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Submerged or partially floating seagrasses in marine or brackish waters form productive seagrass beds, feeding grounds for a rich and varied associated biota, play key ecological roles in mitigating climate change and provide ecosystem services for humanity. The objective of this study was to perform a temporal quali- and quantitative analysis on the scientific production on seagrasses in the Atlantic Ocean during last 64 years (1960 to 2024) through defined workflow by scientometric analysis on Scopus database. Publications in this database date back to 1969, comprising a total of 3.482 scientific articles, primary focused on seagrass ecology. These articles were published in 574 distinct peer-reviewed scientific ecological journals, and are divided into four periods based on the number of articles, keywords and biograms, with an average annual increase of 8.28% in the number of articles published. Zostera marina , Halodule wrightii and Thalassia testudinum were the most researched species, especially in Atlantic coastal areas of Europe and North/Central America. Studies on seagrasses along the Atlantic coast have been well consolidated by a few authors with prolific scientific output, but much of the research has been conducted by non-specialists who published only one or a few articles. We also found that researches from each continent tend to focus on specific topics: North America researches investigated future climate change scenarios and seagrass ecology, while those from Europe prioritize on restoration plans. Additionaly, European researchers from Europe predominantly collaborate with local scientists, a trend also observed among American researches. This indicates a need for increase research and scientific production in the South Atlantic region. [ABSTRACT FROM AUTHOR]

Research on Actinomycetota species is becoming increasingly significant, not only for their ecological and taxonomic aspects, but primarily for their unique metabolites that hold potential for therapeutic uses. In this study, Actinomycetota bacteria strains were isolated from the sediments of two seagrass meadows, Thalassia hemprichii and Syringodium isoetifolium, as well as from plain sediment (without seagrasses) at Mjimwema, Tanzania, in the Western Indian Ocean. The isolates were identified through their morphological and biochemical characteristics, along with molecular techniques. Additionally, antimicrobial and cytotoxicity tests were also conducted. Fifteen different strains of Actinomycetota were isolated, and based on phenotypic and phylogenetic characteristics, they were grouped into seven different genera, namely: Micrococcus, Microbacterium, Ornithinimicrobium, Cellulomonas, Cellulosimicrobium, Luteimicrobium, and Dietzia. Results of 16S rRNA gene sequence analysis showed eight potential new species of Actinomycetota from these sediments. Genus Micrococcus was dominant in all samples, followed by Microbacterium. Furthermore, genera Ornithinimicrobium and Cellulosimicrobium appeared only in T. hemprichii sediment, while Luteimicrobium and Cellulomonas were observed in plain sediment only. To the best of our knowledge, genera Cellulomonas and Luteimicrobium are reported for the first time in marine sediment. The crude extract of the isolates exhibited antimicrobial effects against Candida albicans, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The results revealed that sediments within seagrass meadows harbor unique Actinomycetota species capable of producing secondary metabolites with potential therapeutic uses. Therefore, additional research is necessary to thoroughly characterize the novel species and identify the chemical compounds responsible for the observed antimicrobial activity and bioprospecting. [ABSTRACT FROM AUTHOR]

Aim: The potentially cascading consequences of climate changes on redistribution of habitat‐forming species, like seagrasses, remain a major research gap. Empirical demonstrations of local population changes are increasingly reported without a globally integrated predictive framework as a leading testable hypothesis. Therefore, here, we aimed to estimate changes in species richness, community composition, and areas of climatic refugia under future climate scenarios. Location: Global scale. Time Period: Present‐day conditions (from 2010 to 2020) and for three Shared Socioeconomic Pathway (SSP) scenarios of future climate change (from 2090 to 2100). Major Taxa Studies: Seagrasses (plantae). Methods: We coupled seagrass occurrences with environmental predictors (temperature, salinity, nitrate, wave energy, and ice) in stacked species distribution modelling. Results: Models estimated a present global extent of 917,169 km2 with high species richness in Temperate Australasia, Indo‐Pacific, and Temperate North Pacific. Future projections predicted widespread spatial redistribution, with Arctic expansions, losses in lower latitudes, and deeper vertical ranges, while globally maintaining the area extent occupied worldwide by seagrass species (only 5% of change). Species richness increased poleward under more drastic scenarios (SSP3‐7.0 and SSP5‐8.5), with losses in tropical zones (30oN to 30oS). Local climatic refugia are retained in all scenarios but decrease under higher emissions. Additionally, even where seagrass species remain, widespread community composition changes were predicted. Main Conclusions: Our findings serve as baselines to inform, anticipate, and mitigate cascading consequences of shifts in seagrass ecosystems that provide essential services for humanity. [ABSTRACT FROM AUTHOR]

This study aimed to assess the alterations in the community structure of macroinvertebrates associated with two seagrass-dwelling sponge species following a shift in the environmental conditions. Individuals of the sponge Amorphinopsis atlantica, whose optimal distribution is in areas exposed to wind-driven waves, were transplanted to a less exposed area and, contrarily, individuals of Haliclona implexiformis, whose optimal distribution is in less exposed areas, were transplanted to an exposed area. After 71 days, individuals of A. atlantica showed a decrease in the density (75.5%), family richness (29.8%), and diversity (22.2%) of associated macroinvertebrates regarding controls, whereas those of H. implexiformis showed an increase in the density (85.9%), family richness (57.7%), and diversity (20.8%). These changes were attributed to species turnover, recruitment of some associated taxa, and morphological changes in one of the host sponge species. In the exposed site, the associated communities were more influenced by the hydrodynamism and sedimentation rate, and in the protected site, by salinity and the concentrations of organic matter in surface sediments and the water column. Overall, this study highlights the complex interactions between environmental conditions and marine biodiversity, providing valuable data for the conservation and management of seagrass meadow ecosystems and their associated sponge communities. [ABSTRACT FROM AUTHOR]

Physical disturbances typically cause ecological impacts within areas of direct contact (primary disturbances) but can also impact surrounding areas through other mechanisms (secondary disturbances). Secondary disturbances are often overlooked, especially in marine ecosystems where sufficiently detailed observation can be difficult to obtain. For example, boat moorings create circular clearings in seagrass meadows by physically scouring the seabed, but visible impacts extend beyond this into surrounding areas due to disturbances such as increased sediment transport, edge effects, and shading from boats. Previous studies on impacts of moorings have not distinguished between primary and secondary disturbances, and secondary disturbances are rarely accounted for in environmental management. We used spatial modelling to examine the primary and secondary disturbances associated with moorings in a meadow of the threatened seagrass Posidonia australis. We compared the disturbance from traditional 'swing' moorings with 'environmentally friendly' moorings (EFM) designed to reduce scour. Within the scour zone (0-5 m from moorings), we compared seagrass cover around swing moorings with cover around EFM. Further from moorings (5-25 m), we tested the degree of association between seagrass cover and secondary disturbances that may accumulate with mooring density and be influenced by mooring design. We found that mooring design affected the degree of direct disturbance, with cover of P. australis in the scour zone of standard moorings ~49% lower than that of EFMs (p < 0.01). Mooring density had cumulative negative effects on P. australis cover in the surrounding meadow, but the influence of mooring density was reduced when most moorings were EFMs. This suggests that secondary effects contingent on direct physical disturbance (e.g. sediment transport, fragmentation, edge effects) may be stronger than the general influence of moored boats (shading). We use the findings to simulate two broad policy scenarios for mooring designs in P. australis meadows: installing only EFM, or only traditional moorings. The simulations suggest that using only EFM would lead to a 14.2% increase (~164 m2), whereas installing only traditional moorings would lead to a 16% (~187 m2) loss of P. australis cover in this already highly disturbed meadow. Synthesis and applications: We demonstrate a nondestructive approach to assessing primary and secondary disturbances driving the distribution of a threatened seagrass and simulate a range of potential management scenarios that could assist in conserving the species. [ABSTRACT FROM AUTHOR]

Zostera japonica , as one of the major seagrasses in the Yellow River Estuary, plays a critical ecological role, particularly in providing habitat for marine organisms, stabilizing sediment, and contributing significantly to carbon sequestration. In recent years, Zostera japonica seagrass beds have receded extensively due to multiple impacts of natural factors and human activities. This study investigates the complex effects of extreme climate events and human activities on the growth mechanisms of Zostera japonica in the Yellow River Estuary using a combination of field sampling, laboratory analysis, and quantitative calculations. The result shows that there are significant differences in sediment characteristics between the north and south shores, with the south shore having finer sediments and higher nutrient content, which support more robust seagrass growth. The Water and Sediment Regulation Scheme (WSRS) dramatically alters water quality by reducing salinity and increasing turbidity, thus inhibiting photosynthesis and disrupting the physiological functions of Zostera japonica. Additionally, WSRS introduces an increase in heavy metals, which could potentially impact plant health and stress levels. Extreme weather events, particularly Super Typhoon Lekima, further compound these impacts by causing soil erosion, uprooting seagrass beds, and reducing biomass and seed production. The interplay of WSRS, climate change, and anthropogenic activities necessitates integrated management strategies to mitigate adverse effects and enhance habitat resilience. This study underscores the need for specific management strategies, such as controlling heavy metal inflows, implementing sediment stabilization techniques, and regulating freshwater discharge during key growth periods, to mitigate adverse effects and enhance habitat resilience for Zostera japonica in the Yellow River Estuary. [ABSTRACT FROM AUTHOR]

