Environmental filtering of macroinvertebrate traits influences ecosystem functioning in a large river floodplain

Environmental characteristics shape macroinvertebrate community structure across spatiotemporal scales in a subtropical African river system

Understanding the impact of human activities and environmental drivers on macroinvertebrate communities is critical to adequately manage river ecosystems under multiple stressors. In this study, we assessed macroinvertebrate community structure in relation to water and sediment chemistry. Samples (i.e., water, sediment and macroinvertebrates) were collected from 16 sites along the subtropical Luvuvhu River (South Africa) mainstem and its tributaries across two seasons (i.e., cool-dry (June), hot-wet (November)). The analysed data was assessed using multivariate analyses and diversity matrices. Significant differences were observed across seasons and river sections for most water (i.e., pH, temperature, resistivity, ammonium, phosphates) and sediment (i.e., potassium, sodium, copper, zinc, boron, sediment organic carbon) variables. Macroinvertebrates exhibited high diversity during hot-wet season compared to the cool-dry season, with a six distinct macroinvertebrates families (i.e., Odonata, Diptera, Coleoptera, Hemiptera, Trichoptera, Ephemeroptera) having a high taxon abundances. Based on CCA analysis, seasons were positively associated with CCA axis 2, and were characterised by high Mg, Na, pH, sediment organic carbon, ammonium and phosphates, with all highlighted variables having a significant effect on macroinvertebrate community composition. The results obtained from this study highlighted that water and sediment chemistry had significant associations with changes in macroinvertebrate communities and composition. Therefore, understanding the relationship between water and sediment chemistry, and macroinvertebrates diversity matrices in rivers that are impacted by human activities is essential for comprehending the integrity of river ecosystem and for providing guidance to conservation managers. This knowledge will assist on how to effectively manage and safeguard these systems against further deterioration from anthropogenic activities.

Exploring the quality of ecosystem services and the segmental impact of influencing factors in resource-based cities

The changes in ecosystems of resource-based cities are closely related to human activities and resource extraction. Understanding the temporal and spatial differentiation characteristics of ecosystems and identifying the main influencing factors on ecosystem services are crucial for optimizing the spatial security pattern of resource-based cities. Previous studies have seldom examined how different factors affect various levels of ecosystem service value (ESV) in segmented ways. This study presents a case study of a typical resource-based city to examine the temporal and spatial evolution characteristics of ecosystem services. Furthermore, it employs a spatial quantile regression model to investigate the differentiated impacts of various influencing factors on these ecosystem services. The results indicate that: (1) In the past two decades, the intensity of land use in Tangshan continued to increase, with significant transfer effects between arable land and construction land. The overall ESV in Tangshan showed a fluctuating decline. (2) The area of low-ESV clustering has significantly expanded, with regulating and supporting services being the primary types of ecosystem services, and there is a significant synergistic effect among various ecosystems. (3) Precipitation is the dominant factor enhancing ESV in the region, while mineral extraction activities are the main pressure source threatening high-ESV areas, and the integrity of land use presents a major barrier to improving low-ESV areas. It is crucial to effectively control the boundaries of mineral resource extraction, delineate key protected areas, and restricted development zones.

Cross-taxa assessment of species diversity and phylogenetic structure of benthic communities in a dam-impacted river undergoing habitat restoration

Exploring diversity and community composition patterns across evolutionary and functionally diverse organisms is critical for understanding the general processes that shape biodiversity in response to environmental changes. Knowledge of multi-trophic relationships offers valuable insights to support the effective assessment and management of freshwater ecosystems. In this study, we conducted a cross-taxa assessment of benthic macroinvertebrates and microorganisms using metabarcoding-based surveys to evaluate habitat restoration in a dam-impacted river. We found no correlation between the α-diversity of the benthic macroinvertebrate and microbial communities. This suggests that factors influencing the α-diversity of different trophic groups might operate independently or through different mechanisms, even within the same habitat. In contrast, we observed positively correlated β-diversity patterns between the two benthic communities influenced by dam fragmentation and gravel bar restoration. This suggests that environmental heterogeneity between sites may have a common influence on the patterns of pairwise dissimilarities in the benthic communities, even though they have significant differences in key traits, e.g., species composition, functional roles, or trophic level. Additionally, phylogenetic structure analysis revealed a greater dam impact on benthic macroinvertebrates than microbial communities. Benthic microorganisms consistently formed phylogenetically clustered communities regardless of dam impact, while the macroinvertebrates shifted from competitive exclusion to environmental filtering in response to dam fragmentation. Our cross-taxa assessment further explained the relationships among benthic communities and their associations with environmental factors in a river ecosystem undergoing habitat restoration. Our study highlights the significant implications of evaluating different biological communities across trophic levels for river restoration strategies and ecosystem assessment.

How effective are ecological metrics in supporting conservation and management in degraded streams?

