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Fine-scale fronts as hotspots of fish aggregation in the open ocean [article]

Alberto Baudena, Enrico Ser-Giacomi, Donatella d'Onofrio, Xavier Capet, Cedric Cotté, Yves Cherel, Francesco d'Ovidio
2019 bioRxiv   pre-print
Oceanic Lagrangian Coherent Structures have been shown to deeply influence the distribution of primary producers and, at the other extreme of the trophic chain, top predators. However, the relationship between these structures and intermediate trophic levels is much more obscure. In this paper we address this knowledge gap by comparing acoustic measurements of mesopelagic fish concentrations to satellite-derived fine-scale Lagrangian Coherent Structures in the open ocean. The results
more » ... unambiguously that higher fish concentrations are significantly associated with stronger Lagrangian Coherent Structures, and we observe that these features represent a limiting condition for high fish concentrations. A model, specifically built for mid trophic levels with realistic parameters, provides a possible mechanism of fish aggregation, and is coherent with the observations. These results may help to integrate intermediate trophic levels in trophic models, which can ultimately support management and conservation policies.
doi:10.1101/2019.12.16.877571 fatcat:plnbycmplbaoxc7p3bwantwg44

Frontal Systems as Mechanisms of Fish Aggregation [chapter]

Alberto Baudena, Francesco d'Ovidio, Guido Boffetta, Silvia De Monte
2016 First Complex Systems Digital Campus World E-Conference 2015  
In contrast to terrestrial environments, the open ocean has a dynamics whose timescales overlap with the demography of the organisms it hosts. In particular, so called meso-and submeso-scale processes (1-100 km, days to weeks) have been shown to play a key role in structuring the distribution of phytoplankton, which form the large majority of the base of the trophic chain [2] . However, how the (sub)mesoscale turbulence affect higher trophic levels, which have typically swimming capabilities,
more » ... largely not known. Here we explore the capability of frontal system to aggregate swimming organisms (fish) by analyzing an idealised model of the stretching region which is often found in between mesoscale vortices. The rationale behind this approach is that an optimal niche for fish, defined in terms of physical properties or prey availability, may shrink with time under the coupled effect of stretching and diffusion. If the shrinking speed is less than the fish swimming capability, fish schools originally dispersed over a wide region may move inside a smaller area, and therefore increase their local density. The model is parameterised for one of the most abundant mesopelagic fish, the myctophid [4], particularly important in the Southern Ocean, using physical conditions representative of their environment.
doi:10.1007/978-3-319-45901-1_19 fatcat:tcscaw5lg5cbhhngkosipjk7ma

Drifting Speed of Lagrangian Fronts and Oil Spill Dispersal at the Ocean Surface

Gina Fifani, Alberto Baudena, Milad Fakhri, Georges Baaklini, Yannice Faugère, Rosemary Morrow, Laurent Mortier, Francesco d'Ovidio
2021 Remote Sensing  
Due to its dire impacts on marine life, public health, and socio-economic services, oil spills require an immediate response. Effective action starts with good knowledge of the ocean dynamics and circulation, from which Lagrangian methods derive key information on the dispersal pathways present in the contaminated region. However, precise assessments of the capacity of Lagrangian methods in real contamination cases remain rare and limited to large slicks spanning several hundreds of km. Here we
more » ... address this knowledge gap and consider two medium-scale (tens of km wide) events of oil in contrasting conditions: an offshore case (East China Sea, 2018) and a recent near-coastal one (East Mediterranean, 2021). Our comparison between oil slicks and Lagrangian diagnostics derived from near-real-time velocity fields shows that the calculation of Lagrangian fronts is, in general, more robust to errors in the velocity fields and more informative on the dispersion pathways than the direct advection of a numerical tracer. The inclusion of the effect of wind is also found to be essential, being capable of suddenly breaking Lagrangian transport barriers. Finally, we show that a usually neglected Lagrangian quantity, the Lyapunov vector, can be exploited to predict the front drifting speed, and in turn, its future location over a few days, on the basis of near-real-time information alone. These results may be of special relevance in the context of next-generation altimetry missions that are expected to provide highly resolved and precise near-real-time velocity fields for both open ocean and coastal regions.
doi:10.3390/rs13224499 fatcat:qouci6h5hrgkhmpnjrj6pdg5he

