The impacts of agriculture on macroinvertebrate communities: From structural changes to functional changes in Asia's cold region streams

Taxonomic and functional responses of benthic macroinvertebrates to wastewater effluents in the receiving river of ecologically vulnerable karst areas in Southwest China

Discharges of wastewater effluents have a profound impact on the health of receiving river ecosystems, especially with regard to benthic macroinvertebrate communities. However, the effects of different wastewater types on the taxonomy and function of benthic macroinvertebrates in the receiving rivers in vulnerable karst regions of China are still rarely known. Here, we collected benthic macroinvertebrate samples from the Yanjin River, which could be divided into reaches mainly influenced by industrial, domestic and mixed wastewater, as well as from its adjacent Guanyinsi River, which was unaffected by wastewater. We found that both taxonomic and functional structures of benthic macroinvertebrates in the receiving river differed significantly under the influence of various wastewater types, which was linked to fluctuations in nutrient-related water quality, despite seasonal variation. Watershed-scale anthropogenic activities played important roles in determining the water quality, thereby indirectly driving the functional trait adaptation of benthic macroinvertebrate communities. Notably, we observed that the expansion of cropland dramatically decreased the functional diversities of benthic macroinvertebrates. Threshold responses of multi-faceted diversities in benthic macroinvertebrates to pollutants suggested that the critical concentrations of chemical oxygen demand (CODMn) and ammonia nitrogen (NH4-N) were 4.16 mg/L and 0.23 mg/L, respectively. Our study provided insights into the impacts of anthropogenic activities on benthic macroinvertebrates from both taxonomic and functional perspectives, highlighting the need to incorporate watershed-scale human activity management into water quality control strategies for urban river ecosystems, tailored to local conditions.

Road crossings change functional diversity and trait composition of stream-dwelling macroinvertebrate assemblages

Functional diversity is regarded as a key concept in understanding the link between ecosystem function and biodiversity, and is therefore widely investigated in relation to human-induced impacts. However, information on how the intersection of roads and streams (hereafter road crossings, representing a widespread habitat transformation in relation to human development), influences the functional diversity of stream-dwelling macroinvertebrates is still missing. The general aim of our study was to provide a comprehensible picture on the impacts of road crossing structures on multiple facets of the functional diversity of stream-dwelling macroinvertebrates. In addition, we also investigated changes in trait structure. Our research showed that road crossing structures had negative impacts on functional richness and dispersion; i.e., functional diversification. However, we found no significant impact on functional divergence and evenness components. We found a decrease in functional redundancy at road crossing structures. This indicates a reduced ability of the community to recover from disturbances. Finally, we found that road crossings drive stream habitat and hydrological changes in parallel with modification of the trait composition of stream-dwelling macroinvertebrate assemblages. All these results suggest that road crossings cause notable changes in the functional diversity of stream-dwelling macroinvertebrate assemblages.

Salinization and sedimentation drive contrasting assembly mechanisms of planktonic and sediment-bound bacterial communities in agricultural streams

Agriculture is the most dominant land use globally and is projected to increase in the future to support a growing human population but also threatens ecosystem structure and services. Bacteria mediate numerous biogeochemical pathways within ecosystems. Therefore, identifying linkages between stressors associated with agricultural land use and responses of bacterial diversity is an important step in understanding and improving resource management. Here, we use the Mississippi Alluvial Plain (MAP) ecoregion, a highly modified agroecosystem, as a case study to better understand agriculturally associated drivers of stream bacterial diversity and assembly mechanisms. In the MAP, we found that planktonic bacterial communities were strongly influenced by salinity. Tolerant taxa increased with increasing ion concentrations, likely driving homogenous selection which accounted for ~90% of assembly processes. Sediment bacterial phylogenetic diversity increased with increasing agricultural land use and was influenced by sediment particle size, with assembly mechanisms shifting from homogenous to variable selection as differences in median particle size increased. Within individual streams, sediment heterogeneity was correlated with bacterial diversity and a subsidy-stress relationship along the particle size gradient was observed. Planktonic and sediment communities within the same stream also diverged as sediment particle size decreased. Nutrients including carbon, nitrogen, and phosphorus, which tend to be elevated in agroecosystems, were also associated with detectable shifts in bacterial community structure. Collectively, our results establish that two understudied variables, salinity and sediment texture, are the primary drivers of bacterial diversity within the studied agroecosystem, whereas nutrients are secondary drivers. Although numerous macrobiological communities respond negatively, we observed increasing bacterial diversity in response to agricultural stressors including salinization and sedimentation. Elevated taxonomic and phylogenetic bacterial diversity likely increases the probability of detecting community responses to stressors. Thus, bacteria community responses may be more reliable for establishing water quality goals within highly modified agroecosystems that have experienced shifting baselines.

