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1. Future directions for deep ocean climate science and evidence-based decision making

Author

Helen R. Pillar, Elizabeth Hetherington, Lisa A. Levin, Laura Cimoli, Jonathan M. Lauderdale, Jesse M. A. van der Grient, Kristen Johannes, Patrick Heimbach, Leslie Smith, Charles I. Addey, Pavanee Annasawmy, Sandra Antonio, Narissa Bax, Henri F. Drake, Elva Escobar, Laura G. Elsler, Mara A. Freilich, Natalya D. Gallo, Fanny Girard, Matthew J. Harke, Daniel O. B. Jones, Siddhi Joshi, Xinfeng Liang, Paige J. Maroni, Otmane Sarti, Paris V. Stefanoudis, Olivier Sulpis, and David Trossman

Subjects
deep sea, climate science, evidence-based decision making, IPCC, uncertainty, vulnerability and risk, Environmental sciences, GE1-350
Abstract

IntroductionA defining aspect of the Intergovernmental Panel on Climate Change (IPCC) assessment reports (AR) is a formal uncertainty language framework that emphasizes higher certainty issues across the reports, especially in the executive summaries and short summaries for policymakers. As a result, potentially significant risks involving understudied components of the climate system are shielded from view.MethodsHere we seek to address this in the latest, sixth assessment report (AR6) for one such component—the deep ocean—by summarizing major uncertainties (based on discussions of low confidence issues or gaps) regarding its role in our changing climate system. The goal is to identify key research priorities to improve IPCC confidence levels in deep ocean systems and facilitate the dissemination of IPCC results regarding potentially high impact deep ocean processes to decision-makers. This will accelerate improvement of global climate projections and aid in informing efforts to mitigate climate change impacts. An analysis of 3,000 pages across the six selected AR6 reports revealed 219 major science gaps related to the deep ocean. These were categorized by climate stressor and nature of impacts.ResultsHalf of these are biological science gaps, primarily surrounding our understanding of changes in ocean ecosystems, fisheries, and primary productivity. The remaining science gaps are related to uncertainties in the physical (32%) and biogeochemical (15%) ocean states and processes. Model deficiencies are the leading cited cause of low certainty in the physical ocean and ice states, whereas causes of biological uncertainties are most often attributed to limited studies and observations or conflicting results.DiscussionKey areas for coordinated effort within the deep ocean observing and modeling community have emerged, which will improve confidence in the deep ocean state and its ongoing changes for the next assessment report. This list of key “known unknowns” includes meridional overturning circulation, ocean deoxygenation and acidification, primary production, food supply and the ocean carbon cycle, climate change impacts on ocean ecosystems and fisheries, and ocean-based climate interventions. From these findings, we offer recommendations for AR7 to avoid omitting low confidence-high risk changes in the climate system.

Published
2024
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2. Impact of the citizen science project COLLECT on ocean literacy and well-being within a north/west African and south-east Asian context

Author

Marine I. Severin, Lazare Kouame Akpetou, Pavanee Annasawmy, Francis Emile Asuquo, Fiona Beckman, Mostapha Benomar, Annette Jaya-Ram, Mohammed Malouli, Jan Mees, Ivanice Monteiro, Joey Ndwiga, Péricles Neves Silva, Olubunmi Ayoola Nubi, Yee Kwang Sim, Zacharie Sohou, Aileen Tan Shau-Hwai, Sau Pinn Woo, Soukaina Zizah, Ann Buysse, Filip Raes, Lilian A. Krug, Sophie Seeyave, Gert Everaert, Edem Mahu, and Ana I. Catarino

Subjects
plastic pollution, beach sampling, citizen science, ocean literacy, pro-environmental intentions, well-being, Psychology, BF1-990
Abstract