Fine-scale structures as spots of increased fish concentration in the open ocean

Alberto Baudena, Enrico Ser-Giacomi, Donatella D'Onofrio, Xavier Capet, Cedric Cotté, Yves Cherel, Francesco D'Ovidio
2021 Scientific Reports  
The authors would also like to thank Mara Baudena, Bettina Fach, Philippe Koubbi, Mark Ohman, Sara Sergi, Lars Stemmann and Jost von Hardenberg for their helpful advice, and the editor and the anonymous  ... 
doi:10.1038/s41598-021-94368-1 pmid:34349142 pmcid:PMC8338936 fatcat:rzo7u57kpjfwlc7pusblqbd3p4

Lagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples

Enrico Ser-Giacomi, Alberto Baudena, Vincent Rossi, Mick Follows, Sophie Clayton, Ruggero Vasile, Cristóbal López, Emilio Hernández-García
2021 Nature Communications  
AbstractThe study of connectivity patterns in networks has brought novel insights across diverse fields ranging from neurosciences to epidemic spreading or climate. In this context, betweenness centrality has demonstrated to be a very effective measure to identify nodes that act as focus of congestion, or bottlenecks, in the network. However, there is not a way to define betweenness outside the network framework. By analytically linking dynamical systems and network theory, we provide a
more » ... ry-based formulation of betweenness, called Lagrangian betweenness, as a function of Lyapunov exponents. This extends the concept of betweenness beyond the context of network theory relating hyperbolic points and heteroclinic connections in any dynamical system to the structural bottlenecks of the network associated with it. Using modeled and observational velocity fields, we show that such bottlenecks are present and surprisingly persistent in the oceanic circulation across different spatio-temporal scales and we illustrate the role of these areas in driving fluid transport over vast oceanic regions. Analyzing plankton abundance data from the Kuroshio region of the Pacific Ocean, we find significant spatial correlations between measures of diversity and betweenness, suggesting promise for ecological applications.
doi:10.1038/s41467-021-25155-9 pmid:34400636 pmcid:PMC8368092 fatcat:mjso3guf3bgwbo3lg56ujs5zqy

Lagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples [article]

Enrico Ser-Giacomi, Alberto Baudena, Vincent Rossi, Mick Follows, Sophie Clayton, Ruggero Vasile, Cristobal Lopez, Emilio Hernandez-Garcıa
2021 arXiv   pre-print
The study of connectivity patterns in networks has brought novel insights across diverse fields ranging from neurosciences to epidemic spreading or climate. In this context, betweenness centrality has demonstrated to be a very effective measure to identify nodes that act as focus of congestion, or bottlenecks, in the network. However, there is not a way to define betweenness outside the network framework. By analytically linking dynamical systems and network theory, we provide a
more » ... formulation of betweenness, called Lagrangian betweenness, as a function of Lyapunov exponents. This extends the concept of betweenness beyond the context of network theory relating hyperbolic points and heteroclinic connections in any dynamical system to the structural bottlenecks of the network associated with it. Using modeled and observational velocity fields, we show that such bottlenecks are present and surprisingly persistent in the oceanic circulation across different spatio-temporal scales and we illustrate the role of these areas in driving fluid transport over vast oceanic regions. Analyzing plankton abundance data from the Kuroshio region of the Pacific Ocean, we find significant spatial correlations between measures of diversity and betweenness, suggesting promise for ecological applications.
arXiv:1910.04722v2 fatcat:cqu6c7i26rfhdiyyswswwntzzi

