Roscoff Marine Station

Climate change is predicted to drive geographical range shifts that will result in changes in species diversity and functional composition and have potential repercussions for ecosystem functioning. However, the effect of these changes on species composition and functional diversity (FD) remains unclear, especially for mammals, specifically bats. We used species distribution models and a comprehensive ecological and morphometrical trait database to estimate how projected future climate and land‐use changes could influence the distribution, composition, and FD of the European bat community. Future bat assemblages were predicted to undergo substantial shifts in geographic range and trait structure. Range suitability decreased substantially in southern Europe and increased in northern latitudes. Our findings highlight the potential for climate change to drive shifts in bat FD, which has implications for ecosystem function and resilience at a continental scale. It is important to incorporate FD in conservation strategies. These efforts should target species with key functional traits predicted to be lost and areas expected to experience losses in FD. Conservation strategies should include habitat and roost protection, enhancing landscape connectivity, and international monitoring to preserve bat populations and their ecosystem services.

Stocks of the European flat oyster, Ostrea edulis, have collapsed due to overfishing, habitat destruction, and pathogen outbreaks across most of their distribution range. Nonetheless, as a result of lower exploitation pressure and the absence of pathogens in the most northern part of the range, a large part of the remaining wild population can be found in relatively high densities in Scandinavia, a region in Northern Europe. However, despite recent studies focusing on flat oyster population structure along the European coast, little is known about the population structure of oysters in the Skagerrak marginal sea in Scandinavia, and how it is related to neighbouring regions. This study, therefore, aimed to investigate the population structure of flat oysters in Scandinavia, with a special emphasis on the Skagerrak. We gathered low‐coverage whole‐genome sequencing data from oysters in Sweden, Norway, and Denmark, the three countries that border the Skagerrak. Genetic diversity appeared to be homogeneously distributed over the sampled area in the Skagerrak, while samples collected from the east coast of Denmark and from a location with known historical farming activity on the Norwegian West Coast were genetically distinct from Skagerrak samples. A genetic barrier analysis indicated barriers to gene flow in the Baltic Sea transition zone and on the west coast of Norway. Overall, our results suggest that flat oysters from the Swedish Skagerrak coasts form a single panmictic population that is distinct from neighbouring seas, potentially allowing for regional management of stocks and restoration translocations in the area. However, the genetic composition of donor and recipient stocks should be assessed on a case‐by‐case basis, genetic diversity effects of hatchery practices should be monitored, and biosecurity measures need to be considered prior to any movement of stock.

Macroalgae‐bacteria interactions play pivotal ecological roles in coastal ecosystems. Previous characterisation of surface microbiota from various macroalgae evidenced fluctuations based on host tissues, physicochemical and environmental parameters. However, the dynamics and degree of similarity of epibacterial communities colonising phylogenetically distant algae from the same habitat are still elusive. We conducted a year‐long monthly epimicrobiota sampling on five algal species inhabiting an English Channel rocky shore: Laminaria digitata, Ascophyllum nodosum, Fucus serratus (brown algae), Palmaria palmata (red alga) and Ulva sp. (green alga). To go beyond relative compositional data and estimate absolute variations in taxa abundance, we combined qPCR measurements of 16S rRNA gene copies with amplicon metabarcoding. A core microbiome composed of 10 genera was consistently found year‐round on all algae. Notably, the abundant genus Granulosicoccus stood out for being the only one present in all samples and displayed an important microdiversity. Algal host emerged as the primary driver of epibacterial community composition, before seasonality, and bacterial taxa specifically associated with one or several algae were identified. Moreover, the impact of seasons on the epimicrobiota varied depending on algal tissues. Overall, this study provides an extensive characterisation of the microbiota of intertidal macroalgae and enhances our understanding of algal‐bacteria holobionts.