Erosion, shoreline retreat and accelerated beach loss at maritime heritage sites in Southern Kenya, is on the rise. Consequences ranging from gradual decay, collapse to outright catastrophic loss of pillars, mosques, tombs, wells and historic ruins are indicative of absent coastal management and climate adaptation plans. Unfortunately, the susceptibility of this heritage to suffer damage remains high due to its location, age, material and methods of construction. The archival research method, was selected to establish shoreline movement based on multi-temporal Landsat images from 1994–2023. Shoreline positions of the study area were analysed using geo-spatial statistical techniques executed in the GIS environment. These include Net Shoreline Movement, End Point Rate and Linear Regression Rate. Results of total shoreline change between 1994 and 2023 were −96.47 m. A mean erosion rate of −3.57 m/year with a maximum of −6.18 m/year reveals that erosion trends are significant in the cultural landscape. Short-term priorities include: physical stabilisations and relocation of built heritage from vulnerable zones. Long-term priorities include: restoration of mangroves, preservation of salt marshes and protection of seagrass beds. This paper contributes to the promotion of coping capacities and priorities for adapting maritime heritage to climate change. [ABSTRACT FROM AUTHOR]

Human activities have caused a rise in atmospheric carbon dioxide (CO2) levels, leading to greater absorption of CO2 by oceans and causing ocean acidification (OA). This phenomenon, marked by a reduction in pH, represents substantial risks to marine ecosystems, including seagrass meadows. Seagrasses are vital elements of coastal ecosystems, performing important functions in carbon storage, stabilizing shorelines, and preserving biodiversity; however, reactions to OA are not well understood, especially in molecular terms. This research study examined alterations in gene expression within seagrass meadows, namely Cymodocea nodosa, in reaction to simulated OA conditions. A climate chamber system was used to adjust CO2 levels to simulate future projections of OA, specifically following the RCP 8.5 scenario. Gene expression dynamics were assessed by collecting samples at different time intervals across a 36-h period. Research has demonstrated that genes related to photosynthesis are suppressed quickly after being exposed to increased amounts of CO2. Gene expression levels were found to change often over time, which is crucial for adaptation and acclimatization. However, antioxidant genes have varied responses to OA, with CAT and SOD being downregulated in distinct ways. Our findings offer valuable insights into the molecular mechanisms of seagrass responses to OA. They highlight the significance of examining short-term responses when evaluating the susceptibility of coastal ecosystems to climate change. [ABSTRACT FROM AUTHOR]

Background: Combined impacts from anthropogenic pressures and climate change threaten coastal ecosystems and their capacity to protect communities from hazards. One approach towards improving coastal protection is to implement "nature-based solutions" (NBS), which are actions working with nature to benefit nature and humans. Despite recent increases in global implementation of NBS projects for coastal protection, substantial gaps exist in our understanding of NBS performance. To help fill this gap, we systematically mapped the global evidence base on the ecological, physical, economic, and social performance of NBS interventions related to coastal protection. We focused on active NBS interventions, such as restoring or creating habitat, adding structure, or modifying sediment in six shallow biogenic ecosystems: salt marsh, seagrass, kelp forest, mangrove, coral reef, and shellfish reef. Methods: We identified potentially relevant articles on the performance of NBS for coastal protection using predefined and tested search strategies across two indexing platforms, one bibliographic database, two open discovery citation indexes, one web-based search engine, and a novel literature discovery tool. We also searched 45 organizational websites for literature and solicited literature from 66 subject matter experts. Potentially relevant articles were deduplicated and then screened by title and abstract with assistance from a machine learning algorithm. Following title and abstract screening, we conducted full text screening, extracted relevant metadata into a predefined codebook, and analyzed the evidence base to determine the distribution and abundance of evidence and answer our research questions on NBS performance. Results: Our search captured > 37,000 articles, of which 252 met our eligibility criteria for relevance to NBS performance for coastal protection and were included in the systematic map. Evidence stemmed from 31 countries and increased from the 1980s through the 2020s. Active NBS interventions for coastal protection were most often implemented in salt marshes (45%), mangrove forests (26%), and shellfish reefs (20%), whereas there were fewer NBS studies in seagrass meadows (4%), coral reefs (4%), or kelp beds (< 1%). Performance evaluations of NBS were typically conducted using observational or experimental methods at local spatial scales and over short temporal scales (< 1 year to 5 years). Evidence clusters existed for several types of NBS interventions, including restoration and addition of structures (e.g., those consisting of artificial, hybrid, or natural materials), yet evidence gaps existed for NBS interventions like alteration of invasive species. Evaluations of NBS performance commonly focused on ecological (e.g., species and population, habitat, community) and physical (e.g., waves, sediment and morphology) outcomes, whereas pronounced evidence gaps existed for economic (e.g., living standards, capital) and social (e.g., basic infrastructure, health) outcomes. Conclusions: This systematic map highlights evidence clusters and evidence gaps related to the performance of active NBS interventions for coastal protection in shallow, biogenic ecosystems. The synthesized evidence base will help guide future research and management of NBS for coastal protection so that active interventions can be designed, sited, constructed, monitored, and adaptively managed to maximize co-benefits. Promising avenues for future research and management initiatives include implementing broad-scale spatial and temporal monitoring of NBS in multidisciplinary teams to examine not only ecological and physical outcomes but also economic and social outcomes, as well as conducting further synthesis on evidence clusters that may reveal measures of effect for specific NBS interventions. Since NBS can deliver multiple benefits, measuring a diverse suite of response variables, especially those related to ecosystem function, as well as social and economic responses, may help justify and improve societal benefits of NBS. Such an approach can help ensure that NBS can be strategically harnessed and managed to meet coastal protection goals and provide co-benefits for nature and people. [ABSTRACT FROM AUTHOR]

Seagrass meadows are important marine ecosystems in coastal areas, offering ecological and economic services to the mankind. However, these ecosystems are facing declines due to climate changes and human activities. Rhizosphere-associated microbiomes play critical roles in the survival and adaptation of seagrasses. While prior studies have explored the general microbial communities and their roles in seagrass meadows, there is a gap in understanding the specific rhizosphere microbiomes of different seagrass species and their interdependent relationships. Our study analyzed the microbial community composition and their metabolism in the rhizosphere of Ruppia sinensis (RS), Zostera japonica (ZJ), and Zostera marina (ZM) obtained from the coastal area of Shandong, China, using high throughput and metagenome sequencing. We found that Rhodobacteraceae, Desulfocapsaceae, and Sulfurovaceae were enriched in RS, ZJ, and ZM samples, respectively, compared with the other two seagrass species, and the bacterial connections were decreased from RS to ZM and ZJ samples. The abundances of nirKS and norBC, mediating denitrification, were higher in RS samples with 2.38% ± 0.59% and 2.14% ± 0.24%, respectively. RS samples also showed a higher level of genes in assimilatory sulfate reduction but lower levels in dissimilatory sulfate reduction and oxidation, with a greater ability to convert sulfide into L-cysteine and acetate. Metagenome-assembled genomes from metagenome of RS rhizosphere had a higher diversity and were assigned to eight phyla. Our study could provide a typical project to analyze the bacterial community structures and metabolic functions in the rhizosphere microbiomes of different seagrasses. [ABSTRACT FROM AUTHOR]

There is increasing interest in the role that seagrasses play in storing carbon in the context of climate mitigation, but many knowledge gaps in the factors controlling this storage exist. Here, we provide a small case study that examines the role of infaunal biodiversity in influencing seagrass and the carbon stored in its sediments. A total of 25 species of invertebrate were recorded in an intertidal Zostera marina meadow, where these species were dominated by polychaete worms with no bivalves present. We find organic carbon storage (within the top 20 cm) measured by AFDW to be highly variable within a small area of seagrass meadow ranging from 2961 gC.m−2 to 11,620 gC.m−2 with an average (±sd) of 64602 ± 3274 gC.m−2. Our analysis indicates that infaunal communities are significantly and negatively correlated with this sediment organic carbon. However, this effect is not as influential as hypothesised, and the relatively small sample size of the present study limits its ability to provide strong causality. Other factors, such as algal abundance, curiously had a potentially stronger influence on the carbon in the upper sediments. The increasing richness of infauna is likely reducing the build-up of organic carbon, reducing its ecosystem service role. We believe this to likely be the result of bioturbation by specific species such as Arenicola marina and Ampharete acutifrons. A change in sediment organic carbon suggests that these species could be key drivers of bioturbator-initiated redox-driven organic matter turnovers, influencing the microbial processes and remobilizing sediment compounds. Bioturbators should be considered as a limitation to Corg storage when managing seagrass Corg stocks; however, bioturbation is a natural process that can be moderated when an ecosystem is less influenced by anthropogenic change. The present study only provides small-scale correlative evidence with a range of surprising results; confirming these results within temperate seagrasses requires examining this process at large spatial scales or with targeted experiments. [ABSTRACT FROM AUTHOR]