Plastic pollution is both a societal and environmental problem and citizen science has shown to be a useful tool to engage both the public and professionals in addressing it. However, knowledge on the educational and behavioral impacts of citizen science projects focusing on marine litter remains limited. Our preregistered study investigates the impact of the citizen science project Citizen Observation of Local Litter in coastal ECosysTems (COLLECT) on the participants’ ocean literacy, pro-environmental intentions and attitudes, well-being, and nature connectedness, using a pretest-posttest design. A total of 410 secondary school students from seven countries, in Africa (Benin, Cabo Verde, Côte d’Ivoire, Ghana, Morocco, Nigeria) and Asia (Malaysia) were trained to sample plastics on sandy beaches and to analyze their collection in the classroom. Non-parametric statistical tests (n = 239 matched participants) demonstrate that the COLLECT project positively impacted ocean literacy (i.e., awareness and knowledge of marine litter, self-reported litter-reducing behaviors, attitudes towards beach litter removal). The COLLECT project also led to higher pro-environmental behavioral intentions for students in Benin and Ghana (implying a positive spillover effect) and higher well-being and nature connectedness for students in Benin. Results are interpreted in consideration of a high baseline in awareness and attitudes towards marine litter, a low internal consistency of pro-environmental attitudes, the cultural context of the participating countries, and the unique settings of the project’s implementation. Our study highlights the benefits and challenges of understanding how citizen science impacts the perceptions and behaviors towards marine litter in youth from the respective regions.

Published
2023
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3. Addressing data gaps in marine litter distribution: Citizen science observation of plastics in coastal ecosystems by high-school students

Author

Ana I. Catarino, Edem Mahu, Marine I. Severin, Lazare Kouame Akpetou, Pavanee Annasawmy, Francis Emile Asuquo, Fiona Beckman, Mostapha Benomar, Annette Jaya-Ram, Mohammed Malouli, Jan Mees, Ivanice Monteiro, Joey Ndwiga, Péricles Neves Silva, Olubunmi Ayoola Nubi, Patricia Martin-Cabrera, Yee Kwang Sim, Zacharie Sohou, Sau Pinn Woo, Soukaina Zizah, Gert Everaert, Aileen Tan Shau-Hwai, Lilian A. Krug, and Sophie Seeyave

Subjects
citizen science, plastic pollution, marine litter, microplastics, beach sampling, ocean literacy, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

The Citizen Observation of Local Litter in coastal ECosysTems (COLLECT) project (2021-2022) is a citizen science initiative, supported by the Partnership for Observation of the Global Ocean (POGO), which aimed to acquire distribution and abundance data of coastal plastic litter in seven countries: in Africa (Benin, Cabo Verde, Côte d’Ivoire, Ghana, Morocco, Nigeria) and Asia (Malaysia). In this paper, we describe the workflow used to establish and run this project, as well as the methodologies to acquire data. The COLLECT project consisted of training local students (15 - 18 years old) from ten second cycle institutions (“high schools”) on sampling and analyzing macro-, meso- and microplastics in beach sediments, using a quantitative assessment protocol. We further describe in detail the methodologies applied in assessing the impact of participating in the activities from a social sciences perspective. All documents and materials resulting from this project will be open access and available according to the FAIR Principles (Findable, Accessible, Interoperable, and Reusable). The results and outcomes from COLLECT will contribute to expanding knowledge and establishing baseline information on coastal plastic pollution, with citizen science being an enabler of open science, allowing data to be freely available to the public, academics and policymakers. Expected results from the use of the COLLECT protocol globally will further contribute to the identification of hotspots of coastal plastic litter, and bring awareness to local communities on the potential consequences of plastic pollution. The COLLECT project actively contributes with data suitable to survey plastic litter to the United Nations’ Sustainable Development Goals (UN SDGs), in particular to SDG 14, on the sustainable use of the ocean.

Published
2023
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4. Antarctic krill (Euphausia superba) distributions, aggregation structures, and predator interactions in Bransfield Strait

Author

Pavanee Annasawmy, John K. Horne, Christian S. Reiss, George R. Cutter, and Gavin J. Macaulay

Subjects
General Agricultural and Biological Sciences
Abstract

Aggregation structures of Antarctic krill (Euphausia superba) and predator interactions were investigated using active acoustic data collected for approximately one month by WBAT and Signature100 echosounders deployed on moorings in two hydrographically different sites in Bransfield Strait. Near Nelson Island, water flows from the northwest to southeast while Deception Island is influenced by the Bransfield Front with stronger net current velocities from the southwest to northeast. Krill aggregations were identified and then classified in three clusters using a swarm-identification algorithm and hierarchical clustering using aggregation morphological characteristics: acoustic density, mean depth, center of mass, inertia, equivalent area, aggregation index, and proportion occupied. A total of 693 and 736 aggregations were detected at the mooring sites close to Nelson and Deception Islands. The three aggregation categories ranged from high to low densities, evenness and dispersion and were distributed throughout the water column. Krill aggregation densities and mean thickness are influenced by current velocities, direction, mean depth, and predator foraging. The majority of observed predator dive profiles occurred over the aggregation type with highest krill densities at both Nelson and Deception Islands, and within the first 25 m of the water column. The heterogeneity of krill aggregations potentially impacts predator foraging strategies and predator-krill interactions in the hydrodynamically active Bransfield Strait.

