26 research outputs found
Seguridad y defensa en SuramĂ©rica: regionalismo, cooperaciĂłn y autonomĂa en el marco de UNASUR
Depto. de Relaciones Internacionales e Historia GlobalFac. de Ciencias PolĂticas y SociologĂaTRUEpu
The natural ocean acidification and fertilization event caused by the submarine eruption of El Hierro
VersiĂłn del edito
Importance of N2 fixation vs. nitrate diffusion along a latitudinal transect in the Atlantic Ocean
We present ocean, basin-scale simultaneous measurements of N2-fixation, nitrate diffusion, and primary
production along a south–north transect in the Atlantic Ocean crossing three biogeographic provinces: the south
subtropical Atlantic (SSA; , 31uS–12uS), the equatorial Atlantic (EA; , 12uS–16uN), and the north subtropical
Atlantic (NSA, , 16uN–9uN) in April–May 2008. N2-fixation and primary production were measured as 15N2
and 14C uptake, respectively. Dissipation rates of turbulent kinetic energy (e) were measured with a microstructure
profiler. The vertical input of nitrate through eddy diffusion was calculated from the product of diffusivity,
derived from e, and the gradient of nanomolar nitrate concentration across the base of the euphotic zone. The
mean N2-fixation rate in EA was 56 6 49 mmol N m22 d21, whereas SSA and NSA had much lower values
(, 10 mmol N m22 d21). Because of the large spatial variability in nitrate diffusion (34 6 50, 405 6 888, and
844 6 1258 mmol N m22 d21 in SSA, EA, and NSA, respectively), the contribution of N2-fixation to new
production in the SSA, EA, and NSA was 44% 6 30%, 22% 6 19%, and 2% 6 2%, respectively. The differences
between SSA and NSA in the contribution of N2 fixation were partly due to the contrasting seasonal forcing in
each hemisphere, which likely affected both N2 fixation rates and vertical nitrate diffusion. The variability in the
nitrogen budget of the Atlantic subtropical gyres was unexpectedly high and largely uncoupled from relatively
constant phytoplankton standing stocks and primary production rates.CTM2004-05174-C02
CTM2007-28295-E/MAR
Programa I. Parga-Ponda
Significant Release of Dissolved Inorganic Nutrients From the Shallow Submarine Volcano Tagoro (Canary Islands) Based on Seven-Year Monitoring
Tagoro, the shallow submarine volcano that erupted south of El Hierro (Canary Islands, Spain) in October 2011, has been intensely monitored for over 7 years, from the early eruptive stage to the current degassing stage characterized by moderate hydrothermal activity. Here, we present a detailed study of the emissions of inorganic macronutrients (NO2– + NO3–, PO4, and Si(OH)4) comprising a dataset of over 3300 samples collected through three different sampling methodologies. Our results show a significant nutrient enrichment throughout the whole studied period, up to 8.8-fold (nitrate), 4.0-fold (phosphate), and 16.3-fold (silicate) in the water column, and larger enrichments of phosphate (10.5-fold) and silicate (325.4-fold), but not of nitrate, in the samples collected directly from the vents. We also provide some preliminary results showing ammonium (NH4+) concentrations up to 1.97 μM in the vent fluids as compared to 0.02 μM in the surrounding waters. Nutrient fluxes from the volcano during the degassing stage were estimated as 3.19 ± 1.17 mol m–2 year–1 (NO2– + NO3–), 0.02 ± 0.01 mol m–2 year–1 (PO4), and 0.60 ± 1.35 mol m–2 year–1 (Si(OH)4), comparable to other important nutrient sources in the region such as fluxes from the NW-African upwelling. Nutrient ratios were affected, with a minimum (NO3– + NO2–):PO4 ratio of 2.36:1; moreover, a linear correlation between silicate and temperature enabled the use of this nutrient as a mixing tracer. This study sheds light on how shallow hydrothermal systems impact the nutrient-poor upper waters of the ocean.En prens
Spatial patterns of plankton biomass and stable isotopes reflect the influence of the nitrogen-fixer Trichodesmium along the subtropical North Atlantic.