Biodiversity loss is increasing worldwide, necessitating effective approaches to counteract negative trends. Here, we assessed aquatic macroinvertebrate biodiversity in two river catchments in Switzerland; one significantly degraded and associated with urbanisation and instream barriers, and one in a near-natural condition. Contrary to our expectations, environmental heterogeneity was lower in the near-natural stream, with enhanced productivity in the degraded system resulting in a greater range of environmental conditions. At face value, commonly employed alpha, beta and gamma biodiversity metrics suggested both catchments constituted healthy systems, with greater richness or comparable values recorded in the degraded system relative to the near-natural one. Further, functional metrics considered to be early indicators for anthropogenic disturbance, demonstrated no anticipated differences between degraded and near-natural catchments. However, investigating the identity of the taxa unique to each river system showed that anthropogenic degradation led to replacement of specialist, sensitive species indicative of pristine rivers, by generalist, pollution tolerant species. These replacements reflect a major alteration in community composition in the degraded system compared with the near-natural system. Total nitrogen and fine sediment were important in distinguishing the respective communities. We urge caution in biodiversity studies that employ numerical biodiversity metrics alone. Assessing just one aspect of diversity, such as richness, is not sufficient to track biodiversity changes associated with environmental stress. We advocate that biodiversity monitoring for conservation and management purposes must go beyond traditional richness biodiversity metrics, to include indices that incorporate detailed nuances of biotic communities that relates to taxon identity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10531-024-02933-7.

Stream macroinvertebrate communities in restored and impacted catchments respond differently to climate, land-use, and runoff over a decade

Identifying which environmental drivers underlie degradation and improvements of ecological communities is a fundamental goal of ecology. Achieving this goal is a challenge due to diverse trends in both environmental conditions and ecological communities across regions, and it is constrained by the lack of long-term parallel monitoring of environmental and community data needed to study causal relationships. Here, we identify key environmental drivers using a high-resolution environmental - ecological dataset, an ensemble of the Soil and Water Assessment Tool (SWAT+) model, and ecological models to investigate effects of climate, land-use, and runoff on the decadal trend (2012-2021) of stream macroinvertebrate communities in a restored urban catchment and an impacted catchment with mixed land-uses in Germany. The decadal trends showed decreased precipitation, increased temperature, and reduced anthropogenic land-uses, which led to opposing runoff trends - with decreased runoff in the restored catchment and increased runoff in the impacted catchment. The two catchments also varied in decadal trends of taxonomic and trait composition and metrics. The most significant improvements over time were recorded in communities of the restored catchment sites, which have become wastewater free since 2007 to 2009. Within the restored catchment sites, community metric trends were primarily explained by land-use and evaporation trends, while community composition trends were mostly associated with precipitation and runoff trends. Meanwhile, the communities in the impacted catchment did not undergo significant changes between 2012 and 2021, likely influenced by the effects of prolonged droughts following floods after 2018. The results of our study confirm the significance of restoration and land-use management in fostering long-term improvements in stream communities, while climate change remains a prodigious threat. The coupling of long-term biodiversity monitoring with concurrent sampling of relevant environmental drivers is critical for preventative and restorative management in ecology.

Effects of biodiversity on functional stability of freshwater wetlands: a systematic review

Freshwater wetlands are the wetland ecosystems surrounded by freshwater, which are at the interface of terrestrial and freshwater ecosystems, and are rich in ecological composition and function. Biodiversity in freshwater wetlands plays a key role in maintaining the stability of their habitat functions. Due to anthropogenic interference and global change, the biodiversity of freshwater wetlands decreases, which in turn destroys the habitat function of freshwater wetlands and leads to serious degradation of wetlands. An in-depth understanding of the effects of biodiversity on the stability of habitat function and its regulation in freshwater wetlands is crucial for wetland conservation. Therefore, this paper reviews the environmental drivers of habitat function stability in freshwater wetlands, explores the effects of plant diversity and microbial diversity on habitat function stability, reveals the impacts and mechanisms of habitat changes on biodiversity, and further proposes an outlook for freshwater wetland research. This paper provides an important reference for freshwater wetland conservation and its habitat function enhancement.

The impacts of reduced connectivity on multiple facets of aquatic insect diversity in floodplain wetlands, Northeast China