Published
2023
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5. Trace elements and δ

Author

Pavanee, Annasawmy, Paco, Bustamante, David, Point, Carine, Churlaud, Evgeny V, Romanov, and Nathalie, Bodin

Subjects
Manganese, Zinc, Fishes, Animals, Cobalt, Indian Ocean, Copper, Trace Elements, Cadmium, Arsenic
Abstract

Trace elements and δ

Published
2022

6. Trace elements and δ15N values in micronekton of the south-western Indian Ocean

Author

Pavanee Annasawmy, Paco Bustamante, David Point, Carine Churlaud, Evgeny V. Romanov, Nathalie Bodin, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Centre technique de recherche et de valorisation des milieux aquatiques (CITEB), and Sustainable Ocean Seychelles (SOS)

Subjects
Myctophids, Principal Component Analysis, Squids, Fishes, Seamounts, Body size, [SDV.TOX.ECO]Life Sciences [q-bio]/Toxicology/Ecotoxicology, Aquatic Science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Oceanography, Pollution, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Crustaceans
Abstract

International audience; Trace elements and δ 15 N values were analysed in micronekton (crustaceans, fishes and squids) sampled in the southwestern Indian Ocean. Myctophids were associated with high concentrations of arsenic at La Pérouse and MAD-Ridge seamounts, and with lead and manganese at MAD-Ridge and in the Mozambique Channel. The difference in cadmium, copper and zinc concentrations between micronekton broad categories reflected differing metabolic and storage processes. When significant, negative relationships were found between micronekton body size and trace element concentrations, which can possibly be attributed to differing metabolic activity in young and old individuals, dietary shifts and/or dilution effect of growth. No relationships were found between trace element concentrations and δ 15 N values of micronekton (except cobalt which decreased with increasing δ 15 N values), since most trace elements are not biomagnified in food webs due to regulation and excretion processes within organisms. All trace element pairs were positively correlated in fishes suggesting regulation processes.

Published
2022
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7. Mercury concentrations and stable isotope ratios (δ

Author

Pavanee, Annasawmy, David, Point, Evgeny V, Romanov, and Nathalie, Bodin

Subjects
Food Chain, Nitrogen Isotopes, Humans, Mercury, Indian Ocean, Water Pollutants, Chemical, Environmental Monitoring
Abstract

Mercury (Hg) concentrations and stable isotope values (δ

Published
2021

8. Micronekton distribution as influenced by mesoscale eddies, Madagascar shelf and shallow seamounts in the south-western Indian Ocean: an acoustic approach

Author

Pascal Cotel, Steven Herbette, Pavanee Annasawmy, Jean-François Ternon, Anne Lebourges-Dhaussy, Francis Marsac, Frédéric Ménard, Gildas Roudaut, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), University of Cape Town, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), The study was mainly supported by the Flotte Océanographique Française (French Oceanographic Fleet) and the Institut de Recherche pour le Développement (IRD) in relation to the logistics of the RV Antea. Additional funding was received from the Conseil Régional de la Reunion (Réunion Regional Council, Bop 123/2016) for the La Pérouse cruise, and from the Fonds Français pour l’Environnement Mondial (FFEM) as part of the FFEM-SWIO project on Areas Beyond National Jurisdiction (ABNJ) of the South West Indian Ocean for the MAD-Ridge cruise. The first author was the beneficiary of a doctoral bursary granted by IRD (France) and the ICEMASA French-South African International Laboratory., Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Diel vertical migration, 010504 meteorology & atmospheric sciences, Mesopelagic zone, Seamount, Mesoscale meteorology, Oceanography, 01 natural sciences, South-western indian ocean, Water column, Ocean gyre, Mesoscale eddies, 14. Life underwater, Micronekton, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Multi-frequency, 010604 marine biology & hydrobiology, Acl, Madagascar shelf, 13. Climate action, Anticyclone, Cyclone, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract

