Ocean acidification impairs seagrass performance under thermal stress in shallow and deep water.

Despite the effects of ocean acidification (OA) on seagrasses have been widely investigated, predictions of seagrass performance under future climates need to consider multiple environmental factors. Here, we performed a mesocosm study to assess the effects of OA on shallow and deep Posidonia oceanica plants. The experiment was run in 2021 and repeated in 2022, a year characterized by a prolonged warm water event, to test how the effects of OA on plants are modulated by thermal stress. The response of P. oceanica to experimental conditions was investigated at different levels of biological organization. Under average seawater temperature, there were no effects of OA in both shallow and deep plants, indicating that P. oceanica is not limited by current inorganic carbon concentration, regardless of light availability. In contrast, under thermal stress, exposure of plants to OA increased lipid peroxidation and decreased photosynthetic performance, with deep plants displaying higher levels of heat stress, as indicated by the over-expression of stress-related genes and the activation of antioxidant systems. In addition, warming reduced plant growth, regardless of seawater CO2 and light levels, suggesting that thermal stress may play a fundamental role in the future development of seagrass meadows. Our results suggest that OA may exacerbate the negative effects of future warming on seagrasses.

DNA methylation dynamics in a coastal foundation seagrass species under abiotic stressors.

DNA methylation (DNAm) has been intensively studied in terrestrial plants in response to environmental changes, but its dynamic changes in a temporal scale remain unexplored in marine plants. The seagrass Posidonia oceanica ranks among the slowest-growing and longest-living plants on Earth, and is particularly vulnerable to sea warming and local anthropogenic pressures. Here, we analysed the dynamics of DNAm changes in plants collected from coastal areas differentially impacted by eutrophication (i.e. oligotrophic, Ol; eutrophic, Eu) and exposed to abiotic stressors (nutrients, temperature increase and their combination). Levels of global DNAm (% 5-mC) and the expression of key genes involved in DNAm were assessed after one, two and five weeks of exposure. Results revealed a clear differentiation between plants, depending on environmental stimuli, time of exposure and plants' origin. % 5-mC levels were higher during the initial stress exposure especially in Ol plants, which upregulated almost all genes involved in DNAm. Contrarily, Eu plants showed lower expression levels, which increased under chronic exposure to stressors, particularly to temperature. These findings show that DNAm is dynamic in P. oceanica during stress exposure and underlined that environmental epigenetic variations could be implicated in the regulation of acclimation and phenotypic differences depending on local conditions.

Signs of local adaptation by genetic selection and isolation promoted by extreme temperature and salinity in the Mediterranean seagrass Posidonia oceanica.

Adaptation to local conditions is known to occur in seagrasses; however, knowledge of the genetic basis underlying this phenomenon remains scarce. Here, we analysed Posidonia oceanica from six sites within and around the Stagnone di Marsala, a semi-enclosed coastal lagoon where salinity and temperature exceed the generally described tolerance thresholds of the species. Sea surface temperatures (SSTs) were measured and plant samples were collected for the assessment of morphology, flowering rate and for screening genome-wide polymorphisms using double digest restriction-site-associated DNA sequencing. Results demonstrated more extreme SSTs and salinity levels inside the lagoon than the outer lagoon regions. Morphological results showed significantly fewer and shorter leaves and reduced rhizome growth of P. oceanica from the inner lagoon and past flowering events were recorded only for a meadow farthest away from the lagoon. Using an array of 51,329 single nucleotide polymorphisms, we revealed a clear genetic structure among the study sites and confirmed the genetic isolation and high clonality of the innermost site. In all, 14 outlier loci were identified and annotated with several proteins including those relate to plant stress response, protein transport and regulators of plant-specific developmental events. Especially, five outlier loci showed maximum allele frequency at the innermost site, likely reflecting adaptation to the extreme temperature and salinity regimes, possibly due to the selection of more resistant genotypes and the progressive restriction of gene flow. Overall, this study helps us to disentangle the genetic basis of seagrass adaptation to local environmental conditions and may support future works on assisted evolution in seagrasses.

The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea.

