French Research Institute for Exploitation of the Sea
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Rapport de campagne des nourriceries côtières: Campagnes NOURMANCHE 2024
No full textLa campagne scientifique NOURMANCHE est un dispositif du sous-programme de surveillance du descripteur 1 « Biodiversité – Poissons et céphalopodes ». Elle permet d'acquérir des données en vue du calcul des indicateurs nécessaires au renseignement des critères du bon état écologique pour le D1 (Décision 2017/848/UE). Cette campagne contribue également à la compréhension du fonctionnement des écosystèmes côtiers, au niveau régional (échelle d’une baie ou d'un bassin) et au niveau national (échelle inter-baies et inter-façades).
Le présent rapport décrit les caractéristiques de la campagne NOURMANCHE réalisée en baie du Mont-Saint-Michel, en baie de Seine et en baie de Canche-Authie en 2024. Il compare les résultats des dernières campagnes à ceux collectés depuis le début des séries historiques.
En 2024, 111 opérations de pêche ont été réalisées dans trois nourriceries côtières en Manche. Ces campagnes ont permis la collecte des données concourant au suivi et à la compréhension du fonctionnement des nourriceries en zone côtière, ces habitats essentiels jouant un rôle déterminant dans le recrutement de juvéniles de plusieurs espèces halieutiques
Lieux et périodes à risque 2026 pour les toxines lipophiles. Complément aux prescriptions REPHYTOX
No full textCe document met à jour le complément à la Procédure nationale de la surveillance sanitaire des phycotoxines réglementées dans les zones de production de coquillages. Prescriptions du réseau de surveillance des phycotoxines dans les organismes marins (REPHYTOX). Novembre 2020 - ODE/VIGIES/20-11. https://doi.org/10.13155/56600 Il définit les lieux et les périodes à risque concernant les toxines lipohiles produites par les Dinophysis et pouvant être accumulées par les coquillages. Sur ces lieux, en période à risque, le suivi hebdomadaire systématique est mis en oeuvre
Resource partitioning and trophic niche differentiation in riparian predators of vernal ponds
No full textUnderstanding the factors that drive niche size and overlap is fundamental to predicting species coexistence and community assembly. Predator foraging strategies and interspecific competition play central roles in shaping trophic niches, but many species mitigate competition through trophic or microhabitat differentiation. Environmental factors, such as habitat size and prey availability, can further influence species interactions by altering prey diversity and accessibility. In this study, we investigated isotopic niche partitioning and specialization within a riparian invertebrate carnivore guild, focusing on arachnids and odonates – two dominant predators in vernal pond ecosystems of the New Jersey Pine Barrens. Using stable isotope analysis of carbon (δ13C) and nitrogen (δ15N), we quantified the trophic niches of each group across eight ponds, assessing differences in niche size, overlap, and the role of environmental drivers. Odonates exhibited significantly larger isotopic niches than arachnids, a pattern that may reflect broader, foraging behavior or aggregation of more ecologically variable taxa. Despite these differences, the trophic niches of arachnids and odonates overlapped by approximately one-third, indicating moderate overlap consistent with partial resource partitioning. Such differentiation may reflect divergent prey use or foraging modes that facilitate coexistence despite shared habitat use. Odonate niche size was negatively correlated with pond size and the abundance of certain prey taxa, particularly Coleoptera and Hymenoptera, while arachnid niche size was unaffected by environmental factors. These results suggest that coexistence in this predator guild is maintained through niche differentiation, potentially via differences in spatial or temporal resource use. Our findings highlight the complex interplay between predator behavior and environmental context in shaping trophic interactions within riparian food webs
Early rearing of European seabass (Dicentrarchus labrax) with mild current enrichment modifies fish swimming behavior without altering their growth performance.
No full textThe implementation of conditions that favor optimum swimming activity (e.g., suitable flow regimes), has been associated with enhanced growth and improved welfare in some farmed fish species. Despite the importance of European seabass in aquaculture, the potential beneficial effects of rearing flow conditions have not been sufficiently explored in this species. This study investigates how the application of fast (F, 0.01–0.20 m s-1) or slow (S, <0.01 m s-1) steady flows in rearing tanks for 75-77 days affected physiological and behavioral traits in seabass fingerlings. Growth performance, external and internal morphology, and several physiological variables, including hematocrit, plasma cortisol concentration, and osmotic and ionic balance were not affected by flow conditions during rearing. Also, behavioral tests implemented in groups or isolated individuals suggest that coping styles were not affected by the two tank-rearing conditions. On the contrary, the swimming behavior assessed in tests was modified by the flow condition experienced during rearing. Mean swimming speed, peak acceleration, swimming distance, angular velocity, and meander showed some variability across different tests and time, although consistently displaying higher values in seabass reared in the F condition, suggesting increased activity and more consistent swimming patterns in that group. However, the cumulative time in proximity between individuals measured in behavioral group tests suggested that group cohesion was variable, without displaying differences between F and S groups. These findings have particularly important implications for fish welfare and may suggest plasticity in the behavioral response to rearing conditions for this species, although not affecting the assignment of the individuals to the different coping styles.
