The Experts below are selected from a list of 40176 Experts worldwide ranked by ideXlab platform
Encarni Montoya - One of the best experts on this subject based on the ideXlab platform.
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Aquatic Community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record
Journal of Paleolimnology, 2017Co-Authors: Frazer Matthews-bird, Stephen J. Brooks, William D. Gosling, Pauline Gulliver, Patricia Mothes, Encarni MontoyaAbstract:Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of Aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132′S–78°04.847′W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328′S–78°09.175′W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other Aquatic and semi-Aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the Aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and Aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer -type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid Community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the Aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes.
Udo Hommen - One of the best experts on this subject based on the ideXlab platform.
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Environmental quality standards for mixtures: A case study with a herbicide mixture tested in outdoor mesocosms
Ecotoxicology and Environmental Safety, 2012Co-Authors: Katja Knauer, Udo HommenAbstract:Abstract Traces of pesticides are frequently detected in surface waters. As a consequence, specific environmental quality criteria (EQS) for a set of single pesticides in surface waters were defined by the environmental authorities in several countries. In this context, the aim of this study was to investigate if the sum of the five percentile hazard concentration (ΣHC5–95percent, meaning that 5 percent of the Aquatic assemblage remains affected considering a 95 percent confidence interval) of three herbicides with the same mode of action derived from a species sensitivity distribution based on acute toxicity data (EC50 values) of the most sensitive taxonomic group is a suitable EQS for surface water addressing the occurrence of herbicide mixtures as common exposure scenario. Therefore, an outdoor mesocosm study was performed with three replicates per treatment for a period of 173 days. Results demonstrated that a constant long-term exposure over 35 days to the HC5–95 percent of a mixture of three PSII inhibitors did not lead to adverse effects on the Aquatic Community in this field mesocosm study. Neither adverse effects on very sensitive functional endpoints such as photosynthesis measurements of algae and macrophytes nor adverse effects on structural endpoints such as abundance data and species composition were determined. In contrast and as a positive control, the HC30 treatment affected statistically significant all investigated endpoints and it was demonstrated that the PSII inhibitors acted additive on various level of organization ( Knauert et al., 2008 ). This study is filling the gap that no empirical evidence is published indicating that the chronic exposure at the HC5–95 percent estimate is leading to no adverse effects for the Aquatic Community and is therefore a suitable EQS for surface waters in the agriculture landscape.
Silvia Pajares - One of the best experts on this subject based on the ideXlab platform.
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mesocosms of Aquatic bacterial communities from the cuatro cienegas basin mexico a tool to test bacterial Community response to environmental stress
Microbial Ecology, 2012Co-Authors: Silvia Pajares, German Bonillarosso, Michael Travisano, Luis E Eguiarte, Valeria SouzaAbstract:Microbial communities are responsible for important ecosystem processes, and their activities are regulated by environmental factors such as temperature and solar ultraviolet radiation. Here we investigate changes in Aquatic microbial Community structure, diversity, and evenness in response to changes in temperature and UV radiation. For this purpose, 15 mesocosms were seeded with both microbial mat communities and plankton from natural pools within the Cuatro Cienegas Basin (Mexico). Clone libraries (16S rRNA) were obtained from water samples at the beginning and at the end of the experiment (40 days). Phylogenetic analysis indicated substantial changes in Aquatic Community composition and structure in response to temperature and UV radiation. Extreme treatments with elevation in temperature or UV radiation reduced diversity in relation to the Control treatments, causing a reduction in richness and increase in dominance, with a proliferation of a few resistant operational taxonomic units. Each phylum was affected differentially by the new conditions, which translates in a differential modification of ecosystem functioning. This suggests that the impact of environmental stress, at least at short term, will reshape the Aquatic bacterial communities of this unique ecosystem. This work also demonstrates the possibility of designing manageable synthetic microbial Community ecosystems where controlled environmental variables can be manipulated. Therefore, microbial model systems offer a complementary approach to field and laboratory studies of global research problems associated with the environment.
Daoxian Yuan - One of the best experts on this subject based on the ideXlab platform.
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Diel-scale variation of dissolved inorganic carbon during a rainfall event in a small karst stream in southern China
Environmental Science and Pollution Research, 2019Co-Authors: Tao Zhang, Jonathan B. Martin, Mitra B. Khadka, Daoxian YuanAbstract:Metabolic processes of the submerged Aquatic Community (photosynthesis and respiration) play important roles in regulating diel cycles of dissolved inorganic carbon (DIC) and sequestering carbon in a karst stream. However, little is known of whether diel DIC cycling occurs during rainfall in a karst groundwater-fed stream, even though this question is critical for the accurate estimation of what may be a major terrestrial carbon sink. Here, we measured diel variations of water chemical composition in a small karst groundwater-fed stream in southwest China during a rainfall event to assess the influences of rainfall and rising discharge on DIC diel cycling and the potential carbon sink produced by in-stream metabolism. Our results show that water chemical composition at the source spring (CK site) is relatively stable due to chemostatic behavior during rising discharge after a rainfall period. This site lacked submerged Aquatic vegetation and, thus, had no diel variations in water chemistry. However, diel cycles of all hydrochemical parameters occurred at a site 1.3 km downstream (LY site). Diel variations in pH, DO, and δ13CDIC were inversely related to diel changes in SpC, DIC, Ca2+, and pCO2. These results indicated that diel cycling of DIC due to in-stream metabolism of submerged Aquatic Community was still occurring during elevated discharge from rainfall. We estimate the carbon sink through the in-stream metabolism of the submerged Aquatic Community to be 5.6 kg C/day during the studied rainfall event. These results imply that submerged Aquatic communities in a karst stream can significantly stabilize carbon originating from the carbonate rock weathering processes in karst areas.
Michael J Lydy - One of the best experts on this subject based on the ideXlab platform.
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toxicity of fluoroquinolone antibiotics to Aquatic organisms
Environmental Toxicology and Chemistry, 2005Co-Authors: April A Robinson, Jason B Belden, Michael J LydyAbstract:Toxicity tests were performed with seven fluoroquinolone antibiotics, ciprofloxacin, lomefloxacin, ofloxacin, levofloxacin, clinafloxacin, enrofloxacin, and flumequine, on five Aquatic organisms. Overall toxicity values ranged from 7.9 to 23,000 μg/L. The cyanobacterium Microcystis aeruginosa was the most sensitive organism (5-d growth and reproduction, effective concentrations [EC50s] ranging from 7.9 to 1,960 μg/L and a median of 49 μg/L), followed by duckweed (Lemna minor, 7-d reproduction, EC50 values ranged from 53 to 2,470 μg/L with a median of 106 μg/L) and the green alga Pseudokirchneriella subcapitata (3-d growth and reproduction, EC50 values ranged from 1,100 to 22,700 μg/L with a median 7,400 μg/L). Results from tests with the crustacean Daphnia magna (48-h survival) and fathead minnow (Pimephales promelas, 7-d early life stage survival and growth) showed limited toxicity with no-observed-effect concentrations at or near 10 mg/L. Fish dry weights obtained in the ciprofloxacin, levofloxacin, and ofloxacin treatments (10 mg/L) were significantly higher than in control fish. The hazard of adverse effects occurring to the tested organisms in the environment was quantified by using hazard quotients. An estimated environmental concentration of 1 μg/L was chosen based on measured environmental concentrations previously reported in surface water; at this level, only M. aeruginosa may be at risk in surface water. However, the selective toxicity of these compounds may have implications for Aquatic Community structure.