigeria on the impacts of urban pollution on the functional organisation of Afrotropical macroinvertebrates

Anthropogenic activities, including urbanisation and industrialisation threaten stream ecological integrity, ecosystem community structure and ecosystem functioning of rivers and streams worldwide. However, developing sustainable monitoring strategies for ecological health remains a critical challenge in Africa. We examined the effects of urban disturbance on macroinvertebrate Functional Feeding Groups in selected streams in the Niger Delta Region of Nigeria. We sampled 11 sites between 2008 and 2012 and grouped into three site groups (Site groups 1 > 2 > 3). The groups represent an increasing gradient of urban pollution. Our result showed that urban-induced disturbances affected physicochemical variables in the study area (PERMANOVA; p < 0.05), with nutrients NO₂-N, PO₄-P, and electrical conductivity being significantly higher in impacted Site group 3 (ANOVA, p < 0.05). Predators and gatherers were the most dominant Functional Feeding Group recorded in the study area, while shredders were the least abundant macroinvertebrate Functional Feeding Groups. The multivariate RLQ analysis revealed that shredders, predators, and scrapers were tolerant of urban pollution, whereas gatherers were sensitive to increasing urban pollution. Overall, macroinvertebrates Functional Feeding Groups responded differentially to urban pollution in the Niger Delta Region. Identifying pollution indicator Functional Feeding Groups is seen as an important step towards developing a reliable, low-cost tool for riverine monitoring of urban pollution effects in Africa.

Nonlinear effects of environmental drivers shape macroinvertebrate biodiversity in an agricultural pondscape

Agriculture is a leading cause of biodiversity loss and significantly impacts freshwater biodiversity through many stressors acting locally and on the landscape scale. The individual effects of these numerous stressors are often difficult to disentangle and quantify, as they might have nonlinear impacts on biodiversity. Within agroecosystems, ponds are biodiversity hotspots providing habitat for many freshwater species and resting or feeding places for terrestrial organisms. Ponds are strongly influenced by their terrestrial surroundings, and understanding the determinants of biodiversity in agricultural landscapes remains difficult but crucial for improving conservation policies and actions. We aimed to identify the main effects of environmental and spatial variables on α‐, β‐, and γ‐diversities of macroinvertebrate communities inhabiting ponds (n = 42) in an agricultural landscape in the Northeast Germany, and to quantify the respective roles of taxonomic turnover and nestedness in the pondscape. We disentangled the nonlinear effects of a wide range of environmental and spatial variables on macroinvertebrate α‐ and β‐biodiversity. Our results show that α‐diversity is impaired by eutrophication (phosphate and nitrogen) and that overshaded ponds support impoverished macroinvertebrate biota. The share of arable land in the ponds' surroundings decreases β‐diversity (i.e., dissimilarity in community), while β‐diversity is higher in shallower ponds. Moreover, we found that β‐diversity is mainly driven by taxonomic turnover and that ponds embedded in arable fields support local and regional diversity. Our findings highlight the importance of such ponds for supporting biodiversity, identify the main stressors related to human activities (eutrophication), and emphasize the need for a large number of ponds in the landscape to conserve biodiversity. Small freshwater systems in agricultural landscapes challenge us to compromise between human demands and nature conservation worldwide. Identifying and quantifying the effects of environmental variables on biodiversity inhabiting those ecosystems can help address threats impacting freshwater life with more effective management of pondscapes.

Ecological integrity assessment of streams in the light of natural ecoregions and anthropic land use

Reference conditions for river bioassessment should be established inside ecoregions. Our objectives were (1) to implement a bioassessment methodology for Uruguayan prairie streams regarding ecoregions and land use and (2) to assess the ecological integrity of streams of the Río Negro basin in Uruguay. Due to logistical constraints, sampling was divided into two collection trips: one including the upper basin in fall 2015 and the other including the lower basin in spring 2016. Basins were analyzed separately due to seasonal and geographical differences. In the streams sampled in fall 2015, conductivity, total nitrogen (TN), and total phosphorus (TP) were higher in sedimentary ecoregions than in crystalline ones, independent on land use. In those sampled in spring 2016, these variables showed the highest values in the ecoregions dominated by agriculture. Eighty percent of the sampled streams presented the impact of cattle in their riparian zone. Discriminant analysis showed a similar composition of macroinvertebrates among ecoregions in 2015, but different composition between land uses. Conversely, in 2016, there were differences among some ecoregions, but not between land uses. Agriculture was correlated with tolerant invertebrates, while natural land use and afforestation were correlated with sensitive ones. The BMWP-Colombia showed the impact of livestock on streams, but in general good water quality, while an index of genera for Uruguay, indicated that all streams are eutrophic, thereby confirming the importance of using different types of metrics. Due to its geographical homogeneity and small size, a smaller number of ecoregions could be defined for stream assessments in the Río Negro basin.

Ecological River Health Assessment Using Multi-Metric Models in an Asian Temperate Region with Land Use/Land Cover as the Primary Factor Regulating Nutrients, Organic Matter, and Fish Composition

This study was performed to determine the ecological health of a temperate river over nine years (2011−2019); it also analyzed the trophic structure and linkage of nutrients (nitrogen [N] and phosphorus [P]), sestonic chlorophyll-a (CHL-a), and the top trophic fish in the Asian monsoon region. Water chemistry, trophic indicators, and tolerance guilds were primarily influenced by land use and land cover (LULC); the magnitude of variation was also related to geographic elevation, artificial physical barriers (weirs), and point sources. Levels of nutrients, organic matter, and CHL-a largely influenced by the intensity of the monsoon seasonality for a particular LULC and stream order. Mann−Kendall tests based on a long-term annual dataset showed that annual organic matter and CHL-a increased over time because of longer hydraulic residence time after weir construction. The results of empirical nutrient models suggested that P was the key determinant for algal growth (CHL-a); the strong P-limitation was supported by N:P ratios > 17 in ambient waters. Linear regression models and canonical correspondence analysis (CCA) were used to determine the influences of LULC and water quality on the trophic/tolerance linkages, fish community compositions and structures, and river health. Tolerant species had a positive functional relationship with nutrient enrichment through total phosphorus (TP) (R2 = 0.55, p < 0.05) and total nitrogen (TN) (R2 = 0.57, p < 0.05), organic pollution in terms of biological oxygen demand (BOD) (R2 = 0.41, p < 0.05) and chemical oxygen demand (COD) (R2 = 0.49, p < 0.05), and algal growth (R2 = 0.47, p < 0.05); sensitive species exhibited the opposite pattern. The degradation of river health, based on the multi-metric index of biotic integrity (IBI) model, was evident in the downriver region (“fair−poor” condition) and was supported by the quantitative fish community index (QFCI) model. The outcomes suggested that the degradation and variation of ecological river health, trophic linkages of water chemistry (N, P)-algal biomass-fish, were largely controlled by the land use pattern and construction of physical barriers in relation to the Asian monsoon.

