Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼ 30° S) based on a high-resolution atmospheric regional model
Bravo, L., Ramos, M., Astudillo, O., Dewitte, B., & Goubanova, K.
Two physical mechanisms can contribute to coastal upwelling in eastern boundary current systems: offshore Ekman transport due to the predominant alongshore wind stress and Ekman pumping due to the cyclonic wind stress curl, mainly caused by the abrupt decrease in wind stress (drop-off) in a cross-shore band of 100 km. This wind drop-off is thought to be an ubiquitous feature in coastal upwelling systems and to regulate the relative contribution of both mechanisms. It has been poorly studied along the central-northern Chile region because of the lack in wind measurements along the shoreline and of the relatively low resolution of the available atmospheric reanalysis. Here, the seasonal variability in Ekman transport, Ekman pumping and their relative contribution to total upwelling along the central-northern Chile region (∼ 30° S) is evaluated from a high-resolution atmospheric model simulation. As a first step, the simulation is validated from satellite observations, which indicates a realistic representation of the spatial and temporal variability of the wind along the coast by the model. The model outputs are then used to document the fine-scale structures in the wind stress and wind curl in relation to the topographic features along the coast (headlands and embayments). Both wind stress and wind curl had a clear seasonal variability with annual and semiannual components. Alongshore wind stress maximum peak occurred in spring, second increase was in fall and minimum in winter. When a threshold of −3 × 10−5 s−1 for the across-shore gradient of alongshore wind was considered to define the region from which the winds decrease toward the coast, the wind drop-off length scale varied between 8 and 45 km. The relative contribution of the coastal divergence and Ekman pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate coastline. Roughly, coastal divergence predominated in areas with low orography and headlands. Ekman pumping was higher in regions with high orography and the presence of embayments along the coast. In the study region, the vertical transport induced by coastal divergence and Ekman pumping represented 60 and 40 % of the total upwelling transport, respectively. The potential role of Ekman pumping on the spatial structure of sea surface temperature is also discussed.
Referencia APA: Bravo, L., Ramos, M., Astudillo, O., Dewitte, B., & Goubanova, K. (2016). Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼ 30° S) based on a high-resolution atmospheric regional model (WRF). Ocean Science, 12(5), 1049-1065. http://dx.doi.org/10.5194/os-12-1049-2016
ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing
Yeh, S., Cai, W., Min, S., McPhaden, M., Dommenget, D., & Dewitte, B., Collins, M., Ashok, K., Soon‐Il, A., Bo‐Young, Y., Jong‐Seong, K.
El Niño and Southern Oscillation (ENSO) is the most prominent year‐to‐year climate fluctuation on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) sea surface temperature (SST) conditions in the tropical Pacific. ENSO exerts its impacts on remote regions of the globe through atmospheric teleconnections, affecting extreme weather events worldwide. However, these teleconnections are inherently nonlinear and sensitive to ENSO SST anomaly patterns and amplitudes. In addition, teleconnections are modulated by variability in the oceanic and atmopsheric mean state outside the tropics and by land and sea ice extent. The character of ENSO as well as the ocean mean state have changed since the 1990s, which might be due to either natural variability or anthropogenic forcing, or their combined influences. This has resulted in changes in ENSO atmospheric teleconnections in terms of precipitation and temperature in various parts of the globe. In addition, changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events. However, the short observational record does not allow us to clearly distinguish which changes are robust and which are not. Climate models suggest that ENSO teleconnections will change because the mean atmospheric circulation will change due to anthropogenic forcing in the 21st century, which is independent of whether ENSO properties change or not. However, future ENSO teleconnection changes do not currently show strong intermodel agreement from region to region, highlighting the importance of identifying factors that affect uncertainty in future model projections.
Palabras claves: ENSO, Ocean mean state, Atmospheric teleconnections, Extreme event, Anthropogenic forcing, Climate models
Referencia APA: Yeh, S., Cai, W., Min, S., McPhaden, M., Dommenget, D., Dewitte, B., Collins, M., Ashok, K., Soon‐Il, A., Bo‐Young, Y., Jong‐Seong, K. (2018). ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing. Reviews Of Geophysics. http://dx.doi.org/10.1002/2017rg000568
From whaling to whale watching: Identifying fin whale critical foraging habitats off the Chilean coast
Sepúlveda, M., Pérez-Álvarez, M., Santos-Carvallo, M., Pavez, G., Olavarría, C., Moraga, R., & Zerbini, A.
