Taxonomic and nontaxonomic responses to ecological changes in an urban lowland stream through the use of Chironomidae (Diptera) larvae

Potential use of morphological deformities in Chironomus (Diptera: Chironomidae) as a bioindicator of heavy metals pollution in North-East Algeria

Human activities have led to profound changes in aquatic environments and degradation at several levels. Preserving the quality of aquatic environments, their good functioning, and the species that are dependent on them has become a crucial element. In order to monitor the overall health of aquatic ecosystems, it is necessary to develop early indicators of environmental quality. In this work, we have tried to evaluate whether the analysis of morphological deformities affecting Chironomidae larvae could tell us about the state of degradation of water courses that are subjected to different discharges. To do this, water, sediment, and larvae of Chironomidae were sampled in dry weather in August-September of 2017 at three sites located in the North-East of Algeria. The heavy metals in the three compartments as well as the deformities affecting the mentum and mandibles of Chironomus were analyzed. The results showed a metal contamination especially in sediments; the highest values were found in Meboujda River and Seybouse River. The three sites have high deformities incidences, more than 33%, which suggests the presence of toxic stress. This study reflected the relationship between heavy metal concentrations in water, sediments, and deformities larval mouthparts (mentum and mandibles) in Chironomus. The use of deformities in Chironomus sp. can serve as an effective tool for bioassessment of freshwater ecosystems.

Chironomid genera distribution related to environmental characteristics of a highly impacted basin (Argentina, South America)

The objective of the present study was to investigate the responses of the chironomid communities (Diptera: Chironomidae) to environmental variables in four moderately and highly disturbed rivers located in one of the most degraded watersheds in South America. Sampling campaigns were carried out during 2014-2016 in four sites of the Matanza-Riachuelo basin. The physical-chemical and hydrological variables were measured and, the ecological indices were calculated and evaluated by ANOVA. The responses of Chironomidae to the environmental variables were evaluated by redundancy analysis (RDA), and the sampling sites were grouped according to the populations of chironomids and the main environmental variables. Finally, the Spearman correlation was made to determine which of these variables were significant. In total, 13 chironomid taxa were found in 36 samples during the study period. The greatest density registered belongs to Rheotanytarsus and Cricotopus. The ANOVA detected the greatest Chironomidae density and taxonomic richness in the sites with agricultural-urban impact. The changes in the distribution of Rheotanytarsus, Thienemanniella, and Polypedilum were mainly explained by the increase in current velocity, organic matter, and hardness, and the decrease of NH3 and BOD. On the other hand, Goeldichironomus, Chironomus, Parachironomus, Dicrotendipes, and Cricotopus were explained by the increase in conductivity, dissolved oxygen, and temperature, and the decrease of the variables NO3, BOD, and Cu. In addition to this, the sites with urban-agricultural impact were clearly separated from sites with urban-industrial impact. The last one was more related to the increase in BOD, Cu, and NO3 that indicates moderate to poor water quality. In conclusion, we can infer that the physical and chemical variables are correlated with changes in the structure and distribution of the chironomid community and there are genera that respond differently at high and intermediate situations of disturbances. This knowledge contributes to the execution of strategies for the conservation and restoration of the lotic ecosystems.

Green synthesis of silver-nanoparticles from Annona reticulata leaves aqueous extract and its mosquito larvicidal and anti-microbial activity on human pathogens

Silver nanoparticles play a important role in controlling mosquito population as well as multi drug resistant pathogens without causing much harm to humans. In the present study was focused on green synthesis of silver nanoparticles against dengue causing vector (Aedes aegypti) and pathogens affecting humans. The synthesized silver nanoparticle was confirmed using UV- absorption spectrum range obtained at 416 nm, XRD, FTIR and HR-TEM analysis were used to determine the silver nanoparticle morphology and size with ∼6.48 ± 1.2-8.13 ± 0.18 nm and face centered cubic structure. The synthesized silver nanoparticles were exposed to fourth instar larvae of A. aegypti with different concentration (3-20 μg/mL) for 24 h and its elicit maximum mortality (100%) at their final concentration of 20 μg/mL and it's LC50 value was 4.43 μg/mL and LC90 value was 13.96 μg/mL, respectively. The minimum inhibitory activities of the tested pathogens were 125, 31.25, 62.5, 62.6 and 62.5 μg/mL for the Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans respectively. Further, the synthesized silver nanoparticle shows a potent antimicrobial activity against all tested pathogens. Moreover the effect of silver nanoparticle against Red Blood Cells belonging to 'O' positive blood group were tested and does not cause higher hemolysis to the cells even at the highest concentration. Based on these finding, we strongly suggested that face centered cubic structured A. reticulata AgNPs is an eco-friendly and potent bio-medical agent and can be apply in wide range of application an alternative chemically synthesized metal nanoparticle.