Improved management of farm dams increases vegetation cover, water quality, and macroinvertebrate biodiversity

In many farming landscapes, aquatic features, such as wetlands, creeks, and dams, provide water for stock and irrigation, while also acting as habitat for a range of plants and animals. Indeed, some species threatened by land‐use change may otherwise be considerably rarer—or even suffer extinction—in the absence of these habitats. Therefore, a critical issue for the maintenance of biodiversity in agricultural landscapes is the extent to which the management of aquatic systems can promote the integration of agricultural production and biodiversity conservation. We completed a cross‐sectional study in southern New South Wales (southeastern Australia) to quantify the efficacy of two concurrently implemented management practices—partial revegetation and control of livestock grazing—aimed at enhancing the vegetation structure, biodiversity value, and water quality of farm dams. We found that excluding livestock for even short periods resulted in increased vegetation cover. Relative to unenhanced dams (such as those that remained unfenced), those that had been enhanced for several years were characterized by reduced levels of turbidity, nutrients, and fecal contamination. Enhanced dams also supported increased richness and abundance of macroinvertebrates. In contrast, unenhanced control dams tended to have high abundance of a few macroinvertebrate taxa. Notably, differences remained between the macroinvertebrate assemblages of enhanced dams and nearby “natural” waterbodies that we monitored as reference sites. While the biodiversity value of semilotic, natural waterbodies in the region cannot be replicated by artificial lentic systems, we consider the extensive system of farm dams in the region to represent a novel ecosystem that may nonetheless support some native macroinvertebrates. Our results show that management interventions such as fencing and grazing control can improve water quality in farm dams, improve vegetation structure around farm dams, and support greater abundance and diversity of aquatic macroinvertebrates.

Influence of the catchment area use on the water quality in the Utrata River

The present paper discusses the impact of land use and seasons on the concentration of nutrients in the waters of the Utrata River (Pruszków Poviat, Mazowieckie Voivodeship) from April 2018 to March 2019. The pollution of rivers by nutrients is a major problem for society. Surface water is a source of drinking water, water used for industrial and agricultural purposes. With the increasing pollution of rivers, the purification process for these purposes becomes more expensive and more challenging. To assist in carrying out activities aimed at reducing the inflow of biogenic substances into large river systems and then down to the Baltic Sea, we analyzed the spatial and temporal dynamics of loads from the entire Utrata River catchment area. We divided the entire catchment area into three impact zones: grasslands and wastelands, urbanized areas, and agricultural land and examined changes in nutrient concentrations (total phosphorus, nitrate nitrogen, ammonium nitrogen) in each of the zones. The results were statistically processed using the 1-factor ANOVA method with the p-value of significance below 0.05. Research indicates an increase in the concentration of total phosphorus and nitrogen forms down the course of the river in urban and agricultural areas with persistently low concentrations of these biogenic substances in grasslands.

Assessing the health of forested riverine systems in the Niger Delta area of Nigeria: a macroinvertebrate-based multimetric index approach

Forested catchments surround most of the riverine systems in the Niger Delta area of Nigeria. Presently, there are no biomonitoring tools to assess the ecological health of forested rivers in the area. Hence, this study is aimed at developing a macroinvertebrate-based multimetric index for assessing the health forested riverine systems in the Niger Delta area of Nigeria. Physico-chemical variables and macroinvertebrates were sampled from 18 sites in 11 rivers. Physico-chemical variables were used to categorise river sites into three ecological classes, which include near natural sites (NNS), slightly disturbed sites (SDS) and moderately disturbed sites (MDS). Fifty-four(54) macroinvertebrate candidate metrics in four groups which include abundance, composition, richness and diversity were selected for the development of the Niger Delta forested rivers multimetric index (FoMIND). Of the 54 metrics selected, four were integrated into the FoMIND, and they include EPT/Chironomidae abundance, %ETOC, Diptera richness and evenness index. Correlation of integrated metrics with physico-chemical variables on redundancy analysis (RDA) ordination showed that EPT/Chironomidae abundance and evenness index positively associated with dissolved oxygen at NNS which confirmed the near-natural conditions of most of the forested riverine systems in the Niger Delta. Therefore, FoMIND is recommended as a rapid diagnostic tool for monitoring and assessing water quality conditions of rivers within forested catchments in Nigeria.

Contrasting land-uses in two small river basins impact the colored dissolved organic matter concentration and carbonate system along a river-coastal ocean continuum

Human activities have led to an increase in land use change, with effects on the structure and functioning of ecosystems. The impact of contrasting land uses along river basins on the concentration of colored dissolved organic matter (CDOM) reaching the coastal zone, and its relationship with the carbonate system of the adjacent coastal ocean, is poorly known. To understand the relationship between land use change, CDOM and its influence on the carbonate system, two watersheds with contrasting land uses in southern Chile were studied. The samples were collected at eight stations between river and adjacent coastal areas, during three sampling campaigns in the austral summer and spring. Chemical and biological samples were analyzed in the laboratory according to standard protocols. Landsat 8 satellite images of the study area were used for identification and supervised classification using remote sensing tools. The Yaldad River basin showed 82% of native forest and the Colu River basin around 38% of grassland (agriculture). Low total alkalinity (A_T) and Dissolved Inorganic Carbon (DIC), but high CDOM proportions were typically observed in freshwater. A higher CDOM and humic-like compounds concentration was observed along the river-coastal ocean continuum in the Yaldad basin, characterized by a predominance of native forests. In contrast, nutrient concentrations, A_T and DIC, were higher in the Colu area. Low CaCO₃ saturation state (Ω_Ar < 2) and even undersaturation conditions were observed at the coastal ocean at Yaldad. A strong negative correlation between A_T, DIC and Ω_Ar with CDOM/fDOM, suggested the influence of terrestrial material on the seawater carbon chemistry. Our results provide robust evidence that land uses in river basins can influence CDOM/fDOM proportion and its influence on the carbonate chemistry of the adjacent coastal, with potential implications for the shellfish farming activity in this region.

