French Research Institute for Exploitation of the Sea
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Characterization of mangrove mudflat sediment contamination by fecal bacteria and trace metals: A multivariate assessment in equatorial marine protected areas in Gabon, Western Central Africa
No full textAmong the most productive ecosystems worldwide, mangroves contribute to global carbon sequestration and play a pivotal role for many species, including supporting the sustainable provision of intertropical fisheries resources. Despite the many essential ecosystem services they provide, mangrove ecosystems are facing increasing anthropogenic pressure, primarily because they develop in littoral areas where human activities are rapidly expanding, causing deforestation, urban extension and pollution. Mangroves cover over 1,700 km² of Gabon’s coastline, stretching within protected zones or located alongside populated areas, raising concerns about the potential impact of pollution. This study assessed pollution levels in mangrove surface sediments from 24 stations in the capital city of Libreville and the two adjacent Marine Protected Areas (MPAs), Akanda and Pongara, where human impact has not been fully characterized. From 2021 to 2023, we measured chlorophyll a, fecal indicator bacteria (FIB: Escherichia coli and fecal streptococci) and six trace metals (As, Cd, Cr, Cu, Pb and Zn). Our results show that while Pongara National Park remains relatively pristine, human influence has resulted in significant contamination of sediments by FIB and trace metals, with Cu, Pb and Zn being associated with boat traffic and fuel spills. Chlorophyll a at the surface of sediments, indicative of microphytobenthic biomass, reflect the eutrophication from urban discharge. Spatial differences in contamination patterns are significant between Libreville and Akanda, and between Akanda and Pongara parks (p 0.05), suggesting a possible rapid dispersion of urban pollution. Despite localized pollution, contamination levels remained generally low, suggesting that patterns are influenced more by the specific characteristics of each area than by MPA status. This study provides a first assessment of pollution pressure on mangrove tidal flats within protected areas in Gabon, emphasizing that the success of MPAs could be enhanced through contamination monitoring to achieve long-term conservation goals.
On the Generalized Dimensions of Physical Measures of Chaotic Flows
No full textWe prove that if µ is the physical measure of a C 2 flow in R d , d ≥ 3, diffeomorphically conjugated to a suspension flow based on a Poincaré application R with physical measure µR, then Dq(µ) = Dq(µR) + 1, where Dq denotes the generalized dimension of order q ̸= 1. The proof is different from those presented in [BSau] and [PS] for uniformly hyperbolic flows, therefore it extends this result also to the case of flows generated by three-dimensional vector fields having a global singular hyperbolic attractor ([AP], [AMe]). We also show that a similar result holds for the local dimensions of µ and, under the additional hypothesis of exact-dimensionality of µR, that our result extends to the case q = 1. We apply these results to estimate the Dq spectrum associated with Rossler systems and turn our attention to Lorenz-like flows, proving the existence of their information dimension and giving a lower bound for their generalized dimensions
Effects of copepod chemical cues on intra- and extracellular toxins in two species of Dinophysis
No full textCopepods may contribute to harmful algal bloom formation by selectively rejecting harmful cells. Additionally, copepods and the chemical cues they exude, copepodamides, have been shown to induce increased toxin production in paralytic and amnesic toxin producing microalgae. However, it is unknown if diarrhetic shellfish toxin (DST) producers such as Dinophysis respond to copepods or copepodamides in a similar fashion. Here we expose laboratory cultures of Dinophysis sacculus and D. acuminata to direct grazing by Acartia sp. copepods or copepodamides and measure their toxins after three days. Total Dinophysis-produced toxins (DPTs), okadaic acid, pectenotoxin-2, and C9-diol ester of okadaic acid, increased by 8 - 45% in D. sacculus but was significantly different from controls only in the highest (10 nM) copepodamide treatment whereas toxin content was not affected in D. acuminata. Growth rate was low across all groups and explained up to 91% of the variation in toxin content. DPTs were redistributed from internal compartments to the extracellular medium in the highest copepodamide treatments (5 - 10 nM), which were two to three times higher than controls and indicates an active release or passive leakage of toxins. Untargeted analysis of endometabolomes indicated significant changes in metabolite profiles for both species in response to the highest copepodamide treatments, independent of known toxins. However, it is not clear whether these are stress responses or caused by more complex mechanisms. The relatively small grazer-induced effect in Dinophysis observed here, compared to several species of Alexandrium and Pseudo-nitzschia reported previously, suggests that DPT production in Dinophysis is likely not induced by copepods, except perhaps in patches with high copepod densities. Thus, DPTs may, represent either a constitutive chemical defence for Dinophysis, or serve an altogether different purpose
Cracking the myth: Bivalve farming is not a CO2 sink
