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Evolution in chronic cold: varied loss of cellular response to heat in antarctic notothenioid fish
(BMC Campus, 2018-09-19) Bilyk, Kevin T.; Vargas-Chacoff, Luis; Cheng, Chi - Hing Christina
Background: Confined within the freezing Southern Ocean, the Antarctic notothenioids have evolved to become both cold adapted and cold specialized. A marked signature of cold specialization is an apparent loss of the cellular heat shock response (HSR). As the HSR has been examined in very few notothenioid species to-date, it remains unknown whether HSR loss pervades the Antarctic radiation, or whether the broader cellular responses to heat stress has sustained similar loss. Understanding the evolutionary status of these responses in this stenothermal taxon is crucial for evaluating its adaptive potential to ocean warming under climate change.
Results: In this study, we used an acute heat stress protocol followed by RNA-Seq analyses to study the evolution of cellular-wide transcriptional responses to heat stress across three select notothenioid lineages - the basal temperate and nearest non-Antarctic sister species Eleginops maclovinus serving as ancestral proxy, the cryopelagic Pagothenia borchgrevinki and the icefish Chionodraco rastrospinosus representing cold-adapted red-blooded and hemoglobinless Antarctic notothenioids respectively. E maclovinus displayed robust cellular stress responses including the ER Unfolded Protein Response and the cytosolic HSR, cementing the HSR as a plesiomorphy that preceded Antarctic notothenioid radiation. While the transcriptional response to heat stress was minimal in P. borchgrevinki, C rastrospinosus exhibited robust responses in the broader cellular networks especially in inflammatory responses despite lacking the classic HSR and UPR.
Conclusion: The disparate patterns observed in these two archetypal Antarctic species indicate the evolutionary status in cellular ability to mitigate acute heat stress varies even among Antarctic lineages, which may affect their adaptive potential in coping with a warming world.
Occasional acoustic presence of antarctic blue whales on a feeding ground in southern Chile
(Wiley & Sons, 2018-01) Buchan, Susannah J.; Hucke-Gaete, Rodrigo; Stafford, Kathleen M.; Clark, Christopher W.
Low spring primary production and microplankton carbon biomass in sub- antarctic patagonian channels and fjords (50–53°S)
(Inst. Arctic Alpine Res., 2018-10-15) Iriarte, José Luis; Cuevas, Luis Antonio; Cornejo, Fernanda; Silva, Nelson; González, Humberto E.; Castro, Leonardo; Montero, Paulina; Vargas, Cristian A.; Daneri, Giovanni
It is relevant to understand the processes and factors that modulate the efficiency of the carbon pump throughout the ecosystem of Patagonian fjords. Spatial variability of primary productivity and bacteria-microplankton biomass was assessed in relation to inorganic nutrients and stratification across nearshore zones of southern Patagonia (50-53 degrees S) in austral spring 2009. Estimates of primary productivity (300-500 mg C m(-2) d(-1)) and phytoplankton biomass (9-180 mg chlorophylla m(-2)) were low at offshore and inshore waters. Synergistic effects of low silicic acid concentrations and poor light penetration because of salinity-driven stratification of glacier meltwater in springtime appeared to negatively affect phytoplankton carbon biomass and primary production in this sub-Antarctic region. The knowledge of the relative importance of nutrient sources and light is especially significant for Patagonian glacier-fjord systems that are expected to receive higher freshwater inputs and will be more stratified in the future.
Predicting the cover and richness of intertidal macroalgae in remote areas: a case study in the antarctic peninsula
(Wiley & Sons, 2018-09) Kotta, Jonne; Valdivia, Nelson; Kutser, Tiit; Toming, Kaire; Rätsep, Merli; Orav - Kotta, Helen
Antarctica is an iconic region for scientific explorations as it is remote and a critical component of the global climate system. Recent climate change causes a dramatic retreat of ice in Antarctica with associated impacts to its coastal ecosystem. These anthropogenic impacts have a potential to increase habitat availability for Antarctic intertidal assemblages. Assessing the extent and ecological consequences of these changes requires us to develop accurate biotic baselines and quantitative predictive tools. In this study, we demonstrated that satellite-based remote sensing, when used jointly with in situ ground-truthing and machine learning algorithms, provides a powerful tool to predict the cover and richness of intertidal macroalgae. The salient finding was that the Sentinel-based remote sensing described a significant proportion of variability in the cover and richness of Antarctic macroalgae. The highest performing models were for macroalgal richness and the cover of green algae as opposed to the model of brown and red algal cover. When expanding the geographical range of the ground-truthing, even involving only a few sample points, it becomes possible to potentially map other Antarctic intertidal macroalgal habitats and monitor their dynamics. This is a significant milestone as logistical constraints are an integral part of the Antarctic expeditions. The method has also a potential in other remote coastal areas where extensive in situ mapping is not feasible.
Facing the climate change conundrum at the south pole: actors’ perspectives on the implications of global warming for chilean antarctic governance
(Taylor & Francis, 2018-05-23) Gladkova, Ekaterina; Blanco - Wells, Gustavo; Nahuelhual, Laura
Antarctica is recognized as being geopolitically and scientifically important, and as one of the regions with the greatest potential to affect and be affected by global climate change. Still, little is known in practice about how climate change will be handled within the main governance framework of the continent: the Antarctic Treaty System (ATS). Using qualitative interviews, participant observations and policy document analysis, this paper explores the perspectives of Chilean scientific, political and non-governmental actors regarding the implications of climate change for the current Antarctic governance framework. Results corroborate a misalignment of the climate change agenda and the ATS, stemming from the divergent views displayed by a wide network of actors. From the interviews, two predominant visions emerge: (i) climate change as an opportunity, where actors recognize the role of Antarctica in regulating global climate and stress greater opportunities to conduct Antarctic-based climate change research, the need for strategic international collaboration, and the reinforcement of Chile's position in Antarctica through science; (ii) climate change as a burden where actors acknowledge climate change as a global problem, largely external to Antarctica, express disbelief regarding the effectiveness of local actions to tackle climate change and do not associate with climate change governance. The study concludes that climate change may become a dividing, rather than a unifying, field of action in Chilean Antarctic governance, reinforcing previously existing geopolitical tendencies.