Globally, anthropogenic climate change has caused declines of seagrass ecosystems necessitating proactive restoration approaches that would ideally anticipate future climate scenarios, such as marine warming. In eastern Australia, estuaries with meadows of the endangered seagrass Posidonia australis have warmed and acidified over the past decade, and seagrass communities have declined in some estuaries. Securing these valuable habitats will require proactive conservation and restoration efforts that could be augmented with restoration focussed on boosting resilience to future climate. Understanding patterns of selection and where seagrass meadows are adapted to particular environmental conditions is key for identifying optimal donor material for restoration. We used single nucleotide polymorphisms and genotype by environment analyses to identify candidate loci under putative selection to environmental stressors and assess genomic variation and allelic turnover along stressor gradients. The most important physicochemical variables driving selection were associated with temperature, water turbidity, and pH. We developed a preliminary 'donor registry' of pre‐adapted P. australis genotypes by mapping the distribution of alleles to visualise allelic composition of each sampled seagrass meadow. The registry could be used as a first step to select source material for future‐proofing restoration projects. A next step is to establish manipulative experiments that will be required to test whether pre‐adapted genotypes confer increased resistance to multiple environmental stressors. [ABSTRACT FROM AUTHOR]

Seagrass meadows provide an important nursery and feeding habitat for fish, globally. However, limited data exist on how these vegetated coastal ecosystems affect local fish stocks over longer time periods. By means of beach seine hauling with a bio‐monitoring seine net, we collected fish data in Kronborg Bay (Denmark) over 4 years. The bay contains both vegetated and bare sediment areas in close proximity to Kronborg Castle in Elsinore and is part of the Øresund strait; a dynamic marine environment linking the Baltic Sea with the inner Danish waters (Kattegat). We investigated the biodiversity and fish abundance in a healthy seagrass meadow and compared it with a bare adjacent sediment area. We show that seagrass is important for fish species like the Atlantic cod, the two‐spotted goby, and the broadnosed pipefish. The seagrass meadow harboured more fish species and higher biodiversity, while the number of individuals was higher in the adjacent bare sediment area as a result of high abundances of lesser sand eel. Pilou's evenness and the Shannon‐Wiener index showed 2–4‐fold higher biodiversity in the seagrass meadow. The seagrass meadow harboured about 35% more fish species than the bare adjacent sediment. The Atlantic cod was almost entirely found in the seagrass meadow, while lesser sand eel that showed an overall increase in abundance in both habitats, represented the largest proportion of the total number of fish individuals (up to about 60%) and was mostly found on the bare adjacent sediment. Species abundance was analysed for changes over time, where, for example the European plaice showed an increase in abundance over the 4‐year period of investigation. Seagrass meadows can thus be very important for the Atlantic cod population in the Øresund strait and generally for local fish productivity, abundance and diversity. [ABSTRACT FROM AUTHOR]

Coastal areas support seagrass meadows, which offer crucial ecosystem services, including erosion control and carbon sequestration. However, these areas are increasingly impacted by human activities, leading to habitat fragmentation and seagrass decline. In situ surveys, traditionally performed to monitor these ecosystems, face limitations on temporal and spatial coverage, particularly in intertidal zones, prompting the addition of satellite data within monitoring programs. Yet, satellite remote sensing can be limited by too coarse spatial and/or spectral resolutions, making it difficult to discriminate seagrass from other macrophytes in highly heterogeneous meadows. Drone (unmanned aerial vehicle—UAV) images at a very high spatial resolution offer a promising solution to address challenges related to spatial heterogeneity and the intrapixel mixture. This study focuses on using drone acquisitions with a ten spectral band sensor similar to that onboard Sentinel-2 for mapping intertidal macrophytes at low tide (i.e., during a period of emersion) and effectively discriminating between seagrass and green macroalgae. Nine drone flights were conducted at two different altitudes (12 m and 120 m) across heterogeneous intertidal European habitats in France and Portugal, providing multispectral reflectance observation at very high spatial resolution (8 mm and 80 mm, respectively). Taking advantage of their extremely high spatial resolution, the low altitude flights were used to train a Neural Network classifier to discriminate five taxonomic classes of intertidal vegetation: Magnoliopsida (Seagrass), Chlorophyceae (Green macroalgae), Phaeophyceae (Brown algae), Rhodophyceae (Red macroalgae), and benthic Bacillariophyceae (Benthic diatoms), and validated using concomitant field measurements. Classification of drone imagery resulted in an overall accuracy of 94% across all sites and images, covering a total area of 467,000 m2. The model exhibited an accuracy of 96.4% in identifying seagrass. In particular, seagrass and green algae can be discriminated. The very high spatial resolution of the drone data made it possible to assess the influence of spatial resolution on the classification outputs, showing a limited loss in seagrass detection up to about 10 m. Altogether, our findings suggest that the MultiSpectral Instrument (MSI) onboard Sentinel-2 offers a relevant trade-off between its spatial and spectral resolution, thus offering promising perspectives for satellite remote sensing of intertidal biodiversity over larger scales. [ABSTRACT FROM AUTHOR]

This study evaluated the effectiveness of Planet satellite imagery in mapping seagrass coverage in Santa Rosa Sound, Florida. We compared very-high-resolution aerial imagery (0.3 m) collected in September 2022 with high-resolution Planet imagery (~3 m) captured during the same period. Using supervised classification techniques, we accurately identified expansive, continuous seagrass meadows in the satellite images, successfully classifying 95.5% of the 11.18 km2 of seagrass area delineated manually from the aerial imagery. Our analysis utilized an occurrence frequency (OF) product, which was generated by processing ten clear-sky images collected between 8 and 25 September 2022 to determine the frequency with which each pixel was classified as seagrass. Seagrass patches encompassing at least nine pixels (~200 m2) were almost always detected by our classification algorithm. Using an OF threshold equal to or greater than >60% provided a high level of confidence in seagrass presence while effectively reducing the impact of small misclassifications, often of individual pixels, that appeared sporadically in individual images. The image-to-image uncertainty in seagrass retrieval from the satellite images was 0.1 km2 or 2.3%, reflecting the robustness of our classification method and allowing confidence in the accuracy of the seagrass area estimate. The satellite-retrieved leaf area index (LAI) was consistent with previous in situ measurements, leading to the estimate that 2700 tons of carbon per year are produced by the Santa Rosa Sound seagrass ecosystem, equivalent to a drawdown of approximately 10,070 tons of CO2. This satellite-based approach offers a cost-effective, semi-automated, and scalable method of assessing the distribution and abundance of submerged aquatic vegetation that provides numerous ecosystem services. [ABSTRACT FROM AUTHOR]

Plant traits which vary both within and between species often drive biogeochemical cycling. Understanding the relative role of within‐ and between‐species trait variability in driving carbon cycling is essential to scaling site measurements to global carbon budgets. In seagrass meadows, carbon and nitrogen mineralization rates and associated greenhouse gas emissions are highly variable, impeding our ability to reliably predict whether meadows are net carbon sinks. Evaluating the influence of within‐ and between‐species trait variability on greenhouse gas fluxes will improve our understanding of local‐scale drivers of greenhouse gas production and consumption in seagrass meadows.To test the effects of plant traits on dissolved greenhouse gas fluxes, we performed mesocosm incubations with live, intact seagrass plants. We compared methane (CH4) and nitrous oxide (N2O) fluxes under dark and light conditions from sediments dominated by Halodule wrightii and Thalassia testudinum across dormant, early and peak growing seasons in a subtropical meadow along the west coast of peninsular Florida. We also measured oxygen (O2) fluxes to interpret greenhouse gas fluxes within the context of community metabolism. We measured several seagrass traits, such as above‐ and below‐ground biomass and leaf and root area and assessed their impact as well as the impact of species identity on dissolved gas fluxes.We found that abiotic factors linked to metabolism (i.e. light and temperature) influenced greenhouse gas fluxes across seasons. In addition to light conditions and sampling month, plant size (a composite trait variable) was a significant predictor of O2 consumption and CH4 production under dark conditions, and better predicted fluxes than individual plant traits. CH4 production was slightly higher in H. wrightii‐dominated sediments, but species identity was less important than plant size in driving CH4 production. N2O fluxes were low and not influenced by plant traits or species identity.Synthesis: Our results indicate that within‐species more so than between‐species trait variability drives the direction and magnitude of CH4 fluxes in seagrass meadows. We identified a trade‐off where seagrass biomass is often associated with enhanced sediment carbon storage, but in our study, plant size promoted CH4 production, potentially offsetting the benefits of long‐term storage. [ABSTRACT FROM AUTHOR]

