Línea de investigación:

Zona costera

Aunque representa solo el 10% de la superficie del océano, la zona costera alberga el 90% de todas las especies marinas y presenta dinámicas capaces de modular el clima regional y generar efectos globales. Las principales ciudades chilenas están ubicadas en esta área y se ven cada vez más expuestas a los impactos del cambio climático. Para el (CR)2, la investigación en la zona costera aborda la influencia de la variabilidad climática y el forzamiento antropogénico en el océano y el fondo marino costeros en zonas clave de surgencia en Chile, así como en los sistemas socioecológicos contenidos.

El fenómeno de surgencia costera (ascenso de aguas profundas ricas en nutrientes) favorece el desarrollo de la industria pesquera en nuestro país. Evaluar los riesgos e impactos asociados a esta actividad requerirá una mejor observación y modelado por parte de nuestros investigadores, así como el diseño y la implementación de acciones de adaptación y mitigación.

Las floraciones microalgales, la eutrofización, así como la mayor incidencia de tormentas y marejadas plantean nuevos desafíos para la gobernanza en las costas chilenas. La regulación en esta zona es diversa y compleja, lo que genera problemas institucionales que deben abordarse desde la línea de investigación.

Las proyecciones climáticas para Chile indican cambios que los regímenes de vientos regionales que favorecerán la surgencia costera. Además, se espera que la disponibilidad de agua dulce se vea afectada por los cambios en los sistemas de precipitación. Estas tendencias pueden afectar el flujo de calor, los aerosoles y la concentración de gases en la costa chilena, entre otros impactos. Por esta razón, los esfuerzos de la línea de investigación se centrarán en el forzamiento climático actual para comprender los procesos que pueden tener implicaciones climáticas, como las modificaciones en la advección o la circulación estuarina.

INVESTIGADORA PRINCIPAL

CO-INVESTIGADOR PRINCIPAL

INVESTIGADORES ASOCIADOS

INVESTIGADORES ADJUNTOS

INVESTIGADORES POSTDOCTORALES

ESTUDIANTES

Nombre Apellido
Francisca Clemo
Giovanni Testa
Mirko del Hoyo
Valeria Moreno
Catalina Barra
Maura Francisca Araneda Silva
Pablo Ignacio Garrido Darricarrere
Angeline González
Javier Alejandro Ignacio Tamayo Leiva
José Ignacio Arroyo González
Myriam Macarena Troncoso
Maximo Quezada
Diego Campos
Felipe Toledo
María del Pilar Aparicio Rizzo
Cristóbal Garrido
Diego Andrés Silva Díaz
Flor Uribe Ruiz
Felipe Andrés Vargas Goméz
María José Araya Lobos
Patricio Morales Pacheco
Sergio Guajardo Leiva
Susana Rodríguez Marconi
Sandy Elizabeth Tenorio Sanchéz