Seagrasses colonized the sea on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet. Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes, genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae and that is important for ion homoeostasis, nutrient uptake and O2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming, to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants.

Harnessing positive species interactions as a tool against climate-driven loss of coastal biodiversity.

Habitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.

Partitioning resilience of a marine foundation species into resistance and recovery trajectories.

The resilience of an ecological unit encompasses resistance during adverse conditions and the capacity to recover. We adopted a 'resistance-recovery' framework to experimentally partition the resilience of a foundation species (the seagrass Cymodocea nodosa). The shoot abundances of nine seagrass meadows were followed before, during and after simulated light reduction conditions. We determined the significance of ecological, environmental and genetic drivers on seagrass resistance (% of shoots retained during the light deprivation treatments) and recovery (duration from the end of the perturbed state back to initial conditions). To identify whether seagrass recovery was linearly related to prior resistance, we then established the connection between trajectories of resistance and recovery. Finally, we assessed whether recovery patterns were affected by biological drivers (production of sexual products-seeds-and asexual propagation) at the meadow-scale. Resistance to shading significantly increased with the genetic diversity of the meadow and seagrass recovery was conditioned by initial resistance during shading. A threshold in resistance (here, at a ca. 70% of shoot abundances retained during the light deprivation treatments) denoted a critical point that considerably delays seagrass recovery if overpassed. Seed densities, but not rhizome elongation rates, were higher in meadows that exhibited large resistance and quick recovery, which correlated positively with meadow genetic diversity. Our results highlight the critical role of resistance to a disturbance for persistence of a marine foundation species. Estimation of critical trade-offs between seagrass resistance and recovery is a promising field of research to better manage impacts on seagrass meadows.

m6A RNA Methylation in Marine Plants: First Insights and Relevance for Biological Rhythms.

Circadian regulations are essential for enabling organisms to synchronize physiology with environmental light-dark cycles. Post-transcriptional RNA modifications still represent an understudied level of gene expression regulation in plants, although they could play crucial roles in environmental adaptation. N6-methyl-adenosine (m6A) is the most prevalent mRNA modification, established by "writer" and "eraser" proteins. It influences the clockwork in several taxa, but only few studies have been conducted in plants and none in marine plants. Here, we provided a first inventory of m6A-related genes in seagrasses and investigated daily changes in the global RNA methylation and transcript levels of writers and erasers in Cymodocea nodosa and Zostera marina. Both species showed methylation peaks during the dark period under the same photoperiod, despite exhibiting asynchronous changes in the m6A profile and related gene expression during a 24-h cycle. At contrasting latitudes, Z. marina populations displayed overlapping daily patterns of the m6A level and related gene expression. The observed rhythms are characteristic for each species and similar in populations of the same species with different photoperiods, suggesting the existence of an endogenous circadian control. Globally, our results indicate that m6A RNA methylation could widely contribute to circadian regulation in seagrasses, potentially affecting the photo-biological behaviour of these plants.

Heat-stress induced flowering can be a potential adaptive response to ocean warming for the iconic seagrass Posidonia oceanica.

The Mediterranean Sea is particularly vulnerable to warming and the abrupt declines experienced by the endemic Posidonia oceanica populations after recent heatwaves have forecasted severe consequences for the ecological functions and socio-economical services this habitat forming species provides. Nevertheless, this highly clonal and long-lived species could be more resilient to warming than commonly thought since heat-sensitive plants massively bloomed after a simulated heatwave, which provides the species with an opportunity to adapt to climate change. Taking advantage of this unexpected plant response, we investigated for the first time the molecular and physiological mechanisms involved in seagrass flowering through the transcriptomic analysis of bloomed plants. We also aimed to identify if flowering is a stress-induced response as suggested from the fact that heat-sensitive but not heat-tolerant plants flowered. The transcriptomic profiles of flowered plants showed a strong metabolic activation of sugars and hormones and indications of an active transport of these solutes within the plant, most likely to induce flower initiation in the apical meristem. Preflowered plants also activated numerous epigenetic-related genes commonly used by plants to regulate the expression of key floral genes and stress-tolerance genes, which could be interpreted as a mechanism to survive and optimize reproductive success under stress conditions. Furthermore, these plants provided numerous molecular clues suggesting that the factor responsible for the massive flowering of plants from cold environments (heat-sensitive) can be considered as a stress. Heat-stress induced flowering may thus be regarded as an ultimate response to survive extreme warming events with potential adaptive consequences for the species. Fitness implications of this unexpected stress-response and the potential consequences on the phenotypic plasticity (acclimation) and evolutionary (adaptation) opportunity of the species to ocean warming are finally discussed.