Temporal Variability of Macroinvertebrate Assemblages in a Mediterranean Coastal Stream: Implications for Bioassessment

Macroinvertebrates from a small forest stream in central-south Chile were sampled monthly from September 2017 to August 2018 to assess temporal variability in the assemblage and the effects of that variability on ecological indicators. Higher precipitation and flows occurred in winter months, and water quality varied among months. We collected 59 macroinvertebrate taxa, finding higher taxa richness and abundances in summer months than in winter months. Four taxa demonstrated marked seasonality, being abundant in some months and then decreasing in following months (Limnoperla jaffueli (Navás), Nousia maculata (Demoulin), Smicridea sp. (McLachlan), Chironomidae spp.). The scores of the family Hilsenhoff Biotic Index (HBI), Hilsenhoff Species-level Biotic Index (HSBI), Multimetric Macroinvertebrate Index (MMI), and Chilean Biological Monitoring Working Party (ChBMWP) index varied throughout the year reflecting natural variability. However, only HBI and HSBI scores were significantly different among seasons, ranging across three water quality classes (excellent, very good, and good), showing the lowest water classes in spring, coinciding with higher abundances of tolerant species. The MMI and ChBMWP indicated good and very good site conditions throughout the year, respectively. Shannon-Weaver diversity ranged between 2.59 (April) and 1.78 (February); however, Pielou evenness had high values throughout the year (> 0.62), except in February. Changes in macroinvertebrates composition throughout the year were explained primarily by discharge, water temperature, and conductivity. Our findings indicate that natural monthly variability in macroinvertebrate assemblages influences the scores of biological indices throughout the year. Therefore, we recommend that natural stream variability be accounted for in biomonitoring programs. We also emphasize the need to use caution when interpreting biological index scores to avoid misinterpretations in stream quality classification.

Effects of COVID-19 lockdown and unlock on health of Bhutan-India-Bangladesh trans-boundary rivers

The COVID-19 pandemic significantly destructs the rhythm of global modern human civilization but worldwide lockdown radically recovers the health of the total environment. The Himalayan trans-boundary rivers provide huge provisional, regulatory and cultural ecosystem services to millions of people throughout the year but in the recent years the water quality is being deteriorated due to multiple reasons. In the last decade, India-Bangladesh political relationship has been slightly broken down due to water sharing and environmental flow of rivers.The COVID-19 lockdown offered a great scope to execute the comparative study among pre, lockdown and unlock phase. The research attempts to investigate the spatiotemporal water quality of trans-boundary rivers through WAWQI and irrigation water quality indices such as Sodium absorption ratio, Soluble sodium percentage, Potential salinity, Magnesium hazard and Kelly's index considering eighteen water quality parameters (pH, EC, TDS, TSS, Ca²⁺, Mg²⁺, Na²⁺, K⁺, F-, Cl-, NO3-, SO₄²-, PO 4 3 -, DO, T, TUR, COD and BOD). The result shows the strong positive correlation between EC and TDS during three phases. Significant reduction of BOD, COD and TUR has been noticed almost 70% stations during lockdown compared with prelockdown while augmentation of DO has been recorded around 40% stations. WQI of most of the stations shows around 80% improvement of water quality during lockdown period. Moreover, worst kind of WQI was found in the Mathabhanga-Churni river followed by Mahananda. During lockdown, the striking results show that SAR and MH were significantly amplified in most of the stations due to agricultural run-off.

Response of aquatic insects to an environmental gradient in Amazonian streams

The increasing land use in the Amazon region has resulted in the widespread substitution of forest areas with pasture and bauxite mining. These land uses reduce the forest cover of streams and modify their characteristics, reducing the diversity of aquatic insect assemblages. In the present study, we aimed to identify the threshold of the assemblages of the larvae of insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (collectively known as EPT), and adults of the order Odonata, along an environmental gradient of land use and land cover (LULC). We sampled 30 streams along an environmental gradient determined by the proportion of forest, pasture, and bauxite mining observed within the catchment of each stream. We identified 12 taxa associated with forest (nine positively and three negatively) and four negatively associated with pasture. However, no taxa were associated explicitly with the bauxite mining gradient. As forest is converted to pasture, the abundance and frequency of occurrence of the taxa sensitive to pasture are reduced, reflecting their environmental sensitivity and their potential as sentinels of preserved streams. The identification of the thresholds of the EPT and odonates taxa allowed us to determine which of these organisms are positively or negatively associated with the environmental gradient of LULC in Amazonian streams. We hope that the results of the present study can be applied in future biomonitoring programs, particularly for monitoring the response of aquatic insects to the degradation of streams.

Improving river hydromorphological assessment through better integration of riparian vegetation: Scientific evidence and guidelines

River hydromorphology has long been subjected to huge anthropogenic pressures with severe negative impacts on related ecosystems' functioning and water quality. Therefore, improving river hydromorphological conditions represents a priority task in sustainable river management and requires proper assessment tools. It is well known that riparian vegetation plays a crucial role in sustaining river hydromorphological conditions. However, it has been nearly neglected in most hydromorphological assessment protocols, including the European Water Framework Directive (WFD). This paper reviews and synthesizes the relevance of riparian vegetation for river hydromorphology, focusing on its contribution to streamflow and sediment regime conditions. We also examine how riparian vegetation is considered in the WFD and how it is included in national hydromorphological protocols currently in use. Our findings point to a temporal mismatch between the date when the WFD came into force and the emergence of scientific and technologic advances in riparian vegetation dynamism and bio-geomorphic modeling. To overcome this misalignment, we present promising approaches for the characterization and assessment of riparian vegetation, which include the identification of vegetation units and indicators at multiple scales to support management and restoration measures. We discuss the complexity of riparian vegetation assessment, particularly with respect to the establishment of river-type-based reference conditions and the monitoring and management targets, and propose some attributes that can serve as novel indicators of the naturalness vs. artificiality of riparian vegetation. We argue that the hydromorphological context of the WFD should be revisited and offer guidance to integrate riparian vegetation in river hydromorphological monitoring and assessment.

Effects of different types of land-use on taxonomic and functional diversity of benthic macroinvertebrates in a subtropical river network

Expansion of agricultural and urban areas and intensification of catchment land-use increasingly affect different facets of biodiversity in aquatic communities. However, understanding the responses of taxonomic and functional diversity to specific conversion from natural forest to agriculture and urban land-use remains limited, especially in subtropical streams where biomonitoring programs and using functional traits are still under development. Here, we conducted research in a subtropical stream network to examine the responses of macroinvertebrate taxonomic and functional diversity to different types of land-use in central China. Our results showed that medium body size, univoltine, gill respiration, and slow seasonal development were much higher in natural forest sites, while certain traits related to strong resilience and resistance (e.g., small body size, fast seasonal development, bi-or multivoltine, abundant occurrence in drift, sprawler) dominated in high-intensity agriculture and urbanization sites. We further found that land-use compromised water quality (e.g., increases in total phosphate, conductivity and water temperature) and habitat conditions (e.g., high proportion of sand and silt, gravel, and channel width) accounted for the changes in trait composition based on a combination of RLQ and fourth-corner analysis. Moreover, natural forest sites presented relatively high values of functional richness than other land-use, demonstrating the importance of natural forest maintenance to promote high levels of functional diversity. However, taxonomic diversity indexes showed higher sensitivity to distinguish different types of land-use compared to functional diversity measures. Even so, given that certain trait categories showed significant relationships with specific local environmental stressors, trait-based approaches can provide reliable evidence to diagnose the cause of impairment and complement the results of the taxonomic-based approaches. Our findings support the idea that taxonomic and functional approaches should be integrated in river restoration and land-use management.