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.

Functional groups of Afrotropical EPT (Ephemeroptera, Plecoptera and Trichoptera) as bioindicators of semi-urban pollution in the Tsitsa River Catchment, Eastern Cape, South Africa

We examined the distribution patterns of Ephemeroptera, Plecoptera, and Trichoptera functional feeding groups (EPT FFGs) in five streams that drain semi-urban landscapes in the Tsitsa River catchment, Eastern Cape Province of South Africa. We undertook macroinvertebrate and physicochemical analysis over four seasons between 2016 and 2017 at eight sites in three land-use categories (Sites 1, 2 and 3), representing an increasing gradient of semi-urban pollution. Five EPT FFGs (shredders, grazers/scrapers, predators, collector-gatherers and collector-filterers) were fuzzy coded and analyzed using RLQ-R (environmental characteristics of samples), L (taxa distribution across samples) and Q (species traits) and fourth-corner analyses. Physicochemical variables, including phosphate-phosphorus, total inorganic nitrogen and temperature, were the most influential variables that significantly influenced the distribution patterns of EPT FFGs in the Tsitsa River. RLQ and the fourth-corner model revealed varying responses of FFGs to semi-urban pollution. Of the five FFGs, collectors were the most abundant EPT FFGs in the study area, exhibiting disparate responses to disturbances, with collector-gatherers associated with impacted sites and significantly associated with phosphate-phosphorus. On the other hand, collector-filterers decreased with increasing semi-urban disturbance and exhibited a significant negative association with phosphate-phosphorus, total inorganic nitrogen and temperature. Overall, this study provides further insights into the environmental factors that influence the distribution patterns of FFGs in Afrotropical streams and the potential use of FFGs as indicators of anthropogenic pollution in tropical streams and rivers.

Bioaccumulation of 35 metal(loid)s in organs of a freshwater mussel (Hyriopsis cumingii) and environmental implications in Poyang Lake, China

Benthic bioaccumulation of hazardous materials has been a great challenge to the health of lake ecosystems. As representative benthic macroinvertebrates, freshwater mussels and their accumulation characteristics have been regarded as effective indicators for assessing potential risks induced by sedimentary metal(loid)s in lakes. Here we profile organ-specific accumulation of 35 metal(loid)s in a freshwater mussel (Hyriopsis cumingii) and their correlations to metal speciation in sediments of Poyang Lake, the largest lake of China. Significant organ-specific characteristics of metal accumulation were found in gills, though higher thallium (Tl) and selenium (Se) were found in the hepatopancreas, and greater arsenic (As) mostly accumulated in gonads. Pearson correlation analysis revealed that the bioaccumulation of silver (Ag), cobalt (Co), and rare earth elements (ΣREE) in gills and As in gonads were closely associated with those in bioavailable fraction of sediments. Based on the biochemical analysis in the major organs, gills exhibited the highest enzymatic activity compared with hepatopancreas and gonads. Sedimentary metals, particularly for available Ag, Co, and ΣREE, play key roles in causing lipid peroxidation in gills and significantly promote the activities of superoxide dismutase (SOD)/glutathione reductase (GR), while many metals (e.g., cadmium, manganese, Se) inhibit the glutathione (GSH) content in gonads and hepatopancreas. Our study indicates a high physiological sensitivity of mussels to these target metals, which highlights the significance of organ-specific accumulation of metal(loid)s in understanding the potential ecological risks of sedimentary metal(loid)s in lake ecosystems.

