Composition and distribution of the larval decapod community in the deep sea of the Western Mediterranean Sea Balearic Sub-basin

Mechanisms facilitating larvae transport from continental to more oceanic areas were investigated in the Balearic sub-basin (BSB), Western Mediterranean Sea. The abundance, distribution, and development stages of decapod larvae were recorded for a transect of 28 stations crossing the central eddy of the BSB. Zooplankton samples were taken to 1,800 m depth by horizontal and oblique 500-μm mesh size nets hauls towed near the benthic boundary (BBL) and in deep scattering layers (DSL). In total, 67 taxa belonging to Decapoda and one Stomatopoda were identified. Advanced development represented 75% of the individuals recorded. 75% of the species corresponded to adults of deep-sea species, 9% were sergestids (mesopelagic species), and the remaining 16% corresponded to shelf and coastal species. Cluster assemblages formed were related to the hydrological conditions, water masses dynamics, and geomorphologic structures mainly associated with nepheloid layers. Advanced and juvenile specimens of commercial species such as Parapenaeus longirostris, Geryon longipes, and Aristeus antennatus were found close to seafloor BBL. The influence of trophic ecology should be considered as the priority factor of larvae concentrations in deep.En prens

Is the Mediterranean Sean Outflow conditioning cold water corals in the North Atlantic?

posterWithin the context of the UE project ATLAS, in September - October 2016 on board RV Sarmiento de Gamboa, the MEDWAVES (MEDiterranean out flow WAter and Vulnerable EcosystemS) targeted areas under the potential influence of the MOW (Mediterranean Water Outflow) within the Mediterranean and Atlantic realms. These include seamounts where cold-water corals (CWC) have been reported, they may act as essential “stepping stones” connecting fauna of seamounts in the Mediterranean with those of seamounts in the continental shelf of Portugal, the Azores and the Mid‐ Atlantic Ridge. During MEDWAVES sampling was conducted through several seamounts: Formigas (Azores), Ormonde & Gazul (North Atlantic) and Seco de los Olivos (Alboran Sea). High quality CO2 measurements were conducted in the 500 meters above the bottom in order to characterize the water masses and detect the MOW spreading. MOW is warm and salty, but also high in alkalinity and pH. Is MOW conditioning CWC

Variabilidad de la clorofila a fitoplanctónica y de los nutrientes inorgánicos en aguas de la plataforma insular de las Islas Baleares

A lo largo de cuatro campañas llevadas a cabo en abril, julio y octubre de 2008 y marzo de 2009, se han tomado nuevos datos de clorofila a y nutrientes inorgánicos (nitratos, nitritos, fosfatos y silicatos), en diversas estaciones oceanográficas distribuidas en aguas de las plataformas insulares de Mallorca, Menorca e Ibiza, a tres niveles de profundidad (5, 25 y 50m o en las proximidades del fondo en algunos casos). Poniendo especial énfasis en la variabilidad estacional de la clorofila a (basada en los promedios de la zona muestreada), se ha constatado una ligera disminución de su concentración al pasar de abril a julio con un aumento hacia octubre y especialmente en marzo de 2009), en los niveles más superficiales. Los nutrientes, a excepción de los fosfatos, han mostrado un comportamiento similar aunque no siempre tan claro. Comparando los promedios globales de este ciclo estacional con los del ciclo anterior (2005-2006), se observa una disminución en algunos parámetros, así como un cierto aumento en otros, aunque, sin que existan cambios importantes que afecten al carácter, en general oligiotrófico, de estas agua

Seasonal and interannual variability of dissolved oxygen around the Balearic Islands from hydrographic data

Oceanographic data obtained between 2001 and 2011 by the Spanish Institute of Oceanography (IEO, Spain) have been used to characterise the spatial distribution and the temporal variability of the dissolvedoxygen around the Balearic Islands (Mediterranean Sea). The study area includes most of the Western Mediterranean Sea, from the Alboran Sea to Cape Creus,atthe border between France and Spain. Dissolved Oxygen (DO) at thewatersurface is found to be in a state of equilibrium exchange with the atmosphere. In the spring and summer a subsurface oxygen supersaturation is observed due to the biological activity, above the subsurface fluorescence maximum. Minimum observed values of dissolved oxygen are related to theLevantine Intermediate Waters (LIW). An unusual minimum of dissolved oxygen concentrations were also recorded in the Alboran Sea Oxygen Minimum Zone. The Western Mediterranean Deep Waters (WMDW) and the Western Intermediate Waters (WIW) show higher values of dissolved oxygenthanthe Levantine Intermediate Waters due to their more recent formation. Using these dissolved oxygen concentrations it is possible to showthat the Western Intermediate Waters move southwards across the Ibiza Channel and the deep water circulates around the Balearic Islands. It has also been possible to characterise the seasonal evolution of the different watermassesandtheir dissolved oxygen content in a station in the Algerian sub-basin. Keywords: Ocean circulation, dissolved oxygen, water masses, Western Mediterranean Sea, Balearic SeaPost-print

Is Deep Sea Cold Water Corals distribution constrained by CO2 distinct signatures?

