Benthic Macroinvertebrate Communities Research Articles

Ecological Impact of Hydraulic Dredging from an Alpine Reservoir on the Downstream River

The evacuation of impounded sediments is one of the most critical aspects associated with reservoirs, with possible drawbacks on the water quality, biodiversity, and ecosystem integrity of downstream river reaches. In this study, the impacts of hydraulic dredging at the Ambiesta Reservoir (Eastern Italian Alps) on the physical habitat and the biological communities (i.e., benthic macroinvertebrates and fish) of the downstream river were assessed by comparing the pre-dredging conditions with data collected on three post-dredging occasions. The dredging operation lasted 68 days and removed an overall sediment volume of 30,600 m3. During this operation, suspended sediment concentration (SSC) was monitored by turbidimeters and, on average, it was considerably lower than the SSC limit of 1.5 g/L, which exceeded approximately 15% of the overall operation time. Additionally, the dredging operation resulted in negligible deposition of fine sediment on/into the riverbed (0.24–0.7 kg/m2). Results for fish and benthic macroinvertebrate communities indicated weak differences in the density (~20% reduction) and diversity of these organisms between pre- and post-dredging sampling occasions. Moreover, the results on the biomonitoring indices based on macroinvertebrates showed a recovery during the last two sampling occasions. Compliance with the SSC limit and avoidance of high SSC peaks, along with limited fine sediment deposition, allowed to successfully mitigate the ecological impacts of this relatively long operation of sediment removal.

Long-term trends in stream benthic macroinvertebrate communities are driven by chemicals

BackgroundRecent studies indicate a partial recovery of European stream macroinvertebrate diversity. However, the key determinants shaping the overall community trends are only partly explored, owing to insufficient long-term environmental data collected in parallel with community responses. We investigate long-term trends in stream macroinvertebrate communities (i.e., taxonomic and trait composition and metrics), and explore their relationships to diverse environmental drivers (i.e., land-use, runoff, water temperature, and in-stream chemicals). We use macroinvertebrate data collected annually in spring and summer between 2007 and 2021 at four sampling sites within the Rhine-Main-Observatory Long-Term Ecological Research site. These sampling sites encompass a gradient from less-disturbed to disturbed conditions.ResultsOver time, shifts in taxonomic and trait composition and metrics indicated an improvement in environmental conditions. Long-term trends of biological trait metrics mirrored those for taxonomic metrics; for example, increases over time in taxonomic richness were paralleled by increases in functional richness and functional dispersion. Meanwhile, trends of ecological trait metrics were particularly driven by changes in environmental drivers. Land-use, water temperature, and runoff explained around 20% of the overall variance in long-term trends of macroinvertebrate communities. Water temperature and land-use played relatively equal roles in shaping taxonomic and trait composition and metric responses in spring, while water temperature emerged as the most influential driver in summer. However, when incorporating long-term chemical data as a more direct measurement of changes in land-use, the overall variance explained in macroinvertebrate community trends increased to c.a. 50% in both seasons.ConclusionsExamining more relevant driver variables beyond land-use and climate improves insights into why biodiversity exhibits long-term trends. We call for an increase in initiatives to link biodiversity monitoring with parallel sampling of relevant environmental drivers.

Freshwater biodiversity loss in urbanised rivers

Since the second half of the 20th century, when monitoring programmes were implemented as a measure to improve the water quality of rivers, numerous advantages have been achieved. one of the most remarkable advances was the integration of bioindicators as a suitable and quick tool to complement the assessment based on the evaluation of physical and chemical parameters. This paper evaluated which of the already used water quality indices based on macroinvertebrates would be more suitable to assess the ecological status of 6 rivers (Barxas, Deva, Tea, Manco, Louro and Furnia rivers) within the Miño River international basin (NW Spain and N Portugal) applying the methodology proposed by the Water Framework Directive (WFD). In addition, the relationship between the water quality and the land uses within a buffer zone of 100 along the watershed of each river was studied. Our findings demonstrate that the IBMWP (Iberian Biomonitoring Working Party) is the most suitable index to evaluate the water quality of rivers from this geographical zone. Nevertheless it is necessary to use other more sensitive index like EPT and PT indices to identify any potential pressures that might be concealed by IBMWP. The tributaries of the Miño River generally presented a good ecological status according to the IBMWP. Nevertheless, the Louro River had the lowest score for all the indices being the worst preserved among all within the basin. On the contrary Barxas, Deva and Furnia rivers showed the higher values. The results indicated that the most urbanised river was the Louro River (13 %) followed, to a lesser extent, by Manco River (7 %) and Tea River (2 %). Consequently, the Louro River had the worst water quality (poor quality) and a less diverse benthic macroinvertebrate community, in which more generalist taxa such as Chironomids, Ceratopogonids, or Crustaceans were found. On the other hand, the rivers with the best water quality were the Barxas, Deva, and Furnia, all of them with a negligible proportion of artificial cover surface (<1 %) within the delimited buffer zone. This would suggest a negative influence of the proportion of artificial areas over diversity and quality indices.