Noticias relacionadas a esta línea

Línea de InvestigaciónAñoAutoresTítuloRevistaFicha de PublicaciónDOIAbstractAccesoPáginasVolumenIndex
Zonas Costeras2017Hamisi, Mi., Lugomela, C., Lyimo, Tj., Bergman, B., Díez, B.Plankton composition, biomass, phylogeny and toxin genes in Lake Big Momela, TanzaniaAfrican Journal of Aquatic Science10.2989/16085914.2017.1334621
Lake Big Momela, one of the East African soda lakes in Northern Tanzania characterised by highly saline-alkaline conditions, making them inhospitable to a range of organisms, although supporting massive growths of some adapted planktonic microorganisms that serve as food for birds, such as Lesser Flamingo. The temporal dynamics of plankton, with an emphasis on cyanobacteria, were examined in 2007 using morphological traits and ribosomal genetic markers (16S and 18S rRNA). Cyanobacterial genes encoding for hepatotoxins (mcyE and ndaF) were also screened. Rotifers and copepods dominated the zooplankton, whereas cyanobacteria, such as Anabaenopsis elenkinii and Arthrospira fusiformis dominated the phytoplankton community, and these being related to representatives in other East African soda lakes. The cyanobacteria community also showed distinct seasonal patterns influenced by environmental parameters, mainly salinity, pH and nitrate. Significant positive correlations were found between phytoplankton abundance and nitrate concentrations (r = 0.617, p = 0.033). No signals of the hepatotoxin synthetase genes mcyE and ndaF were retrieved from cyanobacteria during the whole year. In general, our data illustrate the presence of rich planktonic communities, including some unique and potentially endemic cyanobacteria.https://www.tandfonline.com/doi/full/10.2989/16085914.2017.1334621109-121vol.42Thomson Reuters ISI
Zonas Costeras2017Toledo, F., Rodriguez, R., Rondanelli, R., Aguirre, R., Diaz, M.SDR Cloud Radar development with reused radio telescope componentsIEEE Geoscience and Remote Sensing10.1109/GRSS-CHILE.2017.7996016The ongoing implementation of a fog observatory in a coastal fog forest in northern Chile is expected to provide valuable information to improve our comprehension of these ecosystems alongside retrieving valuable data to fog scientists. Observing this opportunity and the increase on radio astronomy instrumental it is proposed to develop a low-cost Cloud Radar reutilizing obsolete but operative radio telescope components and software defined radios for modulation. Only preliminary tests have been conducted so far to test the viability of this approach. These tests show that it is in fact possible to build an emitter and receiver operating at 35 GHz using radio telescope components as a Radio Frequency front-end, and that the detected echo coming from the signal is affected by the presence of liquid water droplets in the air. Further development is being carried on the prototype to enable the detection of fog droplets in the boundary layer up to 2 km of height.http://ieeexplore.ieee.org/document/7996016/1-5vol.published onlineNot indexed
Zonas Costeras2017Galán, A., Thamdrup, B., Saldías, G. S., Farías, L.Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystemBiogeosciences10.5194/bg-14-4795-2017The upwelling system off central Chile (36.5 S) is seasonally subjected to oxygen (O2)-deficient waters, with a strong vertical gradient in O2 (from oxic to anoxic conditions) that spans a few metres (30-50€m interval) over the shelf. This condition inhibits and/or stimulates processes involved in nitrogen (N) removal (e.g. anammox, denitrification, and nitrification). During austral spring (September 2013) and summer (January 2014), the main pathways involved in N loss and its speciation, in the form of N2 and/or N2O, were studied using 15N-tracer incubations, inhibitor assays, and the natural abundance of nitrate isotopes along with hydrographic information. Incubations were developed using water retrieved from the oxycline (25€m depth) and bottom waters (85€m depth) over the continental shelf off Concepción, Chile. Results of 15N-labelled incubations revealed higher N removal activity during the austral summer, with denitrification as the dominant N2-producing pathway, which occurred together with anammox at all times. Interestingly, in both spring and summer maximum potential N removal rates were observed in the oxycline, where a greater availability of oxygen was observed (maximum O2 fluctuation between 270 and 40€μmol€L'1) relative to the hypoxic bottom waters ( < €20€μmol€O2€L'1). Different pathways were responsible for N2O produced in the oxycline and bottom waters, with ammonium oxidation and dissimilatory nitrite reduction, respectively, as the main source processes. Ammonium