conferenceObjectThe MEDWAVESThe MEDWAVES (MEDiterranean out flow WAter and Vulnerable EcosystemS) cruise was developed in the framework of the ATLAS project, with the main objective of determining areas under the influence of the Mediterranean Overflow Water within the Mediterranean and Atlantic areas. MEDWAVES cruise (LEG 1: Cadiz – Punta Delgada and LEG 2: Punta Delgada – Málaga) was completed between September-October 2016 on board the Spanish R/V Sarmiento de Gamboa. Within the specific aim of evaluating the biogeochemichal role of the Mediterranean Water, over and around the Formigas, Ormonde and Seco de los Olivos seamounts, and the Gazul Mud volcano, some CO2 system variables were measured on board (pH, total alkalinity and carbonate ion concentration) together with dissolved oxygen samples. The chemistry of the CO2 in the Mediterranean Sea is very particular, characterised by warm, salty and high alkalinity waters [1]. The Mediterranean Water goes into the Atlantic Ocean through the strait of Gibraltar, being clearly identified as the most saline water of the water column located at approximately 1000 dbar [2]. Apart from the water mass characteristic, other properties and organism characteristics of the Mediterranean Sea are spilt into the Atlantic. According to the objectives of MEDWAVES cruise and taking into account the fine scale sampling made over the 400m above the bottom, we will characterise the CO2 system of the four different areas, trying to distinguish the signature of the Mediterranean Water in each seamount. The presence of depth cold water coral in those seamounts is poorly known and we would like to connect those of Mediterranean Sea with those of the continental shelf of Portugal, the Azores and the Mid-Atlantic Ridge with the CO2 variables. Hence, a second step will be to evaluate the connexion between the cold water corals and the CO2 system

Larval fish assemblage structure in the surface layer of the northwestern Mediterranean under contrasting oceanographic scenarios

During the summer, the relative influence of resident Atlantic Waters (AW) and new AW largely drives the mesoscale dynamics around the Balearic Islands (NW Mediterranean). Two principal summer hydrographic scenarios were identified in the region, differentiated by the relative position of the density front between new and resident AW within the archipelago and its associated mesoscale activity. In this study, we investigated how those early summer mesoscale scenarios influence larval fish assemblages, by analyzing data from two cruises representative of these two scenarios (2004 and 2005). Redundancy analysis was used to assess the variance in the larval fish assemblage that could be significantly explained by the most parsimonious combination of available environmental variables in both years. While depth was the most important variable in explaining the larval fish assemblage structure variability observed under both scenarios, indicators of mesoscale activity (dynamic height, geostrophic velocity) contributed significantly to understanding the dynamics of the larval fish community. Mesoscale activity was higher in summer 2004, leading to higher larval fish abundances and zooplankton biomass and lower larval fish diversity than in the unusually warm summer 2005, which showed lower mesoscale activity. The larval assemblage dynamics are discussed in terms of extrinsic and species-specific factors.Postprint1,749

Ocean Circulation over Formigas and Ormonde Seamounts

Seamounts constitute an obstacle to the free ocean flow, modifying the patter of circulation. As a result of these alterations, a variety of hydrodynamical processes and phenomena may take place in seamounts, among others, Taylor columns/caps. These oceanographic effects may turn seamounts into very productive ecosystems with high biodiversity. Under these conditions seamounts provide a particularly good environment for the settle of some organisms, acting as stepping stones and contributing to its dispersal. In this study, we verify if these oceanographic effects explain the presence of cold-water corals of Mediterranean origin in the Atlantic. To achieve this, three seamounts in the path of the Mediterranean Outflow Water (MOW) through the Eastern North Atlantic were selected: the Gazul mud volcano, and the Ormonde and Formigas seamounts. In order to determine the hydrographic and dynamical conditions in each one of the three locations, CTD, LADPC and biochemical observations were carried out. Taylor columns were not observed in any of the three sampled areas. Although we found suggestions of upwelling/downwelling systems, their effect was barely noticed in the circulation pattern. The oceanographic processes in those areas are more influenced by the vertical distribution of water masses, which determine the stability of the water column. Moreover, the high values of the Brunt-Väisälä frequency around the MOW halocline can lead to the formation of internal waves. These perturbations in the water column can enhance the vertical mixing, producing suspension, which, in turn, could affect the vertical distribution of cold-water corals

Vertical distribution of Atlantic bluefin tuna Thunnus thynnus and bonito Sarda sarda larvae is related to temperature preference

As part of the endeavor aiming at the domestication of Atlantic bluefin tuna (BFT; Thunnus thynnus), first sexual maturity in captivity was studied by documenting its occurrence and by characterizing the key hormones of the reproductive axis: follicle stimulating hormone (FSH) and luteinizing hormone (LH). The full length sequence encoding for the related hormone b-subunits, bftFSHb and bftLHb, were determined, revealing two bftFSHb mRNA variants, differing in their 50 untranslated region. A quantitative immuno-dot-blot assay to measure pituitary FSH content in BFT was developed and validated enabling, for the first time in this species, data sets for both LH and FSH to be compared. The expression and accumulation patterns of LH in the pituitary showed a steady increase of this hormone, concomitant with fish age, reaching higher levels in adult females compared to males of the same age class. Conversely, the pituitary FSH levels were elevated only in 2Y and adult fish. The pituitary FSH to LH ratio was consistently higher (>1) in immature than in maturing or pubertal fish, resembling the situation in mammals. Nevertheless, the results suggest that a rise in the LH storage level above a minimum threshold may be an indicator of the onset of puberty in BFT females. The higher pituitary LH levels in adult females over males may further support this notion. In contrast three year-old (3Y) males were pubertal while cognate females were still immature. However, it is not yet clear whether the advanced puberty in the 3Y males was a general feature typifying wild BFT populations or was induced by the culture conditions. Future studies testing the effects of captivity and hormonal treatments on precocious maturity may allow for improved handling of this species in a controlled environment which would lead to more cost-efficient farmingVersión del edito