Identifying habitat affinities and demographic characteristics associated with high invasion potential is a key ecological challenge. However, testing invasion hypotheses exclusively in the invaded range is inherently flawed, as it conflates the intrinsic pre-adaptations that allowed the species to invade with the habitat shifts they adopted post-invasion. To elucidate how invasion potential is related to habitat affinities and post-invasion ecological dynamics, we investigated the unique paired-basin system of the Red Sea and Eastern Mediterranean. We captured in situ realized niche data (e.g. abundance, depth limits and habitat affinities) using standardized stereo underwater video surveys across 179 populations. We then applied a three-comparison framework to evaluate native-range invasion potential, post-invasion habitat shifts and recipient-community integration. Within the native Red Sea, future introduced species were distinct from non-introduced natives primarily due to their lack of reliance on coral habitats, shallower minimum depth limits, and broader habitat and depth ranges. Comparing the native and invaded ranges of introduced species revealed post-invasion niche shifts. Rather than shifting uniformly, introduced species exhibited high habitat lability, successfully abandoning affinities for tropical substrates to utilize available Mediterranean habitats. Within the Mediterranean, introduced species were assimilated into the recipient community, becoming indistinguishable from natives in habitat use rather than occupying distinct habitats. By synthesizing linear discriminant and mixed-modelling approaches into a cross-validated ensemble index, we prioritized specific Red Sea species as high-risk candidates for future Mediterranean invasion. Ultimately, this in situ framework highlights that while specific native-range habitat filters predict invasion potential, post-invasion habitat lability means that relying solely on native affinities could severely underestimate their spread and impact in novel environments.

Bioinvasions are considered mostly as a biodiversity and conservation hazard, but in specific situations, introduced species can bring ecological or socioeconomic benefits. We assessed the social-ecological role of marine introduced species in the eastern Mediterranean Sea-a global hotspot of bioinvasions and extirpations-and their potential relevance for achieving conservation and sustainability targets set by the Kunming-Montreal Global Biodiversity Framework (GBF). The adverse effects of introduced species include predation and competition with native species, alteration of food webs, habitat degradation, disruption of fisheries and coastal infrastructure, and risks to human health. Their beneficial effects on biodiversity, ecosystem functions, and services include the creation of novel habitats, trophic support for native species, partial functional compensation for declining native taxa, and substantial contributions to fisheries production and food provision. These effects can co-occur and generate trade-offs. Conservation practice should move beyond rigid origin-based assumptions and explicitly account for the context-dependent impacts of introduced species, particularly in regions where native biodiversity and associated functions are rapidly declining due to ocean warming. Introduced species considerations need to be integrated in conservation planning to meet the goal of protecting 30% of the land, sea, and inland waters (GBF Targets 1 and 3) and to sustain ecosystem services, such as food provision, through fisheries (GBF Targets 10 and 11) amid rapid climate change. Incorporating the positive and negative aspects of introduced species into systematic conservation planning can optimize conservation investments through transparent trade-off analyses. By adopting a pragmatic, holistic approach to conservation that recognizes the varied and dynamic roles of introduced species, decision makers can more effectively achieve the GBF conservation and sustainability targets in the eastern Mediterranean.

Climate change is reshaping biodiversity globally, but not uniformly. Many regions are severely impacted by losses, yet areas and habitats of varying scales exist where climate change impacts are expected to remain comparatively low. The identification and forecasting of such areas, termed climate change refugia, represents conservation capacity for improving resilience of natural and managed ecosystems. However, we still lack methods for detecting and integrating refugia into spatial management plans that incorporate physiological information, especially in marine environments. We offer a new framework to bridge the gap between large-scale environmental modelling and individual- to species-level physiology to identify current and future ocean refugia for biological conservation. We introduce the concept of the “physiological seascape”, which integrates spatial-temporal heterogeneity in climatic drivers, stability and uniqueness of those drivers at organism-relevant scales, and direct and indirect assessments of physiological sensitivity. We provide two theoretical exploratory examples and recommend that mapping the intersection of refugia and biodiversity become part of priority setting within spatial conservation instruments (e.g., as part of cumulative effects assessments), to inform climate-ready biodiversity conservation and restoration actions.

