RRS "Charles Darwin" Cruise 169, 17 Feb-19 Mar 2005. Hydrothermal exploration of the southern Mid-Atlantic Ridge

The principal objective of this cruise was to identify the first site or sites of high temperature hydrothermal venting anywhere on the southern Mid-Atlantic Ridge, to characterize their geological setting, preliminary chemical nature and to identify, where possible, the nature of any vent-endemic species that might inhabit such vents to investigate whether this ridge system might represent a new biogeographic province. Initially we used the TOBI deep-tow sidescan system equipped with a CTD system and optical backscatter sensors, together with Miniature Autonomous Plume Recorders (MAPRs) to identify two new sites in which diagnostic chemically- and particle-laden plumes indicated the presence of high-temperature hydrothermal venting. Subsequently, we used the ABE autonomous underwater vehicle to (1) locate the core of one of these hydrothermal plumes, (2) obtain a detailed map of the underlying seafloor and (3) photograph three discrete hydrothermal sites (2 black-smoker systems, 1 diffuse-flow) and their associated ecosystems. A series of CTD stations were occupied for water column investigations and a number of rock-coring and dredging stations were also undertaken to provide groundtruthing of sidescan sonar images of the Mid-Atlantic Ridge seafloor

RV Atlantis Voyage 7 Leg XXX, 06 Mar – 12 Mar 2004. UK ROV Isis – engineering trials

This report describes the first engineering trials dives of the new UK 6500m-rated ROV Isis during Voyage 7, Leg XXX of the RV Atlantis, 6-13 March 2003. Mobilisation occurred in Jacksonville, Florida following a period of refit for the ship between March 2nd-5th and first FAT (factory-acceptance) testing was achieved on March 7th during transit from Florida to the Bahamas in ca. 850m of water. Upon arrival in Bahamian waters a swath bathymetric survey was conducted of the northeast Providence Channel immediately west of northernmost Eleuthra Island where a tongue of >4000m-deep ocean intrudes among the shelter of the Bahamas islands. Three further dives of the ROV were conducted in this area between March 8th and 11th 2003 to depths of, respectively, >2000m, >4000m and >1000m. The first two of these dives proved the extensive depth capability of the new ROV and provided first opportunity for the UK ROV team to work with the vehicle. The third dive in Bahamian waters allowed imaging of the local seafloor fauna and collection of sample material with the manipulator arms – important for proving the capability of the vehicle for demonstration to both the scientific community and the wider public in the UK following significant Government investment. Because of insurmountable bow-thruster problems aboard ship, however, dive operations had to be abandoned early on March 11th and could not be recommenced pending further dry-dock maintenance. To that end the cruise was ended ahead of schedule with the scientific party disembarking in Nassau, Bahamas, by pilot boat on Wednesday March 12th. Despite this disappointing end to the cruise three important objectives were achieved:• Preliminary FAT testing demonstrated the viability of the core system for the ROV.• Dives to >2000m were achieved (max > 4,300m) with up to 7 hours on the seafloor.• Basic seafloor imaging & sampling capabilities were demonstrated & documented

RRS Discovery Cruise 228, 21 May-28 Jun 1997. The Fluxes at AMAR Experiment: FLAME

The principle objectives of the cruise were to study the physical, geochemical and biological dispersion of the neutrally-buoyant hydrothermal plume overlying the Rainbow hydrothermal field on the Mid-Atlantic Ridge, near 36°15'N; to investigate the interacting processes active within the dispersing plume; to better constrain the source of active venting on the seabed; and to quantify the physical, geochemical and biological fluxes to the water column on the segment scale. A secondary objective was to better constrain the source of strong dissolved methane concentrations which had been observed previously in the FAMOUS segment further north. An additional objective, which evolved during the course of the cruise programme, was to investigate the dispersion of vent-larvae through hydrothermal plumes along a section of the MAR extending from the Rainbow area to the previously known Lucky Strike hydrothermal field at 37°17'N. Initially, a series of hydrographic CTD stations were occupied, complete with a lowered Acoustic Doppler Current Profiler (L-ADCP) to provide instantaneous measurements of prevailing current directions with depth in the water column. This was coupled with a suite of deep-tow CTD tow-yo sections using the hydrothermal plume instrument BRIDGET. This preliminary data set yielded an understanding of the nature of plume dispersion which was then utilised to target further water column sampling using a combination of further CTD hydrocasts for water column samples, in situ filtration of particles for mineralogical, geochemical and microbiological investigations and RMT 1+8 Net trawls for biology. The strategy was largely successful and the neutrally buoyant plume, which was revealed to be dispersing under topographic control, was traced to a distance of greater than 50km down-stream. As the programme progressed a grid of closely spaced (0.5 nautical miles) orthogonal survey lines were occupied across the suspected site of venting, yielding a resolution of closest approach to the source of better than 200m. Finally at Rainbow, a suite of 8 current-meter moorings were deployed around the vent-site to monitor long-term (>12 month) fluxes of physical parameters including suspended particulate material away from the site of venting. In addition to sampling at Rainbow, 6 CTD stations were occupied in the southern portion of the FAMOUS segment and RMT 1+8 Net Trawls were completed in the Southern AMAR, AMAR, FAMOUS, North FAMOUS and Lucky Strike segments as well as in the non-transform discontinuity (NTD) offset immediately to the south of the Lucky Strike segment

