Search

The two‐toned pygmy squid (Idiosepius pygmaeus, Steenstrup, 1881) is a small, tropical cephalopod that inhabits seagrass meadows and is known to attach to blades of seagrass using a specialised adhesive organ. A global decline in seagrass habitat due to anthropogenic disturbances may threaten the species that rely on seagrass meadows for shelter, foraging and other crucial activities. It is unclear if I. pygmaeus can utilise alternative habitats in the absence of seagrass. Here, we test the effect of habitat type, material and composition type, and the presence of conspecifics on the settlement preferences of I. pygmaeus. Individuals each underwent three separate experiments: (1) testing the preference between their known habitat, Zostera muelleri subsp. Capricorni and potential substitute, Sargassum, (2) testing the preference to attach to a natural or artificial structure of similar shape and size, and (3) testing the preference of identical habitats, one with a conspecific adhered to and one without. We found that I. pygmaeus did not have a strong preference for either Zostera or Sargassum. However, a strong preference was found for attachment to the natural structure over the artificial one. There was also strong evidence for the use of conspecific cues in habitat choice, with 75% of individuals selecting the habitat that contained a conspecific. As habitat loss is the leading cause of species extinction, the knowledge of habitat preferences for I. pygmaeus is vital in order to assess their risk of population decline. The findings of this study suggest that I. pygmaeus could utilise an alternative habitat in the presence of seagrass meadow reduction, which is under threat from human activity. [ABSTRACT FROM AUTHOR]

Overcoming ecological feedbacks is a major limiting factor reducing the success of many seagrass restoration projects. Negative feedbacks occur when biotic or abiotic conditions of a site are changed sufficiently after the loss of seagrass to prevent its recovery, even after the original stressors are remediated. While negative feedbacks in seagrass restoration are common, there remain limited studies of ways to reduce them and kick‐start the necessary positive feedbacks to promote recovery. We used field and laboratory experiments to investigate key ecological feedbacks in seagrass (Zostera marina) restoration by testing the role of hessian bags and seed burial in reducing seed predation and promoting plant development. We used a double‐hurdle model approach to predict "seagrass emergence success" and "seagrass growth success" across planted field plots. We found that planting seeds in hessian bags and burying them in the sediment improved the likelihood of seeds developing into mature plants. We recorded an average 13‐fold increase in shoot density for seeds planted in buried bags relative to raked furrows. This could be the combined result of reduced predation as well as bags mimicking emergent traits of mature seagrass to withstand physical impacts. We supplement these findings with laboratory evidence that hessian bags provide protection from predation by green shore crabs. Overall, we found a low and variable success rate for seed‐based restoration and indicate other feedbacks in the system beyond those we controlled. However, we show that small methodological changes can help overcome some key feedbacks and improve restoration success. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems play a vital role in marine environments, providing essential services, including physical habitat that supports a species diversity critical to robust trophic structures. However, seagrass loss due to various influences raises concerns about the persistence of these ecosystems. Seagrass‐associated macrofauna serve as indicators of environmental health, noting change or stability. This study investigated the structural and environmental drivers influencing macrofaunal communities associated with seagrass (Zostera capensis) in a temperate lagoon. Variation in macrofaunal community structure across phenotypically distinct seagrass populations found large‐leaved morphotypes in deeper intertidal stands to support higher species diversity and richness. Conversely, small‐leaved populations in higher shore positions had a greater abundance of desiccation‐resistant gastropods. Seasonal differences were significant, with higher abundances generally observed during spring and summer, while diversity and richness peaked in autumn and winter. Structural equation modelling revealed shoot densities and leaf width to have positive direct effects on macrofaunal abundance, while temperature and tidal exposure produced significant indirect effects. Temperature had a direct effect on seagrass structure and significantly influenced five out of six seagrass metrics measured. Observations of seagrass distribution in the lagoon indicate significant declines in large‐leaved populations with likely adverse consequences for associated macrofauna and related trophic levels. [ABSTRACT FROM AUTHOR]

Numerical experiments have been carried out to model hydrodynamic and morphodynamic processes to explain the nature of the spatial distribution of Zostera marina (eelgrass) in the inner bays of Posyet Bay. Hydrodynamic modeling has been performed using the Delft3D flow model. The Simulating WAves Near shore (SWAN) spectral wave model has been used to simulate wind wave parameters (direction of propagation, wave length and height, and near-bottom orbital velocities). The restructuring of the bottom topography under the influence of wind waves and the hydrodynamic influence of tidal and wind currents has been calculated with the Delft3D software package. The results of numerical experiments showed that the dynamics of the coastal bottom topography is determined by the nature of sediment motion in the coastal zone under the combined influence of waves and currents. A comparison of the modeling results with data on the distribution of Zostera showed a high correlation with model simulations of erosion and accumulation in the coastal zone. [ABSTRACT FROM AUTHOR]

Aim: The seagrass Zostera japonica is a dramatically declined endemic species in the Northwestern Pacific from the (sub)tropical to temperate areas, however, it is also an introduced species along the Pacific coast of North America from British Columbia to northern California. Understanding the population's genetic patterns can inform the conservation and management of this species. Location: North Pacific. Methods: We used sequences of the nuclear rDNA internal transcribed spacer (ITS) and chloroplast trnK intron maturase (matK), and 24 microsatellite loci to survey 34 native and nonnative populations (>1000 individuals) of Z. japonica throughout the entire biogeographic range. We analysed the phylogeographic relationship, population genetic structure and genetic diversity of all populations and inferred possible origins and invasion pathways of the nonnative ones. Results: All markers revealed a surprising and significant deep divergence between northern and southern populations of Z. japonica in the native region separated by a well‐established biogeographical boundary. A secondary contact zone was found along the coasts of South Korea and Japan. Nonnative populations were found to originate from the central Pacific coast of Japan with multiple introductions from at least two different source populations, and secondary spread was likely aided by waterfowl. Main Conclusions: The divergence of the two distinct clades was likely due to the combined effects of historical isolation, adaptation to distinct environments and a contemporary physical barrier created by the Yangtze River, and the warm northward Kuroshio Current led to secondary contact after glacial separation. Existing exchanges among the nonnative populations indicate the potential for persistence and further expansion. This study not only helps to understand the underlying evolutionary potential of a widespread seagrass species following global climate change but also provides valuable insights for conservation and restoration. [ABSTRACT FROM AUTHOR]