The use of Passive Acoustic Monitoring (PAM) for estimating biodiversity often entails the use of acoustic indices that summarize the acoustic properties of the recordings. Although acoustic indices have been shown to successfully track biodiversity in limited contexts, the recurrent failure of acoustic indices generalization across domains has raised doubts regarding the reliability and scalability of PAM. Variation across ecological communities is often cited as a principal limit to the generalizability of acoustic indices-based biodiversity estimation, while environmental noise variability is often overlooked. Background noise can change between recordings because of environmental (e.g., wind) and system (e.g., microphone) variability that make noise equalization across studies difficult. In this study, we use both synthetic soundscapes and field recordings to assess the effects of background noise on acoustic index generalization. We reveal a dramatic effect of background noise on the ability of acoustic indices to generalize biodiversity estimates across datasets. We demonstrate that careful selection of noise-invariant acoustic indices, accounting for the signal-to-noise ratio, training across noise types and segmentation of the recordings to concentrate biophony all improve acoustic index-based biodiversity generalization. We also demonstrate the use of soundscape simulation training for acoustic index-based biodiversity estimations and generalization. We conclude that acoustic indices may have more potential as a simple and cost-effective biodiversity monitoring tool than previously thought and we highlight several possibilities for mitigating background noise variability during training to improve generalization.

The number of species introduced outside of their historical ranges by human activity continues to rise 1 . A subset of these species establishes, form self-sustaining populations, and some – invasive alien species – go on to cause substantial harm to biodiversity and ecosystems 2 . Preventing new invasive alien species from establishing is the key focus of interventions, because post-establishment management is costly and often fails 3,4 . However, it remains unclear how effective multilateral efforts have been in curbing the rise. Here we show that the emergence of new invasive alien species across countries is slowing, and trends are similarly negative across geographically diverse countries. Using data and modelling advances, we find a 35% reduction in the establishment of new invasive alien species over a policy-relevant 50-year time frame. The findings directly inform the assessment of progress for the invasive alien species target of the Kunming-Montreal Global Biodiversity Framework 5 , and provide a global baseline for monitoring rates of invasive alien species establishment. Furthermore, the slowdown suggests that policy and investment over recent decades to prevent invasive alien species from entering and establishing in countries have had a positive effect.

The depth distribution of marine species is essential ecological information, especially within hotspots of biological invasions and given the increasing evidence of climate-driven depth shifts. Due to the scarcity of systematic surveys across depths, most studies rely on coarse-scale compilations of opportunistic data. High-quality depth estimates are particularly lacking in the eastern Mediterranean, a global hotspot of climate change and biological invasions, and the adjacent Red Sea, which serves as the source for most species introductions. Using baited remote underwater stereo-video systems to depths of 150 m, we report new depth records for fish species in the northern Red Sea and eastern Mediterranean Sea, and model their abundance patterns across depths. We found that 96 of the 230 studied species (42%) were found at novel depths compared to their previously known records, with 84 species showing deeper distributions. The mean deep border extension across these species was 22.4 m. Our results highlight the importance of in-situ observations across depths. We offer a comprehensive dataset including species' depth ranges, modeled central depth niches, abundance, body size, and associated habitat types. This dataset is useful for understanding the role of depth shifts in response to climate change and species introductions into the Mediterranean Sea.

The use of Passive Acoustic Monitoring (PAM) to monitor marine diversity and ecological health is gaining popularity. However, long-term marine ecoacoustics monitoring remains limited, primarily due to technical challenges associated with data storage limitations and energy sources underwater.Acoustic telemetry is a widely used tracking technique in which receivers record signals from acoustic tags, typically over long periods of time. While this method is widely used to record animal location and behavior, the receiver's recorded environment sound levels are mostly overlooked.In this study, we introduce a new PAM method, which we call Telemetry-based PAM, that provides continuous long-term monitoring of the state of marine systems using currently untapped sound levels from acoustic telemetry. We demonstrate strong correlations between sound levels and biophonic sound sources, specifically invertebrate sounds, on a coral reef. We further demonstrate that the spatial and temporal decline and recovery patterns of sound from the receivers on the reef following a major storm closely aligned with parallel information from visual surveys.As acoustic receiver arrays are already widespread globally, Telemetry-based PAM can provide an easy and affordable monitoring tool for marine environments. Importantly, as recordings are continuous, deployed for long durations, and based on multiple receivers, we can use these recordings to detect small-scale variations in sound levels over space and time, offering an unparalleled fine-grained view of reef dynamics.

The world is experiencing notable increases in the duration, intensity and frequency of marine heatwaves (MHWs). Documented effects of MHWs on fishes encompass various population- and community-level impacts, ranging from localized mass mortalities to transient or semi-permanent range shifts, while some populations show little measurable change. However, there is limited information on in situ behavioural responses of individuals before, during and after MHWs. In this study, we used acoustic telemetry to examine the activity levels, depths and daily displacement of 32 terminal-phase male parrotfishes belonging to five species across 12 moderate-sized MHWs (2016-2021). The study took place in the northern Red Sea and coincided with a mass mortality of parrotfishes during a rapid warming event. The parrotfishes exhibited only minuscule behavioural changes during or after the MHWs, regardless of how the MHW was defined or characterized. Thus, within the range of MHWs studied, MHWs have little to no impact on parrotfishes' behaviour. Our observations suggest that either the mechanisms by which parrotfishes respond to thermal stress are not behavioural, or that such responses may only occur under more severe MHWs.