Surface-Generated Mesoscale Eddies Transport Deep-Sea Products from Hydrothermal Vents

International audienceAtmospheric forcing, which is known to have a strong influence on surface ocean dynamics and production, is typically not considered in studies of the deep sea. Our observations and models demonstrate an unexpected influence of surface-generated mesoscale eddies in the transport of hydrothermal vent efflux and of vent larvae away from the northern East Pacific Rise. Transport by these deep-reaching eddies provides a mechanism for spreading the hydrothermal chemical and heat flux into the deep-ocean interior and for dispersing propagules hundreds of kilometers between isolated and ephemeral communities. Because the eddies interacting with the East Pacific Rise are formed seasonally and are sensitive to phenomena such as El Niño, they have the potential to introduce seasonal to interannual atmospheric variations into the deep sea

Evaluación de un modelo de producción de pasturas mediante pruebas empíricas

En el presente trabajo se utilizó un modelo de crecimiento de pasturas desarrollado por McCall y BishopHurley. El objetivo fue evaluar si el modelo es capaz de simular las variaciones en producción primaria neta aérea en la estación húmeda utilizando pruebas empíricas. Se trabajó con una gramínea megatérmica, Chloris gayana. La evaluación empírica se realizó con datos de experimentos realizados en el Instituto de Investigación Animal del Chaco Semiárido (INTA), que incluyeron biomasa seca aérea acumulada durante la estación de crecimiento, y biomasa seca aérea producida entre dos pastoreos. Los estadísticos utilizados fueron raíz cuadrada del cuadrado medio del error, relación RMSE/Media observada, error medio y los coeficientes de la desigualdad de Theil. Los coeficientes de desigualdad de Theil para la producción primaria neta aérea acumulada (Um=0,35, Us=0,1, Uc=0,64) y por cortes (Um=0,08, Us=0,08, Uc=0,84) mostraron que el modelo no presentó errores sistemáticos. El patrón de crecimiento de la producción primaria neta aérea simulado fue 7% oct-nov, 64% dic-ene-feb, 29% mar-abr-may. El trabajo muestra el potencial del modelo de pasturas para simular la dinámica de la producción de Chloris gayana en ambientes del subtrópico argentino, siendo capaz de captar variaciones en el ambiente. En este sentido puede ser útil para estudiar interacciones entre el manejo y la dinámica de las pasturas en climas de alta variabilidad temporal.For this work, a pasture growth model developed by McCall and Bishop-Hurley, was used. The objective was to evaluate the model, using empirical tests. A tropical pasture named Chloris gayana, was used. For the empirical evaluation a database from the Animal Research Institute of Semiarid Chaco (INTA), was used, including information of herbage accumulated during the growing season, and cutting trials based on the difference between pre- and post-grazing herbage. The statistics calculated were root mean square error, relative root mean square error, mean error and Theil coefficients. The Theil coefficients for accumulated herbage (Um = 0.35, Us = 0.1, Uc = 0.64) and cutting trials (Um = 0.08, Us = 0.08, Uc = 0, 84), showed that the model did not present systematic errors. The growth pattern of simulated herbage was 7% Oct-Nov, 64% Dec-Jan-Feb, 29% Mar-Apr-May. The work shows the potential of the pasture model to simulate the forage production of Chloris gayana in subtropical environments, capturing variations in the environment. In this sense, it can be useful for studying interactions between management strategies and dynamics responses of pastures in highly variable climates.Instituto de Investigación Animal del Chaco SemiáridoFil: Nasca, Jose Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Berone, German Dario. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina.Fil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cesáreo Naredo ArgentinaFil: Feldkamp, C.R. Asociación Argentina de Consorcios Regionales de Experimentación Agrícola; Argentina.Fil: Colombatto, Dario. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