Despite their potential in areas such as medicinal chemistry and organic materials, scaffolds in which quinoline and quinoxaline are fused to phosphacycles such as 1,3‐oxaphosphole, 1,3‐azaphosphole, P‐arylated and P‐alkoxylated 2,3‐dihydro‐1,3‐azaphosphole P‐oxides have, to our knowledge, never been reported. In this study we have developed a synthetic approach to [1,3]azaphospholo[4,5‐f]quinolines and ‐quinoxalines from quinolin‐6‐amine and quinoxalin‐6‐amine. These were converted to 5‐phosphanylquino(xa)lin‐6‐amines by regioselective iodination in position 5, cross‐coupling with diethyl phosphite and reduction. Formation of the azaphosphole ring was then achieved by reaction with N,N‐dimethylformamide dimethyl acetal. Attempts at C−H arylation in position 2 did not lead to the desired derivatives but rather to 1‐arylated 2,3‐dihydro‐[1,3]azaphospholo[4,5‐f]quino(xa)line 1‐oxides. Access to 1‐alkoxylated 2,3‐dihydro‐[1,3]azaphospholo[4,5‐f]quinoline 1‐oxides was also developed using as key steps cross‐coupling with ethyl phosphinate formed in situ and the subsequent Kabachnik‐Fields reaction. The resulting tricyclic compounds were finally tested against a panel of disease‐related protein kinases.

Rhodolith beds are diverse and globally distributed habitats. Nonetheless, the role of rhodoliths in structuring the associated species community through a hierarchy of positive interactions is yet to be recognised. In this review, we provide evidence that rhodoliths can function as foundation species of multi-level facilitation cascades and, hence, are fundamental for the persistence of hierarchically structured communities within coastal oceans. Rhodoliths generate facilitation cascades by buffering physical stress, reducing consumer pressure and enhancing resource availability. Due to large variations in their shape, size and density, a single rhodolith bed can support multiple taxonomically distant and architecturally distinct habitat-forming species, such as primary producers, sponges or bivalves, thus encompassing a broad range of functional traits and providing a wealth of secondary microhabitat and food resources. In addition, rhodoliths are often mobile, and thus can redistribute associated species, potentially expanding the distribution of species with short-distance dispersal abilities. Key knowledge gaps we have identified include: the experimental assessment of the role of rhodoliths as basal facilitators; the length and temporal stability of facilitation cascades; variations in species interactions within cascades across environmental gradients; and the role of rhodolith beds as climate refugia. Addressing these research priorities will allow the development of evidence-based policy decisions and elevate rhodolith beds within marine conservation strategies.

Marine eastern boundary current ecosystems, such as the California Current System (CCS), involve productive, mesotrophic transition zones. The CCS exhibits highly variable primary production (PP), yet factors driving the variability and underlying phytoplankton communities remain poorly understood. We integrated physicochemical and biological data from surface waters sampled during 10 CCS expeditions, spanning 13 yr, and resolved regimes with distinct phytoplankton communities. Additional to an oligotrophic regime (OR), mesotrophic waters beyond the coastal area partitioned into Meso‐High and Meso‐Low regimes, differing in nitrate concentrations and PP. The OR was dominated by Prochlorococcus High‐Light I (HLI), and eukaryotic phytoplankton were largely predatory mixotrophs. Eukaryotes dominated Meso‐Low and Meso‐High phytoplankton biomass. Within the Meso‐Low, Pelagomonas calceolata was important, and Prochlorococcus Low‐Light I (LLI) rose in prominence. In the Meso‐High, the picoprasinophyte Ostreococcus lucimarinus was abundant, and Synechococcus Clade IV was notable. The Meso‐High exhibited the highest PP (38 ± 16 mg C m⁻³ d⁻¹; p < 0.01) and higher growth rates for photosynthetic eukaryotes (0.84 ± 0.02 d⁻¹) than for Prochlorococcus (0.61 ± 0.01 d⁻¹) and Synechococcus (0.31 ± 0.05 d⁻¹). An experiment simulating seasonal oligotrophic seawater intrusion into the Meso‐High resulted in growth rates reaching 1.18 ± 0.10 d⁻¹ (O. lucimarinus), 0.75 ± 0.21 d⁻¹ (Prochlorococcus LLI), and 0.50 ± 0.04 d⁻¹ (Synechococcus EPC2). Thus, variable PP is underpinned by distinct phytoplankton communities across CCS mesotrophic regimes, and their dynamic nature is influenced by the rapidity with which specific taxa respond to changing environmental conditions or possibly transient nutrient release from viral encounters. Future work should assess whether these dynamics are consistent across eastern boundary current ecosystems and over temporal variations.