The Impacts of Different Anthropogenic Disturbances on Macroinvertebrate Community Structure and Functional Traits of Glacier-Fed Streams in the Tianshan Mountains

Macroinvertebrates are sensitive to environmental disturbances, however, the effects of human activities on macroinvertebrate community structures and functional traits in glacier-fed streams are concerning. To elucidate the effects of horse, cattle and sheep grazing, hot spring scenic development, and historic iron ore mine development on macroinvertebrate communities, we conducted a study in three glacier-fed streams of the Tianshan Mountains in northwest China in April 2021. Our results showed that the species richness and density significantly decreased due to grazing (p < 0.05). There were more taxa with resilience traits such as “small size at maturity” in the grazing stream. The EPT richness and density affected by hot spring scenic development significantly decreased compared to the undisturbed point (p < 0.05). There was a significant increase in taxa with resistance traits such as “bi-or-multivoltine” in the hot spring stream. The stream affected by historic mine development is currently in the self-recovery stage following the closure of the mine ten years ago. Additionally, the species richness, EPT richness, and density at the mining site were significantly higher than the source site (p < 0.05), reflecting that the habitat fragmentation caused by previous mining activities prevented the upward dispersal of macroinvertebrates. The taxa in the mining stream were also characterized by higher resistance traits such as “abundant occurrence in drift”. These results were attributed to the impacts of human disturbance on habitat stability, habitat heterogeneity, water quality, and material cycling of stream ecosystems, indicating human disturbance on the efficiency of resource utilization and functional diversification. In addition, our results showed that functional indicators of macroinvertebrate communities are helpful for monitoring and evaluating habitat conditions.

The Impacts of the Freezing–Thawing Process on Benthic Macroinvertebrate Communities in Riffles and Pools: A Case Study of China’s Glacier-Fed Stream

Glacier-fed streams are one of the environments most sensitive to global climate change. However, the effects of the freezing–thawing process on benthic macroinvertebrate communities in different habitats of glacier-fed streams are unclear. In this paper, we investigated benthic macroinvertebrates in riffles and pools of a glacier-fed stream in Xinjiang, China, during the pre-freezing period (November, 2018), freezing period (January 2019), and thawing period (April, 2019). Our results showed that the freezing–thawing process resulted in a decline in benthic macroinvertebrate species richness and diversity, both of which were attributed to the effects of the freezing–thawing process on habitat stability, water quality, and cycling of the stream ecosystems. During the whole freezing–thawing process, the indicator taxa of riffles were Rhithrogena sp. and Baetis sp., while the only indicator taxon of pools was Chironomus sp. The species richness, Margalef diversity, and EPT richness (Ephemeroptera, Plecoptera, and Trichoptera) of benthic macroinvertebrates in riffles were higher than those in pools, due to the higher habitat heterogeneity in the riffles. However, the density in riffles was significantly lower than that in pools during the freezing period (p < 0.05). Additionally, pools were dominated by taxa with higher resilience and resistance traits, such as “bi- or multi-voltine”, “abundant occurrence in drift”, and “small size at maturity”. This result indicated that pools provide a temporary refuge for benthic macroinvertebrates in the extreme environment of glacier-fed streams. The freezing–thawing process plays an essential role in the formation of the structure and function of the stream ecosystem. Our results can help us to further understand the winter ecological process of headwater streams, and provide a reference for stream biodiversity conservation in cold regions.