Identifying and classifying macroinvertebrate indicator signature traits and ecological preferences along urban pollution gradient in the Niger Delta

Urbanisation of riverine landscape is an increasing threat to the functionality of river ecosystems. In this study, we identify and classify macroinvertebrates indicator signature traits and ecological preferences.We hypothesised that urban pollution would differentially influence the distribution of macroinvertebrate traits and ecological preferences along a gradient of water quality deterioration. Hence, we identified and classified potential biological indicators traits and ecological preferences that were deemed tolerant of or sensitive to urban pollution gradient in the Niger Delta region of Nigeria. Physico-chemical variables (water temperature, depth, flow velocity, dissolved oxygen, biochemical oxygen demand, electrical conductivity (EC), nitrate, phosphate), and macroinvertebrates were collected from 2008 to 2012 seasonally during the wet and dry seasons once in a month in 11 stations in eight river systems. The results based on RLQ, fourth-corner and Kruskal-Wallis analyses indicate that traits/ecological preferences such as tegumental/cutaneous respiration, cased/tubed body armouring, a preference for silty water, bivoltinism, burrowing and a high tolerance for oxygen depletion, were statistically significantly associated with the heavily impacted stations. These traits were positively correlated with physico-chemical variables such as EC, nitrate and phosphate indicative of urban pollution. On the other hand, traits/ecological preferences such as permanent attachment, crawling, swimming, univoltinism and a moderate sensitivity to oxygen depletion were associated with the least impacted stations and were negatively correlated with physico-chemical variables indicative of urban pollution. Overall, the observed differential responses of traits and ecological preferences to urban pollution along a gradient of water quality impairment suggest that traits and ecological preferences can serve as useful biological indicators and thus supports the growing evidence of the utility of the trait-based approach.

Comparison between water quality indices in watersheds of the Southern Bahia (Brazil) with different land use

The present study evaluated the influence of land use and occupation on water quality indices (WQI); the WQI developed by the National Sanitation Foundation (NSF), the WQI adapted by the Environmental Company of the São Paulo State (CETESB), WQI proposed by Bascarón and the Canadian Council of Ministers of the Environment (CCME) WQI, obtained for watersheds located in the Eastern Water Planning and Management Region (BA). The study also analyzed the divergences and similarities of these WQI methods. Water quality data were obtained from the Monitoring Program (Monitora) of Environment and Water Resources Institute of Bahia (INEMA), covering the period from 2008 to 2015, at thirteen (13) sampling sites, with quarterly collections, as well as land use and occupation data. The influence of land use and occupation on water quality indices was assessed by principal component analysis (PCA). The PCA showed that urban and agricultural/pasture areas were influencing factors on water quality variables, such as total phosphorus, biochemical oxygen demand, total nitrogen, turbidity total residues and consequently lower WQI values in the Cachoeira watershed. Among the tested methods to evaluate the water quality of watersheds in the study area, the most similar were the NSF WQI, CETESB WQI, and Objective Bascarón WQI.

Correlations between land use and stream nitrate-nitrite concentrations in the Yahara River Watershed in south-central Wisconsin

To better inform land management decisions, we explored relationships between land use data and stream nitrate-nitrite (NO₃NO₂) concentration data in the Yahara River Watershed (YRW) in south-central Wisconsin, USA. Three metrics were used to evaluate the extent of different land uses in the watershed: (1) the area percentage of each land use in both the watershed and in a range of riparian zone widths, (2) the area factor, which refers to the ratio of the area of woodland, recreational, open and vacant subdivided land, or wetlands in the riparian zone (6.1-213.4 m widths) to agricultural areas in the rest of watershed, which indicates the buffering capacity of the riparian zone, and (3) the inverse-distance-weighted (IDW) area percentage with proximity to sub-watershed outlet and to stream, which characterizes spatial arrangement in the watershed by assigning a higher weight to patches closer to the outlet or stream and a lower weight to those farther away. We found significant, positive correlations between the extent of agricultural areas and stream NO₃NO₂ concentrations. NO₃NO₂ concentrations were highly correlated to area factor metrics for all riparian zone widths such that as area factor decreased, NO₃NO₂ concentrations increased. There was also a marked increase in NO₃NO₂ concentrations at a threshold of approximately 60% agricultural area with IDW proximity to stream. Wetland area percentage in the entire watershed and IDW wetland area percentage with proximity to stream were negatively correlated to stream NO₃NO₂ concentrations. Compared to the simple area percentage metric, area factor and IDW wetland area percentage with proximity to stream were better indicators of stream NO₃NO₂ concentrations. Results from this study indicate that, in addition to land use area percentage, spatial distributions of land uses should be considered when managing watersheds. This study also demonstrates the value of citizen-based sampling data and reveals opportunities to improve the utility of such data.

Riparian Vegetation Structure Influences Terrestrial Invertebrate Communities in an Agricultural Landscape

Stream and terrestrial ecosystems are intimately connected by riparian zones that support high biodiversity but are also vulnerable to human impacts. Landscape disturbances, overgrazing, and diffuse pollution of agrochemicals threaten riparian biodiversity and the delivery of ecosystem services in agricultural landscapes. We assessed how terrestrial invertebrate communities respond to changes in riparian vegetation in Romanian agricultural catchments, with a focus on the role of forested riparian buffers. Riparian invertebrates were sampled in 10 paired sites, with each pair consisting of an unbuffered upstream reach and a downstream reach buffered with woody riparian vegetation. Our results revealed distinct invertebrate community structures in the two site types. Out of 33 invertebrate families, 13 were unique to either forested (6) or unbuffered (7) sites. Thomisidae, Clubionidae, Tetragnathidae, Curculionidae, Culicidae, and Cicadidae were associated with forested buffers, while Lycosidae, Chrysomelidae, Staphylinidae, Coccinellidae, Tettigoniidae, Formicidae, and Eutichuridae were more abundant in unbuffered sites. Despite statistically equivocal results, invertebrate diversity was generally higher in forested riparian buffers. Local riparian attributes significantly influenced patterns in invertebrate community composition. Our findings highlight the importance of local woody riparian buffers in maintaining terrestrial invertebrate diversity and their potential contribution as a multifunctional management tool in agricultural landscapes.