The maintenance of stocks of estuarine species strongly depends on the ability of the species to cope with environmental stress. In NW Spain, commercial clam beds, which are usually co-occupied by the seagrass Zostera noltei , are often exposed to reduced salinity caused by intense rainfalls. Our goals were to evaluate the effects of low salinity events on both juvenile clams and Z. noltei , including their interactions. A mesocosm experiment was performed to simulate three salinity decreases (35–35, 25–10, and 20–5), and several indicators of clam and seagrass performance were measured after 3 and 6 days of exposure and again after a recovery period of 4 days. No differences were observed in the non-native clam Ruditapes philippinarum , while oxygen consumption, clearance rate and growth decreased significantly in the native clams R. decussatus and Venerupis corrugata in response to low salinity stress. Zostera noltei indicators did not vary in response to low salinity exposure, except the sucrose content, which decreased. Moreover, the seagrass buffered juvenile clams from salinity fluctuations in the short term, although the interactions were weak. The species-specific sensitivity to low salinity should be a major concern in future management plans for the shellfish beds in the context of climate change. [ABSTRACT FROM AUTHOR]

Seagrass extent has declined globally, including in New Zealand. Following the success of an initial trial to transplant and re-establish intertidal seagrass at a former site in Whangarei Harbour, a second trial was initiated. This trial aimed to restore seagrass at a more distant former site and tested the efficacy of transplant units ranging in size from small cores (5 or 9 × 0.01 m diameter cores placed within a 0.25 m2 plot) to larger entire plots (0.25 m2 or 0.5 m2). Seagrass was transplanted in winter when plants were dormant. Plant cover of transplanted and donor plots and light climate at both sites were monitored over a period of four years. All but one of the 24 units survived, and the plants began to spread after 12–18 months to eventually develop patches ranging in size from 5 to 68 m2. Seagrass recolonised all donor plots completely within 10 months. Results show that small cores and larger plots can both be used successfully to transplant and restore populations of Zostera muelleri with no long-lasting damage to donor meadows. However, use of small cores is recommended to minimise extractions and loss of transplanted material, and to simplify logistics. [ABSTRACT FROM AUTHOR]

Restoration is accelerating to reverse global declines of key habitats and recover lost ecosystem functions, particularly in coastal ecosystems. However, there is high uncertainty about the long‐term capacity of restored ecosystems to provide habitat and increase biodiversity and the degree to which these ecosystem services are mediated by spatial and temporal environmental variability. We addressed these gaps by sampling fishes biannually for 5–7 years (2012–2018) at 16 sites inside and outside a rapidly expanding restored seagrass meadow in coastal Virginia (USA). Despite substantial among‐year variation in abundance and species composition, seine catches in restored seagrass beds were consistently larger (6.4 times more fish, p < 0.001) and more speciose (2.6 times greater species richness, p < 0.001; 3.1 times greater Hill–Shannon diversity, p = 0.03) than seine catches in adjacent unvegetated areas. Catches were particularly larger during summer than autumn (p < 0.01). Structural equation modeling revealed that depth and water residence time interacted to control seagrass presence, leading to higher fish abundance and richness in shallow, well‐flushed areas that supported seagrass. Together, our results indicate that seagrass restoration yields large and consistent benefits for many coastal fishes, but that restoration and its benefits are sensitive to the dynamic seascapes in which restoration is conducted. Consideration of how seascape‐scale environmental variability affects the success of habitat restoration and subsequent ecosystem function will improve restoration outcomes and the provisioning of ecosystem services. [ABSTRACT FROM AUTHOR]

Seagrasses are threatened by anthropogenic stressors and climate change, with numerous population declines reported. In South Africa, the eelgrass Zostera capensis is restricted to estuarine environments and has a disjunct distribution and declining status. With the majority of the distribution of Z. capensis on the west and southwest coasts of South Africa, the isolated easternmost populations in KwaZulu-Natal Province (KZN) are of particular interest. Following the extirpation of Z. capensis at Durban and St Lucia, only five populations remain, of which three (in the Amatikulu, Mlalazi and Mhlatuze estuaries) are situated <50 km apart. Previous molecular analyses showed strong population structure between Z. capensis populations, but the geographically close populations on the east coast were not included. In this study, using single nucleotide polymorphisms (SNPs) isolated from 31 individual sampled plants collected from three northern KZN estuaries, we provide evidence for distinct population clusters, with unique evolutionary signals. Zostera capensis in the Mlalazi Estuary has a low level of genomic diversity, likely as a result of a small, dynamic population unable to withstand prolonged freshwater exposure. Our results suggest that conservation efforts need to consider unique population signals even among geographically close populations, in particular within the context of restoration, where genomic compatibility may determine the persistence of restored populations. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems are ecologically important but are declining worldwide, prompting restoration efforts. However, restoration success is partially reliant on ensuring that donor material and planting methods are suitable under the environmental conditions expected within restoration sites. This may require planting at critical densities needed to initiate favorable environmental feedbacks, ensuring plants are pre‐adapted to local conditions, and setting realistic restoration goals. An understanding of the relationship between local environmental conditions (e.g. the local light environment and seagrass structural complexity) can be particularly important in guiding restoration decision‐making. Here, we investigate how sediment‐light conditions interact with seagrass structural complexity (density and above‐ground morphology) to guide restoration planting approaches for the intertidal seagrass Zostera muelleri. Using generalized additive models and empirical data, we identified significant relationships between the local sediment‐light environment and the structural complexity of Z. muelleri meadows present in Western Port, Victoria, southeast Australia. We found a decrease in shoot density and leaf length with decreasing light availability, potentially reflective of an adaptive change in the species morphology in response to low‐light environments. We also found a decrease in sediment sorting and increased fine particles with increasing meadow structural complexity, suggesting that seagrass structural complexity increases sediment stability, and accretion, and may contribute to local water clarity via ecological feedbacks. These findings suggest that understanding both environmental drivers and the potential for ecological feedbacks to occur is needed before large‐scale planting begins and that restoration targets should reflect the meadow form most likely to occur under the environmental conditions present. [ABSTRACT FROM AUTHOR]

Seagrass beds are disappearing at a record pace despite their known value to our oceans and coastal communities. Simultaneously, our coastlines are under the constant pressure of climate change which is impacting their chemical, physical and biological characteristics. It is thus pertinent to evaluate and record habitat use so we can understand how these different environments contribute to local biodiversity. This study evaluates the assemblages of fish found at five Zostera beds in Southern California using environmental DNA (eDNA) metabarcoding. eDNA is a powerful biodiversity monitoring tool that offers key advantages to conventional monitoring. Results from our eDNA study found 78 species of fish that inhabit these five beds around Southern California representing embayment, open coastal mainland and open coastal island settings. While each bed had the same average number of species found throughout the year, the composition of these fish assemblages was strongly site dependent. There were 35 fish that were found at both open coast and embayment seagrass beds, while embayment seagrass sites had 20 unique fish and open coast sites had 23 unique fish. These results demonstrate that seagrass fish assemblages are heterogenous based on their geographic positioning and that marine managers must take this into account for holistic conservation and restoration efforts. [ABSTRACT FROM AUTHOR]

