Assessment of a conservative mixing model for the evaluation of constituent behavior below river confluences, Elqui River Basin, Chile

Autores:

Rossi, C., Oyarzún, J., Pastén, P., Runkel, R. L., Núñez, J., Duhalde, D., Maturana, H., Rojas, E., Arumí, J. L., Castillo, D., & Oyarzún, R.

Resumen:

Fate and transport modeling of water-borne contaminants is a data demanding and costly endeavor, requiring considerable expes such, it becomes important to know when a complex modeling approach is required, and when a simpler approach is adequate. This is the main objective herein, where a conservative mixing model is used to characterize the transport of As, Cu, Fe, and SO4. The study area is divided into three sectors, corresponding to the upstream, middle, and downstream portions of the Elqui River Basin, Chile. In Sector 1, acidic conditions result in the conservative transport of constituents that are sourced from acid rock drainage. In Sector 2, pH increases and transport is influenced by pH-dependent reactions and the subsequent settling of the particulate phase. In Sector 3, there are no additional constituent inputs, and the constituents are conservatively transported downstream. Conservative transport within Sector 3 is confirmed through the development of a regression model that provides monthly estimates of SO4 load. Whereas SO4 and Cu concentrations are adequately approximated by the conservative mixing model, estimates of As and Fe concentrations exhibit larger errors, due to the more reactive behavior of these constituents. The fact that the simple, conservative mixing model describes SO4 transport is a valuable result, as this constituent is known to be one of the primary indicators of mining-related contamination in rivers. The approach could also be a useful starting point for further evaluations of the effects of climate change and hydrological variability on the water quality of rivers.

Año: 2021

Palabras claves:

Schoolchildren discover hotspots of floating plastic litter in rivers using a large-scale collaborative approach

Autores:

Kiessling, T., Knickmeier, K., Kruse, K., Gatta-Rosemary, M., Nauendorf, A., Brennecke, D., Thiel, L., Wichels, A., Parchmann, I., Körtzinger, A., Thiel, M.

Resumen:

Rivers are an important transport route of anthropogenic litter from inland sources toward the sea. A collaborative (i.e. citizen science) approach was used to evaluate the litter pollution of rivers in Germany: schoolchildren within the project “Plastic Pirates” investigated rivers across the entire country during the years 2016 and 2017 by surveying floating macrolitter at 282 sites and taking 164 meso−/microplastic samples (i.e. particles 24.99–5 mm, and 4.99–1 mm, respectively). Floating macrolitter was sighted at 54% of sampling sites and floating macrolitter quantities ranged from 0 to 8.25 items m−1 h−1 (average of 0.34 ± 0.89 litter items m−1 h−1). Floating meso−/microplastics were present at 57% of the sampling sites, and floating meso−/microplastic quantities ranged from 0 to 220 particles h−1 (average of 6.86 ± 24.11 items h−1). As only particles >1 mm were sampled and analyzed, the pollution of rivers in Germany by microplastics could be a much more prevalent problem, regardless of the size of the river. We identified six plastic pollution hotspots where 60% of all meso−/microplastics collected in the present study were found. These hotspots were located close to a plastic-producing industry site, a wastewater treatment plant, at and below weirs, or in residential areas. The composition of the particles at these hotspots indicates plastic producers and possibly the construction industry and wastewater treatment plants as point sources. An identification of litter hotspots would enable specific mitigation measures, adjusted to the respective source, and thereby could prevent the release of large quantities of small plastic particles in rivers. The adopted large-scale citizen science approach was especially suitable to detect pollution hotspots by sampling a variety of rivers, large and small, and enabled a national overview of litter pollution in German rivers.

Año: 2021

Palabras claves: Plastic litter; Floating macrolitter; Microplastics; Rivers; Citizen science

COVID lessons from the global south – Face masks invading tourist beaches and recommendations for the outdoor seasons

Autores:

Thiel, M., de Veer, D., Espinoza-Fuenzalida, N.L., Espinoza, C., Gallardo, C., Hinojosa, I.A., Kiessling, T., Rojas, J., Sanchez, A., Sotomayor, F., Vasquez, N., Villablanca, R.