Adaptive responses along a depth and a latitudinal gradient in the endemic seagrass Posidonia oceanica.

Seagrass meadows provide important ecosystem services and are critical for the survival of the associated invertebrate community. However, they are threatened worldwide by human-driven environmental change. Understanding the seagrasses' potential for adaptation is critical to assess not only their ability to persist under future global change scenarios, but also to assess the persistence of the associated communities. Here we screened a wild population of Posidonia oceanica, an endemic long-lived seagrass in the Mediterranean Sea, for genes that may be target of environmental selection, using an outlier and a genome-wide transcriptome analysis. We identified loci where polymorphism or differential expression was associated with either a latitudinal or a bathymetric gradient, as well as with both gradients in an effort to identify loci associated with temperature and light. We found the candidate genes underlying growth and immunity to be divergent between populations adapted to different latitudes and/or depths, providing evidence for local adaptation. Furthermore, we found evidence of reduced gene flow among populations including adjacent populations. Reduced gene flow, combined with low sexual recombination, small effective population size, and long generation time of P. oceanica raises concerns for the long-term persistence of this species, especially in the face of rapid environmental change driven by human activities.

Molecular level responses to chronic versus pulse nutrient loading in the seagrass Posidonia oceanica undergoing herbivore pressure.

Seagrasses are key marine foundation species, currently declining due to the compounded action of global and regional anthropogenic stressors. Eutrophication has been associated with seagrass decline, while grazing has been traditionally considered to be a natural disturbance with a relatively low impact on seagrasses. In the recent years, this assumption has been revisited. Here, by means of a 16-month field-experiment, we investigated the molecular mechanisms driving the long-term response of Posidonia oceanica to the combination of nutrient enrichment, either as a chronic (press) or pulse disturbance, and herbivory. Changes in expression levels of 19 target genes involved in key steps of photosynthesis, nutrient assimilation, chlorophyll metabolism, oxidative-stress response and plant defense were evaluated through reverse transcription-quantitative polymerase chain reaction (RT-qPCR). High herbivore pressure affected the molecular response of P. oceanica more dramatically than did enhanced nutrient levels, altering the expression of genes involved in plant tolerance and resistance traits, such as photosynthesis and defense mechanisms. Genes involved in carbon fixation and N assimilation modulated the response of plants to high nutrient levels. Availability of resources seems to modify P. oceanica response to herbivory, where the upregulation of a nitrate transporter gene was accompanied by the decline in the expression of nitrate reductase in the leaves, suggesting a change in plant-nutrient allocation strategy. Finally, press and pulse fertilizations altered nitrate uptake and reduction-related genes in opposite ways, suggesting that taking into account the temporal regime of nutrient loading is important to assess the physiological response of seagrasses to eutrophication.

Seagrass collapse due to synergistic stressors is not anticipated by phenological changes.