Searching for indicator macroinvertebrate traits in an Afrotropical riverine system: implication for ecosystem biomonitoring and sustainability

In the past three decades, macroinvertebrate traits have been explored and employed in the biomonitoring of riverine systems globally, but much attention has not been given to the trait-based approach (TBA) in Nigeria. Therefore, in this study, the distribution patterns of macroinvertebrate traits in selected stations exposed to varying degrees of perturbation in River Hadejia, north-western Nigeria, were explored to assess the ecological health of the river. Three stations were selected, representing an increasing gradient of pollution: station 1 > station 2 and station 3, and were used to search for potential indicator traits. Four traits, including body size, respiratory, mobility, and body shape, were selected and classified into 12 trait attributes. The RLQ analysis revealed macroinvertebrates possessing medium and large body sizes, climbing and crawling, tegumental, gills, and aerial: lungs respiratory traits, and streamlined body shape were associated with station 1. Conversely, macroinvertebrates possessing very small and small body sizes, aerial: spiracle and aerial/vegetation, sprawling, swimming, and skating, flattened, spherical, cylindrical, and rhomboidal were mainly associated with stations 2 and 3. In searching for potential indicator macroinvertebrate traits aside from the RLQ analysis conducted, a fourth-corner analysis was further performed, which showed traits including medium and large body sizes, tegumental, and aerial: lung respiratory traits to be sensitive to pollution. Equally, aerial/vegetation, flattened body shape, and very small body size were found to be tolerant of pollution. A more robust trait-based biomonitoring study using more trait classes such as feeding mechanism, food preferences, voltinism, and attachment mechanism is recommended for future study in this region. The study would be helpful in biomonitoring of ecosystem health and enhance the sustainability prowess of the TBA in the studied region.

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.

Taxonomic and functional responses of macroinvertebrates to riparian forest conversion in tropical streams

Land use change threatens the ecological integrity of tropical rivers and streams; however, few studies have simultaneously analyzed the taxonomic and functional responses of tropical macroinvertebrates to riparian forest conversion. Here, we used community structure, functional diversity, and stable isotope analyses to assess the impacts of riparian deforestation on macroinvertebrate communities of streams in southern Mexico. Monthly sampling during the dry season was conducted in streams with riparian forest (forest streams), and in streams with pasture dominating the riparian vegetation (pasture streams). Samples were collected for water quality (physical-chemical variables, nutrient concentrations, and total suspended solids), organic matter (leaf litter abundance and algal biomass), and macroinvertebrate abundance and diversity. Higher temperature, conductivity, suspended solids, and chlorophyll a were detected in pasture streams, while nitrate concentrations and leaf litter biomass were greater in forest streams. Macroinvertebrate density was higher in pasture sites, while no differences in taxonomic diversity and richness were found between land uses. Functional evenness was greater in forest streams, while richness and divergence were similar between land uses, despite differences in taxonomic composition. Environmental variables were associated with taxa distribution but not with functional traits, suggesting current conditions still promote redundancy in ecological function. Isotopic analyses indicated consumers in pasture streams were enriched in ¹³C and ¹⁵N relative to forest streams, potentially reflecting the higher algal biomass documented in pasture systems. Isotopic niches were broader and more overlapped in pasture streams, indicating more generalist feeding habits. No significant losses of taxonomic or functional diversity were detected in pasture streams. However, changes in trophic ecology suggest landscape-level processes are altering macroinvertebrate feeding habits in streams. The changes we observed in habitat, water quality, and macroinvertebrate community were related to the removal of the riparian vegetation, suggesting the structure and function of the focal systems would benefit from riparian restoration.