Lethal and sublethal effects of metal-polluted sediments on Chironomus sancticaroli Strixino and Strixino, 1981

The Cantareira Complex is one of the most important water supplies of the metropolitan region of São Paulo, Brazil. Previously, it was demonstrated that the sediments in this complex were polluted with metals and that Paiva Castro Reservoir-the last reservoir in the sequence, which receives water from the five previous reservoirs-was the reservoir with the greatest concentration of pollutants. Based on field data, it was noticed that copper concentrations in sediments were related to morphological alterations in chironomids. The present study provides novel monitoring methods and results for the complex by isolating the environmental and biological sources of variation. An adaptation of the in situ assay proposed by Soares et al. (Arch Environ Contam Toxicol 49:163-172, 2005), which uses a native tropical Chironomus species and low-cost materials, is also provided. The aim of this study was to isolate the effects of sediments from Paiva Castro on controlled populations of C. sancticaroli larvae using an in situ assay. A seven-day experiment was performed in triplicate. Third instar larvae were inoculated in chambers containing sediments from two distinct regions of Paiva Castro reservoir and a control site with sand. Five biological responses were considered: mouthpart alterations, larval length, width of cephalic capsule, mortality and total damage. The results suggest the effects of sediment toxicity on larvae include a reduction in length and a higher occurrence of total damage.

Evaluating Benthic Recovery Decades after a Major Oil Spill in the Laurentian Great Lakes

The long-term effects of oil spills on freshwater organisms have been little studied. In 1950, a large oil spill (10 million L) covered the harbor area of Parry Sound, Ontario, the deepest port in the Laurentian Great Lakes. Ecological impacts were not studied at the time, but 25 years later three-quarters of the Chironomus cucini larvae (Insecta, Diptera, Chironomidae) living in the harbor area were reported to be deformed. We returned six decades after the spill and found that the frequency of deformities had returned to background levels and that the community of burrowing invertebrates has largely recovered. By dating sediment cores and measuring the depth distribution of oils, we conclude that, although the oil persists six decades after the spill, sufficient uncontaminated sediment has covered the oil thereby putting it out of reach of most burrowing animals. Provided that the sediment remains undisturbed, the buried oil is unlikely to exert further negative effects on the biota in spite of the fact that it will likely persist for centuries.

Environmental quality assessment of reservoirs impacted by Hg from chlor-alkali technologies: case study of a recovery

Mercury (Hg) pollution legacy of chlor-alkali plants will be an important issue in the next decades with the planned phase out of Hg-based electrodes by 2025 within the Minamata convention. In such a context, the present study aimed to examine the extent of Hg contamination in the reservoirs surrounding the Oltchim plant and to evaluate the possible improvement of the environmental quality since the closure of its chlor-alkali unit. This plant is the largest chlor-alkali plant in Romania, which partly switched to Hg-free technology in 1999 and definitely stopped the use of Hg electrolysis in May 2012. Total Hg (THg) and methylmercury (CH₃Hg) concentrations were found to decrease in the surface waters and sediments of the reservoirs receiving the effluents of the chlor-alkali platform since the closure of Hg units. Hence, calculated risk quotients (RQ) indicated no adverse effect of Hg for aquatic organisms from the ambient water exposure. RQ of Hg in sediments were mostly all higher than 1, showing important risks for benthic organisms. However, ecotoxicity testing of water and sediments suggest possible impact of other contaminants and their mixtures. Hg hotspots were found in soils around the platform with RQ values much higher than 1. Finally, THg and CH₃Hg concentrations in fish were below the food safety limit set by the WHO, which contrasts with previous measurements made in 2007 revealing that 92 % of the studied fish were of high risk of consumption. Discontinuing the use of Hg electrodes greatly improved the surrounding environment of chlor-alkali plants within the following years and led to the decrease environmental exposure to Hg through fish consumption. However, sediment and soil still remained highly contaminated and problematic for the river reservoir management. The results of this ecological risk assessment study have important implications for the evaluation of the benefits as well as limits of the Minamata Convention implementation.

Toxicity of cadmium and lead on tropical midge larvae, Chironomus kiiensis Tokunaga and Chironomus javanus Kieffer (Diptera: Chironomidae)

OBJECTIVE

To investigate the acute toxicity of cadmium and lead on larvae of two tropical Chironomid species, Chironomus kiiensis (C. kiiensis) Tokunaga and Chironomus javanus (C. javanus) Kieffer.

METHODS

Different larval instars (first-fourth) were exposed using a static non-replacement testing procedures to various concentrations of cadmium and lead.

RESULTS

In general, younger larvae (first and second instars) of both species were more sensitive to both metals than older larvae (third and forth instars). The toxic effects of the metals on C. kiiensis and C. javanus were influenced by the age of the larvae (first to fourth instars), types of metals (cadmium or lead) and duration of larval exposure (24, 48, 72 and 96 h) to the metals.

CONCLUSIONS

Cadmium was more toxic to the chironomids than lead and C. javanus was significantly more sensitive to both metals than C. kiiensis (P<0.05).