Seagrasses are globally declining and often their loss is due to synergies among stressors. We investigated the interactive effects of eutrophication and burial on the Mediterranean seagrass, Posidonia oceanica. A field experiment was conducted to estimate whether shoot survival depends on the interactive effects of three levels of intensity of both stressors and to identify early changes in plants (i.e., morphological, physiological and biochemical, and expression of stress-related genes) that may serve to detect signals of imminent shoot density collapse. Sediment burial and nutrient enrichment produced interactive effects on P. oceanica shoot survival, as high nutrient levels had the potential to accelerate the regression of the seagrass exposed to high burial (HB). After 11 weeks, HB in combination with either high or medium nutrient enrichment caused a shoot loss of about 60%. Changes in morphology were poor predictors of the seagrass decline. Likewise, few biochemical variables were associated with P. oceanica survival (the phenolics, ORAC and leaf δ34S). In contrast, the expression of target genes had the highest correlation with plant survival: photosynthetic genes (ATPa, psbD and psbA) were up-regulated in response to high burial, while carbon metabolism genes (CA-chl, PGK and GADPH) were down-regulated. Therefore, die-offs due to high sedimentation rate in eutrophic areas can only be anticipated by altered expression of stress-related genes that may warn the imminent seagrass collapse. Management of local stressors, such as nutrient pollution, may enhance seagrass resilience in the face of the intensification of extreme climate events, such as floods.

Genomewide transcriptional reprogramming in the seagrass Cymodocea nodosa under experimental ocean acidification.

Here, we report the first use of massive-scale RNA-sequencing to explore seagrass response to CO2 -driven ocean acidification (OA). Large-scale gene expression changes in the seagrass Cymodocea nodosa occurred at CO2 levels projected by the end of the century. C. nodosa transcriptome was obtained using Illumina RNA-Seq technology and de novo assembly, and differential gene expression was explored in plants exposed to short-term high CO2 /low pH conditions. At high pCO2 , there was a significant increased expression of transcripts associated with photosynthesis, including light reaction functions and CO2 fixation, and also to respiratory pathways, specifically for enzymes involved in glycolysis, in the tricarboxylic acid cycle and in the energy metabolism of the mitochondrial electron transport. The upregulation of respiratory metabolism is probably supported by the increased availability of photosynthates and increased energy demand for biosynthesis and stress-related processes under elevated CO2 and low pH. The upregulation of several chaperones resembling heat stress-induced changes in gene expression highlighted the positive role these proteins play in tolerance to intracellular acid stress in seagrasses. OA further modifies C. nodosa secondary metabolism inducing the transcription of enzymes related to biosynthesis of carbon-based secondary compounds, in particular the synthesis of polyphenols and isoprenoid compounds that have a variety of biological functions including plant defence. By demonstrating which physiological processes are most sensitive to OA, this research provides a major advance in the understanding of seagrass metabolism in the context of altered seawater chemistry from global climate change.

Key genes as stress indicators in the ubiquitous diatom Skeletonema marinoi.

BACKGROUND: The dense phytoplankton blooms that characterize productive regions and seasons in the oceans are dominated, from high to low latitudes and from coast line to open ocean, by comparatively few, often cosmopolitan species of diatoms. These key dominant species may undergo dramatic changes due to global climate change. RESULTS: In order to identify molecular stress-indicators for the ubiquitous diatom species Skeletonema marinoi, we tested stress-related genes in different environmental conditions (i.e. nutrient starvation/depletion, CO2-enrichment and combined effects of these stressors) using RT-qPCR. The data show that these stressors impact algal growth rate, inducing early aging and profound changes in expression levels of the genes of interest. CONCLUSIONS: Most analyzed genes (e.g. antioxidant-related and aldehyde dehydrogenases) were strongly down-regulated which may indicate a strategy to avoid unnecessary over-investment in their respective proteins. By contrast, key genes were activated (e.g. HSPs, GOX) which may allow the diatom species to better cope with adverse conditions. We propose the use of this panel of genes as early bio-indicators of environmental stress factors in a changing ocean.

A meta-analysis reveals a positive correlation between genetic diversity metrics and environmental status in the long-lived seagrass Posidonia oceanica.