The filamentous green alga Chaetomorpha ligustica (Cladophoraceae, Cladophorales) was recorded covering seagrass meadows at Pāuatahanui Inlet, New Zealand. Species of the genus Chaetomorpha are difficult to identify by their morphologically, and the identification of C. ligustica was confirmed by sequencing the 28S rRNA large subunit providing a high level of confidence in the species designation. In November 2019, we found C. ligustica intertwined with Ulva spp. forming dense, heavy and entangled structures. Here we report, for the first time, negative impacts of this species upon meadows of the New Zealand seagrass Zostera muelleri. We observed a significant loss of seagrass cover and evidence of anoxia under C. ligustica mats two weeks from the first sighting. Chaetomorpha ligustica can easily be misidentified in the field. This may lead to over- and under-reporting of species, and we recommend the need for more careful identification of macroalgal blooms in the future and further research on growth requirements and origins of strains. [ABSTRACT FROM AUTHOR]

Seagrass Zostera muelleri has been reported to reproduce mainly asexually in New Zealand. However, a recent study in Tauranga Harbour suggested that flowering might occur more often than previously thought. Here we provide evidence of intertidal seagrass flowering events in six New Zealand estuaries in which it has not before been documented. Further research on seagrass sexual reproduction is desirable as we hypothesise that either flowering events have formerly been missed due to the cryptic nature of the flowers, or that sexual reproduction is emerging as a response to increasing pressures on seagrass ecosystems. In addition, with evidence of seagrass decline occurring globally, and likely also in New Zealand, we recommend collection of seagrass seeds to preserve genetic variability and to attempt restoration efforts through assisted sexual reproduction techniques that have not yet been used in New Zealand. [ABSTRACT FROM AUTHOR]

The extent of seagrasses has declined globally, with restoration through transplantation seen as an important tool for reversing population loss, yet restoration studies for African seagrass species are scarce. This study investigated the use of different planting patterns (straight‐line, compact, and star) and core sizes (11, 18, and 25 cm Ø) in transplanting ecotypes (intertidal and subtidal) in the predominantly open Knysna and temporarily closed Klein Brak estuaries in South Africa. Cores of the endangered seagrass, Zostera capensis, were transplanted in two experimental repeats per ecotype and core size along transects to investigate survival of plants post‐transplant. No significant differences were observed among core sizes, patterns, or ecotypes in the Knysna Estuary, but cores with the compact pattern had better survival rates in the Klein Brak Estuary. Holes left by the smallest cores in donor sites recovered faster through sediment deposition compared to larger holes. Our study demonstrated that seagrass restoration in South Africa is challenging due to limited suitable habitats and strong environmental variability in estuarine ecosystems. It is important that careful consideration, including of genomic diversity and population structure, as well as ecological similarity between donor and recipient populations must be made for each restoration site when assessing its restoration potential. Effective "no‐take bait zones" and upstream catchment management will be important for protecting potential donor meadows. [ABSTRACT FROM AUTHOR]

Seagrasses are habitat-forming species that support biodiversity and a wide range of associated ecosystem services, from blue carbon capture to providing nursery areas for a variety of organisms. Their decline has been documented worldwide and is attributed to human impacts ranging from habitat loss and eutrophication to the effects of climate change. However, recent recovery trends have also been documented due to reductions in stressors, passive and active restoration, and even changes in environmental conditions owing to local management. In this study, we document for the first time the occurrence of Zostera noltei in the downstream area of the River Minho Estuary. This occurrence was unexpected given the hydrological conditions of the estuary, characterised by dredging and siltation. We reconstructed the occurrence and historical distribution of seagrass beds, and showed that they have existed in the region for more than a decade. The current distribution area was mapped using high-resolution multispectral remote sensing techniques, and in situ photoquadrats to complement the remote sensing information with an evaluation of the seagrass cover. A current seagrass area of 0.81 ha was found with an average cover of 70%. However, the Minho Estuary continues to be strongly affected by sediment deposition, which may affect the seagrass population in the long term. Continued surveys are recommended to confirm the long-term trend of colonisation of this important habitat, which ultimately provides so many benefits to coastal ecosystems and humankind. [ABSTRACT FROM AUTHOR]

Together with increasing environmental and anthropogenic pressures, pathogenic diseases are one of the important factors contributing to the ongoing decline of seagrass meadows worldwide; yet the diversity and ecology of the microorganisms acknowledged as seagrass parasites remain critically understudied. Here, we investigate phytomyxid parasites (Rhizaria: Endomyxa: Phytomyxea) of three different eelgrass (Zostera spp.) species found in the Northern hemisphere. We present molecular evidence that Plasmodiophora bicaudata, a long‐recognized parasite of dwarf eelgrass taxa, is closely related to the novel phytomyxid recently discovered in root hairs of Zostera marina, and together they form a distinct clade within the order Phagomyxida, proposed here as Feldmanniella gen. nov. A full life cycle is systematically described in a phagomyxid representative for the first time, proving its conformity with the generalized phytomyxid life history, despite previous uncertainties. The presence of primary infection stages in nearly all collected eelgrass specimens, and subsequent analysis of amplicon sequences from a global Z. marina dataset, reveal phytomyxids to be ubiquitous and one of the predominant microeukaryotes associated with eelgrass roots on a global scale. Our discoveries challenge the current view of Phytomyxea as rare entities in seagrass meadows and suggest their generally low pathogenicity in natural ecosystems. [ABSTRACT FROM AUTHOR]

Soil salt damage has become one of the main biological stresses affecting plant seed germination, crop growth and yield. Salt damage can lead to the accumulation of superoxide anion, hydrogen peroxide and hydroxyl free radicals in plants, and a large amount of accumulated reactive oxygen species will cause the oxidation of lipids, proteins and nucleic acids and then cause cell damage. In this experiment, the seedlings and adult plants of transgenic Arabidopsis with overexpression of Zostera japonica (Z. japonica) DnaJ gene ZjDjB1 were used as materials. Wild-type and transgenic ZjDjB1 Arabidopsis were treated with 100 mM and 200 mM NaCl and root length, fresh weight, leaf water content and dry weight, physiological indexes and antioxidant system enzyme activities were measured. The results showed that overexpression of Z. japonica DnaJ gene ZjDjB1 could significantly alleviate the damage caused by salt stress to transgenic ZjDjB1 Arabidopsis seedlings and adult plants. The results showed that overexpression of Z. japonica DnaJ gene ZjDjB1 could reduce the content of MDA and O2-, increase the content of proline and activate the enzyme activity of antioxidant system under salt stress, to reduce the damage of salt stress to plants. [ABSTRACT FROM AUTHOR]