River-floodplain ecosystems are highly complex and dynamic systems that are subjected to human disturbance, such as the construction of levees. Aquatic insects are among the most widely used indicators to assess human impacts on floodplain wetlands. Most studies are still based on taxonomic biodiversity. However, trait-based approaches remain limited, which could impede the development of effective management strategies. Here, we investigated aquatic insect assemblages in eleven pairs of wetlands along the Wusuli River in two seasons (Spring and Autumn) and assessed their responses to the impact of levee construction, considering taxonomic and functional diversity. We found that pooled species richness (73 taxa) in river-connected wetlands was almost twice of that in levee-blocked wetlands (37 taxa). Six and one indicator taxa for river-connected wetlands were identified in May and October, respectively, while no indicator taxon for the levee-blocked wetlands was identified. Moreover, taxonomic and functional alpha diversity in river-connected wetlands was much higher than in levee-blocked wetlands, but beta diversity showed a contrasting pattern. Additionally, multivariate dispersion analysis indicated a more evident difference in beta diversity between river-connected and levee-blocked wetlands in May than in October, likely due to the temporary lateral connection in summer (i.e., water flowed over levees during flood events). Our results revealed that anthropogenic impacts (e.g., levee construction and agricultural activity) weakened the connectivity of floodplain wetland ecosystems, leading to decreased taxonomic and functional diversity of aquatic insects in isolated wetlands. Our study highlights the importance of combining taxonomic and trait-based approaches in biomonitoring programs of floodplain wetland ecosystems. It also underscores the necessity of restoring habitat connectivity of wetland ecosystems (e.g., river-floodplain connectivity and connections between different wetlands) to facilitate biodiversity recovery and enhance ecological functions and services supported by these valuable ecosystems.

Flow regulation by dams impacts more than land use on water quality and benthic communities in high-gradient streams in a semi-arid region

In semi-arid regions, water policy has strongly promoted the construction of water reservoirs with little or no consideration for their ecological consequences. In order to quantify the effect induced by flow discontinuity on environmental conditions, water quality, and invertebrate communities at high-gradient streams, we investigated unregulated and regulated reaches at 13 watercourses, located in the Dry Chaco Ecoregion (South America). Dams differed in the dominant land uses (rangeland, agriculture, and urban) of the related catchment area. We assessed on-site hydro-geomorphic features, water quality and bacteriological parameters, habitat condition, chlorophyll a, macrophytes cover, and macroinvertebrate communities. Significant increases in mineral parameters and organic contamination indicators were detected at regulated reaches, such as: conductivity, total solids, turbidity, color, and phosphates. Dams negatively affected habitat condition, and macrophyte cover increased at regulated sites. Macroinvertebrates showed a diminution in most of the metrics analyzed, with a decrease of sensitive groups and an increase in the more tolerant ones. Redundancy Analysis revealed that SWQI (physicochemical based index) and the proportion of coarse gravel were stronger predictors on metrics arrangement. Variance partitioning analyses proved that regulation effects prevailed over land use in explaining metrics variation. Invertebrate community was positively related to better ecological conditions, which suggests that restitution of ecological integrity at regulated reaches should include habitat restoration. These results are relevant for the management of regulated water resources in arid and semi-arid regions in a context of climate change.

Observed and projected functional reorganization of riverine fish assemblages from global change

Climate and land-use/land-cover change ("global change") are restructuring biodiversity, globally. Broadly, environmental conditions are expected to become warmer, potentially drier (particularly in arid regions), and more anthropogenically developed in the future, with spatiotemporally complex effects on ecological communities. We used functional traits to inform Chesapeake Bay Watershed fish responses to future climate and land-use scenarios (2030, 2060, and 2090). We modeled the future habitat suitability of focal species representative of key trait axes (substrate, flow, temperature, reproduction, and trophic) and used functional and phylogenetic metrics to assess variable assemblage responses across physiographic regions and habitat sizes (headwaters through large rivers). Our focal species analysis projected future habitat suitability gains for carnivorous species with preferences for warm water, pool habitats, and fine or vegetated substrates. At the assemblage level, models projected decreasing habitat suitability for cold-water, rheophilic, and lithophilic individuals but increasing suitability for carnivores in the future across all regions. Projected responses of functional and phylogenetic diversity and redundancy differed among regions. Lowland regions were projected to become less functionally and phylogenetically diverse and more redundant while upland regions (and smaller habitat sizes) were projected to become more diverse and less redundant. Next, we assessed how these model-projected assemblage changes 2005-2030 related to observed time-series trends (1999-2016). Halfway through the initial projecting period (2005-2030), we found observed trends broadly followed modeled patterns of increasing proportions of carnivorous and lithophilic individuals in lowland regions but showed opposing patterns for functional and phylogenetic metrics. Leveraging observed and predicted analyses simultaneously helps elucidate the instances and causes of discrepancies between model predictions and ongoing observed changes. Collectively, results highlight the complexity of global change impacts across broad landscapes that likely relate to differences in assemblages' intrinsic sensitivities and external exposure to stressors.

Environmental parasitology: stressor effects on aquatic parasites

Anthropogenic stressors are causing fundamental changes in aquatic habitats and to the organisms inhabiting these ecosystems. Yet, we are still far from understanding the diverse responses of parasites and their hosts to these environmental stressors and predicting how these stressors will affect host-parasite communities. Here, we provide an overview of the impacts of major stressors affecting aquatic ecosystems in the Anthropocene (habitat alteration, global warming, and pollution) and highlight their consequences for aquatic parasites at multiple levels of organisation, from the individual to the community level. We provide directions and ideas for future research to better understand responses to stressors in aquatic host-parasite systems.