How does Urban Pollution Influence Macroinvertebrate Traits in Forested Riverine Systems?

The influence of urbanization on macroinvertebrate traits was explored in forested rivers in the Niger Delta area of Nigeria. Physico-chemical variables were sampled on a monthly basis alongside macroinvertebrates in 20 sites of 11 rivers spanning 2008–2012. Physico-chemical variables were used to classify the 20 sites into three ecological classes, namely: least impacted sites (LIS), moderately impacted sites (MIS) and highly impacted sites (HIS) using principal component analysis. Our results based on RLQ (R = physico-chemical variables, L = macroinvertebrate taxa and Q = macroinvertebrate traits) and fourth-corner analyses revealed that large body size, grazing and hardshell were positively significantly associated with LIS on the RLQ. They were also either negatively correlated with any two of water temperature, nutrients, BOD5 and flow velocity or positively significantly correlated with increasing DO. Thus, these traits were considered sensitive to urban pollution in forested rivers. Burrowing, predation and pupa aquatic stage, which were positively associated with HIS, were also significantly negatively correlated with increasing DO, and were deemed tolerant of urban pollution in forested rivers. Box plots and a Kruskal–Wallis test revealed that the three sensitive traits were significantly highest at LIS (p < 0.05) except grazing; while the three tolerant traits were significantly highest at MIS (p < 0.05) except burrowing. Overall, this study revealed that urban pollution influences macroinvertebrate traits differently in forested rivers.

Vegetation influences soil properties along riparian zones of the Beijiang River in Southern China

Riparian soils and vegetation are important factors influencing the biodiversity and biogeochemical processes of river ecosystems. Riparian soils and vegetation form the foundation for multiple ecosystem services provided by river ecosystems. However, it remains poorly understood how riparian soils and vegetation interact with one another to maintain these services. In this study, we sampled four common types of riparian vegetation associated with the Beijiang River in South China. These included forestland, bamboo forest, mixed forest, and grassland ecosystems. Specifically, we analyzed the spatial distribution of riparian soils and their response to environmental factors (i.e., coverage and height of trees, shrubs and grass, distance to river, and altitude). Our results indicate that soil properties in riparian zones were affected significantly by vegetation type. In particular, clay content, soil organic carbon, and nitrate nitrogen content were significantly correlated with vegetation type. In contrast, changes in soil total nitrogen, total phosphorus, and available phosphorus content were not associated with vegetation type. Moreover, soil physical and chemical properties interacted with one an other, as well as with vegetation characteristics. This was indicated by the significant correlation observed between soil organic carbon, total nitrogen, total phosphorus, and soil texture, with structural characteristics of the four vegetation types. We also found that height and cover of trees and shrubs were significantly correlated with soil chemical properties. However, the effects of topographic variables such as altitude and distance to river were not significant. Results from this study can thus provide a basis for the ecological restoration and land management of degraded iparian zones.

Influence of Land-Use Classes on the Functional Structure of Fish Communities in Southern Brazilian Headwater Streams

Changes in landscape composition caused by conversion of natural habitats into human-altered ecosystems can directly influence the physical characteristics of stream networks. Such impacts can modify the functional structure of fish communities, although the exact consequences of anthropic land-use changes can be context-dependent. This study investigated the influence of different land-use classes on the functional structure of fish communities in 32 headwater streams from southern Brazil. Trait composition and indices of functional diversity of the fish community were related to four land-use classes: native forest vegetation, silviculture, agriculture, and urban areas. Streams surrounded by larger areas of native forest were characterized by the predominance of foraging specialist species like grazers. However, as native vegetation is replaced by agriculture and urban areas, specialist species are replaced by species with generalist diet like detritivores. In streams surrounded by larger areas of agriculture, functional richness and divergence increased, while functional evenness decreased. Most likely, these changes were induced by alterations in the water quality, indicated by increased electrical conductivity and water temperature in streams with more agriculture areas. In conclusion, the conservation of the native forest vegetation is essential to maintain habitat characteristics and ecological processes in streams and to avoid the loss of specialist species in fish communities.

Spatially Variable Relationships between Karst Landscape Pattern and Vegetation Activities

Based on the theories of structure–function correlation in Geography, and landscape pattern-ecological function correlation in Landscape Ecology, the correlation between land use fragmentation and vegetation activity was quantified. Effective mesh size (meff) was calculated to represent landscape fragmentation for land use, and the normalized difference vegetation index (NDVI) was used to reflect vegetation activity. The geographically weighted regression (GWR) model was applied to explore the spatial non-stationary relationship between meff and NDVI in a karst basin of the southwestern China, where environmental factors (i.e., climate, topography, and vegetation) are spatially heterogeneous. The spatial variation and scale dependence of landscape fragmentation and its relationship with vegetation activity, as well as the influence of lithology types and landforms relief, were considered. Firstly, the optimal ‘slide window’ size for landscape fragmentation was determined to be 500 m, and spatial pattern of meff displayed clear heterogeneity with a serious degree of fragmentation. Landscape fragmentation was more severe in carbonate areas than non-carbonate areas, reflecting the influence of landforms relief. More serious fragmentation in dolomite areas meant that the impact of human activities on the landscape morphological characteristics was much more significant than that in the limestone areas with steeper slope. Multi-scale analysis was used to verify a neighborhood size of 7 km for GWR in the study area. Negative effects on vegetation activity from landscape structural changes were more significant in limestone areas, which may be due to the more vulnerable ecosystems there. This research can provide scientific guidance for landscape management in karst regions as it considers the multi-scaled and spatially heterogeneous effects of lithology, geomorphology, and human factors on landscape structure and its correlation with vegetation activity.