Sulfide in sediment porewaters, is toxic to rooted macrophytes in both marine and freshwater environments. Current research on sulfide stress in seagrasses primarily focuses on morphological and physiological aspects, with little known about the molecular response and resistance mechanisms. This study first investigated the damage caused by sulfide to eelgrass (Zostera marina L.) using transcriptomic, metabolomic, and other physiological and biochemical indicators and explored the potential resistance of eelgrass at molecular level through laboratory simulated and in‐situ sulfide stress experiments. Comprehensive results showed that sulfide stress severely inhibited the growth, photosynthesis, and antioxidant enzyme activities of eelgrass. Importantly, transcriptome analysis revealed significant activation of pathways related to carbohydrate and sulfur metabolism. This activation served a dual purpose: providing an energy source for eelgrass stress response and achieving detoxification through accelerated sulfur metabolism—a potential resistance mechanism. The toxicity of sulfide increased with rising temperature as evidenced by a decrease in EC50. Results from recovery experiments indicated that when Fv/Fm reduced to about 0 under sulfide stress, the growth and photosynthesis of eelgrass recovered to normal level after timely removal of sulfide. However, prolonged exposure to sulfide resulted in failure to recover, leading ultimately to plant death. This study not only enhances our understanding of the molecular‐level impacts of sulfide on seagrasses but also provides guidance for the management and ecological restoration of seagrass meadows under sulfide stress. Summary statement: Little is known about the molecular response and resistance mechanisms of seagrass to sulfide stress. This study indicates that photosynthesis‐related pathways in eelgrass are significantly inhibited under sulfide stress, while carbohydrate and sulfur metabolism‐related pathways are markedly activated, which may represent potential resistance mechanisms. [ABSTRACT FROM AUTHOR]

Grazing can impart long‐lasting changes in vegetated ecosystems. How ecosystems respond to herbivory depends on the ecological and evolutionary histories of their foundational species. The overall ecosystem functioning and associated biodiversity depend on these responses but there is still little understanding on how the intensity and duration of herbivory interact and impact vegetated ecosystems. We experimentally tested in the field the responses of three seagrass species with distinct life history traits to increasing intensities of herbivory over time. Specifically, we assessed structural responses (i.e., canopy height and shoot density) to reflect the ecosystem state. Additionally, we used mechanistic models to assess induced and constitutive responses in the different seagrass species. Results show that seagrasses coped with herbivory differentially in relation to their life history traits. Posidonia oceanica (persistent species) was resistant and only registered declines in canopy height, whereas both canopy heigh and shoot density rapidly decreased for Cymodocea nodosa (intermediate‐colonizing species) and Zostera noltei (colonizing species). Seagrasses also differed in the type of structural response, with the colonizing species experiencing reductions in shoot density, and the persistent P. oceanica registering declines in canopy height. After months of exposure to cumulative herbivory, all three species showed signs of stability. Interestingly, none of the species disappeared completely even when exposed to extreme herbivory. Mechanistic models indicate that herbivory‐induced responses are a potential explanation for these patterns. This study suggests that given the long evolutionary history of herbivory, some seagrasses may be remarkably well adapted to both intense and cumulative herbivory. [ABSTRACT FROM AUTHOR]

Seagrass beds are composed of foundation species, providing essential nursery grounds, feeding areas, and refuge for various marine life. Several species of fish and invertebrates utilize seagrasses as essential habitat. The Dwarf Seahorse (Hippocampus zosterae) is an understudied species in Texas, and little is known about its density, distribution, and habitat associations in this area of their range. Physicochemical water parameters, nekton community data, habitat data, and Dwarf Seahorse catch data were collected at 80 sites in Texas. The highest catch per unit effort (CPUE) of the target species was in Aransas Bay (0.038/m2). There was a positive relationship between the presence and percent cover of turtle grass (Thalassia testudinum) and the presence and CPUE of Dwarf Seahorses. Dwarf Seahorses were detected more often and at a higher CPUE in locations with a higher seagrass community diversity and richness. The nekton community at sites where Dwarf Seahorses were detected was also more abundant, diverse, and species rich. This is the first comprehensive study of the distribution of the Dwarf Seahorse along the Texas coast. Dwarf Seahorses were generally found in higher abundances in association with mature, stable, and diverse seagrass beds. Recommended conservation strategy to protect Dwarf Seahorses should prioritize the protection of established and mature seagrass beds. Continued directed monitoring of this species is recommended to better understand their distribution and population status. [ABSTRACT FROM AUTHOR]

The Gulf toadfish (Opsanus beta) is a soniferous and abundant species native to Gulf of Mexico estuarine environments—now considered a likely invasive species in coastal Brazil. Males produce distinctive boatwhistle calls during their reproduction behaviors, offering an acoustic cue for ecological functions such as mate selection, prey detection, and predator avoidance. Their calls can also be readily detected with passive acoustics to monitor Gulf toadfish distributions and serve as acoustic indicators for their preferred nesting habitats. In this study, we describe the spatial, annual, seasonal, monthly, daily, daytime, and diel variation of Gulf toadfish call occurrence in Cedar Key, Florida (USA), with multiple sampling efforts at seagrass and dock sampling locations in the years 2019–2022. From April through June during our dock sampling, calls were detected across almost all our sampled dates and often every hour of the day, with daily and diel fluctuations in call occurrence. In our seagrass meadow sampling, call occurrence showed some positive correlation with manatee grass (Syringodium filiforme) and salinity. Moreover, snapshot recordings as short as 5 min were sufficient to detect calls in 37 of our 45 sampling events compared to only five where trawls captured Gulf toadfish. Our findings demonstrate the efficacy of listening to Gulf toadfish calls for monitoring applications and can support future efforts seeking to understand the availability of a prevalent acoustic cue in estuarine soundscapes. [ABSTRACT FROM AUTHOR]

"Blue carbon" refers to the carbon sequestered by the world's oceanic and coastal ecosystems, particularly through coastal vegetation such as mangroves, salt marshes, seagrasses, and marine macroalgae. These ecosystems play a crucial role in the global carbon cycle by serving as significant carbon sinks, absorbing carbon dioxide from the atmosphere and storing it in biomass and sediments over long periods. This study explores the use of environmental DNA (eDNA) to detect marine macrophytes and microalgae assemblages contributing to blue carbon in sediments across various coastal ecosystems. The research addresses the challenges of traditional monitoring methods by utilizing high-throughput sequencing of the 18S-V9 region amplified using eDNA from sediment samples collected at eight locations in the United States and South Korea. The results reveal a diverse array of taxa, underscoring the variability in community composition across different conditions. Notably, sites with seagrass beds and Ulva blooms showed distinct patterns in microalgal community structure. This study underscores the potential of eDNA analysis in providing comprehensive insights into the biodiversity of marine macrophyte ecosystems, thus informing conservation efforts and enhancing the understanding of marine ecological dynamics. [ABSTRACT FROM AUTHOR]

Seagrass meadows, including those formed by Zostera noltei, play a crucial role in marine ecosystem health by providing habitat stability and coastal protection. In the Romanian Black Sea, Z. noltei meadows are critically endangered due to pressures from eutrophication, habitat loss, and climate change. This study presents a comprehensive baseline assessment of Z. noltei meadows near Mangalia, Romania, utilizing in situ field methods and UAV mapping conducted in the spring and summer of 2023. Seven meadow sites (Z1–Z7) were identified, with notable variability in density, shoot counts, and coverage across sites. Site Z1 exhibited the highest density (1223 shoots/m−2) and Z5 and Z7 the longest leaves (an average of 60 cm), reflecting possible environmental influences. Statistical analyses revealed significant inter-site differences in shoot density and leaf length, with density emerging as a primary differentiator. Ex situ analyses of epiphyte load indicated a median, balanced epiphyte load. This baseline dataset supported the selection of Z1 as a reference donor site for seagrass relocation activities along the Romanian coast in 2023. By providing critical insights into Z. noltei structure and health, this study supports future conservation efforts and evidence-based management of these vulnerable coastal habitats. [ABSTRACT FROM AUTHOR]

Seagrass meadows provide ecosystem services (ES) that are critical for humanity. Southeast Asia (SEA) is a hotspot of seagrass diversity, and the region's seagrass-derived ES have been valued at over $100 billion annually; however, the health and extent of seagrass meadows are in decline. Marine plastic pollution (MPP) is an escalating problem and a concern for vulnerable marine habitats such as seagrass meadows. To understand the impacts that MPP has on seagrass ecosystems and their provision of ES, we conducted a mixed methodology study that involved a systematic search of the literature and the synthesis of the results with a risk assessment. The results indicated that MPP negatively impacts seagrass through factors such as spatial competition, chemical leaching, and reduced rates of photosynthesis and rhizome growth. This can lead to a reduction in seagrass biomass, triggering the degradation of all seagrass-derived ES. A risk assessment of the microplastic impact results indicated that seagrass-derived ES are at high risk of decline from the current microplastic concentrations, which in turn indicates a potential threat to the well-being of those dependent on them. [ABSTRACT FROM AUTHOR]

