The viability of kelp microscopic gametophytes is currently analyzed using subjective visual methods based on bright-field (BF) microscope images. Fluorescence microscopy (FM) can be employed, but the dyes used can be toxic and blue/UV light intensity may induce gametogenesis. This study aimed to develop a non-invasive and accurate methodology for assessing gametophyte viability over time, using FM observation of chlorophyll autofluorescence emitted by live gametophytes. Six isolated gametophyte strains of Laminaria ochroleuca (Italy), maintained at CCMAR Biobank, were cultured in triplicate (female, male, and both sexes combined) in Petri dishes containing 10 mL of half-strength Provasoli’s enriched seawater medium (PES), under red light for 1 month. Survival and growth were assessed on days 1, 7 and 14 by photographing 20 fields-of-view, both in BF and FM. Then, cultures were transferred to white light to induce gametogenesis and test whether the autofluorescence analysis (AFA) method affected gametophyte reproduction. Image analysis was performed using FIJI software either by manually counting live gametophytes (survival) and measuring their area (growth), or by implementing a machine-learning (ML) model using FIJI’s WEKA segmentation plugin. Results revealed that both methods were correlated, validating our ML model. However, the AFA method was faster and more accurate than BF image analysis, especially for male gametophytes, and did not compromise reproductive capacity. After 9 days under white light, sporophytes were present in mixed cultures. The AFA method provides a reliable technique for assessing gametophyte viability without compromising gametogenesis.

Octocorals are among the main habitat‐engineering species, generating complex three‐dimensional ecosystems of unquestioned importance. Despite their importance, octocoral habitats have dramatically declined in the last decades due to several stressors. Consequently, octocoral gardens are internationally recognized as Vulnerable Marine Ecosystems. In the last decade, several octocoral restoration methodologies were the object of study, yet long‐term success was sparsely achieved or lacked assessment. To reverse the actual scenario, it is important to develop cost‐efficient methodologies to recover impacted, endangered octocoral habitats. In this 4‐year study, we developed and tested the Direct Substrate Attachment (DSA) method. This novel octocoral transplant method was trialed with two size classes of the species Paramuricea grayi and extended with a third class (20–40 cm) using Leptogorgia sarmentosa. With a recorded 95% attachment success, yearly annual positive growth, and a survival of 75% after 4 years, we prove the suitability of the DSA methodology in habitat restoration. Moreover, transplant size did not influence success; all transplants had verifiable holdfast and growth rates of up to 8.34 ± 1.7 cm. Seasonal growth and health status were monitored and compared to further assess the success of the transplant. The transplant performed with the DSA method is to date the first successful octocoral transplant in the Atlantic temperate seas with proven long‐term success. The results achieved are especially important in a moment where ecological degradation and mitigation efforts are a hot topic among decision‐makers. Using the DSA methodology, octocoral transplantation is possible and should be considered in conservation and restoration efforts.

The widespread decline of coral-dominated ecosystems has highlighted the urgent need for active habitat restoration. Coral restoration using sexually produced individuals instead of clonal fragments is essential to reduce impacts on donor populations and promote genetic diversity, which is vital for adaptability to environmental changes. However, for most coral species critical knowledge of reproduction and larval ecology for ex situ sexual propagation is lacking. To address this gap, this study presents the first report of spawning of the octocoral Eunicella verrucosa in the North-East Atlantic and describes larval development and settlement. The annual reproductive timing in South-West Portugal was determined from samples collected as fisheries bycatch from the same habitat and monitored for comparison across distinct durations and conditions. The species exhibited split spawning (three major events approximately every two weeks) over about one month (mid-September–mid-October). Spawning patterns can suggest lunar periodicity but shifted between colonies kept in distinct conditions. Oocytes were positively buoyant and developed into swimming larvae after three days. Settlement trials using substrates such as natural rock, crustose coralline algae (CCA), and gorgonian skeleton, showed larvae started testing the substrates about two weeks after spawning, with settlement activity continuing over up to three months. Fully developed recruits were observed after one month, with sclerite production starting before tentacle development. The observation of new larval settlement up to three months indicates a prolonged competency period. This study provides crucial data for coral restoration efforts using ex-situ sexual propagation of a vulnerable species.