Ecological variation in invasive brown trout (Salmo trutta) within a remote coastal river catchment in northern Patagonia complicates estimates of invasion impact.

Salmonids were first introduced into the Chilean fresh waters in the 1880s, and c. 140 years later, they are ubiquitous across Chilean rivers, especially in the southern pristine fresh waters. This study examined the brown trout (Salmo trutta) and native taxa ecology in two adjacent but contrasting rivers of Chilean Patagonia. During spring 2016 and spring-fall 2017 we examined the variation in benthic macroinvertebrate and fish community composition and characterized fish size structure, stomach contents, and stable isotopes (δ13 C and δ15 N) to understand population structure, fish diet, and trophic interactions between S. trutta and native taxa. The native Galaxias maculatus (puye) dominated the fish community (74% of abundance). S. trutta was less abundant (16% of survey catch) but dominated the fish community (over 53%) in terms of biomass. S. trutta showed distinct diets (stomach content analysis) in the two rivers, and individuals from the larger river were notably more piscivorous, consuming native fish with a relatively small body size (<100-mm total length). Native fishes were isotopically distinct from S. trutta, which showed a wider isotopic niche in the smaller river, indicating that their trophic role was more variable than in the larger river (piscivorous). This study provides data from the unstudied pristine coastal rivers in Patagonia and reveals that interactions between native and introduced species can vary at very local spatial scales.

Distribution of the riverine benthic macroinvertebrate community along the citarum cascading dam system in West Java, Indonesia

Distribution of the riverine benthic macroinvertebrate community along the citarum cascading dam system in West Java, Indonesia

Benthic Macro-invertebrate Community Diversity of Orhuwhorun River in Udu Wetlands.

Benthic macro-invertebrate studies were done on Orhuwhorun River in Udu wetlands in Delta State, Southern Nigeria from March to December, 2011 in three selected stations. Sampling was done using a hand modified Eckman grab for sand and silt, the kick sampling technique and floatation method. They were sorted and identified using identification keys. A total of 2466 individuals were recorded in 66 taxa species belonging to thirteen (13) groups. Crustacean was the dominant group (36.29%) closely followed by gastropoda (35.60%) and diptera (21.04%). Significant similarity in fauna composition was observed. Station 3 had the highest population density with a relative abundance of 58.19% followed by station 2 (32.03%) and station 1 (9.77%). Diptera had the highest species diversity while nematode and lepidoptera had the least amongst the groups. Station 1 had the highest species richness (d) followed by station 3 and least in station 2. Species diversity showed no significant difference between the stations. Values for pollution tolerance index ranged between 13 and 15 at the stations. The highest value for pollution tolerance (PTI) was recorded in station 2 and the least in station 1. Positive significant correlations existed between most benthic organisms. The water quality is described as “fair”.

Ecological habitat quality assessment of a highly urbanized estuary using macroinvertebrate community diversity and structure