An Estimated Structural Equation Model to Assess the Effects of Land Use on Water Quality and Benthic Macroinvertebrates in Streams of the Nam-Han River System, South Korea

The extent of anthropogenic land use in watersheds determines the amount of pollutants discharged to streams. This indirectly and directly affects stream water quality and biological health. Most studies have therefore focused on ways to reduce non-point pollution sources to streams from the surrounding land use in watersheds. However, the mechanistic pathways between land use and the deterioration of stream water quality and biological assemblages remain unclear. This study estimated a structural equation model (SEM) representing the impact of agricultural and urban land use on water quality and the benthic macroinvertebrate index (BMI) using IBM AMOS in the Nam-Han river systems, South Korea. The estimated SEM showed that the percent of urban and agricultural land in the watersheds significantly affected both the water quality and the BMI of the streams. Specifically, a higher percent of urban land use had directly increased the biochemical oxygen demand (BOD) and total phosphorus (TP), and deteriorated the BMI of streams. Similarly, higher proportions of agricultural land use had also directly increased the BOD, total nitrogen (TN), and total phosphorus (TP) concentrations, and lowered the BMI of streams. In addition, it was observed that the percent of urban and agricultural land use had indirectly deteriorated the BMI through increased BOD. However, we were not able to observe any significant indirect effect of the percent of urban and agricultural land use through increased nutrients including TN and TP. These results indicate that increased urban and agricultural land use in the watersheds had directly and indirectly affected the physicochemical characteristics and benthic macroinvertebrate communities in streams. Our findings emphasize the need to develop more elaborate environmental management and restoration strategies to improve the water quality and biological status of streams.

A Century after! Rediscovery of the ancient catfish Diplomystes Bleeker 1858 (Siluriformes: Diplomystidae) in coastal river basins of Chile and its implications for conservation

ABSTRACT The ancient catfish family Diplomystidae, with seven species endemic to rivers of southern South America, represents one of the oldest branches of the diverse order Siluriformes. With most species endangered, new reports of these species become extremely valuable for conservation. Currently, it is assumed that Diplomystes species inhabit only Andean (large) basins, and that they are extinct from coastal (small) basins from which their presence have not been recorded since 1919. Here, we document new records of the family Diplomystidae in the Laraquete and Carampangue basins, two coastal basins from the Nahuelbuta Coast Range, Chile, with no previous reports. This finding represents the rediscovery of the genus in coastal basins in more than a Century. Based on analysis of mitochondrial DNA sequences, the collected specimens were found to be closely related to Diplomystes nahuelbutaensis from the Andean Biobío Basin, but sufficiently differentiated to suggest that coastal basin populations are a different management unit. These populations are important because, contrary to previous thoughts, they prove these catfish can survive in small river networks, providing unique opportunities for research and conservation. The conservation category of Critically Endangered (CE) is recommended for the populations from the Laraquete and Carampangue basins.

Macroinvertebrate functional feeding group alterations in response to habitat degradation of headwater Austral streams

Protecting the structural and functional integrity of lotic ecosystems is becoming increasingly important as many ecological systems face escalating pressures from human population growth and environmental impacts. Knowledge on the functional composition of macroinvertebrates in austral temperate streams is generally lacking hindering the design and implementation of water management and restoration goals. Therefore, this study examined the effects of urban land-use activities on the benthic macroinvertebrate functional feeding guild structure among different stream orders in an austral river system (Bloukrans River) in the Eastern Cape Province of South Africa. Water quality and macroinvertebrate community data were collected across two seasons from 18 sites in two different stream order categories (i.e. 1, 2 + 3), following standard methods. We separated macroinvertebrates into functional feeding groups (FFGs), which we then used to assess the effects of riparian condition on FFG organization. Linear mixed effects model (LMM) results demonstrated that total dissolved solids (TDS), canopy cover, phosphate and channel width were the key variables that described the major sources of variation in macroinvertebrate FFGs. Based on FFG proportions, collector-gatherers were the most abundant in the Bloukrans River and represented 71.3% of the macroinvertebrate assemblages. The FFG ratios indicated that all the eighteen sites were strongly heterotrophic (i.e. streams received additional sources of energy from leaf litter and other organic matter), showed below expected linkage with riparian input and stable substrates were limited. The FFG ratios offered some insights into the overall functioning of Bloukrans River system. Our results highlight the importance of including macroinvertebrate functional diversity as a complementary approach to assess the ecological integrity in management and restoration plans of river systems.

Is eating wild rainbow trout safe? The effects of different land-uses on heavy metals content in Chile

Cu, Mn, Fe, Zn, Cd and Pb levels were measured in liver and muscle samples of Rainbow Trout Oncorhynchus mykiss collected from three watersheds with different land-uses: native forest, exotic plantation, and agriculture in Chile, during January, April, July, and October 2012. Cd and Pb levels were not detected in the liver and muscle, probably since they are under the detection limits. Higher metal concentrations (liver-muscle tissues) were detected in samples from agriculture and exotic plantation streams, whereas trout from native forest streams had lower metal concentrations. Higher metal concentrations were detected in liver tissue compared to muscle tissue, and both negatively correlated to the length and weight of the fish. This suggest the liver had higher ability to accumulate Cu, Mn, Fe and Zn compared to muscle tissue. The concentration range of Fe and Zn recorded in the muscle are within the range reported by other authors, whereas Mn and Cu concentrations are higher than reported in the literature. However, at all sites the concentration of selected metals were below the limits permitted by current legislation (FAO), and therefore did not put the human population at risk, suggesting that is eating wild rainbow trout safe in Chile.

Examining the influence of human stressors on benthic algae, macroinvertebrate, and fish assemblages in Mediterranean streams of Chile

Changes in land-uses and cover are strong drivers of stream degradation worldwide. In Mediterranean ecoregions, land conversion from forest with native species to tree plantations, agricultural, and urban areas have drastically increased in recent years. Here, we examined the influence of land-use types on water quality (physical and chemical variables) and biota (benthic algae, macroinvertebrates, and fishes). We conducted field surveys between December-March 2016 (dry season) in 24 sites located across four land-use types including native vegetation (NV), tree plantation (TP), agriculture (Ag), and urban (Ur) within the Chilean Mediterranean ecoregion. We calculated metrics and multivariate statistics to assess correlations between biological and environmental variables. Significant differences between land-uses were found for environmental/physicochemical variables and the three biotic groups (i.e., benthic algae, macroinvertebrates, and fishes). We found higher chlorophyll-a biomass for TP, Ag, and Ur compared to NV streams. The macroinvertebrate diversity of sensitive taxa (i.e., Ephemeroptera, Plecoptera, and Trichoptera) and water quality were lower in land draining streams with human uses, other than NV, with the most evident impact found in Ag and Ur streams. NV and TP streams had a lower Diptera density and lower percentage of non-insect taxa. Fish richness and diversity were not affected by land-use. However, cold-water fishes (both native and introduced) were closely associated with NV and TP streams whereas warm-water fishes (mostly introduced) were closely associated with Ag and Ur streams. Multivariate analysis revealed that both local habitat and catchment-scale variables influenced each biological assemblage. Our findings suggest that benthic algae, macroinvertebrates, and fish populations are good indicators of human land-use disturbances, with Ag and Ur areas being the most detrimental for freshwater biota.