proyecto Malaspina-2010 (CSD2008-00077) del programa CONSOLIDER-INGENIO 2010, Ministerio de Ciencia e InnovaciĂłn y proyecto EURO-BASIN (FP7-ENV-2010 264933) e Instituto
Español de Oceanografia (IEO). C.M. recibió un contrato PFPI del IEO.The spatial variability of biomass and stable isotopes in plankton size fractions in the upper 200 m was studied in a high spatial resolution transect along 24°N from the Canary Islands to Florida to determine nitrogen and carbon sources. Vertical advection of waters predominated in lateral zones, while the central Atlantic (30–70°W) was characterized by strong stratification and oligotrophic surface waters. Plankton biomass was low in the central zone and high on both the eastern and the western sides, with most of the variability due to either large (>2000 µm) or small plankton (50% of organic nitrogen in the central zone, and even >30% in the eastern and the western zones. The impact of diazotrophy increased with the size of the organisms, supporting the wide participation of all trophic levels in the processing of recently fixed nitrogen. These results indicate that atmospheric sources of carbon and nitrogen prevail over deep water sources in the subtropical North Atlantic and that the zone influenced by diazotrophy is much larger than reported in previous studies.CONSOLIDER-INGENIO, 7FPPreprint1,749
Hydrography applied to the mapping of submarine volcanoes
Technical advances in hydrographic studies of the seafloor and the progressive use of
these techniques in oceanographic expeditions with scientific objectives, is generating greater
collaborations between the hydrographic and oceanographic institutions. Coordination between the
different institutions and the use of IHO criteria in the acquisition of bathymetric data in
oceanographic expeditions, allow regional hydrographic offices to have an additional source of data
for the improvement of the navigation charts. Meanwhile the Oceanographic Institutions will benefit
by having validated bathymetric data of high precision. This product is of great interest in studies of
submarine geological hazards where is necessary to have a very detailed knowledge of the seabed to
determine possible morphological changes associated with the risk processes and the possible active
structures. In addition, monitoring of active volcanoes need to have a good knowledge of changes in
the physico-chemical properties of the water column, the possible changes in low intensity emissions
(hot water, gas) can be detected with these studies in the overlying water masses.VersiĂłn del edito
The influence of island generated eddies on the carbon dioxide system, south of the Canary Islands
Publicado
Carbon Dioxide and Hydrographic Data Obtained During the R/V Hesperides Cruise in the South Atlantic Ocean on CLIVAR Repeat Hydrography Section A21 (8 February - 10 March, 2010)
The item is made of 2 files, of which 1 is the dataset and the other include a small description of the measured variables.-- Dataset contributed to the Project CarbochangeThis dataset gathers discrete measurements of CO2 (pH and alkalinity) and hydrographic variables (salinity, temperature, dissolved oxygen, nitrate, phosphate and silicate) obtained during the cruise MOC2Austral carried out from 8 February to 10 March 2010.
pH was measured spectrophotometrically following the Clayton and Byrne (1993). This method consists on adding a dye solution to the seawater sample, so that the ratio between two absorbances at two different wavelengths is proportional to the sample pH.
Alkalinity was measured using an automatic potentiometric titrator Titrando 809 Metrohm, with a Metrohm 6.0232.100 combination glass electrode and a Pt-1000 probe for temperature measurement following the methodology given by PĂ©rez and Fraga (1987).
Dissolved oxygen was analyzed following the widely applied Winkler method.
Determinations of nitrate, phosphate and silicate were carried out following methods described by Hansen and Grassoff (1983)
Salinity and Temperature were recorded with a CTD probeSpanish Projects GHG4MOC (CTM2009-07574-E) and MOC2 (CTM2008-06438-C02-02/MAR) supported by Ministerio de Ciencia e InnovaciĂłn, and CARBOCHANGE (264879)N