International audience; An investigation of the vertical and horizontal distributions of micronekton, as influenced by mesoscale eddies, the Madagascar shelf and shallow seamounts, was undertaken using acoustic data collected during two research cruises at an unnamed pinnacle (summit depth ~240 m) thereafter named “MAD-Ridge”, and at La Pérouse seamount (~60 m) in the south-western Indian Ocean. MAD-Ridge is located to the south of Madagascar, in an “eddy corridor”, known both for its high mesoscale activity and high primary productivity. In contrast, La Pérouse is located on the outskirts of the Indian South Subtropical Gyre (ISSG) province, characterised by low mesoscale activity and low primary productivity. During the MAD-Ridge cruise, a dipole was located in the vicinity of the seamount, with the anticyclone being almost stationary on the pinnacle. Total micronekton acoustic densities were greater at MAD-Ridge than at La Pérouse. Micronekton acoustic densities of the total water column were lower within the anticyclone than within the cyclone during MAD-Ridge. Micronekton followed the usual diel vertical migration (DVM) pattern, except within the cyclone during MAD-Ridge where greater acoustic densities were recorded in the daytime surface layer. The backscatter intensities were stronger at the 38 kHz than at the 70 and 120 kHz frequencies in the daytime surface layer at MAD-Ridge cyclonic stations. These backscatter intensities likely correspond to gas-filled swimbladders of epi- and mesopelagic fish actively swimming and feeding within the cyclone or gelatinous organisms with gas inclusions. Our findings evidenced that the distributions of micronekton and DVM patterns are complex and are influenced significantly by physical processes within mesoscale eddies. The mesoscale eddies’ effects were dominant over any potential seamount effects at the highly dynamic environment prevailing at MAD-Ridge during the cruise. No significant increase in total micronekton acoustic densities was observed over either seamount, but dense aggregations of biological scatterers were observed on their summits during both day and night.

Published
2020
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9. Seamount effect on circulation and distribution of ocean taxa in the vicinity of La Pérouse, a shallow seamount in the southwestern Indian Ocean

Author

Francis Marsac, Pascal Bach, Jacques Grelet, Marc Soria, Evgeny V. Romanov, Yves Cherel, Pavanee Annasawmy, Margaux Noyon, Njaratiana Rabearisoa, Hervé Demarcq, Institut de Recherche pour le Développement (IRD) [Sete, France], Institut de Recherche pour le Développement (IRD), Ocean Sciences & Marine Food Security [Port Elizabeth, South Africa], Nelson Mandela Metropolitan University [Port Elizabeth, South Africa], Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Instrumentation, Moyens analytiques, Observatoires en Géophysique et Océanographie (IMAGO), Centre technique d’appui à la pêche réunionnaise (CAP RUN)-NEXA [Ile de la Réunion], Nelson Mandela University [Port Elizabeth], and La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Seamount, Stomach contents, Oceanography, Pelagic longline fisheries, 01 natural sciences, Zooplankton, Mesoscale eddies, Phytoplankton, Bathymetry, 14. Life underwater, L-ADCP, Micronekton, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, biology, Albacore, 010604 marine biology & hydrobiology, Swordfish, Pelagic zone, biology.organism_classification, Mesozooplankton, [SDE]Environmental Sciences, Tuna, Geology
Abstract

International audience; The La Pérouse seamount (60 m depth) has so far been poorly studied despite it being a short distance (160 km) from Réunion Island. As part of the MADRidge project, a multidisciplinary cruise was conducted to evaluate the effect of this shallow seamount on the local hydrology and ecology. Current measurements, temperature and chlorophyll-a profiles, and mesozooplankton and micronekton samples were collected between the summit and 35 km away. Micronekton data were supplemented with stomach content of pelagic top predators as well as fisheries statistics from the domestic longline fleet operating from Réunion. Vertical current profiles revealed distinct patterns between the offshore and seamount-flanked stations, giving evidence of topographical induced flow instabilities, notably on its leeward side (west) relative to the east flank. Distinct patterns in temperature and chlorophyll-a vertical profiles suggest the formation of convergent and divergent circulation cells as a result of the irregular and crescent-like summit topography. Spatial differences in zooplankton abundance were detected with higher biovolumes on the leeward flank. The overall acoustic backscatter for micronekton over the summit was weaker than offshore, but highly concentrated in the upper layer. Albacore tuna and swordfish dominate the longline catch west of Réunion, seemingly in association with a deep (900 m) topographic feature. Yet the largest catch is not directly associated with La Pérouse which would be too shallow for top predators to aggregate around in the long term. Enhanced levels of phytoplankton or zooplankton enrichment at La Pérouse were not demonstrated in this study, nor was there notable diversity of micronekton species. This might explain the relatively limited importance of this seamount to the tuna fisheries in this region.