Aquatic ecosystem health assessment of a typical sub-basin of the Liao River based on entropy weights and a fuzzy comprehensive evaluation method

River ecosystem health assessments provide the foundation for river ecological protection and integrated management. To evaluate the aquatic ecosystem health of the Fan River basin, benthic macroinvertebrate indices (the Multimeric Macroinvertebrates Index Flanders (MMIF) and Family Biotic Index (FBI)), a habitat index (the river habitat quality Index (RHQI)) and a water quality index (the Improved Water Pollution Index (IWPI)) were selected. The entropy weighting method was used to calculate the RHQI and IWPI. A fuzzy comprehensive evaluation method was used to evaluate the aquatic ecosystem health. The evaluation results indicated that the aquatic ecosystem health of the Fan River basin was better in 2018 than in 2011, which respectively belonged to the ends of the 11th and 12th Five-Year Plans of the Major Science and Technology Programs for Water Pollution Control and Treatment in China. The proportions of sampling stations with good, moderate and poor grades in 2011 were 50.0%, 40.0% and 10.0%, respectively, and in 2018, the proportions of stations with excellent, good and moderate grades were 20.0%, 50.0% and 30.0%, respectively. A correlation analysis showed that the RHQI was significantly correlated with the MMIF, FBI and IWPI. The riparian land use pattern was an important factor that influenced changes in the aquatic ecosystem health grade. Of the water quality parameters, total phosphorous (TP) and potassium bichromate index (COD) were the main factors that affected the characteristics of benthic macroinvertebrates and the aquatic ecosystem health.

Making global river ecosystem health assessments objective, quantitative and comparable

Assessing and comparing global river ecosystem health in an objective and quantitative way remains a major challenge. In this study the widely-used semi-quantitative methods Rapid Biological assessment Protocols (RBPs) was used to determine the health of rivers. The findings were then compared to the results derived from our new UAV (Unmanned aerial vehicles) orthophotographic imagery method. This method quantitatively and objectively assesses river ecosystem health. As a comparison, our method was used to quantitatively measure distance and areas of a range of hydrological and biological attributes thus improving the accuracy of distance- and area-related indices, consequently avoiding subjective errors in these estimations that is fraught in methods like the RBPs. To strengthen the objectivity of the assessment the weights of these indices were objectively determined using the entropy weighting method. This new method was then tested using 9551 UAV orthophotographs taken over six field campaigns. It performed satisfactorily, showing that in our study area the health status of mountain rivers was the best with the highest score of 0.94 out of 1.0. Temporally, the health of the river was better in summer (0.65) compared with that in autumn (0.40). Changes in river ecosystem health were driven by variations in biology and water quality. In contrast the outputs of RBPs, especially in relation to distance and area indices, had ~ 20% uncertainty due to visual errors and subjectivity in estimations by observers. The UAV orthophotographic imaging method proposed in this study can improve the ability to compare the health of rivers across different periods and regions throughout the globe.

River health assessment of the Yellow River source region, Qinghai-Tibetan Plateau, China, based on tolerance values of macroinvertebrates

For decades, the river health of the Yellow River source region (YRSR) on the Qinghai-Tibetan Plateau has been a focal issue owing to its unique geographic location and ecological functions. This study investigated the ecological status of the headwater streams, the main stem, and the tributaries of the Yellow River in the YRSR using the tolerance values of macroinvertebrates and those related to biotic indices. The macroinvertebrate assemblages of the headwater streams were characterized by lower biodiversity than the tributaries downstream, based on comparisons of taxonomical composition, functional feeding group composition, and the pollution-tolerant capacity of taxa. The headwater streams had a lower ratio (16%) of pollution-sensitive macroinvertebrate taxa than that of the tributaries downstream (30%). The biotic indices (family- and genus-level biotic indices) indicated that the ecological health of the headwater streams was comparably poorer than that of the downstream tributaries. The combined effect of vulnerable natural conditions and increasing human disturbance is likely the main cause of eco-environmental degradation in the Yellow River headwater streams.

The Buffer Capacity of Riparian Vegetation to Control Water Quality in Anthropogenic Catchments from a Legally Protected Area: A Critical View over the Brazilian New Forest Code

The riparian buffer width on watersheds has been modified over the last decades. The human settlements heavily used and have significantly altered those areas, for farming, urbanization, recreation and other functions. In order to protect freshwater ecosystems, riparian areas have recently assumed world recognition and considered valuable areas for the conservation of nature and biodiversity, protected by forest laws and policies as permanent preservation areas. The objective of this work was to compare parameters from riparian areas related to a natural watercourse less than 10 m wide, for specific purposes in Law No. 4761/65, now revoked and replaced by Law No. 12651/12, known as the New Forest Code. The effects of 15, 30 and 50 m wide riparian forest in water and soil of three headwater catchments used for sugar cane production were analyzed. The catchments are located in the Environmental Protection Area of Uberaba River Basin (state of Minas Gerais, Brazil), legally protected for conservation of water resources and native vegetation. A field survey was carried out in the catchments for verification of land uses, while periodical campaigns were conducted for monthly water sampling and seasonal soil sampling within the studied riparian buffers. The physico-chemical parameters of water were handled by ANOVA (Tukey’s mean test) for recognition of differences among catchments, while thematic maps were elaborated in a geographic information system for illustration purposes. The results suggested that the 10, 30 or even 50 m wide riparian buffers are not able to fulfill the environmental function of preserving water resources, and therefore are incapable to ensure the well-being of human populations. Therefore, the limits imposed by the actual Brazilian Forest Code should be enlarged substantially.

Different responses of taxonomic and functional structures of stream macroinvertebrate communities to local stressors and regional factors in a subtropical biodiversity hotspot

Examining the relative contribution of local environmental stressors and regional factors in structuring biological communities is essential for biodiversity conservation and environmental assessment, yet their relative roles for different community characterizations remain elusive. Here, we examined the responses of taxonomic and functional structures of stream macroinvertebrate communities to local and regional factors across a human-induced environmental gradient in the Han River Basin, one subtropical biodiversity hotspot in China. Our objectives were: 1) to examine the responses of traditional taxonomic measures and functional traits to anthropogenic disturbances; 2) to compare the relative importance of environmental versus spatial variables and catchment-scale versus reach-scale variables for the two community characterizations. We found that both species and trait compositions performed well in differentiating anthropogenic disturbances, indicating that both taxonomic and functional structures of macroinvertebrate communities were strongly altered by human activities. Particularly, some traits related to life history (e.g., voltinism), resilience and resistance (e.g., adult flying ability) are well suited for predicting changes of communities towards anthropogenic disturbances owing to their mechanistic relationship with environmental gradients. We found that environmental variables played more important roles than spatial effects in structuring both taxonomic and functional facets of macroinvertebrate communities. Environmental filtering was more important in determining functional than taxonomic structure, and the opposite was true for spatial effects. In terms of environmental variables, catchment land-uses played the primary role in determining taxonomic composition, whereas reach-scale variables related to local habitat heterogeneity were more influential for functional structure. Our study highlights the importance of employing metacommunity perspectives and different community characterizations in both theoretical and applied research. For stream bioassessment and management, we argue that the combination of taxonomic and functional characterizations of community should be implemented, as different facets of biological communities responded to different types of anthropogenic disturbances.