1. Fin whales (Balaenoptera physalus) have been documented along the coast of Chile since the early 20th century; however, information on their ecology and movement patterns remains poorly known.
2. In the spring of 2015, six implantable satellite tags were deployed on fin whales around the marine reserves of Isla Chañaral and Islas Choros‐Damas (approximately 29°S) to evaluate their movements and habitat use off the coast of Chile. A switching state–space model was used to estimate the predicted track of the whales as well as behavioural modes classified as ‘transiting’ and ‘area‐restricted search’ (ARS).
3. Whales were tracked for periods ranging between 4 and 162 days (mean = 68 ± 52 days), covering an average distance of 3225.7 ± 2871.6 km. Five of the six whales remained at middle latitudes for prolonged periods of time, moving in a north–south pattern near the coast, and spending most of their time in ARS behaviour (72.5% of the locations). Only one individual showed a clear southbound migratory behaviour, and remained in transit behaviour for most of the period it was followed.
4. These results suggest that some of the fin whales that are observed in Chile do follow a migration to high latitudes, whereas others remained at middle latitudes, probably using critical habitats as feeding grounds during the summer. This information not only contributes new information on the behaviour and foraging patterns of this species, but is also of particular interest to promote the growing whale‐watching activity, and also to better inform conservation and management efforts for this species in Chile.
Palabras claves: Coastal, Endangered species, Feeding, Mammals, Marine reserve, Ocean, Recreation, Satellite telemetry
Referencia APA: Sepúlveda, M., Pérez-Álvarez, M., Santos-Carvallo, M., Pavez, G., Olavarría, C., Moraga, R., & Zerbini, A. (2018). From whaling to whale watching: Identifying fin whale critical foraging habitats off the Chilean coast. Aquatic Conservation: Marine And Freshwater Ecosystems. doi: 10.1002/aqc.2899
Geophysical and geochemical constraints on the age and paleoclimate implications of Holocene lacustrine cores from the Andes of central Chile
Tiner, R., Negrini, R., Antinao, J., McDonald, E., & Maldonado, A.
A Holocene paleoclimate record was constructed using two lacustrine cores from the high‐elevation Chilean Andes at ∼30°S latitude. Coarser and more poorly sorted grain‐size distributions and higher C/N ratios were interpreted as evidence for increased storm activity. Wet conditions prevailed from ∼10.8 to 9.5k cal a BP, then transitioned to dry conditions from ∼9.5 to 5.7k cal a BP interrupted by stormy conditions from ∼8.3 to 7.6k cal a BP. Wet conditions returned from ∼5.7k cal a BP to the present, interrupted by aridity from ∼4.1 to 2.2k cal a BP. This paleoclimate record is consistent with others from the region. The wet periods were probably caused by the influence of the Southern Westerlies, while dry conditions resulted from the influence of the Southeast Pacific Anticyclone. The increased storminess from ∼8.3 to 7.7k cal a BP may have been sourced from latitudinal shifts in the Intertropical Convergence Zone and subsequent weakening of the Westerlies, allowing the incursion of convective storms from east of the Andes. This sequence of events is consistent with synoptic conditions during modern easterly sourced storm activity. It is also consistent with modeling studies of the effect on the Southern Hemisphere of the rapid cooling of the North Atlantic Ocean during the 8.2‐ka event.
Palabras claves: Elqui, Holocene, Lakes, Paleoclimate, Paleomagnetic secular variation
Referencia APA: Tiner, R., Negrini, R., Antinao, J., McDonald, E., & Maldonado, A. (2018). Geophysical and geochemical constraints on the age and paleoclimate implications of Holocene lacustrine cores from the Andes of central Chile. Journal Of Quaternary Science, 33(2), 150-165. doi: 10.1002/jqs.3012
New insights into the use of stable water isotopes at the northern Antarctic Peninsula as a tool for regional climate studies
Fernandoy, F., Tetzner, D., Meyer, H., Gacitúa, G., Hoffmann, K., Falk, U., Lambert, F., & MacDonell, S.
