Metal-induced shifts in benthic macroinvertebrate community composition in Andean high altitude streams Loayza Muro, R.A.; Elías-Letts, R.; Marticorena-Ruíz, J.K.; Palomino, E.J.; Duivenvoorden, J.F.; Kraak, M.H.S.; Admiraal, W. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract-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 highaltitude Andean streams, with a replacement of sensitive taxa by more tolerant taxa. Yet relatively species-rich communities persisted under harsh conditions.

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.

The exposure of fresh sulfide-rich lithologies by the retracement of the Nevado Pastoruri glacier (Central Andes, Perú) is increasing the presence of heavy metals in the water as well as decreasing the pH, producing an acid rock drainage (ARD) process in the area. We describe the microbial communities of an extreme ARD site in Huascarán National Park as well as their correlation with the water physicochemistry. Microbial biodiversity was analyzed by FLX 454 sequencing of the 16S rRNA gene. The suggested geomicrobiological model of the area distinguishes three different zones. The proglacial zone is located in the upper part of the valley, where the ARD process is not evident yet. Most of the OTUs detected in this area were related to sequences associated with cold environments (i.e., psychrotolerant species of Cyanobacteria or Bacteroidetes). After the proglacial area, an ARD-influenced zone appeared, characterized by the presence of phylotypes related to acidophiles (Acidiphilium) as well as other species related to acidic and cold environments (i.e., acidophilic species of Chloroflexi, Clostridium and Verrumicrobia). Sulfur- and iron-oxidizing acidophilic bacteria (Acidithiobacillus) were also identified. The post-ARD area was characterized by the presence of OTUs related to microorganisms detected in soils, permafrost, high mountain environments, and deglaciation areas (Sphingomonadales, Caulobacter or Comamonadaceae).

Summary 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.

1. Photoprotective pigments in benthic macroinvertebrates may reduce the damage caused by the blistering UV-B radiation in Andean high-altitude streams above 3500 m. The aim of this study was therefore to determine whether melanisation in macroinvertebrates inhabiting high-altitude Andean streams is an adaptive response to high UV-B radiation. To explore whether altitude-related differences in melanin concentration between taxa were due to a variable community composition or due to population differentiation, mayfly species were identified genetically. 2. We measured UV-B radiation from 650 to 4000 m and compared body melanin concentrations from several benthic macroinvertebrate orders sampled at these altitudes. Five genera belonging to the mayfly family Baetidae were genetically identified to the species level. DNA sequencing was performed in individual larval legs to group genetically similar individuals before pigment analysis in the corresponding bodies. 3. The UV-B radiation at 4000 m was twice that at 3200 m, four times that at 1900 m and five times that at 650 m. The melanin concentration in families belonging to Ephemeroptera, Trichoptera, Diptera and Turbellaria was twice as high at 4000 m as at 3200 m, but did not differ among taxa or between seasons. Five genera of the family Baetidae were identified: Americabaetis, Dactylobaetis, Tupiara, Baetodes and Thraulodes. Genetic differences were evident between Americabaetis sp. at 4000 m from the Cordillera Blanca and at 3200 m from the R ımac River valley, and between Tupiara taxa at 650 and 1900 m in the R ımac River. In Americabaetis, melanin increased fivefold from 1900 to 4000 m, while in Dactylobaetis and Tupiara, it was twice as high at 1900 m as at 650 m. In Baetodes, melanin at 4000 m was twice that at 650 and 1900 m, while in Thraulodes, it was almost three times higher at 4000 m than at 3200 m. 4. In Tupiara, the differences in melanin levels were probably associated with species with different vertical distribution, while in Dactylobaetis, these differences were interpreted as phenotypic plasticity. Our results thus indicate that mayfly species within a single family have both constitutive and adjustable melanin concentrations, enabling them to cope with the strong selective UV-B environment. Adjustable melanin levels have commonly been observed under moderate UV-B regimes, while the constitutive, high melanin concentration is probably an attribute of high-altitude invertebrate fauna in the tropics.