Flujo de partículas en un ambiente costero Antártico de aguas someras: un estudio con trampas de sedimento

Sediment trap arrays were deployed at Potter Cove, King George Island, Antarctica, between December 1991 and August 1992 and in the summer seasons of 1993-1994, and 1995. The sampling sites reached 30 m depth, and traps were placed during the different seasons at various distances from the sea bottom (0.1 to 25 m), some being buried in the sediments. Daily sedimentation rates of total particulate matter (TPM) and chlorophyll-a were estimated. Water column temperature and salinity as well as pigment and TPM concentration were also measured and related to traps´ results. Water column data evidenced processes in relation with phytoplankton dynamics, stormy events and particles containing fresh water runoff. Similar trends were observed in the traps located at 25 m, 1 m and sometimes even in those located to around 0.1 m from sea bottom, although traps buried in the sediments mainly reflected resuspension events. Chlorophyll a fluxes were higher in the bottom traps, but the sedimented organic fraction of the TPM (particulate organic matter, POM) was higher in the traps located remotely from the bottom, being significantly lower in the buried traps (i.e. POM represented 50% of TPM at 1 m and 9% POM in the buried trap on November 23 in 1993, although a great variability among sampling dates was also observed). The significance of these dynamics for the food availability for the macrozoobenthic organisms present in the area is discussed.Entre diciembre de 1991 y agosto de 1992 y durante las campañas de verano de 1993-1994 y 1995 se estudió la tasa de sedimentación de partículas en Caleta Potter, Isla King George - 25 de Mayo, Antártida, mediante el empleo de trampas de sedimento. La profundidad en los sitios de muestreo fue de 30 m. Las trampas fueron colocadas a distintas distancias del fondo (0,1 a 25 m), habiéndose enterrado algunas en los sedimentos. Se estimaron las tasas diarias de sedimentación para el total de material particulado y los pigmentos. Se midieron además la temperatura y la salinidad, así como la concentración de material particulado total y pigmentos en la columna de agua. Estos parámetros fueron relacionados con aquellos de las trampas de sedimento. Los resultados de la columna de agua reflejaron procesos relacionados con la dinámica del fitoplancton, eventos de tormentas y aportes terrígenos de agua dulce. Esto fue válido para las trampas colocadas a 25 m, 1 m y en ocasiones aún para aquellas colocadas a 0,1 m, si bien los datos obtenidos de las trampas enterradas en el sedimento se relacionan con episodios de resuspensión. Los flujos de clorofila a fueron mayores en las trampas más cercanas al fondo, pero la fracción orgánica del material particulado sedimentada fue significativamente menor en las trampas enterradas. Por ejemplo, el porcentaje de materia orgánica en las trampas del 23 de noviembre de 1993 fue de 50% a 1 m y del 9% en la trampa enterrada en los sedimentos, si bien pudo observarse una gran variabilidad entre fechas de muestreo. Se discute la importancia de esta dinámica para la nutrición de los organismos del macrozoobentos presentes en el área

Introduction to the Special Issue on the Gulf of San Jorge (Patagonia, Argentina)

San Jorge Gulf (SJG) is home to a complex ecosystem that provides a variety ofhigh-quality services to the regional andnational economy of Argentina, particularly oil and gas, fisheries, and tourism.The gulf is located in the central region ofPatagonia between 45°S and 47°S, coversan area of 39,340 km2, and is open to theAtlantic Ocean. Until recently, althoughsome interdisciplinary scientific information had been gathered for the SJG,very little had been published in widelyaccessible journals. This special issue ofOceanography aims to document fundamental research into SJG biological,physical, chemical, and sedimentary processes undertaken in the last few years.More than 40 researchers, students, andtechnicians from Québec (Canada) andArgentina participated in the initialefforts of PROMESse (Multidisciplinaryprogram for the study of the ecosystemand geology of the San Jorge Gulf and thecoastal region of the province of Chubut),which closely matches the Argentineangovernment?s Pampa Azul Initiative.The general objective of the PROMESseresearch program is to conduct an integrated study of the SJG, with the resultsserving as a baseline for the sustainablemanagement of the ecosystem services ofthis rich marine ecosystem. This bilateraleffort included two workshops, held in2017, one in Rimouski (Québec, Canada)and another in Comodoro Rivadavia(Chubut, Argentina), that led to the15 articles published in this special issue.Fil: St-Onge, Guillaume. Institut des Sciences de la Mer de Rimouski; CanadáFil: Ferreyra, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Influence of microbial community composition and metabolism on air.sea ΔpCO 2 variation off the western Antarctic Peninsula