The marine protected area (MPA) of the Arrabida Natural Park is a mid-latitude hotspot for biodiversity. To understand its trophic structure, a highly defined food web network was assembled for this ecosystem, consisting of 884 taxa. Network analysis showed that humans are the top predators, as well as various seabirds, dolphins and sharks. This web is dominated by intermediate species, and its general organization follows previously reported patterns for other marine and coastal ecosystems. Two swimming crabs, Polybius navigator and Polybius henslowii, assume important roles as mid-trophic level consumers and prey, due to their high connectivity in the network. The cuttlefish, Sepia officinalis, a cephalopod of high commercial value, assumes the most pivotal role in the network, as it is the species with the highest number of prey and is among the top 10 most highly connected species (with more links to other species). Additionally, the cuttlefish is among the species with shortest path length, that is the lowest number of links connecting it to any other species. Since, this cephalopod is highly mobile and extends its territory outside the MPA, into the Sado estuary, where it is the main target of local fisheries, and is exposed to various pollution sources, close monitoring the local population of cuttlefish is of the utmost importance, not only in the Arrabida MPA but also in the adjacent Sado estuary.

Ruppia drepanensis Tineo ex Guss. is an important habitat-forming aquatic plant in saline and brackish Mediterranean wetlands. The species is declining in several parts of its range due to hydrological changes and habitat degradation. R. drepanensis was considered Critically Endangered, possibly Regionally Extinct in Portugal, due to not being observed since 1986 despite extensive surveys of suitable habitat. We report on a new population, the westernmost known record for the species in Europe, identified with morphological and molecular data. Despite being inside a protected area, this population occupies a single small pond adjacent to a road, making it vulnerable to habitat changes. Ex situ conservation is recommended, including seed banking and/or the establishment of new populations.

Global blue carbon assessments are hindered by a lack of data from understudied seagrass regions, such as those of Western Africa. This study reports the first in situ records of organic carbon (OC) stocks and burial rates for seagrass beds at Arguin Island, Banc d'Arguin (Mauritania), Western Africa, measured in intertidal Zostera noltei and subtidal Cymodocea nodosa meadows. The major blue carbon sources in seagrass meadows since 1900 were assessed using sedimentary environmental DNA (eDNA) and chronostratigraphy. The OC stocks in the top 50 cm of the sediment cores were not significantly different between the beds of the two seagrass species and averaged 27.8 ± 7.14 Mg C ha−1, which is 5 times higher than that in adjacent unvegetated sediments. The OC sequestration rate for the past 100 years was 10.3 ± 1.4 g C m−2 year−1 in C. nodosa sediments and 12.3 ± 5.9 g C m−2 year−1 in Z. noltei sediments. Sedimentary eDNA analysis revealed that the major OC source within the C. nodosa and Z. noltei sediments has been the seagrass species itself, with low contributions from allochthonous eDNA reads. Carbon sources in Z. noltei meadows were more diverse than those in C. nodosa meadows. In bare sediment, diatoms were the major carbon source. The present study demonstrates the potential of sedimentary eDNA to reveal the major sources of organic matter in blue carbon ecosystems, improving our understanding of the provenance of sedimentary OC and thus carbon cycling processes. Additionally, it provides new OC stock and sequestration rate measurements from a region of the world that remains underrepresented in global blue carbon assessments.

