Climatic and nutrient drivers affect long-term phytoplankton temporal trends in coastal lagoons

Understanding how climate influences phytoplankton dynamics is crucial for anticipating temporal trends and cascading consequences on ecosystem functioning under climate change. This study explores long-term dynamics in contrasted Mediterranean lagoons and investigates the effects of climatic (air temperature, rainfall, wind speed) and nutrient (inorganic nutrient concentrations) drivers on phytoplankton chlorophyll a, abundances, and pigment composition. 17 years of summer monitoring were analyzed using univariate trend tests and multivariate approaches to highlight changes and to disentangle the contributions of abiotic factors to phytoplankton variability. Our results revealed contrasts among lagoons in physicochemical conditions and phytoplankton community, which strongly structured their temporal trends. Climatic drivers significantly influenced phytoplankton, but their importance was context-dependent. In nutrient-enriched systems, phytoplankton dynamics were primarily controlled by inorganic nutrient concentrations, while climatic effects were weak by comparison. Conversely, in nutrient-poor systems, climatic signals became more visible and influential: wind events were associated with higher chlorophyll a, warmer conditions with increases in phycoerythrin-rich picocyanobacteria, and rainfall with higher picoeukaryote abundances, potentially through indirect effects on water column stability and nutrient and light availability. However, under nutrient limitation, abundances remained low and dominated by small cells, suggesting that nutrient control exerts the strongest influence on phytoplankton, which may explain why nutrient control tends to mask diffuse climatic signals. Yet, climate change modulates physicochemical patterns and may progressively shape lagoon functioning. This study emphasizes the need to account for lagoon features and vulnerabilities, and supports adaptive and site-specific management strategies to safeguard coastal lagoons under future changes

Platinum and Rare Earth Elements distribution in costal sediments from French western Mediterranean Sea

This study presents the first assessment of Technological Critical Elements (TCE), specifically platinum (Pt) and rare earth elements (REE), in coastal sediments along the French western Mediterranean Sea. These trace elements, increasingly used in advanced technologies, raise particular concerns due to their potential environmental impact. Surface sediment samples were collected from 21 stations along the French Mediterranean coast (from Spain border to Italy including Corsica Island) to evaluate TCE concentrations and identify potential sources. Most of the REE concentrations fell within expected natural levels and were mainly influenced by the geological characteristics of local watersheds, indicating a dominant geogenic origin. When normalized to European Shale, REE distribution patterns exhibited convex shapes, typical of coastal environments. In contrast, localized Pt enrichment were detected at specific sites, particularly in port areas, which could be linked to anthropogenic emissions from vehicular catalytic converters. These results highlight platinum as a relevant emerging contaminant in urban coastal environments. However, unexpected REE and Pt concentrations at the mouth of the Hérault river call for further investigation. This study highlights the importance of integrating geological background and anthropogenic pressures in coastal sediment quality assessments and supports the inclusion of TCE in long -term environmental monitoring programs in the Mediterranean Sea

Plastic Pollution in Leeward, Moorea and Cook Islands (South Pacific): A Baseline Study

Plastic pollution is increasingly affecting the South Pacific, including remote islands and coastal regions of Small Island Developing States (SIDS), yet data remain sparse in many areas. This baseline study presents original data on beach macrolitter and microplastics in surface waters and sediments across six islands of French Polynesia (Moorea, Bora Bora, Tahaa) and the Cook Islands (Aitutaki, Rarotonga), collected during an opportunistic cruise in 2024.Beach surveys revealed high plastic contamination on most sites, with macroplastics (size > 2.5 cm) densities ranging from 18 to 58 items/100 m, exceeding European threshold values (e.g. 22 items/100m) on majority of sampled beaches. Single-use plastics and plastic fragments dominated the debris, with local sources such as tourism and coastal activities clearly identifiable.Surface microplastics (315 µm–5 mm) were found at low densities, ranging from 0 to 4668 particles/km2, confirming relatively low contamination in surface waters. Only 17 particles were detected from 8 manta net tows. Sediment and beach microplastic analysis yielded very limited results, with microplastics found at only two sites (Huahine and Rarotonga), dominated by fragments and colored fibers. These results suggest localized contamination linked to urbanization and tourism rather than widespread oceanic inputs.Despite methodological limitations due to the cruise format, this study contributes rare data from under-sampled regions, supporting long-term monitoring efforts and informing future policy and mitigation actions. The results underline the need to improve regional waste management, which will be beneficial for local societies largely based on tourism