Dissolved carbon dioxide (CO2) in seawater lowers water pH and can disrupt microbial nutrient cycles. It is unclear how acidification impacts hot spots of nutrient cycling in marine ecosystems such as eelgrass (Zostera marina) beds. We measured nutrient and gas fluxes in sediment cores from Z. marina beds and unvegetated-sediment habitats in Shinnecock Bay, New York, USA in a continuous-flow system with acidified and ambient pH treatments. Under ambient conditions, uptake of N2 by nitrogen (N) fixation was greater than production of N2 by denitrification. Denitrification, however, was dominant under acidified conditions. We then enriched flowing seawater with 15NO3− to test the impact of a nutrient pulse with ambient pH or acidified conditions in the eelgrass and unvegetated cores. Sediment N2 efflux was higher in eelgrass than unvegetated sediments under acidified pH with N-enriched treatments. Results suggest that eelgrass beds may serve as sinks rather than sources of N under the combined stressors of acidification and N-loading. Documenting changes to N pathways under acidification can inform efforts to manage marine ecosystems and conserve benthic habitats. [ABSTRACT FROM AUTHOR]

The restoration of seagrass habitats is a relatively young field with several successful restoration attempts highlighting the feasibility of large‐scale restoration. Successful restoration of seagrass habitats requires an understanding of the most appropriate techniques to use for the target species and local conditions of restoration sites, however, there are currently limited studies on Zostera muelleri. Here, we conduct field trials to explore the use of seed‐ and shoot‐based restoration approaches for Z. muelleri in Victoria, Australia. We assessed the feasibility of collecting and germinating seeds in the field for restoration purposes and trialed the success of four shoot‐based transplanting techniques. We found that seed collections for Z. muelleri were highly successful and scalable, with seed collection rates improving from 489 to 1,939 seeds/hour over 2 years. In addition, in situ seedling germination increased from a maximum of 10.80–25.25% over 2 years. In contrast, shoot‐based restoration approaches were more variable, with plants transplanted with their sediment‐intact outperforming all bare‐rooted approaches. Shoot‐based transplanting approaches appear to have more limited application, but may be appropriate for some restoration sites, or used in combination with seeds to achieve the best restoration outcome. Seed‐based approaches have the potential to be viable and scalable for Z. muelleri given that large numbers of seeds can be collected and stored for at least 7 months before successfully germinating in the field. However, further studies are required to overcome the seedling survival bottleneck (approximately 4 months from emergence) and further increase in situ germination rates. [ABSTRACT FROM AUTHOR]

The extent of parallel genomic responses to similar selective pressures depends on a complex array of environmental, demographic, and evolutionary forces. Laboratory experiments with replicated selective pressures yield mixed outcomes under controlled conditions and our understanding of genomic parallelism in the wild is limited to a few well‐established systems. Here, we examine genomic signals of selection in the eelgrass Zostera marina across temperature gradients in adjacent embayments. Although we find many genomic regions with signals of selection within each bay there is very little overlap in signals of selection at the SNP level, despite most polymorphisms being shared across bays. We do find overlap at the gene level, potentially suggesting multiple mutational pathways to the same phenotype. Using polygenic models we find that some sets of candidate SNPs are able to predict temperature across both bays, suggesting that small but parallel shifts in allele frequencies may be missed by independent genome scans. Together, these results highlight the continuous rather than binary nature of parallel evolution in polygenic traits and the complexity of evolutionary predictability. [ABSTRACT FROM AUTHOR]

Estuarine intertidal flats are known for high rates of primary production, however, globally these ecosystems are under threat from rising sea‐level and accelerated inputs of terrestrial sediments. These stressors simultaneously alter the duration of submersion/emersion periods and water‐column turbidity impacting seafloor photoperiods. To assess how changes in submergence time and water‐clarity can affect benthic primary production, we derived in situ seasonal photosynthesis‐irradiance (P‐I) curves over 2 yr. These were conducted during submerged and emerged periods in a seagrass meadow (Zostera muelleri) and an unvegetated sandflat (dominated by microphytobenthos). P‐I curves showed strong light responses during submergence in both habitats and seagrass during emergence, but in the exposed sandflat there was little relationship between light availability and photosynthesis. Light‐saturated measures of gross primary production (GPPsat) were 2.1 (submerged) and 4.1 times (emerged) higher in the seagrass than the sandflat habitat. Submerged GPPsat was always higher than emerged GPPsat, but this difference was much more pronounced in the sandflat habitat (2.4 vs. 1.3 times for seagrass). Integrating seasonally averaged P‐I curves for both tidal states into a simple model suggests that increasing submergence time could increase primary production in both habitats. However, reductions in water‐clarity will decrease submerged primary production; an effect that will be exacerbated with sea‐level rise. The sandflat trophic state was more sensitive to these environmental stressors because emerged production could not compensate for reductions during submergence. Collectively, regional management of water‐clarity may be key to providing resilience to intertidal habitats, against the inevitable effects of sea‐level rise. [ABSTRACT FROM AUTHOR]

Coastal ecosystem restoration is often ineffective and expensive in practice. As a consequence, upscaling restoration efforts to functionally relevant spatial scales remains one of the largest hurdles for coastal restoration practice. On small scales, restoration success of vegetated ecosystems (i.e. salt marshes and seagrasses) can be amplified by spatial designs that harness positive interactions. However, it remains unknown if positive interactions can be harnessed with seed‐based approaches, that are considered to be more cost‐effective and scalable than traditional shoot‐based restoration methods.Here, we investigated with a full‐factorial seeding experiment if (1) restoration scale (4, 40 and 400 m2) and (2) seeding density (10 and 50 injections/m2) affected multi‐year recruitment efficiency (measured as restored plants/seed injection) of annual eelgrass Zostera marina in the Dutch Wadden Sea.We found that the largest restoration scale (400 m2) increased second‐generation recruitment efficiency by suppressing a sedimentation‐related negative feedback. With increased restoration scale, the inner parts of the restoration plots captured less sediment, which decreased the desiccation stress of the restored eelgrass during low tide. Due to this stress alleviation, plants grew larger and produced more seed‐bearing spathes, which the following year resulted in two and three times higher recruitment efficiency at the largest restoration scale compared to the smaller scales. Moreover, lower seeding density more than doubled second‐generation recruitment efficiency compared to the higher density, supporting recent work showing that the effectiveness of 'clumped' spatial designs is context dependent.Synthesis and applications. The efficiency of restoration efforts is seldom taken into account, but can offer restoration projects a valuable metric with which workload, donor material and cost‐requirements can be reduced. We demonstrate that simple modifications to seed‐based coastal restoration designs (e.g. scale and density) can have a substantial impact on recruitment efficiency and multi‐year restoration yields. Thus, optimised restoration designs can strongly contribute to the upscaling potential of coastal ecosystem restoration. However, optimal restoration designs are expected to be strongly context dependent and we therefore argue that investigating optimal designs should be adopted as common practice, providing a crucial steppingstone between 'proof‐of‐concepts' and true large‐scale restoration attempts (km2). [ABSTRACT FROM AUTHOR]