produced by dissimilatory nitrite reduction to ammonium (DNiRA) could sustain both anammox and nitrification rates, including the ammonium utilized for N2O production. The temporal and vertical variability of /15N-NO3' confirms that multiple N-cycling processes are modulating the isotopic nitrate composition over the shelf off central Chile during spring and summer. N removal processes in this coastal system appear to be related to the availability and distribution of oxygen and particles, which are a source of organic matter and the fuel for the production of other electron donors (i.e. ammonium) and acceptors (i.e. nitrate and nitrite) after its remineralization. These results highlight the links between several pathways involved in N loss. They also establish that different mechanisms supported by alternative N substrates are responsible for substantial accumulation of N2O, which are frequently observed as hotspots in the oxycline and bottom waters. Considering the extreme variation in oxygen observed in several coastal upwelling systems, these findings could help to understand the ecological and biogeochemical implications due to global warming where intensification and/or expansion of the oceanic OMZs is projected.https://www.biogeosciences.net/14/4795/2017/4795-4813vol.14Thomson Reuters ISI
Zonas Costeras2017Molina, A., Falvey, M., Rondanelli, R.A solar radiation database for ChileScientific Reports10.1038/s41598-017-13761-x
Chile hosts some of the sunniest places on earth, which has led to a growing solar energy industry in recent years. However, the lack of high resolution measurements of solar irradiance becomes a critical obstacle for both financing and design of solar installations. Besides the Atacama Desert, Chile displays a large array of "solar climates" due to large latitude and altitude variations, and so provides a useful testbed for the development of solar irradiance maps. Here a new public database for surface solar irradiance over Chile is presented. This database includes hourly irradiance from 2004 to 2016 at 90 m horizontal resolution over continental Chile. Our results are based on global reanalysis data to force a radiative transfer model for clear sky solar irradiance and an empirical model based on geostationary satellite data for cloudy conditions. The results have been validated using 140 surface solar irradiance stations throughout the country. Model mean percentage error in hourly time series of global horizontal irradiance is only 0.73%, considering both clear and cloudy days. The simplicity and accuracy of the model over a wide range of solar conditions provides confidence that the model can be easily generalized to other regions of the world.http://www.nature.com/articles/s41598-017-13761-xvol.7Thomson Reuters ISI
Zonas Costeras2018Toledo, F., Garrido, C., Díaz, M., Rondanelli, R., Jorquera, S., Valdivieso, P.AOT Retrieval Procedure for Distributed Measurements With Low-Cost Sun Photometers: AOT RETRIEVAL METHOD FOR SUN PHOTOMETERSJournal of Geophysical Research: Atmospheres10.1002/2017JD027309We propose a new application of inexpensive light-emitting diode (LED)-based Sun photometers, consisting of measuring the aerosol optical thickness (AOT) with high resolution within metropolitan scales. Previously, these instruments have been used at continental scales by the GLOBE program, but this extension is already covered by more expensive and higher-precision instruments of the AERONET global network. For this we built an open source two-channeled LED-based Sun photometer based on previous developments, with improvements in the hardware, software, and modifications on the calibration procedure. Among these we highlight the use of MODTRAN to characterize the effect introduced by using LED sensors in the AOT retrieval, an open design available for the scientific community and a calibration procedure that takes advantage of a CIMEL Sun photometer located within the city, enables the intercomparison of several LED Sun photometers with a common reference. We estimated the root-mean-square error in the AOT retrieved by the prototypes as 0.006 at the 564 nm and 0.009 at the 408 nm. This error is way under the magnitude of the AOT daily cycle variability measured by us in our campaigns, even for distances closer than 15 km. In addition to inner city campaigns, we also show aerosol-tracing applications by measuring AOT variations from the city of Santiago to the Andes glaciers. Measuring AOT at high spatial resolution in urban areas can improve our understanding of urban scale aerosol circulation, providing information for solar energy planning, health policies, and climatological studies, among others.http://doi.wiley.com/10.1002/2017JD0273091113-1131vol.123 is.2Thomson Reuters ISI