Depth plays a crucial role in shaping marine biodiversity patterns, with species richness typically decreasing with depth. Despite extensive documentation of this pattern, the drivers of richness changes across depth remain unclear. Richness–depth patterns can arise from multiple proximate mechanisms acting simultaneously, such as changes in abundance, evenness, and the spatial aggregations of individuals. Using a unified framework, we examined variation in richness patterns and their underlying mechanisms in the northern Red Sea for fishes (down to 150 m), Scleractinia, Octocorallia, and Porifera (down to 45–70 m). Our results reveal taxa-specific richness responses. Overall, abundance changes emerged as the most consistent driver of richness variation with depth, although its direction and magnitude differed among taxa. Fish richness declined with depth, primarily driven by reduced abundance and lower evenness. In contrast, Porifera exhibited increased richness with depth, largely explained by higher abundances. Scleractinia richness peaked at 10 m and slowly declined with depth, similarly linked to changes in abundance. In contrast, Octocorallia showed a slight richness increase with depth, mainly due to higher evenness at greater depths, although gaps in observations at intermediate depths may have obscured fine-scale peaks within the studied range. Increasing sampling scale (by combining sampling units) amplified these patterns. The results highlight the importance of understanding abundance gradients for richness, which may be overlooked when relying solely on cover-based estimates. The taxon-specific variability in richness–depth patterns challenges the conventional expectation of declining richness with depth, yet uncovers important commonality in the underlying mechanisms.

Scientists still have a very limited understanding of marine biodiversity. A new study in PLOS Biology using unprecedented global environmental DNA (eDNA) sampling reveals the extent of our ignorance and charts the way forward.

FISHGLOB brings together experts in, and users of, fish monitoring data to support biodiversity research and conservation across oceans.

Reducing the rates and impacts of biological invasions is a major policy goal of international biodiversity agreements. Yet the extent to which this goal is being achieved and the agreements hence successful in this respect remains unclear. Here we use a comprehensive record of alien species introduction in the terrestrial Antarctic, including its surrounding Southern Ocean Islands, spanning 115 years (1900–2015), to quantify the impact of biosecurity policy on alien species introduction rates in the region, where invasive alien species are a primary environmental conservation threat and management priority. We show that although many parts of the Antarctic have been colonized by non‐indigenous taxa, recent rates of introduction appear to be slowing or static in most parts, compared with increases in the past. Our results vindicate the regional Antarctic focus on biosecurity measures, but also demonstrate the need for stricter enforcement due to rapid socio‐environmental changes.

The difficulties in obtaining species-level abundance estimates of marine larvae have hindered comparisons of diversity across life stages, severely limiting our knowledge of how adult diversity is maintained. To explore factors shaping diversity across life stages, we surveyed adult coral reef fishes, compiled data on their ecological and life history traits and paired these with a unique dataset of species-level larval abundances. Relative larval abundance was more even compared to adults and matched random expectations, whereas the adult community was markedly uneven and less functionally diverse, suggesting species filtering effects. While adult abundance was positively linked to larval abundance, species size and diet altered this association, with larger and non-planktivorous adults being less abundant than expected from their larval supply. Our results illustrate that while larval supply is important in determining adult taxonomic and functional diversity, post-larval processes increase the numerical dominance of particular species, thus reducing overall diversity.

Large‐scale biodiversity assessments and conservation applications require integrated and up‐to‐date datasets across regions. In the oceans, monitoring is fragmented, which affects knowledge exchange and usage. Among existing monitoring programs, scientific bottom‐trawl surveys (SBTS) are long‐term, rich, and well‐maintained data sources at the scale of each sampled region, but these data are under‐utilized in biodiversity applications, especially across regions. This is hampered by the lack of an international community and database maintained through time. To address this, we created FISHGLOB, an infrastructure gathering SBTS and experts. In 5 years, we developed an integrated database of SBTS and a consortium gathering more than 100 experts and users. Here, we are sharing the project history, achievements, challenges, and outlooks. In particular, we reflect on the infrastructure‐building social and technical processes which will guide the development of similar infrastructures. The FISHGLOB project takes ocean monitoring one step forward in working as a unified community across disciplines and regions of the world.