Biogeographic regions arise due to constraints on species ranges, fostering lineage divergence as a result. Yet, convergent evolution means that evolutionary distinct lineages can share similar characteristics when subjected to similar environmental conditions. The ecological convergence of distinct regions has been demonstrated in terrestrial communities, but it remains uncertain if marine systems exhibit similar patterns, given the greater ease of dispersal in the ocean. Using information on the dietary preferences of marine vertebrates, we develop an ocean regionalization that groups regions with similar trophic communities, describing how species are organized into trophic guilds and how guilds overlap with one another. Six types of trophic communities emerge globally, largely explained by temperature, productivity, and depth. Regions with analogous environments support similar numbers of species with analogous feeding strategies, even if the species do not share the same evolutionary origins. These findings support the notion that independently evolving sets of marine species can converge into functionally analogous trophic communities when exposed to similar environmental conditions. They also provide a benchmark for studying the functional consequences of global environmental change.

Ocean currents are fundamental drivers of marine biodiversity distribution, mediating the exchange of genetic material and individuals between populations. Their effect ranges from creating barriers that foster isolation to facilitating long-distance dispersal, which is crucial for species expansion and resilience in the face of climate change. Despite the significance of oceanographic connectivity, comprehensive global estimates remain elusive, hindering our understanding of species’ dispersal ecology and limiting the development of effective conservation strategies. We present the first dataset of connectivity estimates (including probability of connectivity and travel time) along the world’s coastlines. The dataset is derived from Lagrangian simulations of passive dispersal driven by 21 years of ocean current data and can be combined with species’ biological traits, including seasonality and duration of planktonic dispersal stages. Alongside, we provide coastalNet, an R package designed to streamline access, analysis, and visualization of connectivity estimates. The dataset provides a new benchmark for research in oceanographic connectivity, enabling a deeper exploration of the complex dynamics of coastal marine ecosystems and informing more effective conservation strategies.

Global patterns of intraspecific genetic diversity are key to understanding evolutionary and ecological processes. However, insights into the distribution and drivers of genetic diversity remain limited, particularly for marine species. Here, we explain and predict the genetic diversity of cold and temperate brown macroalgae using genetic data from 29 species and a machine-learning algorithm that incorporates contemporary and past climate conditions during the Last Glacial Maximum (~20,000 years ago) based on the niche centroid hypothesis. We apply this model to the distribution of 280 species and predict their global genetic diversity. Our results show reduced genetic diversity away from the niche centroid, identifying past climate conditions as key drivers of contemporary genetic diversity. Regions with high genetic diversity for multiple species emerge, matching biogeographic patterns of species richness. The mapped diversity hotspots establish timely baselines for brown macroalgae biogeography, evolutionary potential and conservation, contributing to the Post-2020 Global Biodiversity Framework.

This study aimed to explore and document putative exotic marine benthic invertebrate species in the Bijagós Archipelago, Guinea-Bissau, to enhance understanding of marine biodiversity and address the extent of marine species introductions. The research was conducted in the Bijagós Archipelago, a UNESCO Biosphere Reserve located in Guinea-Bissau. The study involved the region's first scuba-diving survey of marine biodiversity. DNA barcoding was employed to assist in the identification of benthic invertebrate species. Molecular phylogenetic analyses were conducted with the available DNA barcodes to ensure accurate taxonomic assignments, detect cryptic species, and investigate the phylogeography of the taxa. The survey resulted in the discovery of 28 new species records for the Bijagós Archipelago, including octocorals, scleractinians, hydroids, bryozoans, barnacles, and ascidians. Among these, six species were documented for the first time in the East Atlantic: Stragulum bicolor, Nemalecium lighti, Diphasia sp., Amathia alternata, A. distans, and Symplegma rubra. Molecular analyses revealed pervasive cryptic diversity within species previously listed as exotic, suggesting that some, such as the hydroids Plumularia setacea, Obelia geniculata, and Dynamena disticha, are not exotic due to their restricted biogeographic distributions. Many other species reported as introduced present only a few genetic lineages capable of long-distance dispersal due to human activities. The study highlights considerable gaps in the knowledge of West African marine biodiversity and suggests a substantial underestimation of the anthropogenic trade in exotic marine species between the Tropical East Atlantic and the Americas, and between the Indo-Pacific, Mediterranean, and West Africa. Detailed taxonomic and genomic analyses are necessary for understanding marine exotic species' biogeography and adaptive traits. Our findings challenge current classifications of exotic species and underscore the need for improved monitoring and management to prevent the spread of non-native marine species.