Due to recent atmospheric and oceanic warming, the Antarctic Peninsula is one of the most challenging regions of Antarctica to understand in terms of both local- and regional-scale climate signals. Steep topography and a lack of long-term and in situ meteorological observations complicate the extrapolation of existing climate models to the subregional scale. Therefore, new techniques must be developed to better understand processes operating in the region. Isotope signals are traditionally related mainly to atmospheric conditions, but a detailed analysis of individual components can give new insight into oceanic and atmospheric processes. This paper aims to use new isotopic records collected from snow and firn cores in conjunction with existing meteorological and oceanic datasets to determine changes at the climatic scale in the northern extent of the Antarctic Peninsula. In particular, a discernible effect of sea ice cover on local temperatures and the expression of climatic modes, especially the Southern Annular Mode (SAM), is demonstrated. In years with a large sea ice extension in winter (negative SAM anomaly), an inversion layer in the lower troposphere develops at the coastal zone. Therefore, an isotope–temperature relationship (δ–T ) valid for all periods cannot be obtained, and instead the δ–T depends on the seasonal variability of oceanic conditions. Comparatively, transitional seasons (autumn and spring) have a consistent isotope–temperature gradient of +0.69 ‰ ◦C−1. As shown by firn core analysis, the near-surface temperature in the northern-most portion of the Antarctic Peninsula shows a decreasing trend (−0.33 ◦C year−1) between 2008 and 2014. In addition, the deuterium excess (dexcess) is demonstrated to be a reliable indicator of seasonal oceanic conditions, and therefore suitable to improve a firn age model based on seasonal dexcess variability. The annual accumulation rate in this region is highly variable, ranging between 1060 and 2470 kgm−2 year−1 from 2008 to 2014. The combination of isotopic and meteorological data in areas where data exist is key to reconstruct climatic conditions with a high temporal resolution in polar regions where no direct observations exist.
Referencia APA: Fernandoy, F., Tetzner, D., Meyer, H., Gacitúa, G., Hoffmann, K., Falk, U., Lambert, F., & MacDonell, S. .(2018). New insights into the use of stable water isotopes at the northern Antarctic Peninsula as a tool for regional climate studies. The Cryosphere, 12(3), 1069-1090. doi: 10.5194/tc-12-1069-2018
Alpha-helical domain from IL-8 of salmonids: Mechanism of action and identification of a novel antimicrobial function
Santana, P., Salinas, N., Álvarez, C., Mercado, L., & Guzmán, F.
In this work, the potential antimicrobial role and mechanism of action of α-helix domain of trout and salmon IL-8 against Eschericia coli, Pseudomonas aeruginosa and Staphylococcus aureus was investigated. By an in silico analysis of the primary structure of IL-8 from Oncorhynchus mykiss and salmo salar, it was evidenced that γ-core motif was present, as in the vast majority of kinocidins. The α-helix domain of IL-8 (αIL-8) was synthesized by solid phase peptide synthesis and showed a tendency to form an α-helix conformation, as revealed by circular dichroism. Additionally, it was demonstrated that αIL-8 from both species showed antimicrobial activity against E. coli, P. aeruginosa and S. aureus. Membrane permeabilization and co-localization assay, as well as scanning electron microscopy, showed that these peptides were accumulated on the cell surface and in the cytoplasm, suggesting that they were capable of permeabilizing and disrupt the bacterial membranes and interact with cytoplasmic components. Our results represent the first analysis on the antimicrobial function of IL-8-derived peptide from salmonids.
Palabras claves: Interleukin-8, Synthetic peptide, Antimicrobial activity, Salmonids
Referencia APA: Santana, P., Salinas, N., Álvarez, C., Mercado, L., & Guzmán, F. (2018). Alpha-helical domain from IL-8 of salmonids: Mechanism of action and identification of a novel antimicrobial function. Biochemical And Biophysical Research Communications, 498(4), 803-809. doi: 10.1016/j.bbrc.2018.03.061
Understanding the antimicrobial properties/activity of an 11-residue Lys homopeptide by alanine and proline scan
Carvajal-Rondanelli, P., Aróstica, M., Álvarez, C., Ojeda, C., Albericio, F., Aguilar, L.F., Marshall, S.H., Guzmán, F.
