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.

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:

Mining and Industrial Uses

Autores:

Duhalde D., Castillo D., Oyarzún R., Oyarzún J., Arumí J.L.

Resumen:

This chapter addresses the relationship between water resources and important economic activities in Chile, particularly mining and the manufacturing industry. This assessment involves aspects related to the importance of these industries in the Chilean economy, their water demand throughout the country, associated environmental impacts and, finally, the challenges faced by these sectors in terms of the sustainable use of water resources. To understand the interactions between the aforementioned economic activities and water, one must first consider the climate heterogeneity of Chile. The north of the country has a desert climate while the south is becoming increasingly rainy. On the other hand, mining activity takes place mainly in the area of the country with the greatest water scarcity, while the manufacturing industry is highly diversified throughout Chile. The direct options available to these sectors for achieving sustainable water management are centered on the use of more and better technologies related to recirculation of process water and the use of seawater.

Año: 2021

Palabras claves: Mining, Industry, Water scarcity, Uses, Recirculation, Seawater

The Humboldt Current Large Marine Ecosystem (HCLME), a Challenging Scenario for Modelers and Their Contribution for the Manager

Autores:

Chevallier A., Stotz W., Ramos M., Mendo J.

Resumen:

The Humboldt Current Large Marine Ecosystem (HCLME) is a salient feature of the southeastern Pacific, along the South American coast of Chile and Peru. It is associated with coastal upwelling which generates a very productive ecosystem. However, due to a variety of interconnected biophysical processes at diverse temporal and spatial scales, production varies greatly in time and space. The interplay of the biophysical environment, biological processes involving valuable resources on international markets, the socio-political context, and some management decisions, has shaped the daily life of the HCLME fisheries, marked by booms and busts, offering wealth for short periods of time, followed by collapses. These collapses are generally interpreted as the consequence of a lack of appropriate management, so that a variety of increasingly stricter regulations have been implemented. Nevertheless, this has not significantly reduced the temporal variability of the fisheries landings, which is broadly characterized by a peaks and troughs pattern. While the HCLME is one of the most productive marine ecosystems on Earth, along with a great biophysical and biological variability, it is also a huge but fragile exploited social-ecological system. Modelers can help to understand how to continuously adapt in order to deal with recurrent fisheries “crises,” which, as we are beginning to learn, may simply be an expression of the variability inherent in this complex system. Furthermore, it is essential to increase our capacity to adapt to the expected consequences of climate change.

Año: 2021

Palabras claves:

Climate models capture key features of extreme precipitation probabilities across regions

Autores:

Cristian Martinez-Villalobos and J David Neelin

Resumen:

Quantitative simulation of precipitation in current climate has been an ongoing challenge for global climate models. Despite serious biases in correctly simulating probabilities of extreme rainfall events, model simulations under global warming scenarios are routinely used to provide estimates of future changes in these probabilities. To minimize the impact of model biases, past literature tends to evaluate fractional (instead of absolute) changes in probabilities of precipitation extremes under the assumption that fractional changes would be more reliable. However, formal tests for the validity of this assumption have been lacking. Here we evaluate two measures that address properties important to the correct simulation of future fractional probability changes of precipitation extremes, and that can be assessed with current climate data. The first measure tests climate model performance in simulating the characteristic shape of the probability of occurrence of daily precipitation extremes and the second measure tests whether the key parameter governing the scaling of this shape is well reproduced across regions and seasons in current climate. Contrary to concerns regarding the reliability of global models for extreme precipitation assessment, our results show most models lying within the current range of observational uncertainty in these measures. Thus, most models in the Coupled Model Intercomparison Project Phase 6 ensemble pass two key tests in current climate that support the usefulness of fractional measures to evaluate future changes in the probability of precipitation extremes.

Año: 2021

Palabras claves:

Mathematical modeling and quality parameters of Salicornia fruticosa dried by convective drying

Autores:

Rodríguez-Ramos, F., Leiva-Portilla, D., Rodríguez-Núñez, K., Pacheco, P., Briones-Labarca, V.

