Nutrient limitation can explain a rapid transition to synchrony in an upwelling-driven diatom community

Identifying the mechanisms controlling the temporal dynamics of ecological communities is key to understand their vulnerability to natural and anthropogenic impacts and to identify early warnings of critical transitions. At community level, inter-specific synchrony is an important indicator of ecosystem stability and variation in function. Using wavelet analysis on time-series of abundance of 12 dominant diatom species, sampled monthly (1994-2009) in a coastal upwelling embayment at the northern limit of the Canary Current Upwelling System, we find a sudden onset of synchrony between 1998 and 2002, concomitant with an increase in the amplitude of the upwelling index at different temporal scales. To better understand the underlying mechanism that could generate this sudden onset of synchrony among competitors, we analyzed a general model of competition between two species for two essential nutrients (e.g., nitrogen and silicate). We incorporate environmental variation by varying the concentration of one of the essential nutrients entering the system. Increase in the amplitude of environmental variation always leads to greater synchrony among competitors. This occurs because the system shifts from a state in which species are limited by different nutrients to one where species are often limited by the same nutrient. We show that the transition from asynchronous to synchronous dynamics can occur suddenly as the amplitude of environmental variation increases. While it is not possible to rule out alternative mechanisms, our model demonstrates that sudden changes in the extent of synchronization should be a common feature when species compete for essential nutrients in variable environments.En prensa3,38

A Bayesian model for anchovy (Engraulis encrasicolus): the combined forcing of man and environment

Fishery collapses frequently result from combined pressures of the environment and man, which are difficult to discern because of the complexities involved and our limited knowledge. Models to resolve this complexity often become too sophisticated, with too many assumptions and, consequently, with little capacity to predict beyond calibration data. In this paper we implement a different procedure where the model is kept simple and uncertainty accounts for the equation imperfectness to reproduce ecological complexity. Human and environmental forcing on an anchovy (Engraulis encrasicolus) stock are simulated with only six parameters plus their error terms, and the uncertainty is computed with Bayesian methods. The simple structure is able to reproduce the major dynamical features of this species in the Gulf of Ca´diz, including data on life stages and age structure that had no contact with the model. This is a distinct performance for a frugal approach working on a mid-trophic species and a positive instance where parsimony can simulate the interaction of man, fish and the environment, provided uncertainty is accounted for in the process.Publicado

Spatial and temporal patterns of sea surface chlorophyll concentration and environmental forcing in the southern European Atlantic

Phytoplankton biomass dynamic integrates information about the characteristics of the pelagic ecosystem. Temporal and spatial patterns respond to physical processes. Also, phytoplankton abundance and its temporal dynamic largely determine the structure and dynamics of the food web. The southern European Atlantic (48 ºN – 36 ºS) presents differences in continental margin orientation, upwelling intensity, river runoff, a semi-enclosed oceanic domain (Bay of Biscay), and open oceanic waters to the west. Sea surface chlorophyll concentration (SSChl) monthly averages (from satellites) from 1998 to 2012 were analysed at 4x4 km resolution by Empirical Orthogonal Functions. The study area was regionalized according to rotated EOFs and temporal modes were used to resume the SSChl temporal variability in each region. The environmental forcing of temporal modes was analysed against environmental variables by means of Canonical Correspondence Analysis. More than 50% of the variability in oceanic regions was captured by the seasonal signal, with differences in the timing of the spring bloom and with the shape of the seasonal signal related with the latitudinal gradient and the ‘stagnation effect’ of the Bay of Biscay. In French and western Iberian shelves seasonality represented 50%. The difference between shelf and oceanic regions was due to mesoscale processes in shelf areas; i.e. river runoff in the French shelf and coastal upwelling in the western Iberian shelf. Shelf mesoscale processes impose short frequency variability on to the seasonal cycle and increase SSChl levels. The influence that these patterns of spatial and temporal dynamics have on the structure and dynamics of the rest of the food web can be perceived on the spatial patterns of fisheries catches

On the monitoring of surface displacement in connection with volcano reactivation in Tenerife, Canary Islands, using space techniques