Previous work demonstrated that lysine homopeptides adopt a polyproline II (PPII) structure. Lysine homopeptides with odd number of residues, especially with 11 residues (K11), were capable of inhibiting the growth of a broader spectrum of bacteria than those with an even number. Confocal studies also determined that K11 was able to localize exclusively in the bacterial membrane, leading to cell death. In this work, the mechanism of action of this peptide was further analyzed focused on examining the structural changes in bacterial membrane induced by K11, and in K11 itself when interacting with bacterial membrane lipids. Moreover, alanine and proline scans were performed for K11 to identify relevant positions in structure conformation and antibacterial activity. To do so, circular dichroism spectroscopy (CD) was conducted in saline phosphate buffer (PBS) and in lipidic vesicles, using large unilamellar vesicles (LUV), composed of 2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) or bacterial membrane lipid. Antimicrobial activity of K11 and their analogs was evaluated in Gram-positive and Gram-negative bacterial strains. The scanning electron microscopy (SEM) micrographs of Staphylococcus aureus ATCC 25923 exposed to the Lys homopeptide at MIC concentration showed blisters and bubbles formed on the bacterial surface, suggesting that K11 exerts its action by destabilizing the bacterial membrane. CD analysis revealed a remarkably enhanced PPII structure of K11 when replacing some of its central residues by proline in PBS. However, when such peptide analogs were confronted with either DMPG-LUV or membrane lipid extract-LUV, the tendency to form PPII structure was severely weakened. On the contrary, K11 peptide showed a remarkably enhanced PPII structure in the presence of DMPG-LUV. Antibacterial tests revealed that K11 was able to inhibit all tested bacteria with an MIC value of 5 µM, while proline and alanine analogs have a reduced activity on Listeria monocytogenes. Besides, the activity against Vibrio parahaemolyticus was affected in most of the alanine-substituted analogs. However, lysine substitutions by alanine or proline at position 7 did not alter the activity against all tested bacterial strains, suggesting that this position can be screened to find a substitute amino acid yielding a peptide with increased antibacterial activity. These results also indicate that the PPII secondary structure of K11 is stabilized by the interaction of the peptide with negatively charged phospholipids in the bacterial membrane, though not being the sole determinant for its antimicrobial activity.
Palabras claves: Lysine homopeptide-antimicrobial activity-Ala, Pro scanning-membrane rupture
Referencia APA: Carvajal-Rondanelli, P., Aróstica, M., Álvarez, C., Ojeda, C., Albericio, F., Aguilar, L.F., Marshall, S.H., Guzmán, F. (2018). Understanding the antimicrobial properties/activity of an 11-residue Lys homopeptide by alanine and proline scan. Amino Acids, 50(5), 557-568. doi: 10.1007/s00726-018-2542-6
δ 18 O of Fissurella maxima as a proxy for reconstructing Early Holocene sea surface temperatures in the coastal Atacama desert (25°S)
Flores, C., Gayo, E., Salazar, D., & Broitman, B.
Fissurella maxima is a keyhole limpet that is abundant and well preserved in archaeological shell midden sites along the coast of Chile, making it an appropriate species to use for reconstructions of past sea surface temperature (SST). In the present study we evaluate the potential of F. maxima shells as a proxy of SST by analysing δ18O of modern shells collected alive from the Atacama desert (area of Taltal, 25°S) and archaeological shells from two Early Holocene rockshelter sites: 224A and Paposo Norte 9. Reconstructed SST from modern F. maxima shells were related to SST obtained from in situ thermometers, supporting the use of this mollusc species as a paleotemperature archive. Mean SST reconstructed from Early Holocene archaeological shells (14.13 °C) was 2.86 °C cooler than mean temperature recorded in modern shells (16.99 °C). Mean SST reconstructed from modern shells was ~1.04 °C warmer than the mean temperature of in situ thermometers (15.95°C). Hence the paleo–SST data from archaeological sites 224A and Paposo Norte 9 enrich the Early Holocene nearshore paleoceanographic scenario of the Pacific coast of South America, with mean SST cooler than present-day SST. Our results validate the use of F. maxima shells as a SST proxy and contribute to a better understanding of the latitudinal distribution of the coastal upwelling regime during the Early Holocene, temporal changes in the structure of the Humboldt Current along the Holocene, and its influence on human adaptation through the prehistory of South America.