The role of seagrasses in providing a complex habitat for marine organisms is globally documented; however, few studies have investigated the trophic incorporation of endemic Mediterranean Posidonia oceanica into marine food webs. Meadows of P. oceanica are declining due to climate change and anthropogenic pressures, emphasising the need to determine its contribution in local trophic dynamics. We investigated whether benthic marine invertebrate (BMI) and fish consumers assimilate carbon directly from P. oceanica seagrass or other sources along the seagrass meadow margins in Malta. We sampled and analysed the δ13C and δ15N isotope values of P. oceanica, particulate organic matter (POM), macroalgae, 14 invertebrate taxa, and 10 fishes at three locations marginal to P. oceanica seagrass meadows. Stable isotope ratios were significantly different between all taxa (F26 = 17.37, R2 = 0.68, p < 0.01) and locations (F2 = 34.22, R2 = 0.10, p < 0.01). The source, invertebrate, and fishes were enriched in both 13C and 15N at Baħar iċ-Ċagħaq relative to the other locations, L'Aħrax and Golden Bay, likely due to the increased effluent. Stable isotope mixing models were somewhat confounded as POM and macroalgae had similar δ13C and δ15N values at each site, hampering efforts to define the resource use of the sampled taxa. However, Posidonia oceanica made the lowest contribution for both consumer groups at all locations, consistent with the results of other Mediterranean studies, suggesting that P. oceanica does not contribute significantly to the diet of consumers at seagrass meadow margins within Maltese waters. [ABSTRACT FROM AUTHOR]

The variability in stocks and accumulation rates of organic carbon (Corg), nitrogen (N), and carbonate (CaCO3) was studied in fifteen Posidonia oceanica meadows spread throughout the South Aegean Sea (Greece). In addition, the abiotic and biotic drivers determining the pattern of variability in the accumulation rates were assessed by exploring the influence of sediment characteristics, seagrass traits, and environmental settings. The meadows supported on average (±STDEV) 14.6 ± 5.0 kg Corg m−2, 0.47 ± 0.17 kg N m−2, and 249 ± 210 kg CaCO3 m−2 in the top meter of their sediments, with mean accumulation rates over the last 500 years of 33.6 ± 23.6 g Corg m−2 yr−1, 1.00 ± 0.62 g N m−2 yr−1, and 405 ± 336 g CaCO3 m−2 yr−1 across sites. A redundancy analysis (RDA) explained 70% of the variation in Corg, N, and CaCO3 accumulation rates, with three sediment characteristics (i.e., sediment Corg:N and Corg:Cinorg ratios and P. oceanica contribution to the sediment Corg pool) emerging as the primary set of factors shaping the accumulation of matter, followed by seagrass traits (i.e., leaf biomass and rhizome elongation) and environmental variables (i.e., suspended organic matter). The high degree of variability within the region emphasizes the need for fine‐scale assessments to understand the local conditions influencing sequestration. Our findings underscored the critical role of seagrass meadows in carbon and nitrogen sequestration in the region, urging conservation efforts to protect these ecosystems and prevent potential losses of stored carbon and nitrogen following seagrass degradation. Plain Language Summary: In the present study, we explored the abiotic and biotic factors influencing the accumulation patterns of carbon, nitrogen, and carbonate in 15 seagrass (Posidonia oceanica) meadows across the South Aegean Sea (Greece). Sediment characteristics (i.e., sediment Corg:N and Corg:Cinorg ratios and P. ocenica contribution to the sediment Corg pool) mainly drove the pattern of carbon, nitrogen, and carbonate accumulation, with seagrass traits (i.e., leaf biomass and rhizome elongation) and environmental conditions (i.e., suspended organic matter) contributing to a lesser extent. Overall, seagrass meadows play a crucial role in storing carbon and nitrogen in the studied region, serving as important natural sinks, and thus, protecting these ecosystems is important to prevent the loss of these stored elements. Additionally, understanding the factors that shape the variability in Posidonia oceanica storage capacity is crucial for management and conservation efforts. Key Points: Seagrass (Posidonia oceanica) meadows of the South Aegean Sea (Greece) represent important natural sinks for organic carbon, nitrogen, and carbonate.The accumulation pattern of organic carbon, nitrogen, and carbonate in the underlying seagrass sediments was mainly driven by sediment characteristics, followed by seagrass traits and environmental conditions.Fine‐scale assessments are crucial for understanding the local factors shaping the storage capacity of seagrass meadows to support management decisions. [ABSTRACT FROM AUTHOR]

Context: Seagrasses form an important habitat that provides diverse ecosystem services essential for both the environment and people. In tropical Queensland, Australia, these meadows hold significant economic and cultural value, serving as nurseries for marine species and sustaining dugongs and green turtles. The biomass and size of tropical seagrass meadows in Queensland varies considerably and are influenced by various factors, both biotic and abiotic. Aims: Functional trait-based approaches can improve the estimation of seagrass-meadow resilience and services provision by describing the relationship between environment and individual performance. To support these approaches, we provide a seagrass functional-trait database focusing on resilience and function provision for tropical Queensland. Methods: We employed a combination of literature reviews, database searches, botanical information, and structured expert elicitation to target 17 functional traits across 13 seagrass species in tropical Queensland. Key results: We developed a traits database to inform functional trait-based approaches to assessing seagrass-meadow resilience and dynamics. The outputs included trait information for approximately 78% of the targeted traits (of 221 unique trait–seagrass combinations). Conclusions: With current information on functional traits, we can improve the estimation of resilience and ecosystem services for tropical Queensland seagrass species. We have also highlighted trait data gaps and areas for further research. Implications: We have provided examples of applying this database within the tropical Queensland context, with the potential to facilitate regional comparative studies. Our database complements existing plant-trait databases and serves as a valuable resource for future trait-based seagrass research in tropical Queensland. Tropical seagrasses provide important ecosystem services, but they are dynamic habitats under threat from multiple stressors. Functional trait-based approaches have the potential to increase our understanding of these dynamics. We present a comprehensive trait database for seagrasses in tropical Queensland, with a focus on services and resilience. Photograph by Chieh Lin. [ABSTRACT FROM AUTHOR]

Background/Objectives: Biogenic volatile organic compounds (BVOCs), extensively studied in terrestrial plants with global emissions around 1 PgC yr−1, are also produced by marine organisms. However, benthic species, especially seagrasses, are understudied despite their global distribution (177,000–600,000 km2). This study aims to examine BVOC emissions from key Mediterranean seagrass species (Cymodocea nodosa, Posidonia oceanica, Zostera noltei, and Zostera marina) in marine and coastal lagoon environments. Methods: BVOCs were collected using headspace solid-phase microextraction (HS-SPME) using divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibers and analyzed by gas chromatography–mass spectrometry (GC-MS). Results: An important chemical diversity was found with a total of 92 volatile compounds (61 for Z. noltei, 59 for C. nodosa, 55 for P. oceanica, and 51 for Z. marina), from different biosynthetic pathways (e.g., terpenoids, benzenoids, and fatty acid derivatives) and with several types of chemical functions (e.g., alkanes, esters, aldehydes, and ketones) or heteroatoms (e.g., sulfur). No differences in chemical richness or diversity of compounds were observed between species. The four species shared 29 compounds enabling us to establish a specific chemical footprint for Mediterranean marine plants, including compounds like benzaldehyde, benzeneacetaldehyde, 8-heptadecene, heneicosane, heptadecane, nonadecane, octadecane, pentadecane, tetradecane, and tridecanal. PLS-DA and Heatmap show that the four species presented significantly different chemical profiles. The major compounds per species in relative abundance were isopropyl myristate for C. nodosa (25.6%), DMS for P. oceanica (39.3%), pentadecane for Z. marina (42.9%), and heptadecane for Z. noltei (46%). Conclusions: These results highlight the potential of BVOCs' emission from seagrass ecosystems and reveal species-specific chemical markers. [ABSTRACT FROM AUTHOR]

Competing uses for nearshore coastal space, such as aquaculture, have complex environmental and ecological interactions with surrounding seagrass meadows. Oyster aquaculture is among the fastest-growing aquaculture segments in the United States, and it brings concerns such as increased sedimentation from farm maintenance operations and altered water quality through oyster filtration. Changes in seagrass coverage and growth are common indicators of ecological health used to determine anthropogenic impacts on nearshore environments. This study characterized the effects of a research-scale adjustable long-line oyster aquaculture system on the health of adjacent seagrass meadows in Copano Bay, TX. Four Halodule wrightii meadows were identified at various distances from the research site: 100 m upstream (upstream), directly adjacent (0 m), 30 m downstream (30 m), and 60 m downstream (60 m). Sites were monitored for 1) seagrass health, 2) water quality parameters, and 3) sediment deposition. Over the 18-week sampling period, no significant differences (p >0.05) were found for water quality variables or sediment grain-size analysis using a one-way ANOVA. A linear mixed-effects model was used for repeated measures of seagrass data, with no effect of the site found on mean seagrass length, coverage, or maximum length (p >0.05). These results suggest that seagrass health indicators were unaffected by proximity to the oyster system. It was concluded that an oyster research aquaculture system of the type and size at the project location had no major negative or positive impact on seagrass meadow health due to high background variability and the overall minor footprint of the oyster farm across a comparatively large spatial extent. [ABSTRACT FROM AUTHOR]