The Southern Ocean (SO) plays a key role in regulating global biogeochemical cycles and climate, yet microbial genes sustaining its biological activity remain poorly characterized. We introduce a comprehensive SO microbial genes collection from 218 metagenomes sampled during the Antarctic Circumnavigation Expedition, the majority of which are missing from functional databases. 38% even lack homologs in current reference marine gene catalogs, defining a singular genetic seascape. We show that SO gene assemblages exhibit a common polar signature with the Arctic Ocean while being structured by water masses at the SO-scale. We analyze genomic markers of diverse SO biomes, focusing on adaptations to organic matter consumption in the blooming Mertz polynya and temperature-dependent trace metal utilization by the ubiquist Bacteria Pelagibacter. Our work takes a step towards a more comprehensive understanding of SO’s plankton ecology and evolution, capturing the current state of the unique microbial diversity in this rapidly changing Ocean.

Alginates are abundant linear polysaccharides produced by brown algae and some bacteria. They have multiple biological roles and important medical and commercial uses. Alginates are comprised of D-mannuronic acid (M) and L-guluronic acid (G) and the ratios and distribution patterns of M and G profoundly impact their physiological and rheological properties. The structure/function relationships of alginates have been extensively studied in vitro but our understanding of the in vivo spatiotemporal regulation of alginate fine structures and their biological implications is limited. Monoclonal antibodies (mAbs) are powerful tools for localising and quantifying glycan structures and several alginate-directed mAbs have been developed. We used a library of well-defined alginates, with M and G block ratios determined by NMR, to refine our understanding of the binding properties of alginate-directed mAbs. Using these probes, we obtained new insight into how structural features of alginates are regulated at different scales, from cellular to seasonal.

We have followed the recovery of gaps produced either by harvesters or by scientists in stands of stalked barnacle (Pollicipes pollicipes) during two years in four regions of Europe (SW Portugal, Galicia and Asturias in Spain and Brittany in France; n = 423 gaps), which was extended to four years in Asturias (n = 252 gaps). The presence of adult conspecifics in the margins of the gaps increased by at least four times the probability of initiation of their recovery. After two years of follow-up in the four regions, 90% of the gaps with adjacent conspecifics had initiated recolonization as opposed to only 60% in gaps with no adjacent adults. These figures remained stable after three years of follow up in Asturias, pointing to a large fraction of gaps which are recalcitrant to recolonization. Once initiated, the median rate of recovery after latency was 0.47 cm²/month in the four regions and 0.61 cm²/month in Asturias, increasing from 0.5 to 2.5 cm²/month for a 0 to 25 cm increase of perimeter in contact with adults, which is consistent with heavy recruitment on the stalks of conspecifics. The median estimated time to full recovery of gaps which initiated recovery was 2.65 years, thus recolonization is a slow process. Our results point to the main recommendations that a barnacle clump should never be removed entirely, so that the remaining adults serve as recruitment nuclei for the population, and that a maximum scraper width of 3.5 cm should be set to limit accessory capture of non-target individuals.