An intermediate-depth source of hydrothermal 3He and dissolved iron in the North Pacific

We observed large water column anomalies in helium isotopes and trace metal concentrations above the Loihi Seamount. The 3He/4He of the added helium was 27.3 times the atmospheric ratio, clearly marking its origin to a primitive mantle plume. The dissolved iron to 3He ratio (dFe:3He) exported to surrounding waters was 9.3 ± 0.3 × 106. We observed the Loihi 3He and dFe “signal” at a depth of 1100 m at several stations within ∼100 – 1000 km of Loihi, which exhibited a distal dFe:3He ratio of ∼4 × 106, about half the proximal ratio. These ratios were remarkably similar to those observed over and near the Southern East Pacific Rise (SEPR) despite greatly contrasting geochemical and volcanictectonic origins. In contrast, the proximal and distal dMn:3He ratios were both ∼ 1 × 106, less than half of that observed at the SEPR. Dissolved methane was minimally enriched in waters above Loihi Seamount and was distally absent. Using an idealized regional-scale model we replicated the historically observed regional 3He distribution, requiring a hydrothermal 3He source from Loihi of 10.4 ± 4.2 mola−1, ∼2% of the global abyssal hydrothermal 3He flux. From this we compute a corresponding dFe flux of ∼40 Mmola−1. Global circulation model simulations suggest that the Loihi-influenced waters eventually upwell along the west coast of North America, also extending into the shallow northwest Pacific, making it a possibly important determinant of marine primary production in the subpolar North Pacific

Rare variants in KDR, encoding VEGF Receptor 2, are associated with tetralogy of Fallot

Purpose Rare genetic variants in KDR, encoding the vascular endothelial growth factor receptor 2 (VEGFR2), have been reported in patients with tetralogy of Fallot (TOF). However, their role in disease causality and pathogenesis remains unclear. Methods We conducted exome sequencing in a familial case of TOF and large-scale genetic studies, including burden testing, in >1,500 patients with TOF. We studied gene-targeted mice and conducted cell-based assays to explore the role of KDR genetic variation in the etiology of TOF. Results Exome sequencing in a family with two siblings affected by TOF revealed biallelic missense variants in KDR. Studies in knock-in mice and in HEK 293T cells identified embryonic lethality for one variant when occurring in the homozygous state, and a significantly reduced VEGFR2 phosphorylation for both variants. Rare variant burden analysis conducted in a set of 1,569 patients of European descent with TOF identified a 46-fold enrichment of protein-truncating variants (PTVs) in TOF cases compared to controls (P = 7 x 10(-11)). Conclusion Rare KDR variants, in particular PTVs, strongly associate with TOF, likely in the setting of different inheritance patterns. Supported by genetic and in vivo and in vitro functional analysis, we propose loss-of-function of VEGFR2 as one of the mechanisms involved in the pathogenesis of TOF.Developmen

FS Poseidon Cruise 240, 19 Jun-10 Jul 1998. The Fluxes at AMAR Experiment: FLAME 2

The principal objective of the cruise was to recover a series of 11 long-term (12 month) current meter and sediment trap moorings deployed in Summer 1997 to monitor the neutrally-buoyant hydrothermal plume overlying the Rainbow hydrothermal field on the Mid-Atlantic Ridge, near 36°15’N. Secondary objectives were to continue CTD investigations of the physical and geochemical evolution of the plume and to attempt box-coring in sedimented areas identified from TOBI sidescan sonar records beneath the dispersing neutrally buoyant plume. Mooring recovery was completely successful for all three of the sediment trap moorings with the exception that one 2-week sample was lost from one of the 5 multi-collector sediment traps deployed. Seven of the eight current meter moorings deployed were also recovered, with 100% data-recovery from the 21 current meters recovered inboard. A total of 35 CTD-nephelometer profile stations were occupied to the North and South of the Rainbow hydrothermal field, together with one background station , east of the MAR. In situ CTD and nephel data were complemented by water sampling for He-3 and CH4 and shipboard analysis of rosette samples for salinity and TDMn. A total of 4 box-cores were attempted at depths of 2400-2600m beneath the neutrally buoyant plume. All four cores were successful yielding core lengths of 43, 30, 18 and 18cm at distances of 2, 5, 12 and 29km downstream from the known hydrothermal vent-field, respectively