Shallow estuarine habitats are globally undergoing rapid changes due to climate change and anthropogenic influences, resulting in spatiotemporal shifts in distribution and habitat extent. Yet, scientists and managers do not always have rapidly available data to track habitat changes in real-time. In this study, we apply a novel and a state-of-the-art image segmentation machine learning technique (DeepLab) to two years of high-resolution drone-based imagery of a marine flowering plant species (eelgrass, a temperate seagrass). We apply the model to eelgrass (Zostera marina) meadows in the Morro Bay estuary, California, an estuary that has undergone large eelgrass declines and the subsequent recovery of seagrass meadows in the last decade. The model accurately classified eelgrass across a range of conditions and sizes from meadow-scale to small-scale patches that are less than a meter in size. The model recall, precision, and F1 scores were 0.954, 0.723, and 0.809, respectively, when using human-annotated training data and random assessment points. All our accuracy values were comparable to or demonstrated greater accuracy than other models for similar seagrass systems. This study demonstrates the potential for advanced image segmentation machine learning methods to accurately support the active monitoring and analysis of seagrass dynamics from drone-based images, a framework likely applicable to similar marine ecosystems globally, and one that can provide quantitative and accurate data for long-term management strategies that seek to protect these vital ecosystems. [ABSTRACT FROM AUTHOR]

Below‐ground microbiota play an important role in mediating environmental conditions with important consequences for plant performance. Micro‐organisms involved in plant–soil interactions may be associated with roots or bulk soil; however, the relative influence of these below‐ground microbial assemblages on plant performance is poorly known, particularly for marine plants.We separately manipulated the root and sediment microbial assemblages of the seagrass Zostera muelleri in a fully factorial experiment to determine how these assemblages determined plant response (e.g. growth) to nutrient enrichment, a major stressor in marine systems.Under ambient nutrient conditions, seagrass growth was maintained regardless of root microbial assemblage disruption. Under high nutrient stress, however, seagrasses with disrupted root microbiota had reduced growth, whereas growth was maintained in seagrasses with an intact root microbiota. Disruption of bulk‐sediment microbiota did not affect seagrass growth. Nutrient elevation was correlated with enhanced abundances of several putatively beneficial microbial taxa (e.g. sulphide‐oxidising Beggiatoaceae and denitrifying Geofilum rubicundum) associated with roots.Synthesis. Our results suggest that under ambient nutrient conditions micro‐organisms play a reduced role in influencing plant performance, but under more stressful conditions positive plant–root micro‐organism interactions strengthened. These results are among the first to experimentally determine that interactions between marine plants and the root‐associated microbiota are key drivers of seagrass performance under human‐induced environmental changes. This suggests that as in terrestrial systems, marine plant resilience depends on the stress‐mitigating functions of their root‐associated microbiota and disturbance to those plant–microbiota interactions can be deleterious for plant performance. Improving our understanding of these plant–micro‐organism interactions may be critical for understanding the functioning and resilience of threatened marine plants and developing more effective restoration strategies for them. [ABSTRACT FROM AUTHOR]

Seagrass meadows and their associated biodiverse assemblages have declined globally due to environmental and anthropogenic stressors. Restoration of these critical habitats has the potential to reverse coastal biodiversity loss. Here, we tested the role of patch size (which can affect recruitment, food availability, and/or predation) in driving faunal colonization in an eelgrass (Zostera marina) restoration trial in Sweden. Eelgrass shoots were transplanted in plots with different configurations (continuous vs. checkerboard patterns with three patch sizes), and we followed invertebrate colonization (biodiversity and functional diversity) during the first two growing seasons. We found rapid faunal colonization following the transplantation of eelgrass shoots in all plots with invertebrate densities reaching 50–80% of the reference meadow after only one growing season (3 months). After two growing seasons (15 months), the faunal density, biodiversity, and functional diversity were similar to the reference meadow, despite eelgrass density and biomass still being lower than the reference meadow. Biodiversity, functional diversity, and community structure were similar among the different planted plots, that is, there was no indication that patch size influenced faunal colonization. We therefore consider that smaller patches embedded within larger restoration plots can be as effective for promoting biodiversity as continuous patches, with reduced costs and fewer shoots required. We also noted high natural variability between years both in the reference meadow and planted plots, showing the dynamic nature of seagrass ecosystems, and the importance of a well‐planned monitoring scheme that considers the reference area and restored area within the same temporal scale. [ABSTRACT FROM AUTHOR]

Sandy beach invertebrates depend largely upon allochthonous inputs of macrophytes and the oceanographic processes that deliver them as wrack. While part of this wrack is returned to the sea by the tides, a large portion remains, ages, and decomposes on the supralittoral, becoming colonized and used by macrofaunal organisms. This study quantified faunal colonization in relation to change in wrack nutritional quality, measured here as protein content. We prepared, deployed, and followed for 29 days a series of experimental wrack patches of two of the most common species in the wrack of Atlantic Canada sandy beaches: the rockweed Fucus serratus and the eelgrass Zostera marina. On a weekly basis, we measured the density of the macrofauna with a focus on the most abundant species, the talitroid amphipod Americorchestia longicornis, in both types of wrack and in bare sediments, while simultaneously measuring macrophyte protein contents. Our results show that rockweed patches concentrated higher densities of amphipods compared to eelgrass and bare sediments, a result that was matched by protein differences (higher concentrations in rockweed than eelgrass). However, while protein contents gradually declined over time in both macrophytes, the abundance of amphipods increased. Hence, while nutritional quality may explain between-wrack and wrack-bare sediment differences in faunal colonization, it cannot explain the counterintuitive temporal pattern recorded here. The latter result points to the often-ignored role played by the physical characteristics of the wrack and the conditions they create while decomposing over sandy beaches. [ABSTRACT FROM AUTHOR]