Urban estuaries are subject to a variety of ecological crises caused by humans as a result of rising shore-based human activities. In this study, environmental variables, community composition, structure and diversity indices of benthic macroinvertebrate were studied to assess the ecological health status of an urbanized estuary, Karnaphuli river estuary. The results revealed that dissolved oxygen (DO) was very low, and organic matter was much higher in the estuary. There were significant (p < 0.05) differences among the environmental variables across the sites. 31 taxa were identified yielding a total of 49167 Ind./m2 with overall mean density (±SD) of 159 (±327) Ind./m2. Annelida (61.8%) were the most abundant taxonomic group followed by Polychaeta (34.88%) and Oligochaeta (26.92%). The high abundance of pollution indicator taxa (Tubificidae, Capitellidae) and low abundance of pollution sensitive taxa (Lumbrinidae, Sabellidae, Maldanidae, Nephtyide) indicated detrimental ecological condition. The values of Shannon-Wiener diversity index (1.95–2.63), Pielou’s evenness index (0.60–0.81) and the Margalef diversity index (1.03–2.12) suggested moderate pollution status with extremely low species richness and low abundance in polluted areas. A PERMANOVA showed significant differences in faunal assemblages (F = 2.189, p < 0.001) among sites. Species abundance and density were higher (p = 0.32) at the upper estuary (where pH and salinity were low) and reduced in the middle and lower portion of the estuary which reflected the gradient of pollution level. Cluster analysis (CA) demarcated three distinct communities in terms of species similarity. SIMPER identified the highest average dissimilarity value (66.66%) across all the stations. The Canonical Correspondence Analysis (CCA) results suggested benthic macroinvertebrate community was influenced by environmental variables, for instance, salinity, dissolve oxygen, soil and water pH, total dissolved solids, and sediment texture.

Environmental flow assessment for benthic macroinvertebrate communities using pseudo‐2D hydraulic habitat modelling at a green small hydropower plant

AbstractThe determination of minimum flow requirements for green small hydropower plants (GSHP) in China primarily relies on hydrological methods such as the Tennant method with no seasonal variation. However, the direct application of hydrological methods without local ecological data for calibration lacks ecological validity, potentially resulting in unsuitable minimum flow recommendations for local aquatic biota. Hydraulic‐habitat modelling (HHM) is assumed to provide more ecologically relevant and reliable environmental flow recommendations (EFRs), but benthic macroinvertebrates (BMs), crucial in the aquatic food web, have rarely been the focus in HHM studies. Moreover, the strong subjectivity in HHM processes hinders the comparison of EFRs across different biota and geographical regions. This study aims to investigate the ecological validity of using the Tennant method to set minimum flow requirements for local BM communities and the impacts of various methods used in HHM on derived EFRs. To achieve this, a pseudo‐2D HHM approach is employed, integrating the 1D hydraulic models HEC‐RAS and CASiMiR with the habitat model HABFUZZ. The EFRs downstream of Jiufeng reservoir, one of China's first GSHPs, are derived for wet (April–June) and dry seasons (July–September). Our findings highlight that setting minimum flow alone is inadequate for preserving BM community integrity downstream of GSHPs. It is crucial to incorporate more diverse environmental flow criteria, including minimum flows and peak flows, into GSHP assessment standards, with recommended flow levels varying across different seasons. Additionally, the development of a standardized HHM methodology is essential to mitigate the inherent subjectivity in HHM and facilitate the comparison of EFRs generated from different studies. This study's innovative modelling framework and findings will enhance the optimization of minimum flow assessment criteria for GSHP in China, deepen understanding of seasonal e‐flow requirements of BM communities, and refine the methodology used in BM HHM for e‐flow recommendation.

Distribution of artisanal fishing gears with impacts on sedimentation and benthic macroinvertebrate assemblages in Songkhla Lake, the largest lagoon in Thailand

The present study investigated the distribution and diversity of stationary fishing gears in Songkhla Lake and assessed the effects of the most abundant gear in the lake, the standing trap, on sedimentation and the abundance of benthic macroinvertebrates. Our survey revealed that six types of fishing gear were used: standing traps, fyke nets, fish aggregating devices, seabass net cages, small traps and stationary lift nets. The type of fishing gear used depended on the depth of water. The density of installed standing traps reached a maximum of 357 traps/km2, which was the highest density of any fishing gear installed on the lake. They were mainly set in the middle part of the lake, where the water was less than 2 m deep. Sedimentation was examined inside and outside the areas influenced by standing traps. Sediment samples were collected with sediment traps in the northeast and southwest monsoon seasons. Sedimentation rates inside and outside the areas influenced by standing traps differed at some sites but the pattern was not consistent across seasons. Sedimentation rates were higher in the northeast monsoon season with the average rate 1132.32 ± 43.73 (mean ± SE) g m−2day−1 when precipitation and run-off were higher and 323.98 ± 10.68 g m−2day−1 in the southwest monsoon or dry season. Moreover, the proportion of finer clay particles was greater in the sediment from the areas influenced by traps. Benthic macroinvertebrate communities between the two areas were different. A bivalve, Potamocorbula sp., which dominated benthic macroinvertebrate assemblages, had a higher abundance in areas influenced by traps. The effects of stationary fishing gears on sedimentation and benthic macroinvertebrates highlighted in this study suggest that the long-term deployment of these gears may affect food chain dynamics in this lagoon system. Ultimately, a proper regulation of the use of these gears may be needed.