Three-dimensional management needs of deep-sea hydrothermal vent ecosystems

Deep-sea hydrothermal vents form small, unique, and fragile ecosystems that are widely recognized as sites in need of protection. Deep-seabed mining (DSM) is a future threat to hydrothermal ecosystem integrity. In most areas within, and in all areas beyond national jurisdiction, currently proposed protection measures from DSM are unlikely to be sufficient, as only the known active venting sites on the seafloor are intended to be protected from DSM impacts. To ensure effective protection, we propose protecting not only the active vent sites but the entire hydrothermal ecosystems and their transition zones, embracing the seafloor, subseafloor and overlying water column. We discuss how ecological knowledge supports the proposed three-dimensional (3-D) protection. We suggest no DSM extraction or indirect impacts on the seafloor and entire subseafloor within a minimum 50 km diameter (25 km radius) around visible active vents. This will ensure the maintenance of subseafloor connections that are key for ecosystem integrity, as changes in vent fluid conditions can alter all ecosystem functions and services linked to venting activity. In the water column, protection from pollution from the seafloor to surface is suggested to protect vent larvae. This extent spans the entire length of ridges or back-arc basins, with a cross-axial extent of 80 km. We further discuss how international law can contribute to the effective protection of vent ecosystems and transition zones in international waters, and provide guidance for coastal States to safeguard these ecosystems and transition zones within their own maritime areas

Otolith stable isotopes highlight the importance of local nursery areas as the origin of recruits to yellowfin tuna (Thunnus albacares) fisheries in the western Indian Ocean

Yellowfin tuna (Thunnus albacares) supports the second largest tuna fishery worldwide, and in the Indian Ocean, it is overfished and subject to overfishing. This situation presents a significant challenge to fisheries management, requiring effective measures to rebuild and then maintain the stock at sustainable levels. A single stock of yellowfin is currently assumed by the Indian Ocean Tuna Commission (IOTC) for stock assessments in the Indian Ocean. However, the relative contribution of different spawning components to the total catches, and the degree of mixing rates of yellowfin tuna in the Indian Ocean by individuals from different production zones, are still unknown. This study uses otolith core oxygen and carbon stable isotope composition (δ18O and δ13C) of young-of-the-year yellowfin tuna from nursery areas located in the western (FAO Area 51) and eastern (FAO area 57) Indian Ocean, either side of 80 ºE, to establish a reference baseline of isotopic signatures. Then, a mixed population program (HISEA) and Random Forest (RF) assignment approaches were used to predict the most likely origin (west or east) of sub-adult and adult yellowfin tuna captured from four fishery areas of the western Indian Ocean (offshore Pakistan, Seychelles, Reunion, and South Africa) by comparing their otolith core values to that of the baseline. Both approaches show that the western Indian Ocean fisheries are mainly composed of west origin fish (> 95 %). We also found some individuals with an otolith isotopic signature that was not characteristic of either of the samples available in the baseline. We simulated an alternative baseline group formed by individuals with mean and standard deviation δ13C and δ18O values above the maximum ranges of the original baseline. We then used RF to infer again the most likely origin of fish in the mixed sample considering 3 possible sources (west, east, alternative). About one third of the samples were assigned to the alternative group, possibly indicating that they differ in geographical or temporal terms with the origins represented in the original baseline. Findings of otolith stable isotope composition of yellowfin tuna in the western Indian Ocean can provide a more comprehensive understanding of the species’ spatial structure and connectivity beyond the current assumption of an ocean basin single stock

Phenylobacterium Ferrooxidans Sp. Nov., Isolated from a Sub-Surface Geothermal Aquifer in Iceland

A novel bacterial strain, HK31-GT, was isolated from a subsurface geothermal aquifer (Hellisheidi, SW-Iceland) and was characterized using a polyphasic taxonomic approach. Phylogenetic analysis of 16S rRNA gene along with phylogenomic position indicated that the novel strain belongs to the genus Phenylobacterium. Cells are motile Gram-negative bacilli. Physiological characterization showed that strain HK31-GT is a mesophilic bacterium able to grow from 10 to 30 °C, at pH values between 2 and 12 and at NaCl concentrations between 0 and 0.5%. Optimal growth was observed without sodium chloride at 25 °C and pH 6. Strain HK31-GT is chemoorganoheterotroph and its major saturated fatty acids are C18:1ω7c, C16 :1ω6c and C16:0, the predominant quinone is Q-10 and the major polar lipid is phosphatidylglycerol. The new strain also possesses the capacity to use ferrous iron (Fe(II)) as the sole energy source and can also be considered as a chemolithoautotrophic microorganism. The overall genome of strain HK31-GT was estimated to be 4.46 Mbp in size with a DNA G+C content of 67.95%. Genes involved in iron metabolism were identified, but no genes typically involved in Fe(II) oxidation were found. Average nucleotide identity and digital DNA-DNA hybridization values between the genome of strain HK31-GT and the genomes of its closest relatives are below the species delineation threshold. Therefore, given the polyphasic approach used, strain HK31-GT represents a novel species of the genus Phenylobacterium, for which the name Phenylobacterium ferrooxidans sp. nov. is proposed. The type strain is HK31-GT (DSM 116432T = UBOCC-M-3429T= LMG 33376T)