Plant microbiomes depend on environmental conditions, stochasticity, host species, and genotype identity. Eelgrass (Zostera marina) is a unique system for plant–microbe interactions as a marine angiosperm growing in a physiologically-challenging environment with anoxic sediment, periodic exposure to air at low tide, and fluctuations in water clarity and flow. We tested the influence of host origin versus environment on eelgrass microbiome composition by transplanting 768 plants among four sites within Bodega Harbor, CA. Over three months following transplantation, we sampled microbial communities monthly on leaves and roots and sequenced the V4–V5 region of the 16S rRNA gene to assess community composition. The main driver of leaf and root microbiome composition was destination site; more modest effects of host origin site did not last longer than one month. Community phylogenetic analyses suggested that environmental filtering structures these communities, but the strength and nature of this filtering varies among sites and over time and roots and leaves show opposing gradients in clustering along a temperature gradient. We demonstrate that local environmental differences create rapid shifts in associated microbial community composition with potential functional implications for rapid host acclimation under shifting environmental conditions. [ABSTRACT FROM AUTHOR]

The ability of seagrass meadows to filter nutrients and capture and store CO2 and nutrients in the form of organic carbon (OC) and nitrogen (N) in their sediments may help to mitigate local eutrophication as well as climate change via meadow restoration and protection. This study assesses OC and N sediment stocks (top 50 cm) and sequestration rates within Danish eelgrass meadows. At four locations, eelgrass‐vegetated and nearby unvegetated plots were studied in protected and exposed areas. The average OC and N sediment 50 cm stocks were 2.6 ± 0.3 kg OC m−2 and 0.23 ± 0.01 kg N m−2, including vegetated and unvegetated plots. In general, OC and N stocks did not differ significantly between eelgrass meadows and unvegetated sediments. Lack of accumulation of excess 210Pb suggested sediment erosion or low rates of sediment accumulation at most sites. OC accumulation rates ranged from 6 to 134 g m−2 yr−1 and N from 0.7 to 14 g m−2 yr−1. Generalized additive models showed that ≥ 80% of the variation in sediment OC and N stocks was explained by sediment grain size, organic matter source, and hydrodynamic exposure. Long cores, dated with 210Pb, showed declining OC and N densities toward present time, suggesting long‐term declines in eelgrass OC and N pools. Estimates of potential nation‐wide OC and N accumulation in eelgrass sediments show that they could annually capture up to 0.7% ± 0.5% of CO2 emissions and 6.9% ± 5.2% of the total terrestrial N load. [ABSTRACT FROM AUTHOR]

Declines in eelgrass, an important and widespread coastal habitat, are associated with wasting disease in recent outbreaks on the Pacific coast of North America. This study presents a novel method for mapping and predicting wasting disease using Unoccupied Aerial Vehicle (UAV) with low‐altitude autonomous imaging of visible bands. We conducted UAV mapping and sampling in intertidal eelgrass beds across multiple sites in Alaska, British Columbia, and California. We designed and implemented a UAV low‐altitude mapping protocol to detect disease prevalence and validated against in situ results. Our analysis revealed that green leaf area index derived from UAV imagery was a strong and significant (inverse) predictor of spatial distribution and severity of wasting disease measured on the ground, especially for regions with extensive disease infection. This study highlights a novel, efficient, and portable method to investigate seagrass disease at landscape scales across geographic regions and conditions. Plain Language Summary: Diseases of marine organisms are increasing in many regions worldwide, therefore, efficient time‐series monitoring is critical for understanding the dynamics of disease and examining its progression in time to implement management interventions. In the first study of its kind, we use high‐resolution Unoccupied Aerial Vehicle (UAV) imagery collected to detect disease at 12 sites across the North‐East Pacific coast of North America spanning 18 degrees of latitude. The low altitude UAV visible‐bands imagery achieved 1.5 cm spatial resolution, and analysis was performed at the seagrass leaf scale based on object‐oriented image analysis. Our findings suggest that drone mapping of coastal plants may substantially increase the scale of disease risk assessments in nearshore habitats and further our understanding of seagrass meadow spatial‐temporal dynamics. These can be scaled up by searching for environmental signals of the pathogen, for example, with surveillance of wastewater for signs of Covid in human populations. This application could easily apply to other areas to construct a high‐resolution monitoring network for seagrass conservation. Key Points: First study using low‐altitude high‐resolution Unoccupied Aerial Vehicle (UAV) imagery to detect coastal seagrass diseaseThe low altitude UAV mapping achieved 1.5 cm spatial resolution and the object‐oriented analysis were performed at the seagrass leaf scaleStatistical validation against in situ sampling demonstrated reliable results to use drone imaging for coastal plants disease assessment [ABSTRACT FROM AUTHOR]

The bottom sowing of Manila clam and the interaction of Manila clam and eelgrass seedlings are affected by the exchange fluxes of nutrients at the sediment-water interface. It is considered that body size, abundance, and activity of Manila clam influence the exchange fluxes. To verify the hypothesis, Manila clams with different body sizes, abundances, and activities were cultivated by sediments for 19 d, during which the exchange fluxes were studied. The biomass, body size, abundance, and activity of Manila clam affected the exchange fluxes of nutrients. On the 13th day, the fluxes of NO-2 -N, NH3 -N, TN were affected by body size, and the exchange fluxes of NO-2 -N and NH3 -N increased as body size increased. On the 13th and 19th day, the exchange fluxes of NO-2 -N, NH3 -N, TN, PO³- 4 -P were affected by the abundance and increased as abundance increased. Thus, the roles of biomass, body size, and abundance of shellfish should be considered to determine the carrying capacity for filter-feeding shellfish and clarify the interaction between shellfish and seagrass. [ABSTRACT FROM AUTHOR]

Over the last few decades, there has been an increasing recognition for seagrasses' contribution to the functioning of nearshore ecosystems and climate change mitigation. Nevertheless, seagrass ecosystems have been deteriorating globally at an accelerating rate during recent decades. In 2017, research into the condition of eelgrass (Zostera marina) along the eastern coast of James Bay, Canada, was initiated in response to reports of eelgrass decline by the Cree First Nations of Eeyou Istchee. As part of this research, we compiled and analyzed two decades of eelgrass cover data and three decades of eelgrass monitoring data (biomass and density) to detect changes and assess possible environmental drivers. We detected a major decline in eelgrass condition between 1995 and 1999, which encompassed the entire east coast of James Bay. Surveys conducted in 2019 and 2020 indicated limited changes post‐decline, for example, low eelgrass cover (<25%), low aboveground biomass, smaller shoots than before 1995, and marginally low densities persisted at most sites. Overall, the synthesized datasets show a 40% loss of eelgrass meadows with >50% cover in eastern James Bay since 1995, representing the largest scale eelgrass decline documented in eastern Canada since the massive die‐off event that occurred in the 1930s along the North Atlantic coast. Using biomass data collected since 1982, but geographically limited to the sector of the coast near the regulated La Grande River, generalized additive modeling revealed eelgrass meadows are affected by local sea surface temperature, early ice breakup, and higher summer freshwater discharge. Our results caution against assuming subarctic seagrass ecosystems have avoided recent global declines or will benefit from ongoing climate warming. [ABSTRACT FROM AUTHOR]