Palabras claves: Shell carbonate, Fissurella maxima, Oxygen stable isotope, South–east Pacific coast, Temperature reconstruction, Paleotemperature calibration
Referencia APA: Flores, C., Gayo, E., Salazar, D., & Broitman, B. (2018). δ 18 O of Fissurella maxima as a proxy for reconstructing Early Holocene sea surface temperatures in the coastal Atacama desert (25°S). Palaeogeography, Palaeoclimatology, Palaeoecology, 499, 22-34. doi: 10.1016/j.palaeo.2018.03.031
Respective roles of remote and local wind stress forcings in the development of warm SST errors in the South-Eastern Tropical Atlantic in a coupled high-resolution model
Goubanova, K., Sanchez-Gomez, E., Frauen, C., & Voldoire, A.
Processes involved in the development of the warm sea surface temperature (SST) bias in the Tropical South-Eastern Atlantic (SETA) in a high resolution (HR) version of the CNRM-CM model are evaluated based on full-field initialized seasonal hindcasts starting at 1 February of each year for 2000–2009. Whereas the initial SST growth is likely associated with local atmospheric forcing, its further development is due to remote oceanic processes. A mixed layer heat budget analysis in SETA indicates a spurious warm horizontal advection observed as far as south of 25°S that appears at the beginning of March. It is associated with an erroneous oceanic mean state at the equator resulting from the mean equatorial westerly wind bias. A sensitivity experiment with corrected wind stress over the equatorial region suggests that the remote forcing explains about 57% of the SETA SST bias in March–May. Comparison with a lower resolution (LR) version of the model reveals that in general similar processes are responsible for the SST bias in both models. A strong reduction of the bias in the HR model is observed only over the near-coastal Southern Benguela region due to a better representation of atmospheric and oceanic processes controlling the coastal upwelling. Overall, the results of the inter-comparison of the SETA SST bias evolution in different sensitivity experiments performed in this study can be interpreted in terms of the relative contributions of (erroneous) warm horizontal advection, associated with equatorial forcing, and cold horizontal advection, associated with local offshore Ekman transport.
Palabras claves: General circulation models, Model systematic biases, Atmosphere–Ocean coupling, Tropical Atlantic, Seasonal prediction, Benguela upwelling system
Referencia APA: Goubanova, K., Sanchez-Gomez, E., Frauen, C., & Voldoire, A. (2018). Respective roles of remote and local wind stress forcings in the development of warm SST errors in the South-Eastern Tropical Atlantic in a coupled high-resolution model. Climate Dynamics. doi: 10.1007/s00382-018-4197-0
First Deployment and Validation of in Situ Silicate Electrochemical Sensor in Seawater
Barus, C., Chen Legrand, D., Striebig, N., Jugeau, B., David, A., & Valladares, M., Munoz Parra, P., Ramos, M.E., Dewitte, B., & Garçon, V.
An electrochemical sensor is proposed to measure silicate concentration, in situ, in the ocean without any addition of liquid reagent. From the analytical principle to the laboratory prototype toward the first in situ, immersible sensor, the evolution of the mechanical design is presented and discussed. The developed in situ electronics were compared to the commercial potentiostat and gave promising results to detect low silicate signals with a limit of quantification of 1 μmol L−1.The flow rate of the pump appeared to be a crucial parameter in order to transfer the silicomolybdic complex formed from the “complexation cell” to the “detection cell” without dilution as well as to fill and rinse the whole circuit. The study of temperature effect revealed no influence on the electrochemical signal between ~7° and ~21°C. Finally the sensor was successfully deployed for the very first time on a mooring off Coquimbo, Chile and also integrated onto a PROVOR profiling float in the Mediterranean Sea off Villefranche-sur-Mer, France. The data collected and/or sent through satellite were in good agreement with the 2 reference samples and previously published values illustrating the great potential of this electrochemical sensor. A 7 days silicate time series from the mooring deployment off Chile is also presented.