The seagrass Posidonia oceanica is a key engineering species structuring coastal marine systems throughout much of the Mediterranean basin. Its decline is of concern, leading to the search for short- and long-term indicators of seagrass health. Using ArcGIS maps from a recent, high-resolution (1-4 km) modelling study of 18 disturbance factors affecting coastal marine systems across the Mediterranean (Micheli et al. 2013, http://globalmarine.nceas.ucsb.edu/mediterranean/), we tested for correlations with genetic diversity metrics (allelic diversity, genotypic/clonal diversity and heterozygosity) in a meta-analysis of 56 meadows. Contrary to initial predictions, weak but significantly positive correlations were found for commercial shipping, organic pollution (pesticides) and cumulative impact. This counterintuitive finding suggests greater resistance and resilience of individuals with higher genetic and genotypic diversity under disturbance (at least for a time) and/or increased sexual reproduction under an intermediate disturbance model. We interpret the absence of low and medium levels of genetic variation at impacted locations as probable local extinctions of individuals that already exceeded their resistance capacity. Alternatively, high diversity at high-impact sites is likely a temporal artefact, reflecting the mismatch with pre-environmental impact conditions, especially because flowering and sexual recruitment are seldom observed. While genetic diversity metrics are a valuable tool for restoration and mitigation, caution must be exercised in the interpretation of correlative patterns as found in this study, because the exceptional longevity of individuals creates a temporal mismatch that may falsely suggest good meadow health status, while gradual deterioration of allelic diversity might go unnoticed.

Mass flowering and unprecedented extended pseudovivipary in seagrass (Posidonia oceanica) after a Marine Heat Wave.

Seagrasses are marine flowering plants that create critical coastal ecosystems and are threatened by warming. Clonal expansion is generally the dominant strategy for meadow recovery, while sexual reproduction strongly differs among species (e.g., monoecious and diecious species, some creating seed banks, viviparous seedlings). In 2022, the Western Mediterranean underwent unprecedented warming, and, associated with it, we observed flowering (100 %) across 11 Posidonia oceanica meadows in Mallorca, Balearic Islands. Furthermore, 64 % of the sites also exhibited pseudovivipary, an extremely rare phenomenon in angiosperms whereby plantlets replace sexual reproductive structures, producing clones of the maternal plant. Our results support the notion that P. oceanica flowering and pseudovivipary (genetically confirmed) are triggered by warming, never before being pseudovivipary reported across multiple sites in a marine plant. Considering the negative impacts that warming can have on seagrasses, existence of widespread pseudovivipary is a critical aspect to consider for understanding mechanisms of resilience in seagrasses.

Thermo-priming triggers species-specific physiological and transcriptome responses in Mediterranean seagrasses.

Heat-priming improves plants' tolerance to a recurring heat stress event. The underlying molecular mechanisms of heat-priming are largely unknown in seagrasses. Here, ad hoc mesocosm experiments were conducted with two Mediterranean seagrass species, Posidonia oceanica and Cymodocea nodosa. Plants were first exposed to heat-priming, followed by a heat-triggering event. A comprehensive assessment of plant stress response across different levels of biological organization was performed at the end of the triggering event. Morphological and physiological results showed an improved response of heat-primed P. oceanica plants while in C. nodosa both heat- and non-primed plants enhanced their growth rates at the end of the triggering event. As resulting from whole transcriptome sequencing, molecular functions related to several cellular compartments and processes were involved in the response to warming of non-primed plants, while the response of heat-primed plants involved a limited group of processes. Our results suggest that seagrasses acquire a primed state during the priming event, that eventually gives plants the ability to induce a more energy-effective response when the thermal stress event recurs. Different species may differ in their ability to perform an improved heat stress response after priming. This study provides pioneer molecular insights into the emerging topic of seagrass stress priming and may benefit future studies in the field.

Marine heatwaves recurrence aggravates thermal stress in the surfgrass Phyllospadix scouleri.

The surfgrass Phyllospadix scouleri grows in highly productive meadows along the Pacific coast of North America. This region has experienced increasingly severe marine heatwaves (MHWs) in recent years. Our study evaluated the impact of consecutive MHWs, simulated in mesocosms, on essential ecophysiological features of P. scouleri. Overall, our findings show that the plants' overall physiological status has been progressively declining. Interestingly, the indicators of physiological stress in photosynthesis only showed up once the initial heat exposure stopped (i.e., during the recovery period). The warming caused increased oxidative damage and a decrease in nitrate uptake rates. However, the levels of non-structural carbohydrates and relative growth rates were not affected. Our findings emphasize the significance of incorporating recovery periods in this type of study as they expose delayed stress responses. Furthermore, experiencing consecutive intense MHWs can harm surfgrasses over time, compromising the health of their meadows and the services they offer to the ecosystem.