No full textBivalve farming was usually considered as a CO2 source through respiration and calcification, but recent studies suggest its potential as a CO2 sink, prompting exploration of its inclusion in carbon markets. Here we reviewed the scientific basis behind this idea and found that it is not supported by observational and experimental studies. This idea indeed arises from carbon budget models that are based on theoretical misconceptions regarding seawater carbonate chemistry. The main misunderstanding consists of assuming that the carbon trapped in the shell originates from atmospheric CO2 when it mostly comes from (bi)carbonate ions. While these ions originate from atmospheric CO2 through the erosion of minerals over geological time scales, their incorporation into shells does not prompt short-term CO2 compensation. The opposite occurs—calcification releases CO2 in seawater and limits or even prevents the uptake of atmospheric CO2. Some authors suggest that considering the bivalve farm ecosystem could change the perspective on the source/sink issue but there is no evidence for that now. Most ecosystem-based carbon budget models rely on several unverified assumptions and estimates. Although challenging, field measurements must be conducted for monitoring, reporting, and verifying atmospheric CO2 uptake before qualifying for carbon credits. To achieve scientific consensus, we need reinforcing measurement-based studies of CO2 fluxes in shellfish ecosystems, integrating carbon balance models with observational and experimental science, and fostering interdisciplinary collaboration. Although bivalve farming provides numerous environmental benefits and is vital for sustainable aquaculture, there is currently no evidence that it contributes to CO2 capture
FISH, a new tool for in situ preservation of RNA in tissues of deep-sea mobile fauna
No full textAccessing the metabolic functioning of deep-sea animals in situ remains a technological challenge as the recovery time of samples is incompatible with the short lifespan of such molecules as mRNAs. Tools able to preserve RNA in situ exist but they are incompatible with the study of mobile fauna. Here we describe a new sampling tool, named FISH (Fixer In situ of Homogenized Substrates), implemented on a submersible and equipped with a number of new specific features to collect and preserve in situ tissue of mobile fauna. Connected to the suction pump of a submersible, FISH incorporates a sampling bowl to which two bottles of a preservative reagent are attached, a suction hose, and a support containing a motor connected to the sampling bowl by a magnetic coupling system. We used the deep-sea hydrothermal shrimpRimicaris exoculatafrom the Mid-Atlantic Ridge as a model to test the suitability of our new tool. FISH was compared to two other sampling methods, which use a metatranscriptomic approach targeting microbial communities associated with cephalothorax symbionts. RNA quality, gene assignment and taxonomic and gene function diversity showed differences between in situ and on-board preservation of tissues. Of the alternative sampling methods tested, the suction sampler was clearly not suitable for RNA-based studies, while pressurized recovery showed results closer to the sample quality obtained with FISH sampling. The FISH sampler has therefore demonstrated to be a cost-effective and reliable tool to efficiently preserve RNA recovered from deep-sea environments
Manuel de l'observateur en criées et sur les lieux de débarquement
No full textCe manuel détaille les missions d’observation dans les criées et sur les lieux de débarquement et se veut un guide opérationnel pour l’observateur sur le terrain. Il décrit les tâches à réaliser et les résultats attendu
Chromatin Structure Around Long Non-Coding RNA (lncRNA) Genes in Schistosoma mansoni Gonads
No full textIn this study, we employed a total of eight distinct modifications of histone proteins (H3K23ac, H3K27me3, H3K36me3, H3K4me3, H3K9ac, H3K9me3, H4K12ac, and H4K20me1) to discern the various chromatin colors encompassing lncRNA genes in both mature and immature gonads of the human parasite Schistosoma mansoni. Our investigation revealed that these chromatin colors exhibit a tendency to aggregate based on the similarities in their metagene shapes, leading to the formation of less than six distinct clusters. Moreover, these clusters can be further grouped according to their resemblances by shape, which are co-linear with specific regions of the genes and potentially associated with transcriptional stages
The Ocean System Pathways (OSPs): A New Scenario and Simulation Framework to Investigate the Future of the World Fisheries
No full textThe Fisheries and Marine Ecosystems Model Intercomparison Project (FishMIP) has dedicated a decade to unraveling the future impacts of climate change on marine animal biomass. FishMIP is now preparing a new simulation protocol to assess the combined effects of both climate and socio-economic changes on marine fisheries and ecosystems. This protocol will be based on the Ocean System Pathways (OSPs), a new set of socio-economic scenarios derived from the Shared Socioeconomic Pathways (SSPs) widely used by the Intergovernmental Panel on Climate Change (IPCC). The OSPs extend the SSPs to the economic, governance, management and socio-cultural contexts of large pelagic, small pelagic, benthic-demersal and emerging fisheries, as well as mariculture. Comprising qualitative storylines, quantitative model driver pathways and a “plug-in-model” framework, the OSPs will enable a heterogeneous suite of ecosystem models to simulate fisheries dynamics in a standardised way. This paper introduces this OSP framework and the simulation protocol that FishMIP will implement to explore future ocean social-ecological systems holistically, with a focus on critical issues such as climate justice, global food security, equitable fisheries, aquaculture development, fisheries management, and biodiversity conservation. Ultimately, the OSP framework is tailored to contribute to the synthesis work of the IPCC. It also aims to inform ongoing policy processes within the United Nations Food and Agriculture Organization (FAO). Finally, it seeks to support the synthesis work of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), with a particular focus on studying pathways relevant for the United Nations Convention on Biological Diversity.