Published
2020
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10. Mercury concentrations and stable isotope ratios (δ13C and δ15N) in pelagic nekton assemblages of the south-western Indian Ocean

Author

Pavanee Annasawmy, David Point, Evgeny V. Romanov, and Nathalie Bodin

Subjects
Seamount, Fish, Trophic ecology, Crustacean, Mercury, Aquatic Science, Oceanography, Squid, Pollution
Abstract

Mercury (Hg) concentrations and stable isotope values (δ13C and δ15N) were investigated in micronekton collected from La Pérouse and MAD-Ridge seamounts, Reunion Island and the southern Mozambique Channel. Organisms occupying epipelagic habitats showed lower Hg concentrations relative to deeper dwelling benthopelagic ones. Increasing Hg concentrations with increasing body size were recorded in the Mozambique Channel and Reunion Island. Positive relationships were observed between Hg levels and δ15N values in pelagic nekton assemblages collected at MAD-Ridge seamount and the southern Mozambique Channel, suggesting biomagnification of Hg. Concentrations of Hg in organisms across the south-western Indian Ocean were within the same range of values. Total Hg concentrations depend on a range of factors linked to habitat range, body size and trophic position of the individuals. To our knowledge, this is the first study investigating the patterns of Hg concentrations in pelagic nekton assemblages from the south-western Indian Ocean.

Published
2022
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11. Micronekton distributions and assemblages at two shallow seamounts of the south-western Indian Ocean: Insights from acoustics and mesopelagic trawl data

Author

Gildas Roudaut, Evgeny V. Romanov, Yves Cherel, Pavanee Annasawmy, Frédéric Ménard, Anne Lebourges-Dhaussy, Jean-François Ternon, Pascal Cotel, Francis Marsac, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), University of Cape Town, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre technique d’appui à la pêche réunionnaise (CAP RUN)-NEXA [Ile de la Réunion], Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Aix Marseille Université (AMU), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Marine Research Institute and Department of Biological Sciences, Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD [France-Ouest])

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Mesopelagic zone, Seamount, Mesoscale meteorology, Aquatic Science, 01 natural sciences, Ocean gyre, Sunrise, Deep scattering layer, 14. Life underwater, Micronekton, Diel vertical migration, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, ACL, Geology, South-western Indian Ocean, Acoustics, Seamount-associated fauna, Oceanography, Productivity (ecology), [SDU]Sciences of the Universe [physics], [SDE]Environmental Sciences, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract

International audience; Micronekton distributions and assemblages were investigated at two shallow seamounts of the south-western Indian Ocean using a combination of trawl data and multi-frequency acoustic visualisation techniques. La Pérouse (∼60 m) seamount is located on the outskirts of the oligotrophic Indian South Subtropical Gyre province with weak mesoscale activities and low primary productivity all year round. The “MAD-Ridge” seamount (thus termed in this study; ∼240 m) is located in the productive East African Coastal (EAFR) province with high mesoscale activities to the south of Madagascar. This resulted in higher micronekton species richness at MAD-Ridge compared to La Pérouse. Resulting productivity at MAD-Ridge seamount was likely due to the action of mesoscale eddies advecting larvae and productivity from the Madagascar shelf rather than local dynamic processes such as Taylor column formation. Mean micronekton abundance/biomass, as estimated from mesopelagic trawl catches, were lower over the summit compared to the vicinity of the seamounts, due to net selectivity and catchability and depth gradient on micronekton assemblages. Mean acoustic densities in the night shallow scattering layer (SSL: 10-200 m) over the summit were not significantly different compared to the vicinity (within 14 nautical miles) of MAD-Ridge. At La Pérouse and MAD-Ridge, the night and day SSL were dominated by common diel vertical migrant and non-migrant micronekton species respectively. While seamount-associated mesopelagic fishes such as Diaphus suborbitalis (La Pérouse and MAD-Ridge) and Benthosema fibulatum performed diel vertical migrations (DVM) along the seamounts’ flanks, seamount-resident benthopelagic fishes, including Cookeolus japonicus (MAD-Ridge), were aggregated over MAD-Ridge summit both during the day and night. Before sunrise, mid-water migrants initiated the first vertical migration event from the intermediate to the deep scattering layer (DSL, La Pérouse: 500-650m; MAD-Ridge: 400-700 m) or deeper. During sunrise, the other taxa contributing to the night SSL exhibited a successive series of vertical migration events from the surface to the DSL or deeper. Some scatterers were blocked in their upward and downward migrations due to the seamount topography, more commonly known as the sound scattering layer interception/topographic blockage hypothesis. Possible mechanisms leading to the observed patterns in micronekton vertical and horizontal distributions are discussed. This study contributes to a better understanding of how seamounts influence the diel vertical migration, horizontal distribution and community composition of micronekton and seamount-associated/resident species at two poorly studied shallow topographic features in the south-western Indian Ocean.