Zonas Costeras2017Shaffer, G., Fernández Villanueva, E., Rondanelli, R., Pedersen, J. O. P., Olsen, S. M., Huber, M.
Implementation of methane cycling for deep time, global warming simulations with the DCESS Earth System Model (Version 1.2)
Geoscientific Model Development
10.5194/gmd-10-4081-2017Geological records reveal a number of ancient, large and rapid negative excursions of the carbon-13 isotope. Such excursions can only be explained by massive injections of depleted carbon to the Earth system over a short duration. These injections may have forced strong global warming events, sometimes accompanied by mass extinctions such as the Triassic-Jurassic and end-Permian extinctions 201 and 252 million years ago, respectively. In many cases, evidence points to methane as the dominant form of injected carbon, whether as thermogenic methane formed by magma intrusions through overlying carbon-rich sediment or from warming-induced dissociation of methane hydrate, a solid compound of methane and water found in ocean sediments. As a consequence of the ubiquity and importance of methane in major Earth events, Earth system models for addressing such events should include a comprehensive treatment of methane cycling but such a treatment has often been lacking. Here we implement methane cycling in the Danish Center for Earth System Science (DCESS) model, a simplified but well-tested Earth system model of intermediate complexity. We use a generic methane input function that allows variation in input type, size, timescale and ocean–atmosphere partition. To be able to treat such massive inputs more correctly, we extend the model to deal with ocean suboxic/anoxic conditions and with radiative forcing and methane lifetimes appropriate for high atmospheric methane concentrations. With this new model version, we carried out an extensive set of simulations for methane inputs of various sizes, timescales and ocean–atmosphere partitions to probe model behavior. We find that larger methane inputs over shorter timescales with more methane dissolving in the ocean lead to ever-increasing ocean anoxia with consequences for ocean life and global carbon cycling. Greater methane input directly to the atmosphere leads to more warming and, for example, greater carbon dioxide release from land soils. Analysis of synthetic sediment cores from the simulations provides guidelines for the interpretation of real sediment cores spanning the warming events. With this improved DCESS model version and paleo-reconstructions, we are now better armed to gauge the amounts, types, timescales and locations of methane injections driving specific, observed deep-time, global warming events.https://www.geosci-model-dev.net/10/4081/2017/4081-4103vol.10 is.11Thomson Reuters ISI
Zonas Costeras2018Yevenes, MA., Figueroa, R., Parra., O
Seasonal drought effects on the water quality of the Biobío River, Central Chile
Environmental Science and Pollution Research
10.1007/s11356-018-1415-6
Quantifying the effect of droughts on ecosystem functions is essential to the development of coastal zone and river management under a changing climate. It is widely acknowledged that climate change is increasing the frequency and intensity of droughts, which can affect important ecosystem services, such as the regional supply of clean water. Very little is understood about how droughts affect the water quality of Chilean high flow rivers. This paper intends to investigate the effect of an, recently identified, unprecedented drought in Chile (2010–2015), on the Biobío River water quality, (36°45′–38°49′ S and 71°00′–73°20′ W), Central Chile. This river is one of the largest Chilean rivers and it provides abundant freshwater. Water quality (water temperature, pH, dissolved oxygen, electrical conductivity, biological oxygen demand, total suspended solids, chloride, sodium, nutrients, and trace metals), during the drought (2010–2015), was compared with a pre-drought period (2000–2009) over two reaches (upstream and downstream) of the river. Multivariate analysis and seasonal Mann-Kendall trend analyses and a Theil-Sen estimator were employed to analyze trends and slopes of the reaches. Results indicated a significant decreased trend in total suspended solids and a slightly increasing trend in water temperature and EC, major ions, and trace metals (chrome, lead, iron, and cobalt), mainly in summer and autumn during the drought. The reduced variability upstream suggested that nutrient and metal concentrations were more constant than downstream. The results evidenced, due to the close relationship between river discharge and water quality, a slightly decline of the water quality downstream of the Biobío River during drought period, which could be attenuated in a post-drought period. These results displayed that water quality is vulnerable to reductions in flow, through historical and emerging solutes/contaminants and induced pH mobilization. Consequently, seasonal changes and a progressive reduction of river flow affect the ecosystem functionality in this key Chilean river. The outcomes from this research can be used to improve how low flow conditions and the effects of a reduction in the river volume and discharge are assessed, which is the case under the scenario of more frequent drought periods.http://link.springer.com/10.1007/s11356-018-1415-6Thomson Reuters ISI