The mode of evolution of left-right asymmetries in the vertebrate habenulae remains largely unknown. Using a transcriptomic approach, we show that in a cartilaginous fish, the catshark Scyliorhinus canicula, habenulae exhibit marked asymmetries, in both their medial and lateral components. Comparisons across vertebrates suggest that those identified in lateral habenulae reflect an ancestral gnathostome trait, partially conserved in lampreys, and independently lost in tetrapods and neopterygians. Asymmetry formation involves distinct mechanisms in the catshark lateral and medial habenulae. Medial habenulae are submitted to a marked, asymmetric temporal regulation of neurogenesis, undetectable in their lateral counterparts. Conversely, asymmetry formation in lateral habenulae results from asymmetric choices of neuronal identity in post-mitotic progenitors, a regulation dependent on the repression of Wnt signaling by Nodal on the left. Based on comparisons with the mouse and the zebrafish, we propose that habenular asymmetry formation involves a recurrent developmental logic across vertebrates, which relies on conserved, temporally regulated genetic programs sequentially shaping choices of neuronal identity on both sides and asymmetrically modified by Wnt activity.

Ostrea edulis, the European flat oyster, was once a widespread economically and ecologically important marine species, but has suffered dramatic declines over the past two centuries. Consequently, there has been a surge in European restoration efforts, many of which focus on restocking as a conservation measure. In this study, we used whole-genome sequencing (WGS) data to investigate the population structure, demographic history, and patterns of local adaptation of O. edulis across its natural distribution with increased sampling densities at Scandinavian localities. Results revealed seven distinct genetic clusters, including previously undescribed complex population structure in Norway, and evidence for introgression between genetic clusters in Scandinavia. We detected large structural variants (SVs) on three pseudo-chromosomes. These megabase long regions were characterised by strong linkage disequilibrium and clear geographical differentiation, suggestive of chromosomal inversions potentially associated with local adaptation. The results indicated that genomic traces of past translocations of non-native O. edulis were still present in some individuals, but overall, we found limited evidence of major impacts of translocations on the scale of contemporary population structure. Our findings highlight the importance of considering population structure and signatures of selection in the design of effective conservation strategies to preserve and restore wild native European flat oyster populations, and we provide direct knowledge safeguarding sustainable mitigation actions in this important species. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

During the TONGA cruise (2019), seawater samples were collected to assess the effect of volcanic eruption versus submarine hydrothermal system on the water column. For this purpose, two locations were investigated, the first one located directly under the influence of the New Late’iki island (eruption in October 2019), and the second one showing ongoing submarine hydrothermal activity. At both locations, the total strontium (TSr) and lithium (TLi) concentrations vary between 94.4 and 152.3 µmol/L and 13.2 and 203.5 µmol/L, respectively. When combined, TSr and TLi concentrations of all samples in the water column are higher than those of the oligotrophic water. Both volcanic eruption and submarine hydrothermal activity (e.g. volcanic ashes, particles, gas condensate) can deliver substantial amount of TSr and TLi to the water column. The distribution of TSr versus TLi evidences linear trends either with a negative or positive slope. The negative correlation is observed in the water column at both sites, directly under the influence of the eruption and in the vicinity of the volcano with hydrothermal activity. The positive TSr versus TLi correlation is observed at site under submarine hydrothermal influence and is in line with black smokers related hydrothermal plumes. The ⁸⁷Sr/⁸⁶Sr ratios vary between 0.709147 and 0.709210 and δ⁷Li values vary between +10.1 and +37.6 ‰. While 92% of the measured ⁸⁷Sr/⁸⁶Sr ratios are in line with the mean value of oligotrophic waters, once combined with the δ⁷Li values, only 20% of them remains within this field. The wide range of δ⁷Li values decreases from sea-surface down to ~140 mbsl, before increasing at greater depth, while defining different linear trend according to the dissolved inorganic carbon concentrations. The variability of δ⁷Li values reflect hydrothermal contribution, mineral–seawater interaction and potentially biology–environment interaction. In the particular geological setting of the study, where both hydrothermal and volcanic activities were at play, disentangling both contributions on water column implies a combined use of elemental and isotopic signatures of Sr and Li tracers.