Tracing the scientific trajectory of riparian vegetation studies: Main topics, approaches and needs in a globally changing world

Riparian vegetation is a crucial component of fluvial systems and serves multiple socio-ecological functions. The objective of this review is to follow the scientific trajectory of studies of riparian vegetation throughout history and across regions and fields of knowledge. Such a synthesis is challenging because riparian vegetation is an open co-constructed socio-ecological system at the crossroads of the biosphere, hydrosphere, lithosphere, atmosphere and anthroposphere; thus, it exhibits a wide range of ecological patterns and functioning depending on climatic, morphological and land-use contexts. To address this, we used qualitative and quantitative approaches in our review of the scientific literature. From the scientific perspective, how riparian vegetation is studied has changed over time (e.g. development of modeling and geomatic approaches) and varies among fluvial systems and geographic areas (e.g. its relation to groundwater is usually studied more in Oceania and Asia than on other continents). This review revealed the lack of a single and well-identified scientific community that focuses on riparian vegetation. This is probably due to the nature of the subject, which includes diverse fields of knowledge and several applied issues: biodiversity, forestry, water quality, hydromorphology, restoration, ecology, etc. Some topics are actively regenerated (e.g. biogeomorphological approaches) and others are emerging, which reflects general trends in ecology (e.g. functional approaches). The literature review indicates that a substantial amount of knowledge already exists; therefore, a major priority of our study is to produce a clear and integrative understanding of riparian zone functioning to address the inherent complexity of these zones and remain valid across a wide diversity of geographical contexts. It is also essential to develop detailed analysis of the sociocultural dimension of riparian vegetation to understand the ecology of riparian zones and to improve riparian vegetation management according to local recommendations in order to maintain and improve its functions and services in the face of global changes.

A new method to evaluate the vulnerability of watersheds facing several stressors: A case study in mediterranean Chile

Freshwater systems are subjected to multiple anthropogenic stressors and natural disturbances that act as debilitating agents and modifiers of river systems, causing cumulative and synergistic effects that deteriorate their health and result in watershed vulnerability. This study proposes an easy-to-apply spatial method of watershed vulnerability evaluation using Geographic Information Systems (GIS) in the Andalién River watershed, located in the Chilean mediterranean. A watershed vulnerability index (WVI) based on three sub-indices - anthropogenic stressors, environmental fragility and natural disturbances - was developed. To determine the index grouping weights, expert surveys were carried out using the Delphi method. We subsequently normalized and integrated the factors of each sub-index with relative weights. The ranges of each thematic layer were re-classified to establish vulnerability scores. The watershed was divided into three sections: headwaters zone, transfer zone and depositional zone. The watershed vulnerability index showed that 41% of the watershed had very low vulnerability and 42% had medium vulnerability, while only 1% - in the depositional zone - had high vulnerability. A one-way ANOVA was carried out to analyze the vulnerability differences among the three sections of the watershed; it showed significant differences (F (2, 16) = 8.15: p < 0.05). The a posteriori test showed differences between the headwaters and depositional zones (Tukey test, p = 0.005) and between the transfer and depositional zones (Tukey test, p = 0.014). To validate the WVI, water quality was measured at 16 stations in the watershed; there was a significant correlation between vulnerability level and NO₂^- levels (r = 0.8; p = 0.87; α = 0.05) and pH (r = 0.8; p = 0.80; α = 0.05). The WVI showed the cumulative effects of multiple stressors in the depositional zone of the watershed. This is the first study to evaluate and validate non-regulated watershed vulnerability with GIS using multiple anthropogenic and natural stressors.

Microenvironmental heterogeneity caused by anthropogenic LULC foster lower plant assemblages in the riparian habitats of lentic systems in tropical floodplains

Anthropogenic land use and land cover (LULC) create a heterogeneous environment in the floodplains. This heterogeneity may be governing plant species assemblages, diversity, and dominance patterns in the riparian habitats of the lentic systems in tropical floodplains. We tested this hypothesis in the floodplains of Barak river basin in northeast India following standard methods of plant and soil sampling/analysis and multivariate statistical tools. Plant community studies in the riparian habitats of the selected lentic systems were done at monthly intervals for a period of one year, while soil sampling and analysis were done at bimonthly intervals. Standard data visualization plots and canonical correspondence analysis (CCA) were used to assess spatiotemporal variations in species richness and diversity, environmental heterogeneity, and species-environment association. The study revealed that anthropogenic land use and land cover significantly affects species assemblage, diversity, and dominance in the riparian habitats. The variations in vegetation structure and composition with respect to the adjoining land use type plausibly have implications on the structure and functioning of the lentic systems. Thus, the study recommends that a holistic approach involving the riparian areas is required for effective management of tropical floodplains.

Substrate degradation and nutrient enrichment structuring macroinvertebrate assemblages in agriculturally dominated Lake Chaohu Basins, China

Rapid agricultural development has induced severe environmental problems to freshwater ecosystems. In this study, we aimed to examine the structure and environmental determinants of macroinvertebrate assemblages in an agriculture dominated Lake Chaohu Basin, China. A cluster analysis of the macroinvertebrate communities identified four groups of sites that were characterized by significantly different macroinvertebrate species. These four groups of sites had concentric spatial distribution patterns that followed the variation in the environmental conditions from the less anthropogenically disturbed headwaters towards the more anthropogenically disturbed lower reaches of the rivers and the Lake Chaohu. Moreover, taxa richness decreased from the headwaters towards the Lake Chaohu. The increasing practice of agriculture has reduced the abundances and richness of pollution sensitive species while opposite effects on pollution tolerant species. The study identified substrate heterogeneity and nutrient concentrations as the key environmental factors regulating the changes in the macroinvertebrate communities. We propose that particular attentions should be paid to reduce the nutrient enrichment and habitat degradation in the Lake Chaohu Basin and similar agriculture dominated basins.