Resumen:

In response to the COVID-19 pandemic in 2020, Personal Protective Equipment (PPE) has been extensively used, and discarded PPE has been observed in many different environments, including on tourist beaches. Here we examined the distribution and densities of face masks on some of the main tourist beaches in Chile, and we monitored their daily accumulation rates on one beach in northern-central Chile. Face masks were found on beaches across the country with average densities of 0.006 ± 0.002 (mean ± se) face masks m−2, which are higher than densities reported on Peruvian beaches, but lower than those on some Kenyan beaches. Face masks were also found on more remote beaches and rocky shores in northern-central Chile. Daily accumulation rates on one tourist beach were low during austral fall/winter (0.2 face masks km−1 d−1), but were over ten times higher during austral summer (3.0 face masks km−1 d−1). These values are substantially higher than daily accumulation rates reported from urban streets, which is most likely due to the high densities of beach visitors during the summer tourist season. COVID-19 related infrastructure (signposts and PPE waste bins) was present on most beaches, but while signposts about personal protection were abundant, there were few signposts about littering, and only one of the 12 beaches sampled for COVID infrastructure had a signpost that offered recommendations about the proper disposal of used face masks. Specific waste bins for PPE waste were only available at three beaches. Based on these findings it is recommended to provide sufficient PPE-related signs and waste bins, establish general and strict waste disposal regulations, and to improve enforcement. Educational campaigns should aim at recommending proper use and disposal of face masks, litter prevention, reduction of single-use waste and enhanced pro-environmental behaviors.

Año: 2021

Palabras claves: COVID-19, Personal Protective Equipment (PPE), Littering, Beach pollution, Waste infrastructure, Waste management.

The Effect of Hybridization between Natural and Cultivated Peruvian Scallop Argopecten purpuratus populations on Growth and Tolerance to Abiotic Stress

Autores:

Bavestrello-Riquelme, C., Rios, R.S., Farías, W.J., Cárcamo, C.B., Pérez, H., Brokordt, K.

Resumen:

Intraspecific hybridization has been a strategy used frequently in mollusc aquaculture to improve the performance of traits for productive interest. In this study, the effect of hybridization between a natural population (Arica = A) and a cultivated population (Coquimbo = C; without genetic management for more than 30 y) of the Peruvian scallop Argopecten purpuratus was evaluated to assess the effect of this strategy on the performance of the cultivated population in terms of growth, survival, and stress tolerance due to hypoxia and increased temperature. To this end, progenies from intrapopulation (C × C and A × A) and reciprocal hybrid (C × A and A × C) crosses were produced and were evaluated after 6 mo under sea cultivation and in a controlled environment. Stress responses were evaluated via metabolic rates and the transcriptional level of stress-associated genes [superoxide dismutase (SOD) and HSP70]. The results showed that CC and the reciprocal hybrids CA and AC had greater size and survival rates than AA; on the other hand, AA presented the highest metabolic rates when exposed to stress; and, in parallel, AA and both hybrids (CA and AC) presented greater antioxidant capacity (SOD) when exposed to hyperthermia. Therefore, growth and survival showed positive heterosis because the hybrids performed better in these traits than the parental mean. In addition, hybridization with the Arica population would allow the Coquimbo stock under cultivation to improve its resilience to temperature increases associated to oceanographic oscillations or to climate change.

Año: 2021

Palabras claves: Aquaculture, Argopecten purpuratus, growth, growth genes, hybrids, metabolic rates, Peruvian scallop, stress, stress genes

Symbiotic Interaction Enhances the Recovery of Endangered Tree Species in the Fragmented Maulino Forest

Autores:

Torres-Díaz C, Valladares MA, Acuña-Rodríguez IS, Ballesteros GI, Barrera A, Atala C and Molina-Montenegro MA

Resumen:

Beneficial plant-associated microorganisms, such as fungal endophytes, are key partners that normally improve plant survival under different environmental stresses. It has been shown that microorganisms from extreme environments, like those associated with the roots of Antarctica plants, can be good partners to increase the performance of crop plants and to restore endangered native plants. Nothofagus alessandrii and N. glauca, are among the most endangered species of Chile, restricted to a narrow and/or limited distributional range associated mainly to the Maulino forest in Chile. Here we evaluated the effect of the inoculation with a fungal consortium of root endophytes isolated from the Antarctic host plant Colobanthus quitensis on the ecophysiological performance [photosynthesis, water use efficiency (WUE), and growth] of both endangered tree species. We also, tested how Antarctic root-fungal endophytes could affect the potential distribution of N. alessandrii through niche modeling. Additionally, we conducted a transplant experiment recording plant survival on 2 years in order to validate the model. Lastly, to evaluate if inoculation with Antarctic endophytes has negative impacts on native soil microorganisms, we compared the biodiversity of fungi and bacterial in the rhizospheric soil of transplanted individuals of N. alessandrii inoculated and non-inoculated with fungal endophytes. We found that inoculation with root-endophytes produced significant increases in N. alessandrii and N. glauca photosynthetic rates, water use efficiencies and cumulative growth. In N. alessandrii, seedling survival was significantly greater on inoculated plants compared with non-inoculated individuals. For this species, a spatial distribution modeling revealed that, inoculation with root-fungal endophytes could potentially increase the current distributional range by almost threefold. Inoculation with root-fungal endophytes, did not reduce native rhizospheric microbiome diversity. Our results suggest that the studied consortium of Antarctic root-fungal endophytes improve the ecophysiological performance as well as the survival of inoculated trees and can be used as a biotechnological tool for the restoration of endangered tree species.