Crossroads of the mesoscale circulation

Alberto Baudena, Enrico Ser-Giacomi, Cristóbal López, Emilio Hernández-García, Francesco d'Ovidio
2019 Journal of Marine Systems  
Quantifying the mechanisms of tracer dispersion in the ocean remains a central question in oceanography, for problems ranging from nutrient delivery to phytoplankton, to the early detection of contaminants. Most analyses have been based on Lagrangian concepts of transport, focusing on the identification of features minimizing fluid exchange among regions, or more recently on network tools which focus on connectivity and transport pathways. Neither of these approaches allows ranking the
more » ... cal sites of major water passage and selecting them so that they monitor waters coming from separate parts of the ocean. These are instead key criteria when deploying an observing network. Here we address this issue by estimating at any point the extent of the ocean surface which transits through it in a given time window. With such information we are able to rank the sites with major fluxes that intercept waters originating from different regions. We show that this allows us to optimize an observing network, where a set of sampling sites can be chosen for monitoring the largest flux of water dispersing out of a given region. When the analysis is performed backward in time, this method allows us to identify the major sources which feed a target region. The method is first applied to a minimalistic model of a mesoscale eddy field, and then to realistic satellite-derived ocean currents in the Kerguelen area. In this region we identify the optimal location of fixed stations capable of intercepting the trajectories of 43 surface drifters, along with statistics on the temporal persistence of the stations determined in this way. We then identify possible hotspots of micro-nutrient enrichment for the recurrent spring phytoplanktonic bloom occuring here. Promising applications to other fields, such as larval connectivity, marine spatial planning or contaminant detection, are then discussed.
doi:10.1016/j.jmarsys.2018.12.005 fatcat:g3f7dr2h7vguzc73edncehldky

Interaction of the Antarctic Circumpolar Current With Seamounts Fuels Moderate Blooms but Vast Foraging Grounds for Multiple Marine Predators

Sara Sergi, Alberto Baudena, Cédric Cotté, Mathieu Ardyna, Stéphane Blain, Francesco d'Ovidio
2020 Frontiers in Marine Science  
In the Antarctic Circumpolar Current region of the Southern Ocean, the massive phytoplankton blooms stemming from islands support large trophic chains. Contrary to islands, open ocean seamounts appear to sustain blooms of lesser intensity and, consequently, are expected to play a negligible role in the productivity of this area. Here we revisit this assumption by focusing on a region of the Antarctic Circumpolar Current zone which is massively targeted by marine predators, even if no island
more » ... ilizes this area. By combining high resolution bathymetric data, Lagrangian analyses of altimetry-derived velocities and chlorophyll a observations derived from BGC-Argo floats and ocean color images, we reveal that the oligotrophic nature of the study region considered in low chlorophyll a climatological maps hides in reality a much more complex environment. Significant (chlorophyll a in excess of 0.6 mg/m 3 ) phytoplankton blooms spread over thousands of kilometers and have bio-optical signatures similar to the ones stemming from island systems. By adopting a Lagrangian approach, we demonstrate that these moderate blooms (i) originate at specific sites where the Antarctic Circumpolar Current interacts with seamounts, and (ii) coincide with foraging areas of five megafauna species. These findings underline the ecological importance of the open ocean subantarctic waters and advocate for a connected vision of future conservation actions along the Antarctic Circumpolar Current.
doi:10.3389/fmars.2020.00416 fatcat:eifa62y2fndavacujpyqksnfbi

Matching zooplankton abundance and environment in the South Indian Ocean and Southern Ocean

Claire Godet, Marine Robuchon, Boris Leroy, Cédric Cotté, Alberto Baudena, Ophélie Da Silva, Salomé Fabri-Ruiz, Claire Lo Monaco, Sara Sergi, Philippe Koubbi
2020 Deep Sea Research Part I: Oceanographic Research Papers  
doi:10.1016/j.dsr.2020.103347 fatcat:asrj5wc7jbam7jqg2tf64qefpu

Potenciales cerebrales relacionados con categorización lógica en humanos: estudio descriptivo y planteos experimentales Brain potentiales associated with logic categorization in humans: descriptive study and experimental issues

Angel Tabullo, Patricio Pérez Leguizamón, Federico Sánchez, Pablo Galeano, Enrique Segura, Alberto Yorio
2007 Anuario de Investigaciones  
positivo tardío puede a su vez ser diferenciado por su latencia y topografía en el subcomponente P3a, de latencia mas temprana y predominio en región prefrontal, relacionado con detección de novedad (Baudena  ...  pOTenTialeS aSSOCiaTeD WiTH lOgiC CaTegORiZaTiOn in HUManS: DeSCRipTiVe STUDY anD eXpeRiMenTal iSSUeS Tabullo, angel; pérez leguizamón, patricio; Sánchez, Federico; galeano, pablo; Segura, enrique; Yorio, alberto  ... 
doaj:40e80a60965d4024a0053ecc8384e9d3 fatcat:hy2ncdjwi5hzxgzzxtldigsxcq