Seagrass genomes reveal ancient polyploidy and adaptations to the marine environment.

We present chromosome-level genome assemblies from representative species of three independently evolved seagrass lineages: Posidonia oceanica, Cymodocea nodosa, Thalassia testudinum and Zostera marina. We also include a draft genome of Potamogeton acutifolius, belonging to a freshwater sister lineage to Zosteraceae. All seagrass species share an ancient whole-genome triplication, while additional whole-genome duplications were uncovered for C. nodosa, Z. marina and P. acutifolius. Comparative analysis of selected gene families suggests that the transition from submerged-freshwater to submerged-marine environments mainly involved fine-tuning of multiple processes (such as osmoregulation, salinity, light capture, carbon acquisition and temperature) that all had to happen in parallel, probably explaining why adaptation to a marine lifestyle has been exceedingly rare. Major gene losses related to stomata, volatiles, defence and lignification are probably a consequence of the return to the sea rather than the cause of it. These new genomes will accelerate functional studies and solutions, as continuing losses of the 'savannahs of the sea' are of major concern in times of climate change and loss of biodiversity.

Gene co-expression network analysis for the selection of candidate early warning indicators of heat and nutrient stress in Posidonia oceanica.

The continuous worldwide seagrasses decline calls for immediate actions in order to preserve this precious marine ecosystem. The main stressors that have been linked with decline in seagrasses are 1) the increasing ocean temperature due to climate change and 2) the continuous inputs of nutrients (eutrophication) associated with coastal human activities. To avoid the loss of seagrass populations, an "early warning" system is needed. We used Weighed Gene Co-expression Network Analysis (WGCNA), a systems biology approach, to identify potential candidate genes that can provide an early warning signal of stress in the Mediterranean iconic seagrass Posidonia oceanica, anticipating plant mortality. Plants were collected from both eutrophic (EU) and oligotrophic (OL) environments and were exposed to thermal and nutrient stress in a dedicated mesocosm. By correlating the whole-genome gene expression after 2-weeks exposure with the shoot survival percentage after 5-weeks exposure to stressors, we were able to identify several transcripts that indicated an early activation of several biological processes (BP) including: protein metabolic process, RNA metabolic process, organonitrogen compound biosynthetic process, catabolic process and response to stimulus, which were shared among OL and EU plants and among leaf and shoot apical meristem (SAM), in response to excessive heat and nutrients. Our results suggest a more dynamic and specific response of the SAM compared to the leaf, especially the SAM from plants coming from a stressful environment appeared more dynamic than the SAM from a pristine environment. A vast list of potential molecular markers is also provided that can be used as targets to assess field samples.

A trait-based framework for seagrass ecology: Trends and prospects.

In the last three decades, quantitative approaches that rely on organism traits instead of taxonomy have advanced different fields of ecological research through establishing the mechanistic links between environmental drivers, functional traits, and ecosystem functions. A research subfield where trait-based approaches have been frequently used but poorly synthesized is the ecology of seagrasses; marine angiosperms that colonized the ocean 100M YA and today make up productive yet threatened coastal ecosystems globally. Here, we compiled a comprehensive trait-based response-effect framework (TBF) which builds on previous concepts and ideas, including the use of traits for the study of community assembly processes, from dispersal and response to abiotic and biotic factors, to ecosystem function and service provision. We then apply this framework to the global seagrass literature, using a systematic review to identify the strengths, gaps, and opportunities of the field. Seagrass trait research has mostly focused on the effect of environmental drivers on traits, i.e., "environmental filtering" (72%), whereas links between traits and functions are less common (26.9%). Despite the richness of trait-based data available, concepts related to TBFs are rare in the seagrass literature (15% of studies), including the relative importance of neutral and niche assembly processes, or the influence of trait dominance or complementarity in ecosystem function provision. These knowledge gaps indicate ample potential for further research, highlighting the need to understand the links between the unique traits of seagrasses and the ecosystem services they provide.