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Trabajo final presentado por Núria Patiño Sevillano para el Máster en Oceanografía y Gestión del Medio Marino impartido por la Universitat de Barcelona (UB), realizado bajo la dirección de Marta Coll y Jazel Ouled-Cheikh Bonan del Institut de Ciències del Mar (ICM-CSIC).-- 38 pages, 13 figures, 1 table, 2 annexes ; Marine ecosystems are globally threatened due to the effects of global change as a result of human activities, which can alter them at many scales, from individual physiological damage to the loss of ecosystem structure and subsequent deterioration of ecosystem functioning. This is particularly true in marine biodiversity hotspots, such as the Mediterranean Sea, as its basin is one of the most impacted areas in the world. In this sense, in order to develop informed conservation plans it is essential to understand the relationships among the species inhabiting it, and the interlinkages and dependencies between all its components. Food web analyses provide a representation of these relationships, and allow assessing system complexity and resilience. In this study, we aimed at depicting the qualitative food-web structure of the Mediterranean Sea and its main sub-regions, while visualizing its food-web structure and identifying the main similarities and differences between regions. We used the framework set up in a previous study, which built a general qualitative meta-web of the Mediterranean Sea and we substantially updated the results, providing new analysis of the ecological network per sub-regions: Western, Central, Eastern and the Adriatic Sea. We found that food-web information was lacking for many invertebrate species and other small predators, and it was especially scarce within the sub-region of the Central Mediterranean Sea. We also found that while the four sub-regions had many similarities on their food-web structure, the most complex in terms of trophic linkages was the Central Mediterranean one and the least complex was the Adriatic Sea one. Overall, this study makes a significant contribution to the research about the Mediterranean marine ecosystems, can help scientists to identify future research objectives and can be used by policy makers to make informed decisions within a complex system-thinking context to archive a sustainable future ; This study acknowledges the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019- 000928-S) to the Institute of Marine Science (ICM-CSIC) and it is a contribution to the European Union's Horizon 2020 research and innovation program under grant agreement No 869300 (FutureMARES project)

AbstractWe investigated trophic transfer of cadmium (Cd) through an Arctic marine food web in Hudson Bay and compared it with mercury (Hg), a metal known to strongly biomagnify. We evaluated blue mussel, sea urchin, common eider, sculpin, Arctic cod, and ringed seal for the influence of dietary and biological variables on variation in Cd and Hg concentrations. Age and size influenced metal concentrations among individuals within a vertebrate species. Consumer carbon and sulfur isotope values were correlated with their Cd and Hg concentrations, indicating habitat-specific feeding influenced metal bioaccumulation. Trophic transfer patterns for Cd depended on the vertebrate tissue, with food web biodilution observed for the muscle but not the liver. Liver Cd concentrations were higher in ringed seal and some common eider relative to prey. In contrast, we observed mercury biomagnification for both tissues. Tissue- and species-specific physiology can explain discrepancies of Cd trophic transfer in this Arctic marine food web.

Eutrophication is one of the most important anthropogenic pressures impacting coastal seas. In Europe, several legislations and management measures have been implemented to halt nutrient overloading in marine ecosystems. This study evaluates the impact of freshwater nutrient control measures on higher trophic levels (HTL) in European marine ecosystems following descriptors and criteria as defined by the Marine Strategy Framework Directive (MSFD). We used a novel pan-European marine modeling ensemble of fourteen HTL models, covering almost all the EU seas, under two nutrient management scenarios. Results from our projections suggest that the proposed nutrient reduction measures may not have a significant impact on the structure and function of European marine ecosystems. Among the assessed criteria, the spawning stock biomass of commercially important fish stocks and the biomass of small pelagic fishes would be the most impacted, albeit with values lower than 2.5%. For the other criteria/indicators, such as species diversity and trophic level indicators, the impact was lower. The Black Sea and the North-East Atlantic were the most negatively impacted regions, while the Baltic Sea was the only region showing signs of improvement. Coastal and shelf areas were more sensitive to environmental changes than large regional and sub-regional ecosystems that also include open seas. This is the first pan-European multi-model comparison study used to assess the impacts of land-based measures on marine and coastal European ecosystems through a set of selected ecological indicators. Since anthropogenic pressures are expanding apace in the marine environment and policy makers need to use rapid and effective policy measures for fast-changing environments, this modeling framework is an essential asset in supporting and guiding EU policy needs and decisions.

18 pages, 7 figures, 2 tables, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2021.596797/full#supplementary-material.-- The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author/s ; Eutrophication is one of the most important anthropogenic pressures impacting coastal seas. In Europe, several legislations and management measures have been implemented to halt nutrient overloading in marine ecosystems. This study evaluates the impact of freshwater nutrient control measures on higher trophic levels (HTL) in European marine ecosystems following descriptors and criteria as defined by the Marine Strategy Framework Directive (MSFD). We used a novel pan-European marine modeling ensemble of fourteen HTL models, covering almost all the EU seas, under two nutrient management scenarios. Results from our projections suggest that the proposed nutrient reduction measures may not have a significant impact on the structure and function of European marine ecosystems. Among the assessed criteria, the spawning stock biomass of commercially important fish stocks and the biomass of small pelagic fishes would be the most impacted, albeit with values lower than 2.5%. For the other criteria/indicators, such as species diversity and trophic level indicators, the impact was lower. The Black Sea and the North-East Atlantic were the most negatively impacted regions, while the Baltic Sea was the only region showing signs of improvement. Coastal and shelf areas were more sensitive to environmental changes than large regional and sub-regional ecosystems that also include open seas. This is the first pan-European multi-model comparison study used to assess the impacts of land-based measures on marine and coastal European ecosystems through a set of selected ecological indicators. Since anthropogenic pressures are expanding apace in the marine environment and policy makers need to use rapid and effective policy measures for fast-changing environments, this modeling framework is an essential asset in supporting and guiding EU policy needs and decisions ; BM-K acknowledges funding from EU-H2020 project ClimeFish (grant agreement 677039), CL received support from the project CAMPUS funded by the Natural Environment Research Council and Defra (grant agreement NERC UK NE/RE007241/1). FM was funded by the SOMBEE project of the joint BiodivERsA and Belmont Forum call "BiodivScen 2018" (ANR-18-EBI4-0003-01). KD received support from the National Academies of Sciences Engineering and Medicine Gulf Research Program (Early Career Research Fellowship). MC acknowledges partial funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no 869300 (FutureMARES project). This work acknowledges institutional support of the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000928-S) ; Peer reviewed