Introduction: Seagrass sediments are important 'blue carbon' reservoirs which store climatically significant quantities of organic carbon (Corg) at the global scale. Seagrass meadows that overly these sediments also provide a range of critical ecosystem services including shoreline stabilization, storm surge protection, and fisheries nursery grounds. However, the controls over accumulation and the sources of organic C to these sediments beds are highly variable and poorly understood with the relative importance of hydrodynamic setting, species composition and canopy density being unclear. Methods: Here we address these questions using the first observation-based estimates of Corg stocks and provenance on Turneffe Atoll, Belize, made via remotely-sensed habitat extent, local Corg data and isotopic data. Sedimentary Corg was highest in sediments underlying the most sheltered meadows and decreased with increasing exposure to wind and wave energy with the seagrass meadows in the central lagoon containing an extensive deposit of mangrove derived organic carbon, stabilized and protected by the overlying seagrass meadow. Results: The influence of species composition appeared weak with the ubiquitous species T. testudinum occurring across a wide range of hydrodynamic regimes ranging from the most sheltered to the most energetic and being associated with a wide range of sedimentary organic C concentrations. Importantly from the perspective of remote sensing, org C concentrations were unrelated to canopy density. We hypothesize that this decoupling of organic C concentration from seagrass canopy cover reflects a much longer timescale for carbon storage in the sediments than the lifespan of the seagrass plants themselves and/or a substantial non seagrass derived organic C burden in seagrass sediments. Overall, we conservatively estimate that the top 30cm of sediments underlying the seagrass meadows overlying carbonate sediments on the atoll exterior store 0.58 x 106 Mg Corg, most of which is seagrass-derived, whilst the sediments underlying the meadows within the central lagoon store an additional 1.28 x 106 Mg Corg. When the maximum possible extent of seagrass is considered, this estimate increases to 3.54 x 106 Mg Corg. Substantial Corg stocks extending >1m depth were observed across all sites, and so these inventories are considered conservative. Discussion: A preliminary 'cost of loss' for sedimentary Corg in the top 30 cm of Turneffe Atoll's seagrass meadows, based on a carbon trading value of €60 tCO2 (eq), is estimated at €42 million for the outer atoll, increasing to €136 million when the mangrove-derived sediments of the central atoll are considered and €260 million when turbid areas are assumed to contain seagrass. [ABSTRACT FROM AUTHOR]

Foundation species, such as seagrasses, trees, and corals, form the biotic basis for many ecosystems. They engineer local habitats and can support many faunal species through trophic (e.g. providing feeding grounds) or non‐trophic (e.g. providing predation shelters and spawning grounds) mechanisms. How the supporting effects of foundation species on fauna change across multiple trophic levels remains poorly understood. We investigated how a foundational seagrass supported faunal species at different trophic levels, using a series of comparative surveys, diet analyses, and field experiments. We found that seagrasses substantially enhanced marine fauna across all but one of four trophic levels. Primary, secondary, and top consumers were significantly more abundant, whilst tertiary consumers were similarly or less abundant in seagrass beds than on unvegetated mudflats. Importantly, seagrasses supported fauna of different trophic levels via different trophic or non‐trophic mechanisms; seagrasses provided mainly feeding, refuging and feeding, feeding, and spawning grounds for primary, secondary, tertiary, and top consumers, respectively. Our work reveals that seagrasses support fauna from primary to top trophic levels via different trophic and non‐trophic mechanisms. Our findings highlight that protecting and restoring seagrasses is critical to enhancing fauna across multiple trophic levels and can inform conservation strategies targeted for fauna at different trophic levels. Our study can help stimulate future studies from other ecosystems to test how foundation species affect fauna across different trophic levels. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Marine macroalgae are important primary producers in coastal ecosystems. Within sheltered and shallow bays in the Mediterranean, various Fucalean macroalgae and seagrasses coexist, creating habitats of high ecological importance. These habitats have historically suffered from various disturbances, and on this basis, active restoration actions have been proposed as potential solutions for their recovery. Here, we assessed the restoration success of a 10‐year restored macroalgal forest by evaluating the recovery in terms of oxygen and pH fluxes and comparing those data with those of a healthy marine forest and a degraded habitat counterpart. We estimated the overall changes in dissolved oxygen and pH using light and dark community in situ incubations. We also determined the biomass and composition of macroalgal and macroinvertebrate compartments of each assemblage. During light incubations, the healthy and restored forest assemblages showed similar average net oxygen production, 5.7 times higher than in the degraded one, and a greater increase in pH. More than 95% of the incubated biomass corresponded to macroalgal and seagrass species. The restored forest showed a six‐fold increase in biomass, most likely being responsible for the recovery of primary production. This work provides empirical evidence that the restoration of a single structural species, once successful in the early stages, can yield positive results by recovering processes such as primary production and dark respiration. Moreover, these results showcase differences in ecosystem functions between healthy (either mature or restored) and degraded habitats, highlighting the importance of protecting and preserving coastal marine forests. [ABSTRACT FROM AUTHOR]

Periphyton that lives attached to seagrass leaves is generally a source of autochthonous energy in the waters and has a major role in the food chain system that supports the primary productivity of seagrass beds. The aim of the current study was to study the extent to which mercury (Hg) levels affect the ecosystem by looking at Hg accumulation in the periphyton. This study used the method of species composition analysis, the density of epiphytic periphyton algae on seagrass, and analyzed the level of pollution in the Talawan Bajo estuary waters based on the bioaccumulation of mercury content in the periphyton and analyzed the periphyton as a bioindicator of the level of Hg pollution in the waters. The first stage was to identify the types of seagrass and periphyton and analyze the composition and density; diversity index, uniformity and dominance of periphyton. The second stage of this study included observation of the accumulation of heavy metal Hg on a laboratory scale and visualization of periphyton cells using TEMcell. Based on the results of the analysis, it was shown that the environmental conditions of the Talawaan Bajo estuary were polluted by heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. It was concluded that the environmental conditions of the Talawaan Bajo estuary were contaminated with heavy metal Hg because the Hg content accumulated in seagrass and periphyton exceeded the quality standards for aquatic biota. Hg contamination in aquatic ecosystems affects the life of biota in the environment, especially damage to tissue structures. [ABSTRACT FROM AUTHOR]

Tropical seagrass ecosystems are globally imperiled due to overfishing and anthropogenic disturbances. Sustaining the services they provide will require managing resilience, particularly with increased volatility from climate change. Portfolio theory is touted as a mechanism to increase resilience in ecosystems because it takes advantage of temporal volatility in local production dynamics to increase stability at larger spatial scales. Using an individual‐based model of a network of artificial reefs across multiple seagrass ecosystems that is parameterized with 15 years of field data, we demonstrate that (1) the large fish populations and the low enrichment synergistically increase portfolio effects; (2) the mechanism was via reduced local and increased meta‐ecosystem stability in primary production; and (3) stability was greatest under intermediate production because nutrient enrichment reduces and fish, which have less influence on the amount of production, promote stability. Integrating common‐sense management with portfolio theory can stabilize the services provided by seagrass ecosystems. [ABSTRACT FROM AUTHOR]

Seagrass is a type of marine plant that offers significant ecological and human benefits. It is found in many tropical waters, including those around Morotai Island. However, reliable scientific information about the condition of seagrass beds in Indonesia, particularly in Morotai Island Regency, still needs improvement. This research analyzed the distribution and coverage of seagrass in Morotai Island Regency, conducted from June to September 2024. Seagrass samples were collected from six sub-districts: South Morotai, East Morotai, North Morotai, Morotai Jaya, Southwest Morotai, and Rao Island. Observations were conducted in situ, and distribution maps were created using ArcView GIS. Seagrass coverage was assessed using the transect plot method. The results revealed 12 species of seagrass in Morotai Island Regency. Out of 81 observation points, seagrass was found in 64 locations across the six sub-districts. The distribution of specific species is as follows: Enhalus acoroides at 37 points (45.68%), Thalassia hemprichii at 46 points (56.79%), Cymodocea serrulata at 34 points (41.98%), Cymodocea rotundata at 43 points (53.09%), Halodule uninervis at 25 points (30.86%), Halodule pinifolia at 37 points (45.68%), Thalassodendron ciliatum at 2 points (2.47%), Halophila minor at 16 points (19.75%), Halophila ovalis at 18 points (22.22%), Halophila spinulosa at 5 points (6.17%), Halophila decipiens at 1 point (1.23%), and Syringodium isoetifolium at 27 points (33.33%). The seagrass coverage in Morotai Island ranges from sparse to dense. Overall, the water conditions in Morotai Island Regency are still relatively good for supporting seagrass growth. [ABSTRACT FROM AUTHOR]