Benthic macroinvertebrates community in relation to environmental variables of the Cimandiri River and Estuary, Indonesia

Benthic macroinvertebrates, the community that lives in the river and coastal, play important role in the transfer of organic materials. This study aimed to determine the diversity of it in Cimandiri river and estuary. Also, to understand the relation between the community with environmental variables. The research was conducted in September and November 2020, which taken from 10 locations at Cimandiri waters. Benthic macroinvertebrates were collected using the Ekman grab sampler with three replications. Moreover, physicochemical parameters of water and sediment were measured. In general, about 35 taxa belonging to six Classes, including Gastropod, Bivalve, Insect, Malacostraca, Clitellata, and Polychaeta have been found during sampling. Furthermore, Stenelmis sp., one of Insects was predominant benthic invertebrates in the river, whereas Tarebia granifera predominated inhabit the estuary. Margalef richness and Shannon-Wiener diversity index in the river area were about 2.69 and 1.47, while in the estuary was around 1.59 and 0.87. Canonical Correspondence Analysis shows that the number of individuals of 25 taxa tended to correlate with water temperature, TDS, salinity, total of nitrate (TN), total of phosphorus (TP), and total of organic matters (TOM). While, 10 other taxa correlated with pH, turbidity, dissolved of oxygen (DO), ammonia, and the total of suspended solids (TSS).

DNA metabarcoding captures different macroinvertebrate biodiversity than morphological identification approaches across a continental scale

AbstractDNA‐based aquatic biomonitoring methods show promise to provide rapid, standardized, and efficient biodiversity assessment to supplement and in some cases replace current morphology‐based approaches that are often less efficient and can produce inconsistent results. Despite this potential, broad‐scale adoption of DNA‐based approaches by end‐users remains limited, and studies on how these two approaches differ in detecting aquatic biodiversity across large spatial scales are lacking. Here, we present a comparison of DNA metabarcoding and morphological identification, leveraging national‐scale, open‐source, ecological datasets from the National Ecological Observatory Network (NEON). Across 24 wadeable streams in North America with 179 paired sample comparisons, we found that DNA metabarcoding detected twice as many unique taxa than morphological identification overall. The two approaches showed poor congruence in detecting the same taxa, averaging 59%, 35%, and 23% of shared taxa detected at the order, family, and genus levels, respectively. Importantly, the two approaches detected different proportions of indicator taxa like %EPT and %Chironomidae. DNA metabarcoding detected far fewer Chironomid and Trichopteran taxa than morphological identification, but more Ephemeropteran and Plecopteran taxa, a result likely due to primer choice. Overall, our results showed that DNA metabarcoding and morphological identification detected different benthic macroinvertebrate communities. Despite these differences, we found that the same environmental variables were correlated with invertebrate community structure, suggesting that both approaches can accurately detect biodiversity patterns across environmental gradients. Further refinement of DNA metabarcoding protocols, primers, and reference libraries–as well as more standardized, large‐scale comparative studies–may improve our understanding of the taxonomic agreement and data linkages between DNA metabarcoding and morphological approaches.