Abstract Here we report the first record of the shrimp Lysmata rauli Laubenheimer and Rhyne, 2010 in the eastern Atlantic, from the intertidal at Kere Island, Bijagós archipelago, Guinea-Bissau.

Seagrasses can form vast meadows in coastal areas and provide valuable ecosystem services. Despite their importance, seagrasses are threatened, and their spatial extent and ecological condition have declined worldwide. Globally, there are six seagrass bioregions based on ocean basin and species distribution. The Tropical Atlantic Bioregion encompasses seagrasses in the warm waters off the Atlantic American continent, the eastern Pacific and the west coast of Africa. Here, the extinction risk of the species was determined through the Categories and Criteria of the IUCN Red List of Threatened Species. The extinction risk for the 15 native seagrass species in the bioregion was assessed and summarized as an update to the previous IUCN effort, conducted 15 years ago. The updated regional assessments were based on expert opinion and compilation of revised data on species´ distribution, population status and trend. Of the 15 native species, nine were endemic to the bioregion; thus, the regional assessment was also a global one. Two other species were typical for the region but also occurred beyond bioregional boundaries (Halodule beaudettei and H. wrightii). The remaining species were either distributed circumglobally (2 species), or consisted of peripheral populations of species characteristic of neighboring bioregions (2 species). The detailed information of 15 assessments have been made freely accessible in an open repository. Nine species maintained their previous risk of extinction status, while one species (Thalassia testudinum) changed from the Least Concern to the Near Threatened category. Downgrading of the status of T. testudinum is worrying, as this is the dominant climax species in the wider Caribbean. Its replacement by less resistant and smaller but faster growing species, such as Syringodium filiforme and H. wrightii (both classified as Least Concern), could compromise the ecosystem services of seagrasses in this bioregion. An additional two species had been recently introduced, and are also briefly covered. The assessments included past and present taxonomical uncertainties of various assessed species. Issues concerning the current boundaries of the bioregions themselves were also encountered. To address this and better capture future and ongoing range expansion or reduction associated with climate change, we propose overlapping transitional boundaries with neighboring seagrass bioregions.

Temperate coral gardens are dense coral formations, which support rich marine species diversity, enabling benthic-pelagic coupling. Over the past decades, coral gardens have been increasingly threatened by bottom fishing, oil and gas exploitation, and climate change. Microbiome research bears great potential for assisted resilience in targeted conservation and restoration approaches. Yet, fundamental parameters of the coral garden microbiome remain poorly understood. Here, we provide a first broad record of bacterial communities associated with NE Atlantic coral garden corals and their community changes as response to human maintenance in conservation research. Octocorals (10 species), scleractinians (2 species) and one black coral species, were opportunistically collected from fisheries bycatch at 60–480 m depth around Cape St. Vincent (SW Portugal). Metabarcoding of the 16S-rRNA gene using third-generation sequencing revealed a high microbial host-specificity in the wild-collected coral species analyzed, and supported the importance of bacterial families Endozoicomonadaceae (mean relative abundance ± SE; 28.3 ± 10.5%), Spirochaetaceae (8.2 ± 5.8%) and Spongiibacteraceae (4.6 ± 1.8%). Endozoicomonadaceae were particularly dominant in the octocoral order Malacalcyonacea (67.7 ± 14.5%). The low microbial alpha diversity and limited interspecies differences among the Malacalcyonacea species suggest a conserved microbiome within this group, as compared to orders Scleralcyonacea, Antipatharia, and Scleractinia. Microbial responses to ex-situ maintenance of two branching octocoral species, Eunicella verrucosa and Paramuricea cf. grayi (Order Malacalcyonacea), were investigated (1) over 45 days under standardized aquaria conditions in the research station (Ramalhete Marine Station, CCMAR) and (2) over long-term captivity in two public aquaria, Oceanário de Lisboa and Zoomarine. Eunicella verrucosa displayed a stronger microbial community shift to short-term captivity (45 days), in contrast to greater microbiome stability in P. cf. grayi. However, long-term captivity in public aquaria led to microbiome shifts in both species. The strong host specificity of microbial diversity and its response to maintenance indicate that conservation and restoration of coral gardens require taxon-specific strategies.

