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Loayza-Muro R.A.,Cayetano Heredia Peruvian University | Loayza-Muro R.A.,University of Amsterdam | Elias-Letts R.,Cayetano Heredia Peruvian University | Marticorena-Ruiz J.K.,Cayetano Heredia Peruvian University | And 4 more authors.
Environmental Toxicology and Chemistry | Year: 2010

High altitude creates unique challenging conditions to biota that limit the diversity of benthic communities. Because environmental pollution may add further stress to life at high altitude, the present study explored the effect of metal pollution on the macroinvertebrate community composition in Andean streams between 3,500 to 4,500 meters above sea level (masl) during wet and dry seasons. At polluted sites, showing a high conductivity and a low pH, metal concentrations (e.g., Al, 13.07 mg/L; As, 3.49 mg/L; Mn, 19.65 mg/L; Pb, 0.876 mg/L; Zn, 16.08 mg/L) ranged from 8-fold up to 3,500-fold higher than at reference sites. The cumulative criterion unit allowed quantifying the potential toxicity of metal mixtures at the contaminated sites. Principal component analysis of physical chemical variables showed that reference sites were more likely to be structured by transparency, water discharge, and current velocity, while polluted sites appeared to be determined by metals and conductivity. Canonical correspondence analysis indicated a strong influence of highly correlated metals in structuring invertebrate communities, which were dominated by dipterans, coleopterans, collembolans, and mites at polluted sites. At reference sites crustaceans, ephemeropterans, plecopterans, and trichopterans were the most representative taxa. We concluded that severe metal pollution induced changes in macroinvertebrate community composition in high-altitude Andean streams, with a replacement of sensitive taxa by more tolerant taxa. Yet relatively species-rich communities persisted under harsh conditions. © 2010 SETAC.

Sevink J.,Institute for Biodiversity and Ecosystem Dynamics | Verstraten J.M.,Institute for Biodiversity and Ecosystem Dynamics | Kooijman A.M.,Institute for Biodiversity and Ecosystem Dynamics | Loayza-Muro R.A.,Cayetano Heredia Peruvian University | And 3 more authors.
Water, Air, and Soil Pollution | Year: 2015

The Rio Santiago in the Cordillera Negra of Peru is severely contaminated by acid mine drainage in its headwaters. In a strongly acid stream, at about 3800 m above sea level (masl), microterraces were found with terrace walls built up of dead moss, with encrustations and interstitial fine, creamy sediment. The stream water was turbid due to the presence of similar suspended sediment, which also occurred as a thin basal layer in inter-rim basins. The moss was identified as the rare bryophyte Anomobryum prostratum (Müll. Hal.) Besch. Chemical and mineralogical analyses show that green, living parts of the moss are gradually coated by Al/Fe (hydr)oxides, inducing their senescence and death. The necromass is covered by creamy crusts through precipitation of schwertmannite-type material from the stream water and simultaneous 'capture' of fine sediment. The latter consists of a mixture of precipitate and fine detrital primary minerals. These processes are held responsible for the formation of the microterraces, which regarding their composition and environment seem to be unique. Remarkable is the high As content of the creamy crusts and sediment, attributed to strong sorption of As, whereas its solute concentration is relatively low. This calls for more attention to suspended fine sediment in the assessment of environmental risks of stream water use. Lastly, the results raise serious doubts about the use of aquatic bryophytes as bioindicator for chemical pollution in acid mine drainage-polluted streams. © 2015 The Author(s).

Loayza-Muro R.A.,Cayetano Heredia Peruvian University | Loayza-Muro R.A.,University of Amsterdam | de Baat M.L.,University of Amsterdam | Palomino E.J.,Santiago Antunez de Mayolo National University | And 4 more authors.
Freshwater Biology | Year: 2014