Community recovery of benthic macroinvertebrates in a stream influenced by mining activity: Importance of microhabitat monitoring

The decrease in freshwater biodiversity owing to anthropogenic disturbances such as mining activity is a global challenge; hence, there is an urgent need for systematic approaches to continuously monitor such disturbances and/or the recovery of biodiversity in freshwater habitats. The Hwangjicheon Stream is the source of South Korea's longest river and has been subjected to runoff from coal mining. We investigated changes in the diversity of the benthic macroinvertebrate community in various microhabitats, including riffle, run, and pool, to monitor the recovery of biodiversity in the stream following the improvement of a mining water treatment plant in 2019. The dataset comprised 111 samples obtained from four types of microhabitats (riffle, run, pool, and riparian) over a four-year period from 2018 to 2021. The mining-affected sites had lower macroinvertebrate community complexities according to a network analysis, and grouped into the same cluster based on self-organizing map (SOM) analysis. Moreover, 51 taxa selected as indicator species represented each cluster obtained through the SOM analysis. Among them, only Limnodrilus gotoi and Radix auricularia were included as indicator species at the mining-affected sites. However, after 2020, the benthic macroinvertebrate community complexity increased, and some of the microhabitats at the mining-affected sites were included in the same cluster as the reference sites in the SOM analysis, indicating that the recovery of benthic macroinvertebrate communities had initiated in certain microhabitats (e.g., riparian). Further analysis confirmed that the macroinvertebrate community clearly differed according to the survey year, even in different microhabitats at the same sites. This suggests that more acute microhabitat monitoring may be necessary to quickly confirm biodiversity restoration when assessing the degree of the recovery in river biodiversity from anthropogenic disturbances.

Residual effect of Fipronil used in rice farming on non-target organisms

This study evaluated changes in the composition of the benthic community of non-target organisms in rice crop fields due to residual effect one year after planting seeds treated with different Fipronil doses. Macroinvertebrates were collected during crop irrigation months (February, March and April/2012), with the aid of 1 mm hand net placed close to the ground of each plot, for 20 minutes, collected macroinvertebrates were classified according to its dietary habits function. Orizophagus oryzae larvae, the target organisms, were not found in groups treated with different Fipronil doses; they were only observed in the control treatment. Chironominae (Chironomidae: Diptera) larvae had their population reduced in comparison to the control treatment. However, the herein used insecticide doses did not show significant changes in the benthic macroinvertebrate community one year after their application.

Characteristics of benthic macroinvertebrate community and distribution of golden apple snail in certified environmentally-friendly paddy field complexes of South Korea

Characteristics of benthic macroinvertebrate community and distribution of golden apple snail in certified environmentally-friendly paddy field complexes of South Korea

Habitat development and species arrival drive succession of the benthic invertebrate community in restored urban streams

BackgroundUrban streams are characterised by species-poor and frequently disturbed communities. The recovery of heavily polluted urban streams is challenging but the simple community structure makes recolonisation patterns more transparent. Therefore, they are generally applicable model systems for recolonisation of restored streams. Principal questions of stream restoration concern the drivers and patterns of recolonisation processes. Rarely, recolonisation of restored streams is recorded for a sufficient time to observe patterns of habitat and community development in detail. Over 10 years, we monitored benthic habitat changes and macroinvertebrate communities of eight restored sites in an urban stream network that was formerly used as an open sewer and thus, almost uninhabitable for macroinvertebrates prior to restoration. We analysed changes in environmental variables and communities with a selection of multi-variate analyses and identified indicator species in successional stages.ResultsProportions of stony substrate and conductivity decreased over time since restoration, while the riparian vegetation cover increased along with the amount of sandy substrate. The communities fluctuated strongly after restoration but began to stabilise after around eight years. TITAN analysis identified 9 species, (e.g. the mayfly Cloeon dipterum and the beetle Agabus didymus), whose abundances decreased with time since restoration, and 19 species with an increasing abundance trend (e.g. several Trichopteran species, which colonised once specific habitats developed). Woody riparian vegetation cover and related variables were identified as major driver for changes in species abundance. In the last phase of the observation period, a dry episode resulted in complete dewatering of some sites. These temporarily dried sections were recolonised much more rapidly compared to the recolonisation following restoration.ConclusionsOur results underline that community changes following urban stream restoration are closely linked to the evolving environmental conditions of restored streams, in particular habitat availability initialised by riparian vegetation. It takes about a decade for the development of a rich and stable community. Even in streams that were almost completely lacking benthic invertebrates before restoration, the establishment of a diverse macroinvertebrate community is possible, underlining the potential for habitat restoration in formerly heavily polluted urban areas.