Published
2019
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12. Micronektonic fish species over three seamounts in the southwestern Indian Ocean

Author

Delphine Thibault, Evgeny V. Romanov, Pavanee Annasawmy, Frédéric Ménard, Yves Cherel, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre technique d’appui à la pêche réunionnaise (CAP RUN)-NEXA [Ile de la Réunion], MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Mesopelagic zone, Seamount, Argyripnus, Oceanography, 01 natural sciences, Abundance (ecology), Diaphus, Ceratoscopelus warmingii, 14. Life underwater, Sigmops elongatus, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, biology, 010604 marine biology & hydrobiology, Pelagic zone, biology.organism_classification, Lanternfish, Tropical waters, Taxon, [SDE]Environmental Sciences, Diaphus suborbitalis
Abstract

International audience; Taxonomic composition, abundance and biological features of micronektonic fish were investigated using pelagic trawls conducted near and over the summits of three seamounts located in the western Indian Ocean (La P�erouse, MAD-Ridge and Walters Shoal). Mesopelagic fish from three families accounted for 80% by number of the total catch (5714 specimens, 121 taxa), namely myctophids (59%), gonostomatids (12%) and sternoptychids (9%). Whereas the gonostomatid Sigmops elongatus was the most abundant species around La P�erouse seamount, myctophids were the most diverse and dominant group by number in all three studied areas. Most myctophids were high-oceanic species, which included the numerically dominant Benthosema suborbitale, Ceratoscopelus warmingii, Diaphus perspicillatus, Hygophum hygomii, and Lobianchia dofleini. The few remaining myctophids (Diaphus suborbitalis being the most abundant) were pseudoceanic fish, highlighting the association with land-masses. The study adds one myctophid species new to the Indian Ocean (Diaphus bertelseni), and a second record in the literature of the recently described sternoptychid Argyripnus hulleyi.

Published
2020
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13. Stable isotope patterns of mesopelagic communities over two shallow seamounts of the south-western Indian Ocean

Author

François Le Loc'h, Frédéric Ménard, Francis Marsac, Evgeny V. Romanov, Pavanee Annasawmy, Jean-François Ternon, Yves Cherel, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Marine Research Institute and Department of Biological Sciences, University of Cape Town, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre technique d'appui à la pêche réunionnaise (CAP RUN - CITEB) [France], Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), ICEMASA, This study was mainly supported by the Flotte Océanographique Française (French Oceanographic Fleet) and the Institut de Recherche pour le Développement (IRD) in relation to the logistics of the RV Antea. Additional funding was also received from the Conseil Régional de la Reunion (Réunion Regional Council, Bop 123/2016) for the La Pérouse cruise, and from the Fonds Français pour l’Environnement Mondial (FFEM) as part of the FFEM-SWIO project on Areas Beyond National Jurisdiction (ABNJ) of the South West Indian Ocean for the MAD-Ridge cruise. The first author was the beneficiary of a doctoral bursary granted by the Institut de Recherche pour le Développement (IRD, France) and the ICEMASA French-South African International Laboratory., Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Mesopelagic zone, Seamount, Oceanography, 010603 evolutionary biology, 01 natural sciences, Zooplankton, Trophic level, Predatory fish, 14. Life underwater, Micronekton, Squid, delta N-15, geography, geography.geographical_feature_category, Stable isotope ratio, Acl, 010604 marine biology & hydrobiology, Nekton, Fish δ13C δ15N, δ15N, Crustaceans, Fish, Productivity (ecology), [SDE]Environmental Sciences, δ13C, delta C-13, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract

