There is mounting evidence that terrestrial arthropods are declining rapidly in many areas of the world. It is unclear whether freshwater invertebrates, which are key providers of ecosystem services, ...are also declining. We addressed this question by analysing a long‐term dataset of macroinvertebrate abundance collected from 2002 to 2019 across 5009 sampling sites in English rivers. Patterns varied markedly across taxonomic groups. Within trophic groups we detected increases in the abundance of carnivores by 19% and herbivores by 14.8%, while we estimated decomposers have declined by 21.7% in abundance since 2002. We also found heterogeneity in trends across rivers belonging to different typologies based on geological dominance and catchment altitude, with organic lowland rivers having generally higher rates of increase in abundance across taxa and trophic groups, with siliceous lowland rivers having the most declines. Our results reveal a complex picture of change in freshwater macroinvertebrate abundance between taxonomic groups, trophic levels and river typologies. Our analysis helps with identifying priority regions for action on potential environmental stressors where we discover macroinvertebrate abundance declines.
We addressed the question of whether freshwater invertebrates, which are key providers of ecosystem services, are declining in abundance by analysing a long‐term dataset of macroinvertebrates in English rivers. We found a complex picture of change in abundance between taxonomic groups, trophic levels and river typologies. Within trophic groups we detected 19% increases in carnivore abundance, and 14% for herbivores, while estimating decomposers declined by 21.7% since 2002. Trends are heterogeneous across rivers of different typologies, organic lowland rivers having generally higher rates of increase in abundance across taxa and trophic groups, and siliceous lowland rivers having the most declines.
Road salt (commonly NaCl, CaCl2, and MgCl2) is widely used in the northern United States as a deicing agent for roadways and other byways. Millions of tons of road salt are used annually in the ...United States, resulting in drastic increases in freshwater salinity. This study aims to determine the chloride optima and tolerance ranges of macroinvertebrates using publicly accessible stream monitoring data from the US EPA. We assigned taxa region-specific tolerance values, which we then used to calculate the Salt Belt Index (SBI). In addition to the SBI, we determined new, region-specific, chronic Cl− thresholds, determined using threshold indicator taxa analysis (TITAN). Using generalized linear models, we found the SBI was highly accurate at estimating chloride concentration (mg/L Cl−) across the salt belt states. Macroinvertebrate community richness exhibited a significant negative relationship with increasing chloride concentrations. Newly proposed chloride thresholds, based on the richness-chloride relationship, were far lower than current thresholds. The SBI was able to differentiate between Low-, Medium-, and High-Impact sites, grouped based on proposed chloride thresholds. Based on our findings, it is clear current salinity thresholds are too high, and management practices should factor in regional variability, taxon-specific physiology, and historical instream chemistry when implementing salinity thresholds.
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•The proposed Salt Belt Index is an accurate predictor of stream salinity (r2 = 0.49).•New chloride thresholds were determined for each region of the United States.•These thresholds were calculated using threshold indicator taxa analysis (TITAN).•Proposed regional thresholds are far lower than current US thresholds (230 mg/L).•Thresholds should reflect regional characteristics and historical conditions.
Microplastics (1–1000 μm) are ubiquitous in the marine, freshwater and terrestrial environments. These microsized plastics are considered freshwater pollutants of emerging concern, although the ...impacts on organisms and ecosystems are not yet clear. In particular, effects of microplastics on freshwater aquatic plants and the fate of microplastics in the freshwater trophic chain remain largely unexplored. Here we demonstrate that 10–45 μm polyethylene (PE) microplastics can strongly adsorb to all surfaces of the duckweed species Lemna minor. Despite adsorbance of up to 7 PE microplastics per mm2, seven day exposure experiments showed that photosynthetic efficiency and plant growth are not affected by microplastics. Rather, dense surface coverage suggests L. minor as a potential vector for the trophic transfer of microplastics. Here we show that the freshwater amphipod Gammarus duebeni can ingest 10–45 μm PE microplastics by feeding on contaminated L. minor. In this study, ingestion of microplastics had no apparent impact on amphipod mortality or mobility after 24 or 48 h exposure. Yet, the feeding study showed that the fate of microplastics in the environment may be complex, involving both plant adsorbance and trophic transfer.
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•Polyethylene microplastics strongly adsorb to L. minor.•Acute exposure to microplastics had no effect on L. minor photosynthesis and growth.•Microplastics can be transferred from L. minor to the macroinvertebrate G. duebeni.•Ingestion of microplastics had no apparent impact on G. duebeni.
First-order streams serve as a nursery of macroinvertebrates which act as secondary producers in the aquatic food chain and indicators of water quality. The present investigation conducted on three ...first-order streams of Badiyar Gad revealed Trichoptera to be the most diverse order followed by Ephemeroptera, Diptera, Coleoptera, Odonata, Lepidoptera, Plecoptera, Hemiptera, Arhynchobdellida, and Decapoda, indicating good water quality for these streams. High density, diversity, and even distribution of benthic macroinvertebrates during the winter season indicated stable ecosystems and healthy water quality. The presence of 35 families and 52 genera indicates a good habitat with numerous ecological niches for the macroinvertebrates. Two genera Maruina and Neophylax were identified as unique in these streams. They have not been previously reported from the Garhwal Himalayan streams.