Benthic macroinvertebrates community structure and physicalchemical characteristics at Lauca River Basin high altitude wetlands, Altiplano, Chile

High Andean freshwater ecosystems are highly threatened by scarce water availability, species invasion, and global climate change, so generating knowledge about their ecological characteristics is extremely important for conservation decision-making. In this work, the seasonal variations and relationships between physico-chemical variables and the structure and composition of the macroinvertebrate community were analyzed considering “season”, “type of ecosystem” and “site” factors. Five sites of representative ecosystems at Lauca River Basin of the Chilean Altiplano were sampled, two of them lentic and three lotic. Two field-sampling periods within a year according to the pre- and post-rain seasons characteristic of the Altiplano climate were considered. Thirty-five taxa were identified, and it was observed that the taxa Orthocladiinae, Austrelmis sp., Hyallela cf kochi, Podonominae and Helicopsychidae were indicator taxa that contributed the most to differences among sites or ecosystems (≥ 10 %.). No significant differences were found in the alpha diversity indicators used, except for some abundance values and Pielou’s Evenness index (J´), which varied significantly between lotic and lentic systems. The results of the ordination analysis showed a significant differentiation considering physical and chemical variables and macroinvertebrates assemblages that responded to “sites” (ANOSIM R Global = 0.64, p = 0.001) and “type of ecosystem” factors (ANOSIM R Global = 0.31, p = 0.02). The “season” factor was not statistically significant to explain the variability of biological data (ANOSIM R Global = -0.003, p = 0.47) and was slight and marginally significant with the physical and chemical data (ANOSIM R Global = 0.1, p = 0.04). In addition, the linear redundancy analysis (RDA) showed that physico-chemical variables related to hardness, temperature, phosphorous, and nitrogen explained most of the variance in the biological data (the first two canonical axes RDA1 and RDA2 explained 45.23 % of the total variation, p = 0.004). These results support the relevance of local conditions for high altitude wetlands and how those environmental characteristics can be reflected in the macroinvertebrate assemblages that inhabit them.

Spatial patterning of benthic macroinvertebrate communities using Geo-self-organizing map (Geo-SOM): A case study in the Nakdong River, South Korea

Characterizing community responses to environmental disturbances is difficult because of the complexity of heterogeneous ecosystems. A geographical self-organizing map (Geo-SOM) was applied to present the spatial distribution patterns of benthic communities in a river. The benthic macroinvertebrate communities were collected in the mainstream of the Nakdong River in South Korea. Geo-SOM is a machine learning technique that extracts spatial patterns of given data across spatial weight k values (0–5), which control the vicinity of the map, to extract geographical information effectively. In the results, clusters were formed mainly according to the topography on a large scale and anthropogenic impacts on a small-scale showing consistency in spatial patterning for benthic communities in the gradient across different degrees of spatial weight. Geo-SOM provided both comprehensive and detailed views for presenting species-space relationships. Corresponding to the decrease in k value (more weight in geographical information), we accumulated data variations to present a comprehensive view of spatial species distributions. Overall, correlations between species were more associated with latitude rather than longitude. The feasibility of spatial clustering was also demonstrated with the effective differentiation of community indices. Community indices were effectively differentiated into clusters in the Geo-SOM. Finally, Geo-SOM is a useful tool for extracting the spatial distribution patterns of communities in a comprehensible manner for the monitoring and management of communities in aquatic ecosystems.

Towards ecological flows: status of the benthic macroinvertebrate community during summer low-flow periods in a regulated lowland river

Climate change along with the increasing exploitation of water resources exacerbates low-flow periods, causing detrimental effects on riverine communities. The main mitigation measure currently adopted to counteract hydrological alterations induced by off-stream diversion is the release of minimum flows (MFs), even if within the European Union Water Framework Directive an upgrade towards ecological flows is urgently required to achieve good ecological status (GES). In this study, we investigated the temporal evolution of the benthic macroinvertebrate community in an Italian-regulated lowland river (Ticino River) to clarify the ecological effects of summer low flows, and we evaluated the current MFs in the perspective of meeting GES standard. Biomonitoring was carried out for four consecutive years (2019-2022), in a river site immediately below a large off-stream diversion. The four study years were characterized by different streamflow patterns, thus allowing us to compare the temporal trajectories of the community under different flow conditions. Moreover, the interruption of the low-flow periods due to overflow spilled by the upstream dam gave us the opportunity to assess the effects of experimental flow peaks. Contrary to the expectation, the macroinvertebrate assemblage kept almost unvaried across the years, showing great resistance and resilience to hydrological changes. Even in extraordinarily dry 2022, the community composition varied only slightly, with a reduction of mayflies and an increase of mollusks. However, a deterioration of the ecological status below GES standard was recorded that summer, indicating the need for an upgrading of the current MFs. This upgrade would include experimental flow peaks in critical periods, which act as intermediate disturbances, enhancing community richness, diversity, and overall quality, as well as compliance with a threshold of an index specifically developed for the hydrological pressure.