Cold-water corals (CWCs) are key ecosystem-structuring species across the world's oceans, yet their global distribution, diversity patterns, and vulnerability to climate change remain poorly understood. Here, we delineated the global biogeography of CWCs and assessed how their biodiversity patterns may shift under future climate change scenarios. Using an ensemble of machine-learning models, we predicted the distributions of 741 CWC species, spanning Octocoralia, Scleractinia, Antipatharia, Zoanthidae, Pennatulacea, and Filifera, under present-day conditions and forecasted changes in species richness, community composition, and climate refugia under two contrasting Shared Socioeconomic Pathways (SSP1-1.9 and SSP3-7.0). Further, we identified biogeographic regions based on species co-occurrence patterns and statistically validated them. Our results showed major biodiversity hotspots in the Gulf of Mexico and the Caribbean Sea, and delineated ten distinct bioregions, each with varying species richness, depth distribution patterns, and generally low levels of endemicity. While the global extent of the CWC biome may persist in the future, we forecasted pronounced poleward and depth shifts in species distributions, particularly under high-emission scenarios, resulting in biodiversity losses in shallow and low-latitude regions and increased community turnover. Our findings highlight the growing threat of climate change to CWC biodiversity and deep-sea ecosystems and the need for urgent climate action, aligned with the Paris Agreement. By identifying biodiversity hotspots, emerging climate refugia, and regions at greatest risk, this study offers a global framework to inform conservation priorities and support efforts to safeguard CWC biodiversity in the long term.

The Banc d'Arguin is the most ecologically significant coastal wetland of West Africa, a UNESCO Marine World Heritage area with one of the most extensive seagrass areas on Earth, used by many marine species as breeding and/or feeding habitat. However, little is known about the subtidal biodiversity supported by these extensive seagrass meadows. This study aimed to assess the influence of subtidal seagrass vegetation on fish assemblages, using beach seines to compare vegetated and unvegetated habitat. Effects of season and site were also assessed. We sampled fish communities predominantly composed of juveniles (98.7 %). Specifically, we analyzed differences in abundance, species richness, diversity, evenness, and assemblage structure across these factors. Season was the most influential driver of fish assemblage structure, even more than habitat, as expected in a nursery area where fish reproduce seasonally. Notably, four species-Atherina boyeri, Eucinostomus melanopterus, Mugil capurrii, and Chelon dumerili-accounted for 53.7 % and 49.2 % of the variation in assemblages across habitat and season, respectively. Moreover, four times as many species were found exclusively in seagrass habitats compared to unvegetated areas, underscoring the critical role of seagrass meadows in the Banc d'Arguin in supporting species that depend on such shallow sheltered habitats, enhancing regional biodiversity, and contributing to the sustainability of fisheries.