Zonas Costeras2018Troncoso, M., Garcia, G., Verdugo, J., Farías, L.Toward High-Resolution Vertical Measurements of Dissolved Greenhouse Gases (Nitrous Oxide and Methane) and Nutrients in the Eastern South PacificFrontiers in Marine Science10.3389/fmars.2018.00148In this study, in situ, real-time and high-resolution vertical measurements of dissolved greenhouse gases (GHGs) such as nitrous oxide (N2O) and methane (CH4) and nutrients are reported for the eastern South Pacific (ESP); a region with marked zonal gradients, ranging from highly productive and suboxic conditions in coastal upwelling systems to oligotrophic and oxygenated conditions in the subtropical gyre.
Four high-resolution vertical profiles for gases (N2O and CH4) and nutrients (NO3- and PO43-) were measured using a Pumped Profiling System (PPS), connected with a liquid degassing membrane coupled with Cavity Ring-Down Spectroscopy (CRDS) and a nutrient auto-analyzer, respectively. The membrane-CRDS system maintains a linear response over a wide range of gas concentrations, detecting N2O and CH4 levels as low as 0.0774±0.0004 and 0.1011±0.001 ppm, respectively.
Continuous profiles for gases and nutrients were similar to those reported throughout the ESP, with pronounced N2O and CH4 peaks at the upper oxycline and at the base of the euphotic zone and pycnocline, respectively, in the coastal zone; but almost constant depth profiles in the subtropical gyre. Additionally, other vertical gas and nutrient structures were observed using continuous sampling, which would not have been detected by discrete sampling. Our results demonstrate that continuous measurements can be a potentially useful methodology for future GHGs cycle studies.
https://www.frontiersin.org/article/10.3389/fmars.2018.00148148vol.5Scopus
Agua y Extremos; Zonas Costeras; Transversal
2018Bozkurt, D., Rondanelli, R., Marín, J. C., Garreaud, R.
Foehn Event Triggered by an Atmospheric River Underlies Record-Setting Temperature Along Continental AntarcticaJournal of Geophysical Research: Atmospheres10.1002/2017JD027796A record‐setting temperature of 17.5°C occurred on 24 March 2015 at the Esperanza station located near the northern tip of the Antarctic Peninsula (AP). We studied the event using surface station data, satellite imagery, reanalysis data, and numerical simulations. The Moderate Resolution Imaging Spectroradiometer Antarctic Ice Shelf Image Archive provides clear evidence for disintegration and advection of sea ice, as well as the formation of melt ponds on the ice sheet surface at the base of the AP mountain range. A deep low‐pressure center over the Amundsen‐Bellingshausen Sea and a blocking ridge over the southeast Pacific provided favorable conditions for the development of an atmospheric river with a northwest‐southeast orientation, directing warm and moist air toward the AP, and triggering a widespread foehn episode. A control simulation using a regional climate model shows the existence of local topographically induced warming along the northern tip of the AP (∼60% of the full temperature signal) and the central part of the eastern AP (>90% of the full temperature signal) with respect to a simulation without topography. These modeling results suggest that more than half of the warming experienced at Esperanza can be attributed to the foehn effect (a local process), rather than to the large‐scale advection of warm air from the midlatitudes. Nevertheless, the local foehn effect also has a large‐scale advection component, since the atmospheric river provides water vapor for orographic precipitation enhancement and latent heat release, which makes it difficult to completely disentangle the role of local versus large‐scale processes in explaining the extreme event.http://doi.wiley.com/10.1002/2017JD0277963871-3892vol.123 is.8Thomson Reuters ISI
Zonas Costeras2017Dätwyler Ch., Neukom R., Abram N., Gallant A., Grosjean M., Jacques-Coper M., Karoly D., Villalba R.
Teleconnection stationarity, variability and trends of the Southern Annular Mode (SAM) during the last millennium