Resumen:

The effect of convective drying at 50, 60 and 70 °C on the drying kinetics and quality parameters of Salicornia fruticosa was investigated. To estimate the equilibrium moisture content a desorption isotherm was performed using five empirical models: Halsey, Caurie, Henderson, Smith and Oswin. The experimental data was also fitted to different drying kinetic models (Logarithmic, Two-Terms, Midilli–Kucuk and Exponential Two-Terms). A numerical simulation using the Finite Volume Method allowed us to describe the evolution of temperature and moisture content distributions during drying. The Henderson model was found to be the most suitable for predicting the equilibrium moisture content of S. fruticosa, with values of Xwe in the drying process of 1.51; 1.54 and 1.36 g water/g d.m for 50, 60 and 70 °C, respectively. A good agreement was found between the numerical and experimental results of temperature and moisture during Salicornia drying. The Midilli–Kucuk model presented the best fitting to the drying curves. The effects of drying on S. fruticosa were significant in two quality parameters. Antioxidant capacity decreased in ca. 45% and lightness (> L*) significantly increased at a drying temperature of 70 °C, compared to the fresh samples. The optimum drying temperature where drying time and nutrients loss was minimum was 70 °C. These results can be used to estimate the best drying conditions for producing dehydrated Salicornia. The use of halophytes as sustainable crops is promising, and the vision of their commercial production must be evaluated and considered, given water scarcity in many areas of the planet.

Año: 2021

Palabras claves: Salicornia fruticosa, Hot air drying, Drying kinetics, Mathematical modeling

Integration of Physiological and Molecular Traits Would Help to Improve the Insights of Drought Resistance in Highbush Blueberry Cultivars

Autores:

Balboa, K.; Ballesteros, G.I.; Molina-Montenegro, M.A.

Resumen:

Water deficit or drought is one of the most severe factors limiting plant yield or fruit quality. Thus, water availability for irrigation is decisive for crop success, such as the case of highbush blueberry (Vaccinium corymbosum L.). Therefore, drought stress may compromise blueberry production due to lower fruit weight or fruit yield. Despite this, it is unclear if there is any difference in the response of blueberry cultivars to water deficit, either in terms of physiological and molecular parameters, or in terms of their sensitivity or resistance to drought. In this study, we determined the effect of drought on different physiological parameters in blueberry plants (relative water content (RWC), photochemical efficiency of photosystem II (Fv/Fm), Carbon Isotopic Discrimination, and proline content) in six V. corymbosum cultivars. We also explored molecular responses in terms of gene expression coding for late embryogenesis abundant proteins. Finally, we estimated cultivar water deficit resistance using an integrative model based on physiological results. Upon water deficit conditions, we found reductions in Fv/Fm, RWC, and isotopic discrimination of 13C (Δ13C), while proline content increased significantly for all cultivars. Additionally, we also found differences in the estimated water deficit resistance index. These results indicate differences in water deficit resistance, possibly due to variations in cultivars’ genetic composition.

Año: 2020

Palabras claves: blueberry cultivar; drought stress; water deficit tolerance index; physiological parameters; late embryogenesis abundant proteins

Genome-wide genetic diversity yields insights into genomic responses of candidate climate-selected loci in an Andean wetland plant

Autores:

Bertin, A., Espinosa, M.I., Bustamante, C.A., Troncoso, A.J., & Gouin, N.

Resumen:


Assessing population evolutionary potential has become a central tenet of conservation biology. Since adaptive responses require allelic variation at functional genes, consensus has grown that genetic variation at genes under selection is a better surrogate for adaptive evolutionary potential than neutral genetic diversity. Although consistent with prevailing theory, this argument lacks empirical support and ignores recent theoretical advances questioning the very concept of neutral genetic diversity. In this study, we quantified genome-wide responses of single nucleotide polymorphism loci linked to climatic factors over a strong latitudinal gradient in natural populations of the high Andean wetland plant, Carex gayana, and then assessed whether genetic variation of candidate climate-selected loci better predicted their genome-wide responses than genetic variation of non-candidate loci. Contrary to this expectation, genomic responses of climate-linked loci only related significantly to environmental variables and genetic diversity of non-candidate loci. The effects of genome-wide genetic diversity detected in this study may be a result of either the combined influence of small effect variants or neutral and demographic factors altering the adaptive evolutionary potential of C. gayana populations. Regardless of the processes involved, our results redeem genome-wide genetic diversity as a potentially useful indicator of population adaptive evolutionary potential.