To inform the performance of ecological engineering designs for artificial structures at sea, it is essential to characterise their impacts on the epibenthic communities colonising them. In this context, the present study aims to compare the community structure among natural and four different artificial hard habitats with different ages and features installed in the Bay of Cherbourg (English Channel): i) cinder blocks and ii) boulders, both installed six years prior to the study, and iii) smooth and iv) rugous concrete dykes, both installed one year prior to this study. Results showed that artificial habitats installed six years ago harboured communities with functional and taxonomic diversity characteristic of mature communities but were still different from those of natural habitat. Conversely, the two dyke habitats installed one year prior to this study presented a poorly diversified community dominated by opportunistic taxa. Furthermore, while the concrete used for the two dyke habitats presented different rugosity properties, both habitats supported similar communities, suggesting that such eco-engineering measures did not affect the settlement of early colonisers. Overall, this study highlights the need for long-term monitoring to comprehensively evaluate epibenthic colonisation of artificial structures.

Background Brown algae belong to the Stramenopiles phylum and are phylogenetically distant from plants and other multicellular organisms. This independent evolutionary history has shaped brown algae with numerous metabolic characteristics specific to this group, including the synthesis of peculiar polysaccharides contained in their extracellular matrix (ECM). Alginates and fucose-containing sulphated polysaccharides (FCSPs), the latter including fucans, are the main components of ECMs. However, the metabolic pathways of these polysaccharides remain poorly described due to a lack of genomic data. Results An extensive genomic dataset has been recently released for brown algae and their close sister species, for which we previously performed an expert annotation of key genes involved in ECM-carbohydrate metabolisms. Here we provide a deeper analysis of this set of genes using comparative genomics, phylogenetics analyses, and protein modelling. Two key gene families involved in both the synthesis and degradation of alginate were suggested to have been acquired by the common ancestor of brown algae and their closest sister species Schizocladia ischiensis. Our analysis indicates that this assumption can be extended to additional metabolic steps, and thus to the whole alginate metabolic pathway. The pathway for the biosynthesis of fucans still remains biochemically unresolved and we also investigate putative fucosyltransferase genes that may harbour a fucan synthase activity in brown algae. Conclusions Our analysis is the first extensive survey of carbohydrate-related enzymes in brown algae, and provides a valuable resource for future research into the glycome and ECM of brown algae. The expansion of specific families related to alginate metabolism may have represented an important prerequisite for the evolution of developmental complexity in brown algae. Our analysis questions the possible occurrence of FCSPs outside brown algae, notably within their closest sister taxon and in other Stramenopiles such as diatoms. Filling this knowledge gap in the future will help determine the origin and evolutionary history of fucan synthesis in eukaryotes.

Marine Stramenopiles (MAST) were first described two decades ago through ribosomal RNA gene (rRNA gene) sequences from marine surveys of microbial eukaryotes. MAST comprise several independent lineages at the base of the Stramenopiles. Despite their prevalence in the ocean, the majority of MAST diversity remains uncultured. Previous studies, mainly in marine environments, have explored MAST’s cell morphology, distribution, trophic strategies, and genomics using culturing-independent methods. In comparison, less is known about their presence outside marine habitats. Here, we analyse the extensive EukBank dataset to assess the extent to which MAST can be considered marine protists. Additionally, by incorporating newly available rRNA gene sequences, we update Stramenopiles phylogeny, identifying three novel MAST lineages. Our results indicate that MAST are primarily marine with notable exceptions within MAST-2 and MAST-12, where certain subclades are prevalent in freshwater and soil habitats. In the marine water column, only a few MAST species, particularly within clades -1, -3, -4, and -7, dominate and exhibit clear latitudinal distribution patterns. Overall, the massive sequencing dataset analysed in our study confirms and partially expands the previously described diversity of MASTs groups and underscores the predominantly marine nature of most of these uncultured lineages.