Exposure to fipronil, 2,4-D and vinasse influences macroinvertebrate assemblage structure: An experimental mesocosm approach

Sugarcane is one of the main monocultures in Brazil and widely uses herbicide 2,4-D and fipronil insecticide. In addition, vinasse can be mentioned as it is widely used in this plantation. These compounds occurring simultaneously in the aquatic environment can potentiate the deleterious effects on organisms. Thus, this study aimed to evaluate the composition, abundance and ecological indices of the benthic macroinvertebrate community, as well as its ability to reestablish itself considering environmental contamination by the pesticides Regent® 800WG (active ingredient - a.i. fipronil) (F) and DMA® 806BR (a.i. 2,4-D) (D) and vinasse (V), alone and in mixtures: pesticides - M and the three contaminants - MV. The study was conducted using open-air mesocosms. The macroinvertebrate community was monitored by colonization structures, the physical-chemical parameters, metals and pesticides were determined and the effects of contaminants were evaluated over the exposure time in 1, 7, 14, 28, 75 to 150 days. A multiple regression was performed between the water parameters and significant relationships were found between parameters associated with vinasse contamination (pH, total nitrogen, turbidity, and dissolved oxygen) and concentration of fipronil and the ecological variables studied. Over time, changes were observed in the composition of the community. The dominance and richness increased in treatments V and MV. The family Chironomidae and subclass Oligochaeta were more sensitive to the treatment V and MV, while individuals from the families Phoridae, Ephydridae and Sciomyzidae were occasionally found (depending on the experimental time) in these treatments. The insects were sensitive to treatments F and M, disappearing in these mesocosms after contamination, reappearing only after 75 days. The results reveal that sugarcane management practices associated with the use of pesticides and vinasse as fertilizer pose risks to the macroinvertebrate community with consequences for the trophic chains, given its importance in freshwater ecosystems and adjacent terrestrial environments.

Effectiveness of landscape indicators for explaining the variability of benthic macro-invertebrates in urban streams

Landscape indicators – measures of land use and land cover – are widely used as proxies for monitoring urban stream conditions, particularly for benthic invertebrates which are often negatively impacted by watershed urbanization. However, multi-scale and nonlinear relationships between benthic macroinvertebrates and landscape configuration derived from fine spatial resolution land cover are not well explored. Here, we developed a series of landscape indicators and assessed their effectiveness in explaining the variability of benthic macroinvertebrate communities in 63 streams across the Greater Vancouver Region in British Columbia, Canada. We asked: 1) How effective are multi-scale landscape indicators in explaining the variability of instream benthic macroinvertebrates? 2) Does the explanatory power of landscape indicators vary at different spatial scales? 3) Do different urban forest classification schemes and their spatial configurations impact the explanatory power of landscape indicators? We developed high spatial resolution (5-m) landscape indicators and evaluated their utility in statistical models explaining taxa richness, instream benthic indices of biological integrity (B-IBI), % Ephemeroptera, Plecoptera, and Trichoptera (EPT), and % Oligochaetes. For all benthic responses, landscape indicators measured at the watershed scale explained 5–25% more variation than riparian-based indicators. Combining indicators mapped at multiple scales further improved the explanatory power of landscape indicators for % EPT and % Oligochaetes, ultimately explaining over 70% of the variability of benthic macro-invertebrates in streams. Distinguishing deciduous and coniferous forest types improved the explanatory power of landscape indicators in a riparian model for B-IBI by 10%. When considering the spatial arrangement of land cover, patch density of forests in the surrounding watersheds of stream explained as much as 47% of the variability in % Oligochaetes. Our results highlight the importance of investigating nonlinear relationships between benthic macroinvertebrates and landscape configuration. This monitoring approach is transferable across cities interested in maintaining the ecological health of urban streams while supporting urban expansion and growth.