Año: 2020

Palabras claves:

A country’s response to tackling plastic pollution in aquatic ecosystems: The Chilean way

Autores:

Urbina, MA, Luna‐Jorquera, G, Thiel, M, Acuña‐Ruz, T., Amenábar, M.A., Andrade, C.C., Ahrendt, C., Castillo, C., Chevallier, A., Cornejo‐D'Ottone, M., Correa‐Araneda, F., Duarte, C., Fernández, C., Galbán‐Malagón, C., Godoy, C., González‐Aravena, M., Hinojosa, I.A., Jorquera, A., Kiessling, T., Lardies, M.A., Lenzi, J., Mattar, C., Munizaga, M., Olguín‐Campillay, N., Perez‐Venegas, D.J., Portflitt‐Toro, M., Pozo, K., Pulgar, J., Vargas, E.

Resumen:

Marine plastic pollution is worse than expected, and we are starting to realize its full extent and severity. Solving the plastic pollution problem is not easy, as it requires the action and commitment of all sectors of our society. With a coastline extending over 4,000 km (from 18°S to 56°S), Chile is a maritime country, and since plastics are potentially harmful for marine and coastal ecosystems, food security, and public health, plastic pollution is a real threat.
Chile is the sixth‐largest exporter of seafood (fish, invertebrates, and algae) in the world, but the extent of plastic contamination of marine organisms, its potential effects on commercial species and aquaculture, and its subsequent effects on human health are mostly unknown.
Chile has recently introduced some legislation to prevent plastics from reaching the environment and the coastal ocean. Governmental and non‐governmental organizations have joined an informal alliance to take action against plastic pollution, both at a national and regional level, but stronger involvement of producers and commerce is required for effective measures.
Chilean scientists working on plastic pollution have created the Scientific Plastic Pollution Alliance of Chile network, aiming to promote collaborative and coordinated research focused on this pollutant. The wide geographical extent of Chile, with researchers working in diverse ecosystems, provides a unique opportunity to better understand the consequences of one of the most recent and severe threats to biodiversity.
Rather than solely presenting the plastic pollution problem from the scientific perspective, this paper includes views from different sectors of society. Mitigating plastic pollution is exceptionally complex, with this study highlighting the importance of local engagement, media, solving social inequities, new legislation, and law enforcement in order to advance on decreasing plastic pollution from a country‐wide perspective.

Año: 2020

Palabras claves: Chilean society, legal commitments, media and social perception, ocean, plastic pollution

Genetic diversity, population structure, and historical demography of a highly vagile and human‐impacted seabird in the Pacific Ocean: The red‐tailed tropicbird, Phaethon rubricauda

Autores:

Varela, A.I., Brokordt, K., Ismar‐Rebitz, S.M.H., Gaskin, C.P., Carlile, N., O'Dwyer, T., Adams, J., VanderWerf, E.A., Luna‐Jorquera, G.

Resumen:

Many seabird breeding colonies have recovered from heavy anthropogenic disturbance after conservation actions. The widely distributed red‐tailed tropicbird, Phaethon rubricauda, was used as a model species to assess potential anthropogenic impacts on the genetic diversity of breeding colonies in the Pacific Ocean.

Cytochrome c oxidase subunit I and control region sequences analyses were conducted across the range of the species in the Pacific Ocean. The study sites were at islands without human‐related disturbance (non‐impacted islands) and with human‐related disturbance (impacted islands). We hypothesized that (i) breeding colonies of the red‐tailed tropicbird on impacted islands have lower genetic diversity compared with colonies on non‐impacted islands, and (ii) breeding colonies of the red‐tailed tropicbird show significant fine and broad‐scale genetic structure across the Pacific Ocean. Bayesian skyline analyses were conducted to infer past changes in population sizes.

Genetic diversity was similar between impacted and non‐impacted islands. There was significant broad‐scale genetic structure among colonies separated by over 6,000 km, but a lack of significant fine‐scale genetic structure within Australasia and Hawai'i, although a significant level of differentiation was found within Chile with ΦST analyses. Skyline analyses showed that effective population sizes remained relatively constant through time, but experienced either a slight decrease or the end of an expansion event through the last 1,000 years. These changes may be related to the arrival of humans on Pacific islands.

Impacted islands may have received immigrants from other relatively close islands, buffering the loss of genetic diversity. However, it is also possible that colonies have retained ancestral variation or that a large effective population size coupled with a long generation time (13 years) has prevented the loss of genetic diversity in human‐impacted islands. Future research using higher‐resolution markers is needed to resolve the population genetic structure of the red‐tailed tropicbird in an ecological time‐scale.

Año: 2020

Palabras claves: Anthropogenic disturbance, breeding seabirds, conservation actions, dispersal, mtDNA sequences, oceanic islands, population differentiation