The stable carbon (delta C-13) and nitrogen (delta N-15) isotope values of soft tissues of micronekton (crustaceans, squid, mesopelagic fish) and zooplankton were measured from organisms collected on the RV Antea at two seamounts located in the south-western Indian Ocean: La Perouse (summit depth similar to 60 m) and "MAD-Ridge" (thus named in this study; summit depth similar to 240 m). Surface particulate organic matter (POM-Surf) showed higher delta C-13 at the more productive MAD-Ridge than at the oligotrophic La Perouse seamount. Particulate organic matter and zooplankton were depleted in N-15 at La Pemuse pinnacle compared with MAD-Ridge. Gelatinous organisms and crustaceans occupied the lowest and intermediate tmphic levels (TL similar to 2 and 3 respectively) at both seamounts. Mesopelagic fish and smaller-sized squid sampled at both seamounts occupied TL similar to 3 to 4, whereas the large nektonic squid, Ommastrephes bartramii, collected at MAD-Ridge only, exhibited a TL of similar to 5. The delta N-15 values of common open-water mesopelagic taxa were strongly influenced by specimen size and feeding habits at both seamounts, with an increase in delta N-15 values with increasing size. Carnivorous fish species sampled exclusively over the seamounts' flanks and summits exhibited TL values of similar to 4, irrespective of their wide size ranges. The work could not demonstrate any differences in delta C-13 values of mesopelagic fish between the seamounts and the surrounding oceanic areas. The study segregated clusters of mesopelagic organisms according to their delta C-13 and delta N-15 values, with variations in stable isotope values reflecting a complex range of processes possibly linked to productivity as well as biological and ecological traits of the species (size and feeding mode).

Published
2020
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14. Micronekton diel migration, community composition and trophic position within two biogeochemical provinces of the South West Indian Ocean: Insight from acoustics and stable isotopes

Author

Gildas Roudaut, Hervé Demarcq, C.L. Moloney, Pavanee Annasawmy, Sébastien Jaquemet, Yves Cherel, J.-F. Ternon, Francis Marsac, Anne Lebourges-Dhaussy, Nolwenn Behagle, Frédéric Ménard, Marine Research Institute and Department of Biological Sciences, University of Cape Town, MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Ecologie marine tropicale dans les Océans Pacifique et Indien (ENTROPIE [Réunion]), Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut de Recherche pour le Développement (IRD), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Biogeochemical cycle, Diel vertical migration, 010504 meteorology & atmospheric sciences, Mesopelagic zone, Aquatic Science, Oceanography, Spatial distribution, 010603 evolutionary biology, 01 natural sciences, Trophic level, East African Coastal province, Ocean gyre, 14. Life underwater, Micronekton, 0105 earth and related environmental sciences, Ecological niche, geography, geography.geographical_feature_category, Swordfish, ACL, 13. Climate action, Indian South Subtropical Gyre, [SDE]Environmental Sciences, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract

Spatial distribution, community composition and trophic roles of micronekton (crustaceans, fishes and squids) were investigated in the Indian South Subtropical Gyre (ISSG) province and the East African Coastal province (EAFR), by combining acoustic surveys, mid-water trawls and stable isotope analyses from scientific cruises conducted in 2009 and 2010. Mesopelagic micronekton performed diel vertical migrations in both provinces, from deep (400–740 m) to surface (0–200 m) layers at dusk and in the opposite direction at dawn, with some species migrating below 740 m. The EAFR province was more dynamic than the oligotrophic ISSG province, with enhanced eddy activity and enhanced yearly productivity. The active enrichment mechanisms in the EAFR, in terms of available primary production, led to high micronekton acoustic density (as a proxy of micronekton abundance) and large micronekton weight and abundance estimates from trawl data. Particulate organic matter in the EAFR exhibited greater enrichment in 13 C and 15 N compared to the ISSG and, consequently, tissues of selected micronekton organisms in the EAFR were more enriched in 15 N (higher δ 15 N values). In both provinces, micronekton encompassed a wide range of isotopic niches, with large overlaps between species. Micronekton and swordfish in the EAFR had an overlapping range of δ 15 N values, contrasting with the ISSG province where swordfish were two trophic levels higher than the sampled micronekton. Our results provide some evidence that the combined action of riverine input and the dynamics of eddies might influence productivity in the EAFR, and hence the abundance of micronekton and the enrichment of tissues in 15 N, compared to the oligotrophic ISSG province.

Published
2018
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