Andean streams cover steep altitude gradients and locally leach metal-rich bedrock, creating highly selective habitat conditions. Chironomids are among the few dominant insect taxa present under the harshest conditions in Andean high altitude streams, but it remains unclear whether their dominance is due to the adaptive capacity of a few species (population differentiation) or to a diversity of species with different capacities to cope with environmental extremes (species composition). Therefore, the aim of this study was to assess whether metals and altitude drive the genetic diversity of chironomids in Andean streams. We measured metal concentrations and altitude-related conditions, such as UV-B radiation, water temperature and oxygen, in reference and metal-rich streams located at both 3000 and 4000 m a.s.l. The genetic composition of the chironomid communities from these streams was determined by mitochondrial cytochrome oxidase I (COI) gene sequencing, and a phylogenetic tree was constructed. The concentrations of all metals were higher in the metal-rich streams than in the references streams. The UV-B radiation level at 4000 m was notably higher than at 3000 m, while the water temperature followed the opposite trend. At 3000 m, the reference site was inhabited by six putative species, completely different from the three present at 4000 m. Only one putative species, which did not occur at the reference sites, was present at both the metal-rich sites at 3000 and 4000 m. The differences in putative species composition between 3000 and 4000 m indicated a strong sorting of species according to altitude. However, the unique putative species present at the metal-rich sites at both 3000 and 4000 m indicated that altitude-driven selection was overridden by the extreme selection pressure exerted by metal exposure. We conclude that altitude limits the distribution of chironomid taxa, but metal selection leads to predominance of a unique metal-tolerant taxon. © 2013 John Wiley & Sons Ltd.

Loayza-Muro R.A.,Cayetano Heredia Peruvian University | Loayza-Muro R.A.,University of Amsterdam | Marticorena-Ruiz J.K.,Cayetano Heredia Peruvian University | Palomino E.J.,Santiago Antunez de Mayolo National University | And 6 more authors.
Environmental Science and Technology | Year: 2013

In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple stress conditions, hypothesizing that melanin counteracts both the adverse effects of solar radiation and of metals. Melanin was determined in chironomids from reference and metal polluted streams at 3000 and 4000 m altitude, being 2-fold higher at 4000 m compared to 3000 m, and 2-fold higher in polluted streams than in reference streams at both altitudes. The field observations were experimentally verified by assessing the combined effects of Cu and UV-B on the survival and melanin concentration in larvae of the model species Chironomus riparius (Chironomidae, Diptera). In laboratory exposures, the highest melanin concentrations were found in larvae surviving toxic Cu concentrations, but not in those exposed to the highest UV-B radiation. Pre-exposure to UV-B decreased the sensitivity of the larvae to UV-B and to Cu+UV-B. It is concluded that in the field, melanin may protect chironomids partially against both elevated metal concentrations and solar radiation, allowing them to persist under the harshest conditions in high altitude streams. © 2012 American Chemical Society.

Mallqui K.S.V.,Federal University of Vicosa | Mallqui K.S.V.,Santiago Antunez de Mayolo National University | Vieira J.L.,Federal University of Vicosa | Guedes R.N.C.,Federal University of Vicosa | And 2 more authors.
Journal of Economic Entomology | Year: 2014

Insecticides can have lethal or sublethal effects upon targeted pest species, and sublethal effects may even favor pest outbreaks if insecticide-induced hormesis occurs. Hormesis is a biphasic dose-response of a given chemical compound that is stimulatory at low doses and toxic at high doses. The former response may result from the disruption of animal homeostasis leading to trade-off shifts between basic ecophysiological processes. A growing interest in the use of biorational insecticides, such as azadirachtin to control stored-product pests, raises concerns about potential sublethal effects. In this study, we explored the hypothesis that azadirachtin can negatively impact the reproductive capacity of the Mexican bean weevil, Zabrotes subfasciatus (Boheman) (Chrysomelidae: Bruchinae), a key pest of stored beans. In addition,weinvestigated whether adults of this species could compensate for any sublethal effect that might have affected any of their reproductive parameters by adjusting the allocation of its reproductive efforts. The results showed that females of Z. subfasciatus increased fecundity daily to compensate for azadirachtin-induced decreased longevity. In addition, a stage-structured matrix study revealed that populations of Z. subfasciatus engendered from females exposed to azadirachtin exhibited a higher rate of population increase (r) and a higher net reproductive rate (Ro). Finally, a projection matrix analysis showed notably higher densities along the generations for azadirachtin-exposed Z. subfasciatus populations. Thus, our study provides empirical evidence for the capacity of Z. subfasciatus to adapt to sublethal effects caused by biorational insecticides; consequently, this study highlights the importance of understanding this phenomenon when devising pest management strategies. © 2014 Entomological Society of America. © 2014 Entomological Society of America.

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