'Food Webs and the Dynamics of Marine Reefs' summarizes recent developments in the ecology of kelp forests and coral reefs in order to develop an understanding of the general principles of their ecological organization and how they might be managed from an ecosystem perspective.

8 pages, 4 figures, 1 table ; Understanding how marine ecosystems are structured and how they function is a scientific challenge. Nowadays, to learn about ecosystem trophic dynamics ecologists use two complementary methodological approximations, mass-balance ecosystem models and isotopic tools. However, despite the wide applications of these methodologies, the comparison and combination of both are still scarce. The aim of this study was to examine the trophic dynamics of representative species of the South Catalan marine ecosystem (North-western Mediterranean) using the Ecopath ecosystem modelling tool and the stable isotope approach. By using the two methodologies we depicted the trophic position (trophic level and δ15N values) and trophic width (omnivory index and total isotopic area) of several species of fish, cephalopods, cetaceans, seabirds and one sea turtle. Our results show a clear correlation between the trophic levels estimated by the Ecopath model and the δ15N values, which validate the trophic position of several species in the study area and indicate that both methodologies are useful to determine the trophic position of marine species in Mediterranean marine food webs. In contrast, the two estimators of trophic width (the omnivore index and the total isotopic area) were not strongly related, since the relationship between modelling and stable isotope results was evident only for some species. Further comparisons of trophic width calculated in other marine food webs may provide a better understanding of our results and validate the accuracy of both methodological approaches to calculate trophic width ; Research funds were provided by three projects from the Spanish Government (REN2000-0878/MAR, P06-RNM-02362, REN2002-00450). J. N. was supported by a postdoctoral contract of the Juan de la Cierva programme (MICINNJDC, Spanish Ministry of Science and Innovation). M. C. was funded by the European Commission through the Marie Curie International Outgoing Fellowships (ECOFUN project, FP7-PEOPLE-2007-4-1-IOF). M.L. was funded by a PhD fellowship of the Balearic Government, as well as by a postdoctoral contract of the Spanish Ministry of Education and Science (EX-2007-1148) and Marie Curie Individual Fellowship (PIEF-GA-2008-220063) ; Peer reviewed

Abstract ; Zs.-Fassung

Trabajo final presentado por Elena Fernandez Corredor para el Máster en Oceanografía y Gestión del Medio Marino impartido por la Universitat de Barcelona (UB) y la Universistat Politècnica de Catalunya (UPC), realizado bajo la dirección de la Dra. Marta Coll y del Dr. Joan Navarro del Institut de Ciències del Mar (ICM-CSIC).-- 49 pages, 15 figures, 4 tables, supplementary material ; Fisheries, climate change and habitat degradation are triggering the depletion of marine animal populations worldwide. In particular, the ecological impacts of the removal of keystone species such as chondrichthyans can be far reaching through the food web. In this study, we investigated the trophic ecology of the 81 Mediterranean chondrichthyan species occurring in the basin through a literature review. We found data for 50 species, which highlights research priorities for the future to complement missing information. Regarding the trophic ecology of studied species, prey composition was compared between taxonomic groups (Batoidea, Selachimorpha and Holocephali), habitats (pelagic and demersal) and sizes (small, medium and large). We found significant differences between taxonomic groups, with dissimilarities mainly due to crustaceans and cephalopods consumption between Batoidea and Selachimorpha. We then represented the Mediterranean meta-web by means of a qualitative modelling approach, putting emphasis on the chondrichthyan groups, with a resulting food web network topology of 73 nodes and 1335 trophic links. Finally, we used the qualitative food web representation to test seven extinction scenarios of chondrichthyans extinctions. We found out that large species, pelagic species and sharks had a major contribution to trophic dissimilarity of the ecosystem when compared to small and medium-sized species, demersal species and rays, respectively. Systems with the former species had also higher omnivory rates. Therefore, conservation efforts within the Mediterranean Sea chondrichthyan community seem to be especially important for these groups. This study provides a first overview of the chondrichthyans ecological role in the Mediterranean Sea marine food web and highlights the urgent need to improve available knowledge on these species and to adopt an ecosystem-based management approach in order to decelerate the depletion of chondrichthyans populations and prevent them from local extinctions, with important effects to the marine food web ; I was supported by a JAE Intro grant of the CSIC (JAEINT200_EX0215) that was extended with funding from the EU FutureMARES project. This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019- 000928-S) and is a contribution to the European Union's Horizon 2020 research and innovation program under grant agreement No 869300 (FutureMARES project)