Año: 2021

Palabras claves: Nothofagus spp., ruil, hualo, endangered tree species, restoration, Antarctica, fungal endophytes, functional symbiosis

Genotoxicity of oxidative stress and UV-B radiation in Antarctic vascular plants

Autores:

Acuña-Rodríguez, I.S., Zúñiga-Venegas, L.A. & Molina-Montenegro, M.A.

Resumen:

For plants, reactive oxygen species (ROS) and ultraviolet B radiation (UV-B) stand out as important genotoxic agents. Hence, the genetic damage among the Antarctic vascular flora, whose individuals frequently experience these abiotic stresses, might be recurrent among their populations. To respond this, the genetic damage associated with these stress factors was evaluated in Colobanthus quitensis and Deschampsia antarctica for the first time in the field and compared with those showed by plants grown at laboratory under less stressful conditions. Fifteen individuals per species from Admiralty Bay populations at King George Island (Maritime Antarctica) were used to semi-quantitatively estimate the genetic damage at the whole genome level by the single-cell gel electrophoresis (SCGE) assay, revealing by means of specific enzymatic treatments the damage generated by oxidative stress (oxidized purines and pyrimidines) and UV-B radiation (pyrimidine dimmers). Compared with laboratory control individuals, the basal genetic damage observed in both species was significantly higher under field conditions. However, while for C. quitensis, oxidative stress (Ox) was more relevant than UV-B radiation (field relative revealed damage: Ox = 29% vs. UV-B = 25%), in D. antarctica, it was UV-B radiation the most relevant genotoxic factor (Ox = 10% vs. UV-B = 33%). This first approach to the genetic damage of the Antarctic vascular flora suggests that the conditions experienced on their natural ecosystems would constitute a genotoxic environment for these species, yet with differential impact between them.

Año: 2021

Palabras claves: Antarctic plants, Comet assay, DNA damage, Oxidative stress, UV-B radiation

Global Plastic Pollution Observation System to Aid Policy

Autores:

Bank, M.S., Swarzenski, P.W., Duarte, C.M., Rillig, M.C., Koelmans, A.A., Metian, M., Wright, S., Provencher, J.F., Sanden, M., Jordaan, A., Wagner, M., Thiel, M, and Ok, Y.S.

Resumen:

Plastic pollution has become one of the most pressing environmental challenges and has received commensurate widespread attention. Although it is a top priority for policymakers and scientists alike, the knowledge required to guide decisions, implement mitigation actions, and assess their outcomes remains inadequate. We argue that an integrated, global monitoring system for plastic pollution is needed to provide comprehensive, harmonized data for environmental, societal, and economic assessments. The initial focus on marine ecosystems has been expanded here to include atmospheric transport and terrestrial and freshwater ecosystems. An earth-system-level plastic observation system is proposed as a hub for collecting and assessing the scale and impacts of plastic pollution across a wide array of particle sizes and ecosystems including air, land, water, and biota and to monitor progress toward ameliorating this problem. The proposed observation system strives to integrate new information and to identify pollution hotspots (i.e., production facilities, cities, roads, ports, etc.) and expands monitoring from marine environments to encompass all ecosystem types. Eventually, such a system will deliver knowledge to support public policy and corporate contributions to the relevant United Nations (UN) Sustainable Development Goals (SDGs).

Año: 2021

Palabras claves: Public policy monitoring reporting plastic waste pollution ecosystem.

Evaluating optically stimulated luminescence rock surface exposure dating as a novel approach for reconstructing coastal boulder movement on decadal to centennial timescales

Autores:

Brill, D., May, S. M., Mhammdi, N., King, G., Lehmann, B., Burow, C., Wolf, D., Zander, A., and Brückner, H.