Humans have been driving a global erosion of species richness for millennia, but the consequences of past extinctions for other dimensions of biodiversity-functional and phylogenetic diversity-are poorly understood. In this work, we show that, since the Late Pleistocene, the extinction of 610 bird species has caused a disproportionate loss of the global avian functional space along with ~3 billion years of unique evolutionary history. For island endemics, proportional losses have been even greater. Projected future extinctions of more than 1000 species over the next two centuries will incur further substantial reductions in functional and phylogenetic diversity. These results highlight the severe consequences of the ongoing biodiversity crisis and the urgent need to identify the ecological functions being lost through extinction.

The bay scallop, Argopecten irradians, is a species of major commercial, cultural, and ecological importance. It is endemic to the eastern coast of the United States, but has also been introduced to China, where it supports a significant aquaculture industry. Here, we provide an annotated chromosome-level reference genome assembly for the bay scallop, assembled using PacBio and Hi-C data. The total genome size is 845.9 Mb, distributed over 1,503 scaffolds with a scaffold N50 of 44.3 Mb. The majority (92.9%) of the assembled genome is contained within the 16 largest scaffolds, corresponding to the 16 chromosomes confirmed by Hi-C analysis. The assembly also includes the complete mitochondrial genome. Approximately 36.2% of the genome consists of repetitive elements. The BUSCO analysis showed a completeness of 96.2%. We identified 33,772 protein-coding genes. This genome assembly will be a valuable resource for future research on evolutionary dynamics, adaptive mechanisms, and will support genome-assisted breeding, contributing to the conservation and management of this iconic species in the face of environmental and pathogenic challenges.

Current evidence suggests that macroalgal-dominated habitats are important contributors to the oceanic carbon cycle, though the role of those formed by calcifiers remains controversial. Globally distributed coralline algal beds, built by pink coloured rhodoliths and maerl, cover extensive coastal shelf areas of the planet, but scarce information on their productivity, net carbon flux dynamics and carbonate deposits hampers assessing their contribution to the overall oceanic carbon cycle. Here, our data, covering large bathymetrical (2–51 m) and geographical ranges (53°N–27°S), show that coralline algal beds are highly productive habitats that can express substantial carbon uptake rates (28–1347 g C m⁻²), which vary in function of light availability and species composition and exceed reported estimates for other major macroalgal habitats. This high productivity, together with their substantial carbonate deposits (0.4–38 kilotons), renders coralline algal beds as highly relevant contributors to the present and future oceanic carbon cycle.

The South Georgia region of the Southern Ocean represents the northernmost range edge for Antarctic krill. Of concern is the extent to which rapid warming of surface water temperatures and reduced oxygen contents around this region might challenge the physiological tolerance of krill, particularly the later maturity stages. Hypoxia is generally considered to be less than 30 to 20% of air saturation, hereafter as threshold hypoxia, while less than 10% of air saturation would qualify as severe hypoxia. These levels are unlikely to occur in the Southern Ocean but might happen in the middle of dense krill swarms. We investigated gene expression and biochemical markers related to aerobic metabolism, antioxidant defence, and heat-shock response under 6-h threshold (4 kPa; TH) and 1-h severe (0.6 kPa; SH) hypoxia exposure, to understand how hypoxia might alter respiratory and biochemical pathways in adult and subadult krill. After 6-h TH, subadults induced expression of citrate synthase (CS), and mitochondrial superoxide dismutase (also after 1-h SH) over normoxic expression levels. The maturity stages responded differently in glutathione peroxidase (1-h SH; lower in subadults and higher in adults), and CS (6-h TH; higher in subadults and lower in adults) activities as for the oxidative damage marker to lipids (6-h TH; lower in subadults and higher in adults). Subadults had a greater capacity than adults to deal with hypoxic conditions. This may be a strategy allowing them to exist in larger swarms to reduce predation pressure before reaching reproductive condition.