Climate Dynamics10.1007/s00382-017-4015-0The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnections are
not consistent across the SH land areas. This suggests that the influence of the SAM index is modulated by regional effects.
However, within key-regions with good proxy data coverage (South America, Tasmania, New Zealand), teleconnections are mostly stationary over the instrumental period. Using different stationarity criteria for proxy record selection, we provide
new austral summer and annual mean SAM index reconstructions over the last millennium. Our summer SAM reconstructions are very robust to changes in proxy record selection and the selection of the calibration period, particularly on the multi-decadal timescale. In contrast, the weaker performance and lower agreement in the annual mean SAM reconstructions
point towards changing teleconnection patterns that may be particularly important outside the summer months. Our results clearly portend that the temporal stationarity of the proxy-climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions. The summer SAM reconstructions show no significant relationship to solar, greenhouse gas and volcanic forcing, with the exception of an extremely strong negative anomaly following the AD 1257 Samalas eruption. Furthermore, reconstructed pre-industrial summer SAM trends are very similar to
trends obtained by model control simulations. We find that recent trends in the summer SAM lie outside the 5–95% range of pre-industrial natural variability.
http://link.springer.com/10.1007/s00382-017-4015-01-19Thomson Reuters ISI
Zonas Costeras2018Testa, G., Masotti, I., Farías, L.Temporal Variability in Net Primary Production in an Upwelling Area off Central Chile (36°S)Frontiers in Marine Science10.3389/fmars.2018.00179The temporal variability of Net Primary Production (NPP) off central Chile (36°S, 73°W), an area subjected to seasonal coastal upwelling, was analyzed using monthly in situ 13C incubations within the photic zone, along with bio-oceanographic variables from a fixed time series station; and satellite NPP estimations (NPPE) from the Vertically Generalized Production Model between 2006 and 2015. NPP and NPPE rates varied from 0.03 to 18.29 and from 0.45 to 9.07 g C m−2 d−1, respectively. Both rates were fairly well correlated with each other (r2 = 0.61), but when these data were separated into two periods, higher r2 value was found during winter (r2 = 0.70) with respect to the rest of the year (r2 = 0.24); the latter correlation was partially due to increased weekly NPPE variability during active and relaxed upwelling events. NPP rates along with other biophysical variables allowed for a division of the annual cycle into three distinct periods: September to January (high productivity, mean integrated NPP rates of 4.0 g C m−2 d−1), February to March (intermediate productivity, mean integrated NPP rates of 1.4 g C m−2 d−1), and May to August (basal level, mean integrated NPP rates of 0.5 g C m−2 d−1). NPP appeared to be partially controlled by nutrient inputs, either from upwelling (September-April) and river discharge (May-August), maintaining high NPP rates throughout the entire year, with an annual mean NPP rate of 1.1 kg C m−2 yr−1. In this region, El Niño Southern Oscillation events did not appear to impact the NPP interannual variability.https://www.frontiersin.org/article/10.3389/fmars.2018.00179/fullvol.5Scopus
Zonas Costeras2018Alcamán-Arias, M., Farías, L., Verdugo, J., Alarcón-Schumacher, T., Díez, B.
Microbial activity during a coastal phytoplankton bloom on the Western Antarctic Peninsula in late summerFEMS Microbiology Letters10.1093/femsle/fny090Phytoplankton biomass during the austral summer is influenced by freezing and melting cycles as well as oceanographic processes that enable nutrient redistribution in the West Antarctic Peninsula (WAP). Microbial functional capabilities, metagenomic and metatranscriptomic activities as well as inorganic 13C- and 15N-assimilation rates were studied in the surface waters of Chile Bay during two contrasting summer periods in 2014. Concentrations of Chlorophyll a (Chla) varied from 0.3 mg m−3 in February to a maximum of 2.5 mg m−3 in March, together with a decrease in nutrients; however, nutrients were never depleted. The microbial community composition remained similar throughout both sampling periods; however, microbial abundance and activity changed with Chla levels. An increased biomass of Bacillariophyta, Haptophyceae and Cryptophyceae was observed along with night-grazing activity of Dinophyceae and ciliates (Alveolates). During high Chla conditions, HCO3− uptake rates during daytime incubations increased 5-fold (>2516 nmol C L−1 d−1), and increased photosynthetic transcript numbers that were mainly associated with cryptophytes; meanwhile night time NO3− (>706 nmol N L−1 d−1) and NH4+ (41.7 nmol N L−1 d−1) uptake rates were 2- and 3-fold higher, respectively, due to activity from Alpha-/Gammaproteobacteria and Bacteroidetes (Flavobacteriia). Due to a projected acceleration in climate change in the WAP, this information is valuable for predicting the composition and functional changes in Antarctic microbial communities.https://academic.oup.com/femsle/article/doi/10.1093/femsle/fny090/49611371574-6968vol.365 is.10Thomson Reuters ISI
