Geographical species distribution in the Barents Sea under climate change - results from the BarEcoRe project

This report presents a study of possible changes in species’ spatial distribution in the Barents Sea as a result of possible future changes in the ocean climate. Species Distribution Models (SDMs) are constructed to describe and quantify the relationship between past distribution of species and environmental conditions. On the basis of simple environmental scenarios, the same models are used to project possible changes in individual species’ spatial distributions. The work was conducted under the NFR funded project BarEcoRe: Barents Sea Ecosystem Resilience under global environmental change

Estimation and classification of temporal trends to support integrated ecosystem assessment

We propose a trend estimation and classification (TREC) approach to estimating dominant common trends among multivariate time series observations. Our methods are based on two statistical procedures that includes trend modelling and discriminant analysis for classifying similar trend (common trend) classes. We use simulations to evaluate the proposed approach and compare it with a relevant dynamic factor analysis in the time domain, which was recently proposed to estimate common trends in fisheries time series. We apply the TREC approach to the multivariate short time series datasets investigated by the ICES integrated assessment working groups for the Norwegian Sea and the Barents Sea. The proposed approach is robust for application to short time series, and it directly identifies and classifies the dominant trends underlying observations. Based on the classified trend classes, we suggest that communication among stakeholders like marine managers, industry representatives, non-governmental organizations, and governmental agencies can be enhanced by finding the common tendency between a biological community in a marine ecosystem and the environmental factors, as well as by the icons produced by generalizing common trend patterns.publishedVersio

Tipología de las estructuras hidrológicas modeladas y observadas en el Golfo de Vizcaya

Collecting hydrological observations over the whole Bay of Biscay continental shelf can require several weeks. As a result, the observations are not truly synoptic and the interpretation of hydrological structures is corrupted by the time-lags between observations at distinct locations. We evaluated the effects of non-synoptic sampling during a spring cruise (17 April to 13 May 2000), using outputs from 3D hydrodynamic models as a substitute for true synoptic sampling. We developed a method for clustering hydrological regions based on the vertical structure of the water column and temporal changes in hydrography. In parallel, outputs from the 3D model were compared with field observations. The results show that in spring 2000 the Bay of Biscay continental shelf could be separated into six principal hydrological regions, one of them being characterised by vertical stability and low temporal variability. This region corresponds to an area where pelagic fish spawning activity is known to be persistently low.La recogida de datos hidrológicos en el conjunto de la plataforma continental del Golfo de Vizcaya puede requerir varias semanas. Como resultado, estas observaciones no son verdaderamente sinópticas y la interpretación de las estructuras hidrológicas está perturbada por los desfases temporales entre observaciones de distintas localidades. En este estudio, se evalúan los efectos del muestreo no sinóptico durante una campaña de primavera (17 de abril al 13 de mayo de 2000), usando los resultados de modelos hidrodinámicos tridimensionales como sustituto de un muestreo verdaderamente sinóptico. A través del método cluster se realizó una agrupación de las regiones hidrológicas, sobre la base de la estructura vertical de la columna de agua y los cambios temporales en la hidrografía. En paralelo, las simulaciones del modelo tridimensional son comparadas con las observaciones in situ. Los resultados muestran que en la primavera de 2000 la plataforma continental del Golfo de Vizcaya puede separarse en 6 regiones hidrológicas principales, una de las cuales se caracteriza por una estabilidad vertical y una baja variabilidad temporal. Esta región corresponde a un área donde se conoce que de manera persistente la freza de peces pelágicos es limitada

Combined effects of temperature and fishing mortality on the Barents Sea ecosystem stability

Temporal variability in abundance and composition of species in marine ecosystems results from a combination of internal processes, external drivers, and stochasticity. One way to explore the temporal variability in an ecosystem is through temporal stability, measured using the inverse of the coefficient of variation for biomass of single species. The effect of temperature and fisheries on the variability of the Barents Sea food web is still poorly understood. To address this question, we simulate the possible dynamics of Barents Sea food web under different temperature and fishery scenarios using a simple food-web model (Non-Deterministic Network Dynamic [NDND]). The NDND model, which is based on chance and necessity (CaN), defines the state space of the ecosystem using its structural constraints (necessity) and explores it stochastically (chance). The effects of temperature and fisheries on stability are explored both separately and combined. The simulation results suggest that increasing temperature has a negative effect on species biomass and increasing fisheries triggers compensatory dynamics of fish species. There is a major intra-scenario variability in temporal stability, while individual scenarios of temperature and fisheries display a weak negative impact and no effect on stability, respectively. However, combined scenarios indicate that fisheries amplify the effects of temperature on stability, while increasing temperature leads to a shift from synergistic to antagonistic effects between these two drivers

Multiple configurations and fluctuating trophic control in the Barents Sea food-web

The Barents Sea is a subarctic shelf sea which has experienced major changes during the past decades. From ecological time-series, three different food-web configurations, reflecting successive shifts of dominance of pelagic fish, demersal fish, and zooplankton, as well as varying trophic control have been identified in the last decades. This covers a relatively short time-period as available ecological time-series are often relatively short. As we lack information for prior time-periods, we use a chance and necessity model to investigate if there are other possible configurations of the Barents Sea food-web than those observed in the ecological time-series, and if this food-web is characterized by a persistent trophic control. We perform food-web simulations using the Non-Deterministic Network Dynamic model (NDND) for the Barents Sea, identify food-web configurations and compare those to historical reconstructions of food-web dynamics. Biomass configurations fall into four major types and three trophic pathways. Reconstructed data match one of the major biomass configurations but is characterized by a different trophic pathway than most of the simulated configurations. The simulated biomass displays fluctuations between bottom-up and top-down trophic control over time rather than persistent trophic control. Our results show that the configurations we have reconstructed are strongly overlapping with our simulated configurations, though they represent only a subset of the possible configurations of the Barents Sea food-web.publishedVersio

An appraisal of the drivers of Norwegian spring‐spawning herring (Clupea harengus) recruitment

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Workshop on hydro-acoustics scrutinizing in the Norwegian Sea

This report presents the international redfish survey carried out in the Norwegian Sea in August 2008 and the methodology used to review and compare the different hydroacoustic scrutinizing procedures. The results of the comparative analysis clearly show that differences in scrutinizing methods have a very large impact on the abundance estimate of redfish. They probably constitute the major source of uncertainty for any quantitative estimate. Efforts towards standardisation of scrutinizing procedures should be amplified or at least maintained

Human impacts on marine ecosystems

Marine Ecosystems and Global Change provides a detailed synthesis of the work conducted under the auspices of the Global Ocean Ecosystems Dynamics (GLOBEC) programme. This research spans two decades, and represents the largest, multi-disciplinary, international effort focused on understanding the impacts of external forcing on the structure and dynamics of global marine ecosystems