We studied CO 2 and O 2 dynamics in the western Antarctic Peninsula (WAP) waters in relation to (1) phytoplankton biomass, (2) microbial community primary production and respiration, and (3), for the first time, phytoplankton composition, during summer and fall in 3 consecutive years (2002, 2003 and 2004). The areal average of ΔpCO 2 (the difference between surface seawater and atmospheric partial pressure of CO 2) for the 3 yr was significantly negative (.20.04 ± 44.3 μatm, p < 0.01) during the summer to fall period in the region, possibly indicating a CO 2 sink. In the southern WAP (i.e. south of Anvers Island), ΔpCO 2 was significantly negative (.43.60 ± 39.06 μatm) during fall. In the northern WAP (north of Anvers Island), ΔpCO 2 values showed a more complex distribution during summer and fall (.4.96 ± 37.6 and 21.71 ± 22.39 μatm, respectively). Chlorophyll a (chl a) concentration averaged 1.03 ± 0.25 μg l.1 and was higher in the south of the peninsula. Phytoplankton composition influenced chl a concentration with higher and lower values for diatom-and phytoflagellate-dominated communities, respectively. A significant negative correlation existed between chl a and ΔpCO 2. From incubation experiments performed in the northern WAP, respiration was low (averaging 5.1 mmol O 2 m.3 d.1), and the net community production (NCP) correlated negatively with ΔpCO 2 and positively with %O 2 saturation. However, despite the high NCP values measured, ΔpCO 2 was significantly positive in the northern WAP during the summer to fall period. Strong mixing and lower chl a concentration may explain this result. In contrast, ΔpCO 2 was significantly negative in the southern WAP, possibly because of high surface water chl a concentration.Facultad de Ciencias Naturales y Muse

Role of plankton communities in sea-air variations in pCO2 in the SW Atlantic Ocean

The influence of the plankton community structure on carbon dynamics was studied in the surface waters of the Argentinean continental shelf (SW Atlantic Ocean) in summer and fall 2002, 2003 and 2004, The horizontal changes in plankton community respiration (R), net community production (NCP) and gross primary production (GPP) were (1) compared with the difference in the partial pressure of CO2 (pCO2) between the sea surface and the atmosphere (ΔpCO2), (2) compared with oxygen saturation and (3) related to the microscopic phytoplankton assemblages, This area, which has recently been shown to be a CO2 sink, had an average surface oxygen saturation of 108.1%, indicating that net photosynthesis could have played a dominant role in the CO2 dynamics. At most stations, the production:respiration (GPP:R) ratio was greater than 1, indicating that planktonic communities were autotrophic; the average GPP:R ratio for the whole study was 2.99, Phytoplankton biomass (chlorophyll a) and NCP showed an inverse relationship with ΔpCO2 and a direct relationship with %O 2 saturation when phytoplankton assemblages were dominated by diatoms (30% of the stations), This was not the case when small (≤5 μm) flagellates were the most abundant organisms, Although NCP was mostly positive for both groups of stations (i.e. diatom-dominated or small flagellate- dominated), other physical and biological processes are thought to modify the CO2 dynamics when small flagellates are the prevailing phytoplankton group.Facultad de Ciencias Naturales y Muse

Influence of microbial community composition and metabolism on air.sea ΔpCO 2 variation off the western Antarctic Peninsula

We studied CO 2 and O 2 dynamics in the western Antarctic Peninsula (WAP) waters in relation to (1) phytoplankton biomass, (2) microbial community primary production and respiration, and (3), for the first time, phytoplankton composition, during summer and fall in 3 consecutive years (2002, 2003 and 2004). The areal average of ΔpCO 2 (the difference between surface seawater and atmospheric partial pressure of CO 2) for the 3 yr was significantly negative (.20.04 ± 44.3 μatm, p < 0.01) during the summer to fall period in the region, possibly indicating a CO 2 sink. In the southern WAP (i.e. south of Anvers Island), ΔpCO 2 was significantly negative (.43.60 ± 39.06 μatm) during fall. In the northern WAP (north of Anvers Island), ΔpCO 2 values showed a more complex distribution during summer and fall (.4.96 ± 37.6 and 21.71 ± 22.39 μatm, respectively). Chlorophyll a (chl a) concentration averaged 1.03 ± 0.25 μg l.1 and was higher in the south of the peninsula. Phytoplankton composition influenced chl a concentration with higher and lower values for diatom-and phytoflagellate-dominated communities, respectively. A significant negative correlation existed between chl a and ΔpCO 2. From incubation experiments performed in the northern WAP, respiration was low (averaging 5.1 mmol O 2 m.3 d.1), and the net community production (NCP) correlated negatively with ΔpCO 2 and positively with %O 2 saturation. However, despite the high NCP values measured, ΔpCO 2 was significantly positive in the northern WAP during the summer to fall period. Strong mixing and lower chl a concentration may explain this result. In contrast, ΔpCO 2 was significantly negative in the southern WAP, possibly because of high surface water chl a concentration.Facultad de Ciencias Naturales y Muse

