Browsing by Author "Galban-Malagon, Cristobal"

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    Individual variation in heat tolerance and metabolism in marine Antarctic organisms
    (2024) Varas, Oscar; Molina, Andres N.; Garcia-Huidobro, M. Roberto; Aldana, Marcela; Rezende, Enrico L.; Carter, Mauricio J.; Galban-Malagon, Cristobal; Pulgar, Jose M.
    Climate change is one of the main concerns to Antarctic biodiversity. Since temperature plays a crucial role in various biological traits, it is key to understand how warming may affect organisms specialized to live in the cold habitats. Although heat tolerance of several polar species is known, little emphasis has been given to individual variation and its relationship with other biological traits such as metabolic performance. In this study, we investigated the association between thermal sensitivity in metabolism (Q10) and heat tolerance (z) in six Antarctic marine organisms, including two fish species (Harpagifer antarcticus and Notothenia coriiceps), three crustaceans (Bovallia gigantea, Glyptonotus antarcticus, and Paraceradocus miersi), and one mollusk (Trophon nucelliformis). For this, we measured routine metabolic rates (RMR, mg O2/h) followed by heat tolerance measurements to reconstruct dose-response curves employing sublethal assays or thermal-collapse time (TCT) curves. Analyses reveal a negative relationship between the intercept and the slope of the temperature tolerance curves (CTmax and z values, respectively) against Q10, but only when T. nucelliformis was included in the generalized linear model. Therefore Q10 may be a good predictor of heat tolerance, but it is not true for chordate or arthropod species studied. Additionally, CTmax and z values exhibited a positive relationship consistent with previous studies. This study represents the first example of temperature tolerance curves quantified on an individual basis, and the analyses provide some evidence that thermal sensitivity in metabolism and heat tolerance are correlated. In future studies, it will be crucial to determine whether this relationship is robust and how it may impact the response of different lineages to accelerated warming.
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    Towards understanding the effects of oceanic plastic pollution on population growth for a South American fur seal (Arctocephalus australis australis) colony in Chile
    (2021) Joaquin Perez-Venegas, Diego; Valenzuela-Sanchez, Andres; Montalva, Felipe; Paves, Hector; Seguel, Mauricio; Wilcox, Chris; Galban-Malagon, Cristobal
    Entanglement of pinnipeds with plastic debris is an emerging conservation and animal welfare issue worldwide. However, the origins and long-term population level consequences of these entanglements are usually unknown. Plastic entanglement could produce a combination of wounds, asphyxiation, or inability to feed that results in the death of a certain percentage of individuals from the total population. In this research, we report on the consequent effect of plastic entanglement on population growth de-mographics in a South American fur seal (Arctocephalus australis australis) colony on Guafo Island, southern Chile. Using a stochastic matrix population model structured according to age and sex, and assuming an otherwise stable population, we explored population growth rates under five scenarios with differing rates of entanglement: A) a zero rate of plastic entanglement, B) entanglement rates (number of entangled individuals as a proportion of the total number of individuals) as observed in our study population (overall entanglement ratio of 1.2 x 10(-3)); and for the other scenarios, entanglement ratios as reported in the literature for other pinniped colonies around the world: C) 3.04 x 10(-3), D) 4.42 x 10(-2), and E) 8.39 x 10(-2). Over the 30 years forecasting period and starting with a population size of similar to 2950 individuals, the population growth rate was lower under all scenarios with rates of entanglement greater than zero (scenarios B-E). In comparison with scenario A, at the end of the 30-year period forecasted, we calculated a projected decrease in population size of between 20.34% (scenario B) and 91.38% (scenario E). These results suggest that even the lowest levels of entanglement in pinnipeds as reported in the literature might have significant effects over time on population-level dynamics. Our research offers potential insight when devising policy for the management and limitation of plastic pollution in the oceans, and indeed for the conservation and management policy of affected marine species. Furthermore, whilst there are some limitations to our methodology, it offers a straightforward and potentially useful approach for the standardized prediction of impacts at a population level of different rates of plastic pollution and entanglement and could be applied in distinct populations of the same species around the world. (C) 2021 Elsevier Ltd. All rights reserved.
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    Upper thermal limits and risk of mortality of coastal Antarctic ectotherms
    (2023) Carter, Mauricio J.; Garcia-Huidobro, M. Roberto; Aldana, Marcela; Rezende, Enrico L.; Bozinovic, Francisco; Galban-Malagon, Cristobal; Pulgar, Jose M.
    Antarctic marine animals face one of the most extreme thermal environments, characterized by a stable and narrow range of low seawater temperatures. At the same time, the Antarctic marine ecosystems are threatened by accelerated global warming. Determining the upper thermal limits (CTmax) is crucial to project the persistence and distribution areas of the Antarctic marine species. Using thermal death time curves (TDT), we estimated CTmax at different temporal scales from 1 minute to daily and seasonal, the predict vulnerability to the current thermal variation and two potential heatwave scenarios. Our results revealed that CTmax at 1 min are far from the temperature present in the marine intertidal area where our study species, showing Echinoderm species higher CTmax than the Chordata and Arthropods species. Simulations indicated that seasonal thermal variation from the intertidal zone contributed to basal mortality, which increased after considering moderate scenarios of heatwaves (+2 degrees C) in the Shetland Archipelago intertidal zone. Our finding highlighted the relevance of including exposure time explicitly on the CTmax estimates, which deliver closer and more realistic parameters according to the species that may be experiencing in the field.