Zonas Costeras2018Farías, L., Faúndez, J., Sanhueza-Guevara, S.Temporal dynamics of dissolved inorganic nitrogen (DIN) in the aphotic layer of a coastal upwelling system with variable dissolved oxygenJournal of Marine Systems10.1016/j.jmarsys.2018.06.001Dissolved O2 (DO) concentration is critical to determining ecosystem functions such as organic matter respiration, which can favor fixed nitrogen loss and the accumulation of compounds such as NH4+. This dynamic is observed in central Chile's coastal upwelling system (36 °S), which presents seasonally O2 deficient waters and high biological productivity. Temporal dynamics for dissolved inorganic nitrogen (DIN: NO3−, NO2− and NH4+) are analyzed based on a ten year time series of monthly measurements of DO and DIN and a three year record of absolute DIN uptake rates (ρDIN), respective turnover rates (νDIN), and O2 utilization rates (OUR). Observed O2 deficit gradually increases from hypoxia to near anoxia as the system becomes more productive, favoring the accumulation of NO2− and NH4+. Three temporal phases within the aphotic layer were distinguished: (I) DO > 62 μmol L−1 (May to August), (II) 5 < DO < 62 μmol L−1 (September to December) and (III) DO < 5 μmol L−1 (January to April). From phase I to III, DO and NO3− inventories decreased by eight and two times, respectively, while NH4+ and NO2 inventories increased two- and five-fold, respectively. Uptake rates for NH4+ varied from 0.23 to 450 nmol N L−1 d−1 and from 1.42 to 184 nmol N L−1 d−1 for NO3−. Notably, integrated ρNH4+ increased during phase III, generating a NH4+ turnover time of 12–29 days; whereas integrated ρNO3− peaked during phase II, and removed the NO3− pool over an extended turnover time (>820 days). Integrated OUR gradually increased from phase I to III (from 225 to 422 mmol m−2 d−1), with DO pools replenished over 2.3 to 26 days. NH4+ regeneration rates ranged from 34 to 62 mmol m−2 d−1 and NH4+ pools were replenished within a few days. Variation in DO, which regulates N cycling, may explain the accumulation of N-species within the aphotic layer. Observed trends could be extrapolated to scenarios of upwelling-favorable winds, eutrophication and hypoxia.https://linkinghub.elsevier.com/retrieve/pii/S0924796317302075Thomson Reuters ISI
Zonas Costeras2018Alcorta, J., Espinoza, S., Viver, T., Alcamán-Arias, M., Trefault, N., Rosselló-Móra, R., Díez, B.
Temperature modulates Fischerella thermalis ecotypes in Porcelana Hot Spring
Systematic and Applied Microbiology
10.1016/j.syapm.2018.05.006
In the Porcelana Hot Spring (Northern Patagonia), true-branching cyanobacteria are the dominant primary producers in microbial mats, and they are mainly responsible for carbon and nitrogen fixation. However, little is known about their metabolic and genomic adaptations at high temperatures. Therefore, in this study, a total of 81 Fischerella thermalis strains (also known as Mastigocladus laminosus) were isolated from mat samples in a thermal gradient between 61–46 °C. The complementary use of proteomic comparisons from these strains, and comparative genomics of F. thermalis pangenomes, suggested that at least two different ecotypes were present within these populations. MALDI-TOF MS analysis separated the strains into three clusters; two with strains obtained from mats within the upper temperature range (61 and 54 °C), and a third obtained from mats within the lower temperature range (51 and 46 °C). Both groups possessed different but synonymous nifH alleles. The main proteomic differences were associated with the abundance of photosynthesis-related proteins. Three F. thermalis metagenome assembled genomes (MAGs) were described from 66, 58 and 48 °C metagenomes. These pangenomes indicated a divergence of orthologous genes and a high abundance of exclusive genes at 66 °C. These results improved the current understanding of thermal adaptation of F. thermalis and the evolution of these thermophilic cyanobacterial species.https://linkinghub.elsevier.com/retrieve/pii/S0723202018302297Thomson Reuters ISI