Distribution and ecology of <i>Pseudo-nitzschia</i> species (Bacillariophyceae) in surface waters of the Weddell Sea (Antarctica)

The distribution of six Pseudo-nitzschia species and their relationship with environmental conditions were studied for the first time in a vast zone of the Weddell Sea (∼61–77°S, Antarctica). Both qualitative and quantitative phytoplankton samples, collected during summer 2004, were examined using light and scanning electron microscopy. Phytoplankton abundance and composition showed great variability along our study area. Diatoms were the most conspicuous phytoplankton group in the northern area while small flagellates were generally dominant in the southern stations. The genus Pseudo-nitzschia was broadly distributed and significantly contributed to total diatom densities. A marked contrast in Pseudo-nitzschia species distribution was observed in three main zones divided by the Weddell Front (WF) and the Antarctic Slope Front (ASF). P. subcurvata and P. turgiduloides were the most abundant species in the neritic Weddell Sea zone, south of the ASF, mainly near the ice-edge in shallower waters and in conditions of long photoperiod. In contrast, P. prolongatoides and P. lineola dominated north of the ASF; the first was associated with deeper and nutrient-rich waters whereas the latter showed a weak relation with environmental variables examined. Finally, P. turgidula and P. heimii were mostly observed in the Weddell–Scotia Confluence Zone in the warmest and far from ice covered waters, north of the WF. A brief morphological Pseudo-nitzschia species description is given in the Appendix, including morphometrics and pictures.Facultad de Ciencias Naturales y Muse

Role of plankton communities in sea-air variations in pCO2 in the SW Atlantic Ocean

The influence of the plankton community structure on carbon dynamics was studied in the surface waters of the Argentinean continental shelf (SW Atlantic Ocean) in summer and fall 2002, 2003 and 2004, The horizontal changes in plankton community respiration (R), net community production (NCP) and gross primary production (GPP) were (1) compared with the difference in the partial pressure of CO2 (pCO2) between the sea surface and the atmosphere (ΔpCO2), (2) compared with oxygen saturation and (3) related to the microscopic phytoplankton assemblages, This area, which has recently been shown to be a CO2 sink, had an average surface oxygen saturation of 108.1%, indicating that net photosynthesis could have played a dominant role in the CO2 dynamics. At most stations, the production:respiration (GPP:R) ratio was greater than 1, indicating that planktonic communities were autotrophic; the average GPP:R ratio for the whole study was 2.99, Phytoplankton biomass (chlorophyll a) and NCP showed an inverse relationship with ΔpCO2 and a direct relationship with %O 2 saturation when phytoplankton assemblages were dominated by diatoms (30% of the stations), This was not the case when small (≤5 μm) flagellates were the most abundant organisms, Although NCP was mostly positive for both groups of stations (i.e. diatom-dominated or small flagellate- dominated), other physical and biological processes are thought to modify the CO2 dynamics when small flagellates are the prevailing phytoplankton group.Facultad de Ciencias Naturales y Muse

(Bio)analytical platforms based on the use of functionalized carbon nanotubes

Trabajo presentado al Eurosensors, celebrado en Freiburg (Alemania) del 6 al 9 de septiembre de 2015.Peer reviewe

Skipper-CCD Sensors for the Oscura Experiment: Requirements and Preliminary Tests

Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark matter (DM) direct detection search that will reach unprecedented sensitivity to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is planning to operate at SNOLAB with 2070 m overburden, and aims to reach a background goal of less than one event in each electron bin in the 2-10 electron ionization-signal region for the full 30 kg-year exposure, with a radiation background rate of 0.01 dru. In order to achieve this goal, Oscura must address each potential source of background events, including instrumental backgrounds. In this work, we discuss the main instrumental background sources and the strategy to control them, establishing a set of constraints on the sensors' performance parameters. We present results from the tests of the first fabricated Oscura prototype sensors, evaluate their performance in the context of the established constraints and estimate the Oscura instrumental background based on these results

Early Science with the Oscura Integration Test

Oscura is a planned light-dark matter search experiment using Skipper-CCDs with a total active mass of 10 kg. As part of the detector development, the collaboration plans to build the Oscura Integration Test (OIT), an engineering test experiment with 10% of the Oscura's total mass. Here we discuss the early science opportunities with the OIT to search for millicharged particles (mCPs) using the NuMI beam at Fermilab. mCPs would be produced at low energies through photon-mediated processes from decays of scalar, pseudoscalar, and vector mesons, or direct Drell-Yan productions. Estimates show that the OIT would be a world-leading probe for low-mass mCPs.Comment: 21 pages, 13 figure