Geodetic volcano monitoring in Tenerife has mainly focused on the Las Cañadas Caldera, where a geodetic micronetwork and a levelling profile are located. A sensitivity test of this geodetic network showed that it should be extended to cover the whole island for volcano monitoring purposes. Furthermore, InSAR allowed detecting two unexpected movements that were beyond the scope of the traditional geodetic network. These two facts prompted us to design and observe a GPS network covering the whole of Tenerife that was monitored in August 2000. The results obtained were accurate to one centimetre, and confirm one of the deformations, although they were not definitive enough to confirm the second one. Furthermore, new cases of possible subsidence have been detected in areas where InSAR could not be used to measure deformation due to low coherence. A first modelling attempt has been made using a very simple model and its results seem to indicate that the deformation observed and the groundwater level variation in the island may be related. Future observations will be necessary for further validation and to study the time evolution of the displacements, carry out interpretation work using different types of data (gravity, gases, etc) and develop models that represent the island more closely. The results obtained are important because they might affect the geodetic volcano monitoring on the island, which will only be really useful if it is capable of distinguishing between displacements that might be linked to volcanic activity and those produced by other causes. One important result in this work is that a new geodetic monitoring system based on two complementary techniques, InSAR and GPS, has been set up on Tenerife island. This the first time that the whole surface of any of the volcanic Canary Islands has been covered with a single network for this purpose. This research has displayed the need for further similar studies in the Canary Islands, at least on the islands which pose a greater risk of volcanic reactivation, such as Lanzarote and La Palma, where InSAR techniques have been used already

Radiales time series: 25 years building monitoring and analytical capacities in the Iberian shelf

The RADIALES program has been monitoring shelf waters in Spain for the last 25 years. This is the oldest field program for multidisciplinary marine research addressing long term variability issues at ecosystem level. Core observations include ship-based hydrographic, biogeochemical and plankton observations at monthly frequency in several oceanographic sections along the Iberian shelf. These observations are complemented with buoy and satellite observations and all these data are used to validate hydrographic and ecological models of plankton at local and regional scales. From the first series initiated in the northwestern shelf other programs extended the observations to the Mediterranean and off shelf waters using the same approach. The success of RADIALES extends beyond pure scientific knowledge, as the expertise gathered with the program has been applied to solve multiple environmental issues, from fisheries and pollution to global change. The program is also instrumental for educational purposes, allowing the specialization of students and technicians. Thanks to a basal funding provided by the Instituto Español de Oceanografía, the program currently obtains more than 60% of its annual budget from competitive calls, as it offers an unique platform for coastal research. Among the results of this program are 400 publications, including peer-review papers, 24 Thesis and 54 scientific reports. The RADIALES data are freely distributed to national and international users as a contribution to the development of cost-effective ocean research and marine servicesIEO (RADIALES

EcoAnchoa-Asturias 2011 Actividades realizadas por el Instituto Español de Oceanografía e informe de resultados