Seagrass meadows are facing structural degradation worldwide, losing both area and biodiversity. Habitat restoration could reverse this degradation, but so far, the success rate of seagrass restoration has been low. Incorporating facilitative interactions between plants and mussels into habitat restoration projects could potentially improve restoration success by increasing eelgrass survival and growth. In this study, we tested whether co-restoring two ecosystem engineers, namely eelgrass Zostera marina and blue mussels Mytilus edulis/trossulus would increase eelgrass restoration success in different sites. We also tested the rope method of eelgrass transplantation in sites where eelgrass was known to have previously existed. These small-scale field experiments were conducted in 2017–2019, in the northeastern Baltic Sea where the eelgrass reproduces only vegetatively. We found that co-restoration of eelgrass and mussels did not work at small scales because mussels were washed away within the first growing season. However, the shoot density of eelgrass increased over time, especially over the second growing season in the sheltered site, indicating that restoration is possible in these areas. Similarly, the restoration was most successful with the rope method in the sheltered site, suggesting that this method also has potential at larger spatial scales. Our results suggest that in such dynamic ecosystems abiotic factors, particularly exposure, play a larger role compared to biotic interactions, and thus the success of habitat restoration largely depends on local environmental conditions. [ABSTRACT FROM AUTHOR]

Ecosystem‐based protection is becoming a viable adaptation option to conventional engineered solutions to rising sea levels and coastal erosion. While the environmental and biological ecosystem services provided by ecosystem‐based adaptation measures such as beach nourishment and/or seagrass plantations are being acknowledged and analysed, less attention has been paid to the social or cultural dimensions of these services. This paper builds upon the emerging body of research that explores cultural ecosystem services in coastal areas and how they are perceived by the people who live, work and recreate in these areas. The aim of the paper is to take stock of and understand public and stakeholder perceptions of the cultural ecosystem services that may accrue through eelgrass Zostera marina restoration in tandem with beach nourishment in southern Sweden. The empirical research is based on an on‐line open‐ended questionnaire in the coastal municipalities of Båstad, Trelleborg, Ystad and Kristianstad. The results demonstrate that virtually all respondents had noticed a change in the coastline in recent years, mainly that the coastline had retreated. While beach nourishment measures were recognized among respondents to counter the shoreline erosion, there was very little understanding of the role that eelgrass plantations can play in creating biodiversity and benefits for society. Still, most acknowledged the importance of making room for water and biodiversity at the coast stating how the coastline was valued for primarily health and spiritual reasons. This knowledge will help local, regional and national decision‐makers and regulatory authorities to make evidence‐based choices for coastal protection, by complementing the analysis of environmental and physical ecosystem‐services with cultural and socio‐economic considerations. Nature‐based solutions such as eelgrass reintroduction or beach nourishment should be tailored to the values, perspectives and perceptions of the local communities to help ensure their continued contribution to biodiversity. [ABSTRACT FROM AUTHOR]

Seagrass degradation in the western Indian Ocean is of serious concerns with numerous severe climate events that has impacted Mozambique, as well as South Africa in recent time, highlighting the need for re‐establishing these critical habitats. The following paper present a field experiment from Mozambique concerning disturbance‐and‐recovery effects of Zostera capensis, a highly impacted seagrass species in the region. We undertook trials mimicking disturbance of meadows in terms of digging to collect clams, a common practice in Maputo Bay. Our results indicated that once such anthropogenic impacts are halted, Z. capensis meadows restore itself after 12 months of impact exclusion. In addition, we also conducted seagrass restoration experiment using a manual method, the so‐called plug method which, demonstrated to improve the survival rate with 75%, which has large implications for seagrass transplantation projects that are both time consuming and financially costly. The results from this study will further guide the appropriate management to build the best practice in seagrasses meadows restoration and awareness. It is clear from this study that a combination of both impact exclusions and active restoration is bound for best results of seagrass management actions. [ABSTRACT FROM AUTHOR]

Despite active seagrass restoration gaining traction as a tool to halt and reverse worldwide seagrass losses, overall success remains limited. Restoration strategies, through seeding or transplantation, face different environmental bottlenecks that limit success. Choosing the most appropriate strategy of the two for a specific location, however, is hampered by lack of direct practical comparisons between strategies within a single system. To investigate potential life stage dependent bottlenecks, we compared seed‐based and transplant‐based restoration of Zostera marina in the subtidal saltwater Lake Grevelingen. Our results demonstrate that seedling recruitment was negatively impacted by bioturbation from the lugworm Arenicola marina and sediment movement due to hydrodynamic exposure. Transplant‐based restoration was clearly more successful but surprisingly best predicted by leaf gluing by the ragworm Platynereis dumerilii. This previously undescribed interaction caused seagrass leaves to clump and reduce effective photosynthetic surface and leaf movement. We suggest that the observed behavior of these worms may result from a lack of foodweb interactions, illustrating the importance of trophic control for seagrass restoration. Thus, in addition to recognizing life stage dependent environmental bottlenecks for restoration strategy selection, seagrass restoration may also require the active recovery of their associated food webs. [ABSTRACT FROM AUTHOR]

As seagrass bed restoration by seeding becomes more common, it is necessary to develop a simple and reliable method to improve the efficiency of seed‐based restoration. In this study, we describe a novel method using seed ball burial for eelgrass restoration. Using this method, seeds were wrapped in a wet mud ball, which represented a transplant unit, and the balls were then buried in the sediment. Three experiments (proof of concept study, main study, and large‐scale restoration) were conducted to test this method at three degraded sites (Rizhao, Qingdao, and Tangshan) with different environmental conditions. The density of seedlings and seedling shoots was 54 and 110 per m2, respectively, in Rizhao, a site with coarser sediment and higher temperatures. Seedling survival in Qingdao reached 46.67 ± 9.46%. Relatively low seedling survival (26.67 ± 7.03%) in Tangshan was induced by local waves and currents. Seedling survival was also low (ca. 15% in April and 2% in July) at the large‐scale restoration site , reflecting a mismatch between the environment at this site and the seed ball restoration method. In conclusion, our study provides evidence of the effectiveness of a novel seagrass seed planting method referred to as seed balls. [ABSTRACT FROM AUTHOR]