The effectiveness of protected areas in preserving diversity is typically assessed by comparing them to control sites. However, studies often report inconsistent effects of protection on diversity. This inconsistency may partly result from hard-to-quantify gradients in habitat quality (i.e., the site's potential to harbor diversity), which can mask the impact of protection. We hypothesize that analyzing patterns of dark diversity, the assemblage of species that fit the site conditions but are locally absent, along with species pool size (the sum of observed and dark diversity), can help distinguish protection effects where protection and habitat quality are confounded. Specifically, protection should reduce dark diversity, as fewer species are absent, but it should not affect species pool size, which is primarily determined by habitat quality. Using marine protected areas and control sites across the Mediterranean Sea, we show that, as predicted, fish dark diversity decreases with protection but is independent of habitat quality, while species pool size was related to habitat quality but not protection. At the same time, we did not find an increase in species richness with protection. These results suggest that, by being less influenced by habitat quality, dark diversity provides a refined understanding of conservation effectiveness compared to richness alone. Since dark diversity can be estimated using species co-occurrence patterns, it remains useful even when habitat quality data are unavailable. Therefore, explicitly considering species pool size and dark diversity, alongside observed diversity, is critical for assessing control site adequacy and disentangling the effects of habitat quality and protection.

The integration of “greening the gray” (GTG) into marine infrastructure represents a transformative approach to enhancing biodiversity and ecosystem services in heavily modified environments. However, the ecological effectiveness of GTG remains hindered by inconsistent methodologies and knowledge gaps. This study proposes a methodological approach for GTG biodiversity assessments, focusing on appropriate control site selection, integration of count and coverage data through occupancy methods, and applying coverage-based rarefaction to address sampling biases. The approach facilitated consistent evaluation of biodiversity data and reliable evaluation of GTG performance across various contexts, specifically using a GTG project at the Port of Vigo in Spain as a case study. This methodology structure supports sustainable marine infrastructure development by providing scalable, evidence-based methodologies for biodiversity assessment and fostering international collaboration among ecologists, developers, and stakeholders.

AimIt has been hypothesised that niche breadth decreases with richness due to interactions, such as competition, forcing species to specialise. This hypothesis has been tested at the community-level using species-level niche breadth estimates. However, evidence for changes in niche-breath among populations of the same species are scant. Our aim was to examine the niche breadth to richness relationship within species, which is crucial for understanding the role of interactions, as opposed to large-scale climate, in altering realised niche breadth.LocationThe Pacific Ocean.Time Period1988-2015.Major Taxa StudiedFishes.MethodsWe focus on reef fishes along a large-scale richness gradient not accompanied by marked environmental changes. Fishes were surveyed in four distinct habitats, which allow to estimate habitat-breadth for each population. We calculated habitat-breadth across multiple populations of 154 species, and tested how habitat-breadth varied with richness. We further tested the effect of traits and trait-distinctiveness on the richness-sensitivity of habitat-breadth.ResultsHabitat-breadth varied with species traits, with larger species more commonly habitat generalists while schooling and planktivorous species more commonly habitat specialists. Importantly, habitat-breadth was negatively correlated with richness for 109 out of the 154 species, and, across all species, the relationship was highly significant. We found some support that species with distinct traits displayed less sensitivity of habitat-breadth to richness, but the relationship was dependent on the type of trait-distinctiveness index used.ConclusionsThis is the first large-scale evidence that population-level habitat-breadth changes with richness. Results suggest that the realised niche is population-specific and that niche breadth is reduced in high-diversity settings where more intense interactions, such as competition, are expected. This implies that populations, specifically in species rich areas, do not use their entire fundamental niche. Therefore, the ability to predict habitat preferences response to global changes based on current habitat associations, without accounting for species interactions, may be limited.

MotivationHere, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R package (BioTIMEr) to facilitate use of the database.Main Types of Variables IncludedThe database is composed of one main data table containing the abundance records and 11 metadata tables. The data are organised in a hierarchy of scales where 11,989,233 records are nested in 1,603,067 sample events, from 553,253 sampling locations, which are nested in 708 studies. A study is defined as a sampling methodology applied to an assemblage for a minimum of 2 years.Spatial Location and GrainSampling locations in BioTIME are distributed across the planet, including marine, terrestrial and freshwater realms. Spatial grain size and extent vary across studies depending on sampling methodology. We recommend gridding of sampling locations into areas of consistent size.Time Period and GrainThe earliest time series in BioTIME start in 1874, and the most recent records are from 2023. Temporal grain and duration vary across studies. We recommend doing sample-level rarefaction to ensure consistent sampling effort through time before calculating any diversity metric.Major Taxa and Level of MeasurementThe database includes any eukaryotic taxa, with a combined total of 56,400 taxa.Software Formatcsv and. SQL.