Summary statement
We investigated how mild current enrichment applied during early rearing in seabass modifies physiological and behavioral responses involving swimming activity, exploring the potential associations to fish welfare
Prymnesium parvum: Correlation between lytic activity and prymnesin content, both increasing with phosphorus-depletion and lower cell density
No full textThe haptophyte Prymnesium parvum is a widespread microalgae associated with fish kill events. It is a mixotrophic alga, which combines different trophic modes of nutrient and energy acquisition, in part relying on the consumption of prey, a process in which its toxins, the prymnesins (PRMs) are suspected to be involved. Investigating toxicity, and more specifically quantifying PRMs, is challenging because of a lack of standards. In this study, two experiments were conducted to better understand the effects of phosphorus sufficiency and deficiency, growth phase and cell density on lytic activity and PRMs content (intra- and extracellular) of one strain of P. parvum (CCAP 946/6). In the first experiment, P. parvum cultures were grown with or without addition of phosphorus as either inorganic nutrient and/or an algal prey (i.e. the cryptophyte Teleaulax amphioxeia). In the second experiment, a phosphorus-starved culture of P. parvum was inoculated at three initial cell densities in phosphorus-deficient medium. Detection and quantification of phagotrophic activity and toxin content were performed using flow cytometry and liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS), respectively. In addition, to assess the lytic activity of P. parvum, microalgal bioassays were performed on the supernatant towards a competitor, T. amphioxeia. Our results show for the first time a positive correlation between PRMs content and lytic effect on T. amphioxeia. Interestingly, predation had no effect on the PRMs, neither intra- nor extracellular forms, and the toxin content was mainly influenced by the depletion of inorganic phosphorus. Secondly and unexpectedly, lytic effect and PRMs content were higher at lower cell densities in phosphorus-deficient medium. These data provide new insights into the factors promoting the toxicity of P. parvum which may support the development of standards that could help to understand the role and mode of action of these toxins, and their impact on ecosystems
Reconstructing monthly 20th century salinity fields using a data-driven method and Argo data
No full textThe distribution of ocean salinity is influenced by factors such as ocean currents, freshwater exchanges with the atmosphere, continental inputs, and sea ice formation and melting. Salinity is a fundamental variable in the seawater's equation of state, influencing density, ocean dynamics, and stratification. To understand its distribution and impact, salinity variability must be accurately estimated from in situ observations. In the 20th century, temperature observations were scarce, but salinity data were even more limited, as many instruments measured only temperature. In 2002, the implementation of the Argo observing system improved sampling and reduced the disparity between both variables. Salinity variability can now be better assessed from the 20-year Argo period. In this study, information from the Argo period and estimates of salinity covariability with temperature are used to reconstruct monthly subsurface salinity fields. The reconstruction uses in situ measurements and employs the data-driven RedAnDA scheme, which combines Data Assimilation, Analog Prediction, and Reduced-space Interpolation, a method previously validated for temperature reconstruction. The coupling of temperature and salinity is achieved using density-weighted three-dimensional empirical orthogonal functions. The method is applied to the tropical Pacific to evaluate its ability to reconstruct variability at monthly, interannual and decadal timescales, with emphasis on ENSO-related variability, which is the primary mode of variability in the region. Compared to Optimal Interpolation results, salinity analysis by RedAnDA shows significant improvements. The results yield a salinity product that provides valuable insights into historical salinity variability, including fresh pool displacements and salinity-driven stratification changes. Changes in subsurface salinity associated with El Ni & ntilde;o and La Ni & ntilde;a events are estimated from 1930 to 2001
Using Niche Analysis as a Foundation for a New Diatom-Based Biotic Index in Transitional Waters
No full textMicrophytobenthos (MPB) are microscopic, photosynthetic organisms that colonise the top millimetres of intertidal sediments, forming biofilms during low tide. This benthic group can constitute the main primary producers in estuaries and deliver several key ecosystem services, yet its potential as bioindicators in transitional waters remains largely untapped, unlike the widespread use of benthic microalgae in freshwater systems. This study employs a niche-based approach to estimate the indicator (vi) and sensitivity (si) values of 160 estuarine benthic diatom taxa, as originally proposed by Zelinka and Marvan (1961). Species’ ecological niches were analysed using the Outlying Mean Index (OMI) ordination method, based on biomass-weighted occurrence data and environmental variables collected from muddy sediments in the polyhaline zones of three European estuaries. Taxonomic harmonisation was ensured across all datasets.Analysis of niche breadth (tolerance) and position (marginality) revealed that 64% occurred under average environmental conditions, exhibiting both low marginality and low tolerance. Species with narrower niches were identified as having greater indication potential, while marginality values informed categorisation into low, intermediate, or high sensitivity classes. High marginality species occurred in fewer than 20% of samples, and marginality was negatively correlated with occurrence frequency. Epipelic diatoms demonstrated significantly higher marginality than tychoplanktonic forms, suggesting greater habitat specificity. A Microphytobenthos Quality Index (indexMPB) was derived using these niche-based parameters and showed a significant negative correlation with ammonium concentration, highlighting its relevance for nutrient pollution assessment. This approach provides a foundation for developing robust, MPB-based indices tailored to transitional water monitoring frameworks