Current and Future Ecological Status Assessment: A New Holistic Approach for Watershed Management

The Paiva River catchment, located in Portugal, integrates the Natura 2000 network of European Union nature protection areas. Resorting to topography, climate and land-use data, a semi-distributed hydrological model (Hydrological Simulation Program–FORTRAN) was run in order to simulate the hydrological cycle of the river and its tributaries. The model was calibrated over a 25-year period and validated within a 31-year period. Its performance was verified by comparing the recorded and simulated daily flows. The values of the Nash–Sutcliffe coefficient of efficiency of 0.95 and 0.76, and coefficient of determination of 0.95 and 0.82, were achieved for calibration and validation, respectively, thus showing a quite satisfactory model performance. Subsequently, the climate change impacts on temperature and precipitation, as well as their extremes, and on the flowrates were also assessed for a future period (2041–2070) under two anthropogenic forcing scenarios (representative concentration pathways 4.5 and 8.5). A procedure for selecting the most relevant metrics for assessing the ecological condition of the Paiva River was developed based upon a set of 52 invertebrate families sampled. Correspondence analyses were carried out for biological datasets (traits/metrics) with physicochemical and land use/land cover matrices separately. Out of all variables, water quality and flow and agriculture land use explained most of the variance observed. The integrated analysis undertaken in the present study is an important advance when compared to previous studies and it provides key information to stakeholders and decision-makers, particularly when planning suitable adaptation measures to cope with changing climates in the forthcoming decades.

Health risk assessment of trace elements exposure through the soil-plant (maize)-human contamination pathway near a petrochemical industry complex, Northeast China

The trace elements contamination of agricultural soils near petrochemical industry complexes is a concern due to the risk of accumulating in food systems and subsequently affecting human health. We measured representative trace elements (Cu, Ni, Cr, Pb, Zn, Pb, Hg and As) through the soil-plant (maize)-human contamination pathway near a petrochemical industry complexes in an agricultural region from September 20 to 28, 2016. We found that the soil was mildly to moderately polluted by multiple trace elements, which was also confirmed by the contamination factor and enrichment factor values. Cd (enrichment factor = 2.28), Cu (2.75), Zn (1.85) and Pb (1.70) should be given more attention and prioritized over the other trace elements due to their higher potential risks. Furthermore, the trace elements contamination in maize grains was lower than the corresponding limits. The sequence of the transfer coefficient values was Zn > Cd > Cu > Hg > Ni > As > Cr > Pb. Maize grain safety was threatened mainly by Zn, Cd and Cu. There was no risk to humans through soil ingestion, while a potential health risk from maize grain consumption existed. Children were more sensitive than adults to the non-carcinogenic risks of maize grain consumption. Trace element As was found to be the priority metal for risk control. For carcinogenic risk, adults were more sensitive than children; As, Cr and Cd were the priority metals for risk control, with CR_maize values exceeding the risk threshold (1 × 10^-4). Overall, strict, intensive monitoring, especially of Cr and Cd, and soil protection measures are needed to prevent any furthertrace elements contamination and to ensure food safety. This study also provides a reference for similar studies worldwide.

Responses of macroinvertebrate communities to land use specific sediment food and habitat characteristics in lowland streams

The input of land use specific organic matter into lowland streams may impact sediment characteristics in terms of food resources and habitat structure, resulting in differences in macroinvertebrate community composition. Therefore, we investigated to what extent land use specific sediment food and habitat characteristics structure macroinvertebrate communities. To this purpose linear multiple regression models were constructed, in which macroinvertebrate biotic indices were considered as response variables and sediment characteristics as predictor variables, analysed in 20 stream stretches running through five different land use types. Sediment characteristics and macroinvertebrate community composition were land use specific. The carbon/nitrogen (C/N) ratio, woody debris substrate cover and the origin of fatty acids influenced macroinvertebrate community composition. Shannon-Wiener diversity was better explained by fatty acids origin, such as in grassland streams, where a higher relative content of plant derived fatty acids related to a higher macroinvertebrate diversity. In cropland and wastewater treatment plant (WWTP) streams with a low C/N ratio and dominated by microbial derived fatty acids, higher abundances of Oligochaeta and Chironomus sp. were observed. Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness was positively related to woody debris substrate cover, which only occurred in forest streams. Hence, macroinvertebrate community composition was influenced by the origin of the organic material, being either allochthonous or autochthonous and when autochthonous being either autotrophic or heterotrophic. It is therefore concluded that sediment food and habitat characteristics are key ecological filters.