Resumen:

Wave-transported boulders represent important records of storm and tsunami impact over geological timescales. Their use for hazard assessment requires chronological information on their displacement that in many cases cannot be achieved by established dating approaches. To fill this gap, this study investigated, for the first time, the potential of optically stimulated luminescence rock surface exposure dating (OSL-RSED) for estimating cliff-detachment ages of wave-transported coastal boulders. The approach was tested on calcarenite clasts at the Rabat coast, Morocco. Calibration of the OSL-RSED model was based on samples with rock surfaces exposed to sunlight for ∼ 2 years, and OSL exposure ages were evaluated against age control deduced from satellite images. Our results show that the dating precision is limited for all targeted boulders due to the local source rock lithology which has low amounts of quartz and feldspar. The dating accuracy may be affected by erosion rates on boulder surfaces of 0.02–0.18 mm yr−1. Nevertheless, we propose a robust relative chronology for boulders that are not affected by significant post-depositional erosion and that share surface angles of inclination with the calibration samples. The relative chronology indicates that (i) most boulders were detached from the cliff by storm waves; (ii) these storms lifted boulders with masses of up to ∼ 24 t; and (iii) the role of storms in the formation of boulder deposits along the Rabat coast is more significant than previously assumed. Although OSL-RSED cannot provide reliable absolute exposure ages for the coastal boulders in this study, the approach has large potential for boulder deposits composed of rocks with larger amounts of quartz or feldspar and less susceptibility to erosion.

Año: 2021

Palabras claves:

Getting ready for the ozone battle: Vertically transmitted fungal endophytes have transgenerational positive effects in plants

Autores:

Ueno, A.C, Gundel, P.E., Molina-Montenegro, M.A., Ramos, P., Ghersa, C.M., Martínez-Ghersa, M.A.

Resumen:

Ground-level ozone is a global air pollutant with high toxicity and represents a threat to plants and microorganisms. Although beneficial microorganisms can improve host performance, their role in connecting environmentally induced maternal plant phenotypes to progeny (transgenerational effects [TGE]) is unknown. We evaluated fungal endophyte-mediated consequences of maternal plant exposure to ozone on performance of the progeny under contrasting scenarios of the same factor (high and low) at two stages: seedling and young plant. With no variation in biomass, maternal ozone-induced oxidative damage in the progeny that was lower in endophyte-symbiotic plants. This correlated with an endophyte-mediated higher concentration of proline, a defence compound associated with stress control. Interestingly, ozone-induced TGE was not associated with reductions in plant survival. On the contrary, there was an overall positive effect on seedling survival in the presence of endophytes. The positive effect of maternal ozone increasing young plant survival was irrespective of symbiosis and only expressed under high ozone condition. Our study shows that hereditary microorganisms can modulate the capacity of plants to transgenerationally adjust progeny phenotype to atmospheric change.

Año: 2021

Palabras claves:

Tracing trophic pathways through the marine ecosystem of Rapa Nui (Easter Island)

Autores:

Zapata‐Hernández, G., Sellanes, J., Letourneur, Y., Harrod, C., Morales, N.A., Plaza, P., Meerhoff, E., Yannicelli, B., Carrasco, S.A., Hinojosa, I., Gaymer, C.F.

Resumen:

The structure of food webs provides important insight into biodiversity, organic matter (OM) pathways, and ecosystem functioning.

Stable isotope analysis (δ13C and δ15N) was used to characterize the trophic structure and the main OM pathways supporting food webs in the Rapa Nui coastal marine ecosystem.

The trophic position of consumers and isotopic niche metrics were estimated for different assemblages (i.e. mesozooplankton, emergent zooplankton, reef invertebrates, reef fishes, pelagic fishes, and seabirds). Furthermore, the relative importance of different OM sources (i.e. macroalgae, zooxanthellate corals, and particulate OM [POM]) was assessed for heterotrophic consumers using Bayesian mixing model (MixSIAR).

Results show a clear pattern of 13C and 15N enrichment from small‐sized pelagic and benthic invertebrates, to reef and pelagic fishes, and seabirds. Most invertebrates were classified as primary consumers, reef fishes as secondary consumers and pelagic predators and seabirds as tertiary and quaternary consumers.

Isotopic niche metrics indicate a low trophic diversity for pelagic assemblages (mesozooplankton and pelagic fishes), in contrast to reef fauna (invertebrates and fishes), whose higher trophic diversity suggest the exploitation of a wider range of trophic resources. Overlapping of standard ellipses areas between reef invertebrates and reef fishes indicates that both assemblages could be sharing trophic resources.

Mixing models results indicate that POM is the main trophic pathway for mesozooplankton, macroalgae (Rhodophyta) for emergent zooplankton, and a mix of coral‐derived OM and Rhodophyta for coral reef assemblages such as macrobenthos and reef invertebrates. In contrast, POM contribution was notably more important for some pelagic fishes and seabirds from upper trophic levels.

This study provides key elements for conservation efforts on coral reefs, management planning and full‐implementation of the recently created Rapa Nui Multiple Use Marine Protected Area.

Año: 2021

Palabras claves: Coral reefs, cryptic fauna, food web, mixing models, organic matter fluxes, stable isotopes, subtropical South Pacific, trophic position, trophic structure.