Eléments d’aide à la décision pour le déclenchement d’alertes préventives dans le cadre du REMI – Edition 2025
No full textUn outil statistique basé sur une approche bayésienne, développé en 2020 par l’Ifremer, a permis de : (i) déterminer quels sont les lieux de surveillance REMI pour lesquels la concentration en E. coli est corrélée à l’abondance des pluies ; (ii) pour ces lieux, modéliser les probabilités d’une contamination supérieure à 700 et 4 600 E. coli/100 g de CLI en fonction de la pluviométrie ; (iii) évaluer l’impact sur l’effort de surveillance supplémentaire induit, en fonction du seuil de pluviométrie retenu. Dans le cadre du travail qui a conduit à la création de ce modèle statistique, la durée de six années de résultats a été retenue pour identifier une éventuelle corrélation entre concentration en E. coli dans les coquillages et pluie. Depuis 2022, les résultats de cette modélisation sont actualisés chaque année afin de mettre à jour la sensibilité des lieux REMI à la pluie. Pour ce faire, les résultats plus récents et les éventuelles modifications de lieux REMI ou de station Météo-France de référence sont pris en compte. Une analyse complémentaire est ensuite menée afin d’identifier les lieux REMI les plus sensibles à la pluviométrie et proposer - pour ces lieux uniquement - des éléments d’aide à la décision afin d’alimenter la réflexion sur la mise en place de protocoles locaux d’alertes préventives liées à la pluie. Cette nouvelle édition des éléments d’aide à la décision présente les trois résultats de modélisation les plus récents pour tous les lieux identifiés au moins « sensibles » sur l’une des trois périodes (2016-2021, 2017-2022 et 2018-2023)
The overlooked contribution of the seasonal mixed layer pump to carbon export in low-latitude oceans
No full textThe seasonal mixed layer pump (MLP) is an important pathway transporting organic carbon from the upper ocean to the ocean interior. While the MLP’s export role has been well-studied in high latitudes, its contribution in low latitudes remains uncertain. Here, we quantify the seasonal MLP-driven carbon export (EMLP) in low-latitude oceans using data from 26 biogeochemical profiling floats. Our analysis reveals that EMLP ranges from −0.9 to 7.6 g C m−2 yr−1, contributing up to 53% of carbon export in certain areas. We find the relative positions of the mixed layer depth, euphotic depth, and nitracline depth regulate EMLP strength in low-latitude oceans. Global extrapolation of these observations across low-latitude oceans yields a total EMLP of 0.07 ± 0.02 Pg C yr−1, 75% higher than previous estimates, underscoring the previously underestimated role of the seasonal MLP in low-latitude oceans. These results reveal the controlling mechanisms of low-latitude seasonal MLP and highlight its disproportionately important role in regional ecosystems, particularly in oligotrophic oceans where carbon export pathways are limited
Experimental Evidence of Climate Change Effects on Plankton Community Respiration in European Coastal Waters: Current Insights and Knowledge Gaps in Tested Disturbances and Studied Areas
No full textPlankton community respiration (PCR) plays a central role in aquatic ecosystems, driving the breakdown of organic matter and influencing global carbon cycling through its contribution to the production and consumption of carbon and oxygen. Coastal areas, which serve as critical interfaces between terrestrial and marine ecosystems, are regarded as metabolic hotspots in the oceans, due to their intense biological and biogeochemical activities. Additionally, they are particularly sensitive to the impacts of global climate change. In this regard, this review synthesizes experimental evidence to explore how environmental constraints and climate drivers affect PCR in European coastal waters. In total, 46 studies were found in which PCR was measured during experiments testing the effects of one or multiple global climate change drivers in European coastal waters. Among them, the majority of experiments focused on changes in temperature, nutrient concentrations and stoichiometry, and/or pH, while other stressors were less studied. Many experiments confirmed theoretical predictions, notably regarding the predicted positive effects of increased temperature and nutrient concentrations on metabolism, but more complex responses, often linked to trophic cascade mechanisms and thresholds between positive and negative feedbacks were also often reported. Overall, this review, the first comprehensive synthesis of experimental evidence on PCR in European coastal waters, highlights critical knowledge gaps, notably regarding non- and understudied areas and understudied interactions between stressors that occurs jointly in natural ecosystems. Future research should aim to integrate controlled experiments, long-term monitoring, and modeling approaches to deepen our understanding of PCR dynamics under changing environmental conditions and to predict potential feedbacks to global climate processes