Key Points
We present new scenarios and models for simulating fisheries and marine ecosystems, accounting for climate and socio-economic changes
Our scenario framework extends the SSPs. It can be utilized by any marine ecosystem model and in particular those contributing to FishMIP
We propose a simulation strategy addressing major research gaps and including policy-targeted simulation experiments
Plain Language Summary
The Fisheries and Marine Ecosystems Model Intercomparison Project (FishMIP) has spent 10 years studying how climate change might affect marine life. FishMIP is now getting ready for simulating how climate and socio-economic changes will affect marine fisheries worldwide. For this purpose, FishMIP develops the Ocean System Pathways (OSPs), a new set of scenarios that extend the scenarios used by the Intergovernmental Panel on Climate Change (IPCC) by considering the socio-economic factors related to different types of fishing and mariculture. The OSPs detail what might happen in the future and provide tools that will allow the ecosystem models involved in FishMIP to simulate fisheries in a consistent way. This paper presents the OSP framework and the simulation strategy adopted to explore how ecosystems and fisheries might change in the future, focusing on key issues such as climate justice, food security, equitable fisheries management, and biodiversity conservation. Ultimately, this work will contribute to the IPCC and to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) in understanding how to manage the impacts of climate change. It will also support the Food and Agriculture Organization of the United Nations (FAO) in assessing fisheries policies in the context of global change
Development of a Zebrafish Embryo-Based Test System for Thyroid Hormone System Disruption: 3Rs in Ecotoxicological Research
No full textThere is increasing concern regarding pollutants disrupting the vertebrate thyroid hormone (TH) system, which is crucial for development. Thus, identification of TH system–disrupting chemicals (THSDCs) is an important requirement in the Organisation for Economic Co-operation and Development (OECD) testing framework. The current OECD approach uses different model organisms for different endocrine modalities, leading to a high number of animal tests. Alternative models compatible with the 3Rs (replacement, reduction, refinement) principle are required. Zebrafish embryos, not protected by current European Union animal welfare legislation, represent a promising model. Studies show that zebrafish swim bladder inflation and eye development are affected by THSDCs, and the respective adverse outcome pathways (AOPs) have been established. The present study compared effects of four THSDCs with distinct molecular modes of action: Propylthiouracil (PTU), potassium perchlorate, iopanoic acid, and the TH triiodothyronine (T3) were tested with a protocol based on the OECD fish embryo toxicity test (FET). Effects were analyzed according to the AOP concept from molecular over morphological to behavioral levels: Analysis of thyroid- and eye-related gene expression revealed significant effects after PTU and T3 exposure. All substances caused changes in thyroid follicle morphology of a transgenic zebrafish line expressing fluorescence in thyrocytes. Impaired eye development and swimming activity were observed in all treatments, supporting the hypothesis that THSDCs cause adverse population-relevant changes. Findings thus confirm that the FET can be amended by TH system–related endpoints into an integrated protocol comprising molecular, morphological, and behavioral endpoints for environmental risk assessment of potential endocrine disruptors, which is compatible with the 3Rs principle. Environ Toxicol Chem 2024;00:1–18. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC
Combining surface drifters and high resolution global simulations enables the mapping of internal tide surface energy
No full textBy dissipating energy and generating mixing, internal tides (ITs) play a major role in the climatological evolution of the ocean. Our understanding of this class of ocean variability is however hindered by the rarity of observations capable of capturing ITs with global coverage. The data provided by the Global Drifter Program (GDP) offer high temporal resolution and quasi-global coverage, thus bringing promising perspectives. However, due to their inherent drifting nature, these instruments provide a distorted view of the IT signal. By theoretically rationalizing this distortion and leveraging a massive synthetic drifter numerical simulation, we are able to map semi-diurnal IT energy levels from GDP data and compare it to three datasets (two numerical simulations, and a satellite altimetry IT atlas). We find that all numerical simulations exhibit biases. Nonetheless, the simulation that benefited from dedicated attention towards ITs representation performs best. This supports renewed efforts in the concurrent numerical modeling of ITs / ocean circulation. The substantial deficit of energy in the IT atlas highlights the inability for altimetric estimates to measure incoherent and finer scale ITs and strongly supports the need to isolate ITs signature in the data collected by the new wide-swath altimetry mission SWOT