Motivation Oceanographic connectivity driven by ocean currents is critical in determining the distribution of marine biodiversity. It mediates the genetic and individual exchange between populations, from structuring dispersal barriers that promote long-term isolation to enabling long-distance dispersal that underpins species expansion and resilience against climate change. Despite its significance, comprehensive estimates of oceanographic connectivity on a global scale remain unavailable, while traditional approaches, often simplistic, fail to capture the complexity of oceanographic factors contributing to population connectivity. This gap hinders a deeper understating of species’ dispersal ecology, survival, and evolution, ultimately precluding the development of effective conservation strategies aimed at preserving marine biodiversity. To address this challenge, we present a comprehensive dataset of connectivity estimates along the world’s coastlines, known for their rich marine biodiversity. These estimates are derived from a biophysical modelling framework that combines high-resolution ocean current data with graph theory to predict multi-generational stepping-stone connectivity. Alongside, we provide coastalNet, an R package designed to streamline access, analysis, and visualization of connectivity estimates. This tool enhances the utility and application of the data, adhering to the FAIR principles of Findability, Accessibility, Interoperability, and Reusability. The dataset and package set a new benchmark for research in oceanographic connectivity, allowing a better exploration of the complex dynamics of coastal marine ecosystems. Main types of variables contained Pairwise connectivity estimates (probability and time) between coastal sites. Spatial location and grain Global, equal-area hexagons with 8.45 km edge length. Time period and grain Daily, from 2000 to 2020. Major taxa and level of measurement Coastal marine biodiversity. Software format A package of functions developed for R software. ### Competing Interest Statement The authors have declared no competing interest.

Aim: Future climate change threatens marine forests across the world, potentially disrupting ecosystem function and services. Nonetheless, the direction and intensity of climate-induced changes in kelp forest biodiversity remain unknown, precluding well-informed conservation and management practices. Location: Global. Methods: We use machine-learning models to forecast global changes in species richness and community composition of 105 kelp forest species under contrasting Shared Socioeconomic Pathway (SSP) scenarios of climate change (decade 2090-2100): one aligned with the Paris Agreement and another of substantially higher emissions. Results: A poleward and depth shift in species distributions is forecasted, translating into similar to 15% less area in the extent of the global biome, coupled with marked regional biodiversity changes. Community composition changes are mostly projected in the Arctic, the Northern Pacific and Atlantic, and Australasia, owing to poleward range expansions and wide low latitude losses. Main Conclusions: By surpassing the Paris Agreement expectations, species reshuffling may simplify and impair ecosystem services in numerous temperate regions of Australasia, Southern Africa, Southern America and the Northern Atlantic, and in the tropical Pacific, where complete species losses were projected without replacement. These estimates, flagging threatened regions and species, as well as refugial areas of population persistence, can now inform conservation, management and restoration practices considering future climate change.

The Banc d'Arguin National Park (PNBA) in Mauritania, a globally significant biodiversity hotspot, faces growing threats from human activities and biological invasions. This study aimed to document marine invertebrate diversity in the PNBA and identify non-native and potentially invasive species. Samples were collected during expeditions in 2021 and 2022, using scuba-diving, drag dredging, and manual intertidal collection across depths of 0 to 20 meters. Through DNA barcoding of COI and 16S genes, 17 species from three phyla-Cnidaria, Bryozoa, and Arthropoda-were identified, with several cryptic taxa detected. Evidence of human-mediated introduction was found in hydroids (Bougainvillia, Pennaria, Obelia), bryozoans (Amathia, Bugula, Schizoporella), and barnacles (Amphibalanus), suggesting invasions from regions like Brazil, and the Indo-Pacific. Notably, Amathia brasiliensis and Amathia cf. vidovici were recorded for the first time in West Africa, alongside the detection of two other Amathia species, raising concerns about their potential impact on the PNBA's biodiversity and ecosystem services. The presence of these exotic species, likely introduced via international maritime traffic and fishing activities, highlights the park's vulnerability. The study underscores the utility of DNA barcoding for detecting cryptic diversity and tracking species dispersal, recommending urgent conservation measures and biosecurity protocols to protect the PNBA's unique marine ecosystems. ### Competing Interest Statement The authors declare no conflicts of interest.