Palabras claves: Autonomous sensor, Reagentless electrochemical detection, Silicate, Seawater, Mooring and float deployments
Referencia APA: Barus, C., Chen Legrand, D., Striebig, N., Jugeau, B., David, A., & Valladares, M., Munoz Parra, P., Ramos, M.E., Dewitte, B., & Garçon, V. (2018). First Deployment and Validation of in Situ Silicate Electrochemical Sensor in Seawater. Frontiers In Marine Science, 5. doi: 10.3389/fmars.2018.00060
Rare long-distance dispersal of a marine angiosperm across the Pacific Ocean
Smith, T., York, P., Broitman, B., Thiel, M., Hays, G., van Sebille, E., Putman N.F., Macreadie P.I., & Sherman C.D.H
Long‐distance dispersal (LDD) events occur rarely but play a fundamental role in shaping species biogeography. Lying at the heart of island biogeography theory, LDD relies on unusual events to facilitate colonization of new habitats and range expansion. Despite the importance of LDD, it is inherently difficult to quantify due to the rarity of such events. We estimate the probability of LDD of the seagrass Heterozostera nigricaulis, a common Australian species, across the Pacific Ocean to colonize South America.
Palabras claves: Biogeography, Clonal organisms, Long distance dispersal, Oceanography, Seagrass
Referencia APA: Smith, T., York, P., Broitman, B., Thiel, M., Hays, G., van Sebille, E., Putman N.F., Macreadie P.I., & Sherman C.D.H. (2018). Rare long-distance dispersal of a marine angiosperm across the Pacific Ocean. Global Ecology And Biogeography, 27(4), 487-496. doi: 10.1111/geb.12713
Species co-occurrence networks: Can they reveal trophic and non-trophic interactions in ecological communities?
Freilich, M., Wieters, E., Broitman, B., Marquet, P., & Navarrete, S.
Co‐occurrence methods are increasingly utilized in ecology to infer networks of species interactions where detailed knowledge based on empirical studies is difficult to obtain. Their use is particularly common, but not restricted to, microbial networks constructed from metagenomic analyses. In this study, we test the efficacy of this procedure by comparing an inferred network constructed using spatially intensive co‐occurrence data from the rocky intertidal zone in central Chile to a well‐resolved, empirically based, species interaction network from the same region. We evaluated the overlap in the information provided by each network and the extent to which there is a bias for co‐occurrence data to better detect known trophic or non‐trophic, positive or negative interactions. We found a poor correspondence between the co‐occurrence network and the known species interactions with overall sensitivity (probability of true link detection) equal to 0.469, and specificity (true non‐interaction) equal to 0.527. The ability to detect interactions varied with interaction type. Positive non‐trophic interactions such as commensalism and facilitation were detected at the highest rates. These results demonstrate that co‐occurrence networks do not represent classical ecological networks in which interactions are defined by direct observations or experimental manipulations. Co‐occurrence networks provide information about the joint spatial effects of environmental conditions, recruitment, and, to some extent, biotic interactions, and among the latter, they tend to better detect niche‐expanding positive non‐trophic interactions. Detection of links (sensitivity or specificity) was not higher for well‐known intertidal keystone species than for the rest of consumers in the community. Thus, as observed in previous empirical and theoretical studies, patterns of interactions in co‐occurrence networks must be interpreted with caution, especially when extending interaction‐based ecological theory to interpret network variability and stability. Co‐occurrence networks may be particularly valuable for analysis of community dynamics that blends interactions and environment, rather than pairwise interactions alone.
Palabras claves: Anthropogenic impacts, Co‐occurrence, Ecological networks, Food webs, Intertidal, Keystone species, Non‐trophic interactions, Species interactions
Referencia APA: Freilich, M., Wieters, E., Broitman, B., Marquet, P., & Navarrete, S. (2018). Species co-occurrence networks: Can they reveal trophic and non-trophic interactions in ecological communities?. Ecology, 99(3), 690-699. doi: 10.1002/ecy.2142