Resumen Las condiciones hidrográficas observadas durante la campaña Pelacus0411, realizada entre el 26 de marzo y 20 de Abril de 2011 en aguas de la plataforma continental Nord Ibérica, son las propias de comienzos de primavera, caracterizadas por una incipiente estratificación térmica y la presencia de agua de baja salinidad cerca de la costa, principalmente en las proximidades de las desembocaduras de los principales ríos. La fluorescencia (variable indicadora de la abundancia de fitoplancton –producción primaria) presentó los valores más elevados en superficie sobre el talud continental en la zona de Galicia, influenciada por la masa de agua de alta salinidad asociada a la contracorriente de talud (‘Corriente Ibérica hacia el Polo’). A partir del Cantábrico Central, frente a la costa Asturiana, y hacia la zona interna del Golfo de Vizcaya, se observó un máximo sub-superficial de clorofila entorno a los 20 o 30 m. La biomasa total de sardina en la zona de estudio estimada mediante métodos acústicos fue de 11.768 toneladas (t) (151106 individuos). Esta especie se localizó preferentemente en la plataforma de Asturias (sub-área ICES VIIIcE-w), en contraste con su práctica ausencia en aguas de la plataforma de Gallicia (sub-áreas ICES IXa-N y VIIIcW). Los individuos más jóvenes, de edades entre 1 y 2 años, predominaron en Galicia (sub-área ICES IXaN), mientras que los de mayor edad, 3 años, fueron más abundantes en la plataforma de Asturias y del País Vasco (sub-áreas ICES VIIIcE-w y VIIIcE-e respectivamente). Las estimas de abundancia de sardina en la campaña de 2011 son las más bajas de la serie desde 2001 y suponen un motivo de preocupación en relación al estado del stock. Si no tiene lugar un reclutamiento importante, el último de los cuales tuvo lugar en 2004, la previsión apunta hacia un descenso continuado de la biomasa de sardina en la plataforma Nord Ibérica. La biomasa estimada de anchoa fue de 2071 t, correspondiente a 142000 individuos. Éstos se localizaron en dos zonas separadas: al sur de Galicia (sub-área ICES IXa-N) y la parte interna del Golfo de Vizcaya (País Vasco y frontera con Francia; ICES sub-área VIIIcE-e y sub-división ICES VIIIb respectivamente), donde predominaron los individuos recién incorporados a la pesquería (i.e. 1 año de edad). Tanto la biomasa como el área ocupada por anchoa son superiores a las registradas en años anteriores. En contraste con la situación de los adultos, los datos proporcionados por la CUFES (muestreados en continuo de huevos de peces) indicaron que los huevos de sardina se localizaron en 6 toda el área prospectada en número similar a los encontrados en la campaña del año anterior, si bien más cerca de costa. Respecto a anchoa, se ha observado un incremento significativo tanto de la abundancia y extensión del área de distribución de huevos, más allá de la tradicional zona de presencia localizada en la parte interna del Golfo de Vizcaya.Consejería de Medio Rural y pesca del Principado de Asturias, Instituto Español de Oceanografí

Marine megafauna niche coexistence and hotspot areas in a temperate ecosystem

Versión del editor2,08

Modelización espacial de la distribución de cetáceos en el norte de la Península Ibérica: la importancia de incluir información de sus presas

Con el fin de identificar áreas ecológicamente significativas, necesitamos relacionar la distribución de especies con descriptores ecológicos que nos ayuden a comprender su distribución. En el medio marino, los modelos de distribución de especies (MDE) han sido tradicionalmente desarrollado en base a descriptores ecológicos indirectos (como clorofila y temperatura superficial del mar) recogidos a través de imágenes de satélite. Aunque las especies marinas pueden utilizar estas señales ambientales para localizar sus presas, el uso de información sobre la distribución de las mismas sería más informativo que el uso de estos descriptores indirectos. Gracias a las campañas oceanográficas multidisciplinares se puede recoger información simultánea de varios niveles tróficos, desde el plancton a los depredadores marinos, incluyendo sus principales presas pelágicas: los pequeños peces pelágicos. Por lo tanto, la inclusión de esta información en los MDE debería ser más relevante que las variables oceanográficas indirectas. Para testar esta hipótesis, desarrollamos MDE para las tres especies más abundantes de cetáceos que se registran en el norte de la Península Ibérica durante las campañas de primavera del Instituto Español de Oceanografía, PELACUS (2007-2013). Estas especies fueron el delfín común Delphinus delphis, el delfín mular Tursiops truncatus y el calderón común Globicephala melas. Dependiendo de las especies consideradas, se identificaron diferentes variables ambientales como importantes a la hora de explicar los patrones de distribución; pero las cifras globales ponen de manifiesto la principal contribución de la batimetría, seguido de la temperatura superficial del mar y la variabilidad espacial en la distribución de los pequeños peces pelágicos. Estos resultados tienen importantes implicaciones en reconocer la importancia de los estudios oceanográficos multidisciplinares para la obtención de descriptores ecológicos directos para mejorar los modelos de distribución de depredadores marinos