Macrophytes, epipelic biofilm, and invertebrates as biotic indicators of physical habitat degradation of lowland streams (Argentina)

Our objective was to assess the effect of the physical habitat degradation in three lowland streams of Argentina that are subject to different land uses. To address this matter, we looked into some physical habitat alterations, mainly the water quality and channel changes, the impact on macrophytes' community, and the structural and functional descriptors of the epipelic biofilm and invertebrate assemblages. As a consequence of physical and chemical perturbations, we differentiated sampling sites with different degradation levels. The low degraded sites were affected mainly for the suburban land use, the moderately degraded sites for the rural land use, and the highly degraded sites for the urban land use. The data shows that the biotic descriptors that best reflected the environmental degradation were vegetation cover and macrophytes richness, the dominance of tolerant species (epipelic biofilm and invertebrates), algal biomass, O2 consumption by the epipelic biofilm, and invertebrates' richness and diversity. Furthermore, the results obtained highlight the importance of the macrophytes in the lowland streams, where there is a poor diversification of abiotic substrates and where the macrophytes not only provide shelter but also a food source for invertebrates and other trophic levels such as fish. We also noted that both in benthic communities, invertebrates and epipelic biofilm supplied different information: the habitat's physical structure provided by the macrophytes influenced mainly the invertebrate descriptors; meanwhile, the water quality mainly influenced most of the epipelic biofilm descriptors.

Relationship between space distribution of the benthic macroinvertebrates community and trophic state in a Neotropical reservoir (Itupararanga, Brazil)

The purpose of this work was to verify the benthic macroinvertebrates community responses through environmental factors along a headwater tropical reservoir. Samplings were taken with a Van-Veen grab along the reservoir in littoral and profundal regions and in the headwater, next to the dam and the middle of the reservoir. Samples were taken during both wet and dry seasons. Dissolved oxygen concentrations, electric conductivity, temperature and pH near the sediment have been performed in situ, at every sampling station by using a multiprobe and Secchi disc. Total water phosphorus and chlorophyll a concentrations were analyzed to determine the trophic state index. Sediment's organic matter, total phosphorus, nitrogen concentrations and granulometric composition were measured. In order to verify which environmental variables would have more influence over the benthic macroinvertebrates community, a canonical correspondence analysis (CCA) was performed. The total number of recorded taxa was 28. Among them, the family Chironomidae (Diptera) was the richest group (19 taxa). It can be proposed that the benthic macroinvertebrates community may be influenced by environmental conditions such as nutrient and organic matter availability, as well as dissolved oxygen concentration. Macroinvertebrates are adequate bioindicators of water quality due to their sensibility to environmental changes mentioned before. Chironomus sp, Limnodrilus hoffmeisteri and Branchiura sowerbyi comprises a group that can be considered bio-indicators of eutrophic conditions. A second group can be considered as indicator of mesotrophic conditions. The presence of two or more members from that group which comprises Tanytarsini spp, Fissimentum sp, Pelomus sp and Goeldichironomus sp, like predominant taxa, may indicates mesotrophic conditions.

Does nature and persistence of substrate at a mesohabitat scale matter for Chironomidae assemblages? A study of two perennial mountain streams in Patagonia, Argentina

Chironomid substrate-specific associations regarding the nature (organic-inorganic) and stability (stable-unstable) of different habitats were investigated at two low order Patagonian streams, during high and low water periods. Nant y Fall and Glyn rivers were visited twice (October 2007 and March 2008) and seven different habitat types were identified. A total of 60 samples were collected using a Surber sampler (0.09 m(-2) and 250 µm) and a set of 23 environmental descriptors including physicochemical parameters and different fractions of particulate organic matter were assessed. 35 Chironomidae taxa were recorded with Orthocladiinae (20), Chironominae (7), and Podonominae (4) being the most well-represented subfamilies. Paratrichocladius sp. 1, Parapsectrocladius sp. 2, Parametriocnemus sp. 1, Pseudochironomus sp., and Rheotanytarsus sp. were the most abundant taxa. According to the relative preference index, at least 14 taxa showed strong affinity for a particular substrate. The structurally complex macrophyte Myriophyllum quitense supported 11 taxa compared with only five taxa found on the less complex Isoetes savatieri. Generally, stable substrates (boulders, cobbles, and rooted plants) supported significantly higher chironomids richness, abundance, and diversity than unstable ones (gravel-sand). Canonical correspondence analysis revealed that detritus (leaves, seeds, and biomass), macrophyte biomass, and secondarily hydraulic variables had high explanatory power on chironomids species composition and structure. This work suggests that more complex substrates showing persistence in the temporal dimension supported a diverse array of chironomids, meaning that the maintenance of natural habitat heterogeneity is essential for the community. Land-use practices having significant effects on ecological stream attributes such as increased turbidity, sediment deposition, and runoff patterns will alter assemblages. Understanding environmental associations of the Chironomidae assemblage at the habitat scale is significant for conservation purposes and for the management of low order streams in Patagonia.