Seagrasses provide a multitude of ecosystem services and act as important carbon sinks. However, seagrass habitats are declining globally, and they are among the most threatened ecosystems on earth. For these reasons, long-term and continuous measurements of seagrass parameters are of primary importance for ecosystem health assessment and sustainable management. This paper presents results from both active and passive acoustical methods for ecosystem monitoring in seagrass meadows. From a propagation perspective, gas bodies contained within the seagrass tissue as well as photosynthetic-driven bubble production result in attenuation, dispersion, and scattering of sound that produce increased transmission loss. For the passive approach, the detachment of gas bubbles from the plants is an important component of the ambient soundscape. Examples of both techniques will be presented based on data collected as part of a two-year continuous deployment of an acoustical measurement system operating in a moderately dense seagrass bed dominated by Thalassia testudinum (turtle grass) in Corpus Christi Bay, Texas. The data show annual trends related to the seasonal growth pattern of Thalassia as well as diurnal trends correlated with photosynthetically active radiation. [ABSTRACT FROM AUTHOR]

Aim: Seagrass meadows represent a key marine ecosystem owing to the significant biodiversity they host. Protection actions are often implemented without considering connectivity between habitats. In this article, we project and prioritise Mediterranean seagrass habitats (Posidonia oceanica and Cymodocea nodosa) based on their potential as sources/retention and stepping stones for dispersal propagules of the associated biotic communities. We use this information to identify gaps in the protection of highly ranked habitats. Location: Mediterranean Sea. Methods: We related seagrass observations with marine environmental predictors to run species distribution models and infer the distribution of Mediterranean seagrasses. We then used a network‐based approach (CONEFOR) to rank patches of seagrass suitable areas based on their contribution to the seascape in terms of patch area, potential as source/retention of propagules and stepping stone. Finally, by overlaying our ranking with the spatial distribution of marine protected areas (MPAs), we identified potential gaps in the protection of important seagrass habitats across the Mediterranean and its basins. Results: Most of the identified patches of seagrass suitable areas are not included in MPAs, only reaching a maximum protection coverage of ~50% in the Northwestern Mediterranean. Relatively few patches contribute disproportionately to connectivity, but top‐ranked habitat patches are not included within the existing MPAs network, both at the Mediterranean scale and for most basins. The largest gaps for the source/sink role are in the Aegean and Ionian Sea, and largest gaps for the stepping stone role are in the Adriatic, Ionian and Tyrrhenian Sea. Main Conclusions: Our results suggest that the current MPAs network fails to protect highly relevant patches of seagrass suitable areas in most of the Mediterranean basins. However, this gap could be filled by a few well‐placed MPAs. Overall, we provide novel insights for the identification of key habitats and planning novel coastal MPAs in the region. [ABSTRACT FROM AUTHOR]

Coastal blue carbon ecosystems sequester carbon, storing it as plant biomass and particulate organic matter in sediments. Recent studies emphasize the importance of incorporating dissolved inorganic and organic forms into carbon assessments. As sediment-stored organic matter decomposes, it releases dissolved inorganic carbon (DIC) and total alkalinity (TA), both of which are critical for regulating the partial pressure of CO2 (pCO2) and thus carbon sequestration. This study investigated the role of benthic DIC and TA fluxes in carbon sequestration within seagrass meadows in Dongsha Island's inner lagoon (IL) during the winter and summer seasons. Chamber incubation experiments revealed elevated benthic DIC and TA fluxes compared to global averages (107 ± 75.9 to 119 ± 144 vs. 1.3 ± 1.06 mmol m−2 d−1 for DIC, and 69.7 ± 40.7 to 75.8 ± 81.5 vs. 0.52 ± 0.43 mmol m−2 d−1 for TA). Despite DIC fluxes being approximately 1.5 times higher than TA fluxes, water pCO2 levels remained low (149 ± 26 to 156 ± 18 µatm). Mass balance calculations further indicated that benthic DIC was predominantly reabsorbed into plant biomass through photosynthesis (−135 to −128 mmol m−2 d−1). Conversely, TA accumulated in the water and was largely exported (−60.3 to −53.7 mmol m−2 d−1), demonstrating natural ocean alkalinity enhancement (OAE). This study highlights the crucial role of IL seagrass meadows in coastal carbon sequestration through net autotrophy and carbonate dissolution. Future research should explore the global implications of these processes and assess the potential of natural OAE in other coastal blue carbon ecosystems. [ABSTRACT FROM AUTHOR]

Seagrass meadows are among the most threatened ecosystems on Earth, with losses attributed to increasing coastal populations, degraded water quality and climate change. As coastal communities work to improve water quality, there is increased concern regarding the use of herbicides within the watersheds of these sensitive ecosystems. Glyphosate is the most widely used herbicide on Earth because it is non-selective and lethal to most plants. Also, the targeted amino acid synthesis pathway of glyphosate is not carried out by vertebrates, and it is generally considered one of the safer but effective herbicides on the market. At least partially due to its cost-effectiveness compared to other techniques, including mechanical harvesting, glyphosate use in the aquatic environment has increased in coastal areas to manage aquatic weeds, maintain navigable waterways and mitigate upland flooding. This has prompted concerns regarding potential ecosystem-level impacts. To test the acute toxicity of glyphosate to seagrasses, mesocosm experiments exposed Ruppia maritima and Halodule wrightii to 1 ppm, 100 ppm and 1000 ppm of glyphosate (as glyphosate acid). No significant decrease in leaf chlorophyll a (Chl a) was identified for either species at 1 ppm versus a control; however, significant decreases were observed at higher concentrations. In all except 1000 ppm mesocosms, water column Chl a increased, with a 7-fold increase at 100 ppm. These data demonstrate that at very high glyphosate concentrations, both acute toxicity and light limitation from enhanced algal biomass may have adverse impacts on seagrasses. Despite these observations, no significant adverse impacts attributed to acute toxicity were observed at 1 ppm, which is >1000 times higher than concentrations measured in the Indian River Lagoon system. Overall, herbicide use and associated decaying biomass contribute nutrients to these systems, in contrast to the removal of nutrients when mechanical harvesting is used. Based on our data and calculations, when used at recommended application rates, contributions to eutrophication, degraded water quality and harmful algal blooms were more likely to impact seagrasses than acute toxicity of glyphosate. [ABSTRACT FROM AUTHOR]

Seagrass meadows are effective sinks of atmospheric carbon dioxide (CO2). However, there is little insight on how methane (CH4) emissions may potentially offset carbon sequestration in seagrass meadows. Here, we resolve diel and seasonal dynamics of CH4 and CO2 water‐air fluxes over a cold‐temperate Zostera marina seagrass meadow using high‐resolution timeseries observations in seawater. CH4 was emitted from the seagrass‐dominated coastal bay year‐round to atmosphere with CH4 fluxes ranging from 0.2 to 2.6 μmol m−2 d−1. These fluxes are at the lower end of earlier estimates based mostly on short‐term (i.e., 1 day) observations. The 13‐fold seasonal fluctuations in CH4 emissions were greater than the 6‐fold diel fluctuation. Radon observations imply that dissolved CH4 was primarily originated from sediment porewater. The main fate of CH4 in the water was outgassing to the atmosphere via wind forcing. Oxygen and temperature partially controlled dissolved CH4 seasonal dynamics. There was an annual average uptake of CO2 from the atmosphere (−0.9 ± 1.5 mmol m−2 d−1) driven by enhanced photosynthesis in the spring and summer. The CO2‐equivalent CH4 outgassing (0.5 ± 0.6 g CO2 eq m−2 yr−1) offsets only 0.8% of the sediment carbon accumulation in this cold‐temperate Z. marina meadows over a 20‐year time horizon. The CO2‐equivalent CH4 flux was 6% of the average annual CO2 uptake. Hence, CH4 emissions from this cold‐temperate seagrass meadow acted as a minor offset to carbon sequestration. Plain Language Summary: Natural carbon sinks help to partially mitigate climate change. Highly productive seagrass beds in coastal areas are natural sinks storing carbon in sediment for thousands of years. However, seagrass meadows also release the potent greenhouse gas methane, potentially counteracting some of the carbon sink. Methane assessments in seagrass meadows are scarce and have been conducted mostly in warm climates over short timescales. Here, we measure air‐sea methane emissions from a seagrass‐dominated ecosystem in a cold climate using continuous measurements over diel and seasonal timescales. Methane emissions were lower than global averages and had larger seasonal than diel variability. Winds, oxygen, and temperature influenced dissolved methane dynamics. The methane released from the seagrass reduced <1% of the climate benefit of carbon storage in sediments over a year. Hence, seagrass meadow preservation in cold climates remains crucial for carbon sequestration, contributing to climate change mitigation efforts. Key Points: Seasonal fluctuations in CH4 emissions were greater than diel variationCH4 emissions counteracted about 6% of the average annual CO2 water‐air uptake over a seagrass meadowSeagrass ecosystem CH4 emissions offset about 1% of sediment carbon sequestration [ABSTRACT FROM AUTHOR]