Caracterización y manejo del grado de complejidad de los componentes y biodiversidad y su efecto en las arvenses y macrofauna edáfica de tres fincas integrales en el occidente de Nicaragua. El ...funcionamiento eficiente de las fincas agropecuarias depende de las interacciones que ocurre en los componentes. El objetivo de este trabajo fue caracterizar el grado de complejidad en tres fincas integrales en el occidente de Nicaragua. El grado de complejidad de los diseños y manejo de la biodiversidad, se determinó con 6 componentes y 64 indicadores, cada indicador se evaluó mediante la escala de Vázquez. Se determinó la diversidad de la macrofauna aplicando la metodología recomendada por el Tropical Soil Biology and Fertility Programme (TSBF), se realizaron 24 monolitos por fincas. Se determinó la diversidad y abundancia de las arvenses, con la técnica de muestreo de transectos con 50 m de largo por un metro de ancho, se aplicó ocho transectos por fincas, en cada transecto se realizó cinco puntos de muestreos a una distancia de 10 m, realizando 40 puntos de muestreo por finca. Las tres fincas estudiadas poseen un coeficiente de diseño y manejo de su biodiversidad medianamente complejo. La mayor abundancia promedio de macrofauna edáfica se encontró en la finca Verdum, La finca Santa Ana y Girasol presentaron resultados similares de densidad promedio de macrofauna edáfica con 0.49 y 0.51 individuos/monolito, la mayor abundancia se encontraron en los primeros 10 cm. En la finca Girasol se encontró el mayor número de taxa de arvenses con 32 especies y 22.58 ind. m-2, finca Verdum y Santa Ana se encontraron 24 especie de arvenses, con 12.1 y 2.98 ind. m-2 respectivamente.
Microplastics (MPs) are emerging contaminants of freshwater ecosystems. Once in aquatic systems, most of these plastic particles undergo processes of fragmentation, biofouling, and sedimentation, ...resulting in increased concentrations of smaller sized and irregularly-shaped particles in the sediment. High levels of MPs in freshwater sediments can denote a potential threat to benthic and sediment-dwelling organisms such as dipteran larvae. This study evaluates the ecotoxicological effect of three pools of irregularly-shaped polyethylene (PE) microplastics (pools containing 90% of the particles within 32–63 μm (size-class A), 63–250 μm (size-class B) and 125–500 μm (size-class C)), with concentrations ranging from 1.25 to 20 g Kg−1 sediment, on the dipteran Chironomus riparius life-history traits. After ten days of exposure, larvae ingested PE particles typically in the 32–63 μm range, even when 90% of the particles possessed higher size (i.e., in size-classes B and C) and the larvae mandible allowed the ingestion of such bigger-sized particles. Thus, the number of ingested particles was higher in size-class A, followed by B and C, and led to a significant reduction with similar magnitude on larval growth (Lowest Observed Effect Concentrations (LOEC) = 2.5 g Kg−1 sediment DW) and a significant delay on imagoes emergence (e.g., LOEC = 1.5 g Kg−1 sediment DW for females).
The results from this study show that the ingestion and persistence of small-sized polyethylene microplastics caused significant impairments on life-history traits of C. riparius. Considering their role on freshwater food-webs and the potential persistence of small-sized PE particles in their larval gut, these results also point for the potential adverse effects of small-sized microplastics at the community and ecosystem level.
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•Chironomus riparius larvae ingested polyethylene (PE) particles.•Polyethylene particles in the larval gut were mainly in the range of 32–63 μm.•Effects of PE particles on C. riparius growth and emergence were dose-dependent.•Emergence was the most sensitive endpoint for female imagoes.
The role of deterministic and stochastic processes in community assembly is a key question in community ecology. We evaluated the effect of an abiotic filter (hydroperiod) on the partitioned ...diversity of three taxonomic groups (birds, vegetation, macroinvertebrates) from prairie pothole wetlands in Alberta, Canada, which naturally vary in water permanence. We observed that alpha and gamma diversity were higher in permanent than temporary wetlands (16–25% and 34–47% respectively, depending on the taxon). This suggests an influence of deterministic constraints on the number of species a wetland can support. Taxa which cannot persist in shallow, temporary wetlands are excluded by the deterministic constraints that a shortened hydroperiod imposes. In contrast, we observed that beta diversity was significantly higher (2–12%) in temporary wetlands than permanent ones, and temporary wetlands supported more unique combinations of community composition than permanent wetlands, despite having a smaller regional species pool. This observation contradicts prior mesocosm studies that found beta diversity mirrored the pattern in gamma diversity along an environmental filtering gradient. We conclude that deterministic processes are more influential in more stable permanent wetlands, whereas stochastic processes play a more important role in assembly in dynamic temporary wetlands that must disassemble and re‐establish annually. Considering three distinct taxonomic groups differing in their relative mobility, our large‐scale field study demonstrates that both stochastic and deterministic processes act together to influence the assembly of multiple communities and that the relative importance of the two processes varies consistently along a gradient of environmental filtering.
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