Temporal dynamics of biotic homogenization and differentiation across marine fish communities

Humans have transformed ecosystems through habitat modification, harvesting, species introduction, and climate change. Changes in species distribution and composition are often thought to induce biotic homogenization, defined as a decline in spatial beta diversity through time. However, it is unclear whether homogenization is common in ocean ecosystems and if changes in beta diversity exhibit linear or more complex dynamics. Here, we assessed patterns of homogenization or its converse (differentiation) across more than 175,000 samples of 2,006 demersal fish species from 34 regions spanning six decades and 20% of the planet’s continental shelf area. While ten regions (29%) recorded significant homogenization, eleven (32%) recorded significant differentiation. Non-monotonic temporal fluctuations in beta diversity occurred in 15 regions, highlighting complex dynamics missed by before-and-after snapshots that can drive spurious conclusions about trends in beta diversity. Fishing pressure and temperature helped explain variance in beta diversity across years and regions. However, the strength and direction of these effects differed by region. Here we showed that, despite intense anthropogenic impacts on the oceans, the majority of demersal marine fish communities do not follow the global homogenization paradigm common in other realms

Absence of Coronavirus in terns in the Western Indian Ocean?

We investigated coronavirus circulation in three tern species on four islands of the Western Indian Ocean (Bird, Reunion, Europa, Juan de Nova). None of the 2019 samples tested positive by reverse-transcription polymerase chain reaction. We discuss the implications of these findings in terms of host-species range, ecological drivers of virus transmission, and diagnostic tools

Regional and local variability in the morphometric traits of two emblematic seagrass species (Zostera marina and Zostera noltei) along the French coast

Zostera marina and Zostera noltei are two foundation species that play a crucial role in the functioning of coastal ecosystems. They occur in a wide range of environmental conditions over a large geographical area in the northern hemisphere. The aim of this study was to investigate the scales of variability in the dynamics of these two species in relation to environmental conditions in four sites along the French coasts. We used community trajectory analysis, a multivariate statistical approach that allows quantitative measures and comparisons of ecosystem temporal trajectories. The results show an effect of site position and tidal regime on the seasonal dynamics of the two species. Populations from the southernmost microtidal site showed a seasonal stability in their morphometric traits and a good resistance to present-day climatic conditions. In the meso- and macrotidal regime sites, hydrodynamic conditions and light have led to very different ecological strategies. On the one hand, high tidal currents increased shoot density and root biomass, while on the other hand, low light and less current favoured the development of long leaves to optimise photosynthesis. Finally, variations in meadow development was also observed at the local scale, which requires further investigation to identify the specific drivers. Our discussion suggests that special attention should be paid to interpreting the dynamics of these species according to the scale of observation, and that this diversity of variation scales should be taken into account in conservation measures. In a global context of seagrass bed decline, our study suggests some avenues of research to improve our understanding of seagrass species ecology in order to properly assess the state of coastal waters

Major data gaps and recommendations in monitoring regulations of activities in EU marine protected areas

Marine Protected Areas (MPAs) play a central role in maritime policies, but there are no comprehensive analyses of regulations in EU MPAs. Using publicly available data on EU MPAs’ regulations for nine activities, we first show that MPA and MSP databases display significant gaps in data comprehensiveness. The regulation of each activity was known in 40% or less of the MPA area (whether allowed, prohibited, or restricted), except for fishing activities (70% of MPA area), albeit with limited detail. Fishing, mining, or dredging/dumping activities were allowed in half of MPA area. Only mining was reported as prohibited in at least 10% of the MPA area. We discuss gaps in MPA regulatory data in light of existing reporting requirements, insufficient connection between various actors and data sources, and challenges in translating legal information into actionable indicators. We provide recommendations for future initiatives to improve the collection and standardization for environmental policies