Cymodocea rotundata Asch. & Schweinf. 1870 (Cymodoceaceae) is a seagrass found in the tropical and temperate Indo-Pacific coastal waters. Seagrass beds composed of C. rotundata and other seagrasses form ecologically valuable ecosystems. In this study, the complete chloroplast genome of C. rotundata was sequenced and characterized for the first time. It is a circular genome of 158,311 bp in length, consisting of a large single-copy region (88,451 bp), a small single-copy region (18,836 bp), and a pair of inverted repeats (25,512 bp). A total of 130 genes were annotated, including 86 protein-coding genes (PCGs), 36 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Seven PCGs and 6 tRNA genes contain 1 intron, and 3 PCGs contain 2 introns. In addition, 7 PCGs, 7 tRNA genes, and all the rRNA genes are multi-copy genes with 2 copies. Phylogenetic analysis shows that C. rotundata clusters with Syringodium isoetifolium in one clade, both belonging to the family Cymodoceaceae. This study provides new information to support further research on the phylogeny of Cymodoceaceae. [ABSTRACT FROM AUTHOR]

Symbioses with fungi are important and ubiquitous on dry land but underexplored in the sea. As yet only one seagrass has been shown to form a specific root-fungus symbiosis that resembles those occurring in terrestrial plants, namely the dominant long-lived Mediterranean species Posidonia oceanica (Alismatales: Posidoniaceae) forming a dark septate (DS) endophytic association with the ascomycete Posidoniomyces atricolor (Pleosporales: Aigialaceae). Using stereomicroscopy, light and scanning electron microscopy, and DNA cloning, here we describe a novel root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum (Alismatales: Cymodoceaceae) from a site in the Gulf of Aqaba in the Red Sea. Similarly to P. oceanica, the mycobiont of T. ciliatum occurs more frequently in thinner roots that engage in nutrient uptake from the seabed and forms extensive hyphal mantles composed of DS hyphae on the root surface. Contrary to P. oceanica, the mycobiont occurs on the roots with root hairs and does not colonize its host intraradically. While the cloning revealed a relatively rich spectrum of fungi, they were mostly parasites or saprobes of uncertain origin and the identity of the mycobiont thus remains unknown. Symbioses of seagrasses with fungi are probably more frequent than previously thought, but their functioning and significance are unknown. Melanin present in DS hyphae slows down their decomposition and so is true for the colonized roots. DS fungi may in this way conserve organic detritus in the seagrasses' rhizosphere, thus contributing to blue carbon sequestration in seagrass meadows. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Understanding the impacts of past and future climate change on genetic diversity and structure is a current major research gap. We ask whether past range shifts explain the observed genetic diversity of surfgrass species and if future climate change projections anticipate genetic diversity losses. Our study aims to identify regions of long‐term climate suitability with higher and unique seagrass genetic diversity and predict future impacts of climate change on them. Location: Northeast Pacific. Time Period: Analyses considered a timeframe from the Last Glacial Maximum (LGM; 20 kybp) until one Representative Concentration Pathway (RCP) scenario of future climate changes (RCP 8.5; 2100). Major Taxa Studied: Two seagrass species belonging to the genus Phyllospadix. Methods: We estimated population genetic diversity and structure using 11 polymorphic microsatellite markers. We predicted the distribution of the species for the present, LGM, and near future (RCP 8.5, no climate mitigation) using Species Distribution Models (SDMs). Results: SDMs revealed southward range shifts during the LGM and potential poleward expansions in the future. Genetic diversity of Phyllospadix torreyi decreases from north to south, but in Phyllospadix scouleri the trend is variable. Phyllospadix scouleri displays signals of genome admixture at the southernmost and northernmost edges of its distribution. Main Conclusions: The genetic patterns observed in the present reveal the influence of climate‐driven range shifts in the past and suggest further consequences of climate change in the future, with potential loss of unique gene pools. This study also shows that investigating climate links to present genetic information at multiple timescales can establish a historical context for analyses of the future evolutionary history of populations.

Silicon is a major driver of global primary productivity and CO2 sequestration, and is a beneficial element for the growth and environmental stress mitigation of many terrestrial and aquatic plants. However, only a few studies have examined the occurrence of silicon in seagrasses, and its function within seagrass ecosystems and the role of seagrasses in silicon cycling remain largely unexplored. This study uses for the first time two methods, the wet-alkaline digestion and the hydrofluoric acid digestion, to quantify silicon content in seagrass leaves using the species Zostera marina and elaborates on the potential role of silicon in seagrass biogeochemistry and ecology, as well as the role of seagrass ecosystems as a silicon reservoir. The results revealed that seagrass leaves contained 0.26% silicon:dry-weight, which is accumulated in two forms of silica: a labile form digested with the alkaline method and a resistant form digested only with acid digestion. These findings support chemical digestions for silicon quantification in seagrass leaves and provide new insights into the impact of seagrasses on the marine silicon cycle. Labile silica will be recycled upon leaf degradation, benefiting siliceous organisms, while refractory silica will contribute to the ecosystem’s buried silica stock and coupled carbon sequestration. In the Bay of Brest (France), the seagrass silicon reservoir was estimated at 0.18 ± 0.07 g Si m⁻2, similar to that of benthic diatoms, underscoring the potential role of seagrasses in silicon biogeochemistry in the land–ocean continuum, where they might act as a buffer for silicon transport to the ocean. [ABSTRACT FROM AUTHOR]

This study evaluates the feasibility of using medium-resolution satellite sensors to monitor changes in the extent of ecosystem functional groups (EFGs) in South African estuaries, for reporting on the 2030 targets of the Global Biodiversity Framework (GBF). Landsat and Sentinel-1 and -2 image collections in Google Earth Engine (GEE) were used to generate output layers for each of the national land cover years—1990, 2014, 2018 and 2020. Image composites of each year’s two growth seasons and one dry season, vegetation indices and topographic data were generated. Changes in the extent and accuracies of three estuarine (mangroves, salt marshes and submerged macrophytes) and three freshwater (forested wetlands, freshwater marshes and large macrophytes) EFGs were calculated and compared to a manually mapped through image interpretation, high-confidence layer. Overall, estuarine EFGs comprised between 10 and 18% of the extent of the EFGs, while freshwater EFGs made up 15% of the extent of estuaries. The overall accuracies of detection of EFGs for 1990 were < 64% compared to the > 71% attained for 2014, 2018 and 2020. In comparison to manual delineations of some of these habitats, the outputs generated from these medium-resolution sensors resulted in overestimation of extent for all EFGs; for mangroves by 115% and for salt marshes and submerged macrophytes by 150–230%. Finer spatial resolution images, and time-series mapping would be critical for improved delineation and monitoring of South Africa’s estuarine habitats. [ABSTRACT FROM AUTHOR]

Seagrass meadows are well-known for their capacity to capture and store blue carbon in sediments. However carbon stocks vary significantly between meadows, spanning more than three orders of magnitude on both local and global scales. Understanding the drivers of seagrass carbon stocks could help improve strategies for incorporating blue carbon into management plans. Here, we measured sediment carbon stocks in eelgrass (Zostera marina) meadows and unvegetated areas along the Norwegian coast, spanning wide gradients in temperature, wave exposure, water depth, salinity, and eelgrass biomass. Carbon stocks were generally higher in eelgrass meadows than in adjacent unvegetated areas, yet they displayed considerable variation (400 − 30 000 g C m−2 at 50 cm sediment depth) even among nearby sites. Overall, the highest carbon stocks were found in deeper, muddier, sheltered meadows near river mouths. These sites likely have the highest input and retention of carbon from different sources. Consequently, they should be prioritized as conservation targets for preserving coastal blue carbon stocks. Despite ever-increasing efforts to quantify seagrass blue carbon globally, high uncertainties still persist, partly due to differing methodologies, processes, and environmental context. Blue carbon stock estimates could be improved through the coordination of standardised mapping and sampling methods. [ABSTRACT FROM AUTHOR]

Coral reefs are facing threats from a variety of global change stressors, including ocean warming, acidification, and deoxygenation. It has been hypothesized that growing corals near primary producers such as macroalgae or seagrass may help to ameliorate acidification and deoxygenation stress, however few studies have explored this effect in situ. Here, we investigated differences in coral growth rates across a natural gradient in seawater temperature, pH, and dissolved oxygen (DO) variability in a nearshore seagrass bed on Dongsha Atoll, Taiwan, South China Sea. We observed strong spatial gradients in temperature (5°C), pH (0.29 pH units), and DO (129 μmol O2 kg-1) across the 1-kilometer wide seagrass bed. Similarly, diel variability recorded by an autonomous sensor in the shallow seagrass measured diel ranges in temperature, pH, and DO of up to 2.6°C, 0.55, and 204 μmol O2 kg-1, respectively. Skeletal cores collected from 15 massive Porites corals growing in the seagrass bed at 4 sites revealed no significant differences in coral calcification rates between sites along the gradients. However, significant differences in skeletal extension rate and density suggest that the dynamic temperature, pH, and/or DO variability may have influenced these properties. The lack of differences in coral growth between sites may be because favorable calcification conditions during the day (high temperature, pH, and DO) were proportionally balanced by unfavorable conditions during the night (low temperature, pH, and DO). Alternatively, other factors were simply more important in controlling coral calcification and/or corals were acclimated to the prevailing conditions at each site. [ABSTRACT FROM AUTHOR]