The onset of a major seagrass initiative in West Africa enabled important seagrass discoveries in several countries, in one of the least documented seagrass regions in the world. Four seagrass species occur in western Africa, Cymodocea nodosa, Halodule wrightii, Ruppia maritima and Zostera noltei. An area of about 62,108 ha of seagrasses was documented in the studied region comprising seven countries: Mauritania, Senegal, The Gambia, Guinea Bissau, Guinea, Sierra Leone and Cabo Verde. Extensive meadows of Zostera noltei were recorded for the first time at Saloum Delta, Senegal, which represents the new southernmost distribution limit of this species. This paper also describes the seagrass morphology for some study areas and explores the main stressors to seagrasses as well as conservation initiatives to protect these newly documented meadows in West Africa. The produced information and maps serve as a starting point for researchers and managers to monitor temporal and spatial changes in the meadows' extent, health and condition as an efficient management tool. [ABSTRACT FROM AUTHOR]

Estimation of carbon stock in seagrass meadows is in challenges of paucity of assessment and low accuracy of the estimates. In this study, we used a fusion of the synthetic aperture radar (SAR) Sentinel-1 (S-1), the multi-spectral Sentinel-2 (S-2), and coupled this with advanced machine learning (ML) models and meta-heuristic optimization to improve the estimation of total organic carbon (TOC) stock in the Zostera muelleri meadows in Tauranga Harbour, New Zealand. Five scenarios containing combinations of data, ML models (Random Forest, Extreme Gradient Boost, Rotation Forest, CatBoost) and optimization were developed and evaluated for TOC retrieval. Results indicate a fusion of S1, S2 images, a novel ML model CatBoost and the grey wolf optimization algorithm (the CB-GWO model) yielded the best prediction of seagrass TOC (R2, RMSE were 0.738 and 10.64 Mg C ha−1). Our results provide novel ideas of deriving a low-cost, scalable and reliable estimates of seagrass TOC globally. [ABSTRACT FROM AUTHOR]

Seagrass beds offer unique and vital ecological services as an important blue carbon ecosystem in coastal wetlands. Zostera japonica is an intertidal seagrass species native to eastern Asia and is one of the most widely distributed seagrass species in China. However, little is known on the long-term variations of Z. japonica extents. Automatic mapping method for Z. japonica seagrass beds is in urgent need to fill this knowledge gap. In this study, we proposed a new SeaGrass Index (SGI) for automatic and rapid mapping of Z. japonica based on time-series Landsat satellite imagery, aiming to alleviate the influence of tidal inundation and enhance the separability from other coastal cover types. The SGI considers both spectral and phenological characteristics of Z. japonica , as well as the spatial location of Z. japonica. We took the Yellow River Delta (YRD), China as our study area, where Z. japonica was first discovered and reported in 2015. Based on SGI, Z. japonica extents during 1985–2018 were extracted using multi-Otsu thresholding algorithm. Accuracy assessments based on field investigations and high-resolution imagery showed that SGI successfully separated seagrass beds from other cover types, especially intertidal salt marshes, with overall accuracies > 95%, producer's accuracies > 90% and user's accuracies > 94%. Our study provides the first long-term maps of seagrass beds in YRD. The area of Z. japonica showed large variations during 1985–2018, ranging from 149 ha in 2005–2006 to 1302.9 ha in 2011–2012. The spatial distribution of Z. japonica varied with the morphological change of the estuary caused by river channel shifts. Since 2011, Z. japonica seagrass beds have undergone area degradation due to the invasion of S. alterniflora. The area was only 332.3 ha in 2017–2018. Coastal erosion and extreme climate events such as drought and typhoon might also explain degradation of seagrass beds in YRD. We expect that the SGI will advance automatic and rapid mapping methods for intertidal seagrass beds, and the Z. japonica maps will provide a baseline data for restoration and management of seagrasses at regional scale. [ABSTRACT FROM AUTHOR]

(a) An eelgrass meadow in Bodega Harbor, CA seemingly lacks diversity given that only one macrophyte species dominates the seascape, the marine angiosperm Zostera marina. Although the magnitude of eelgrass genotypic richness itself was not surprising (Hughes & Stachowicz, 2009; Kamel et al., 2012; Reynolds et al., 2017), coordinate-based mapping showed that these genotypes are naturally intertwined at the scale of only a few centimeters. Eelgrass genotypes show considerable genetically based phenotypic variation in traits that influence the outcome of intergenotypic interactions (Abbott & Stachowicz, 2016). Keywords: clonality; diversity maintenance; diversity mapping; ecological genetics; intraspecific diversity; seagrass; spatial variation EN clonality diversity maintenance diversity mapping ecological genetics intraspecific diversity seagrass spatial variation 1 5 5 11/03/22 20221101 NES 221101 At first glance, images of homogenous-looking green seagrass meadows (Figure 1a) do not epitomize "biodiversity" in the way that species-rich mosaics of coral reefs or rainforests might. [Extracted from the article]

Seagrass meadows provide valuable socio-ecological ecosystem services, including a key role in climate change mitigation and adaption. Understanding the natural history of seagrass meadows across environmental gradients is crucial to decipher the role of seagrasses in the global ocean. In this data collation, spatial and temporal patterns in seagrass meadow structure, biomass, production and reproduction data are presented as a function of biotic and abiotic habitat characteristics. The biological traits compiled include measures of meadow structure (e.g., percent cover and shoot density), biomass (e.g., above-ground biomass), production (e.g., shoot production), and reproduction effort (e.g., flowering intensity and seed bank density). Categorical factors include bioregion, geotype (coastal or estuarine), genera and year of sampling. This dataset contains data extracted from peer-reviewed publications published between 1975 and 2020 based on a Web of Science search, and includes 15 data variables across 12 seagrass genera. The top four most studied genera are Zostera, Thalassia, Halophila and Cymodocea (80% of data), and the least studied genera are Phyllospadix, Amphibolis and Thalassodendron (2.3% of data). The data hotspot bioregion is the Tropical Indo Pacific (25% of data), whereas data for the other five bioregions are evenly spread (ranging between 13 and 16% of total data within each bioregion). From the data compiled, 39% related to seagrass biomass, while the least number of data were related to seagrass production (10% of data). This data collation can inform several research fields beyond seagrass ecology, such as the development of nature-based solutions for climate change mitigation, which include readership interested in blue carbon, engineering, fisheries, global change, conservation and policy. [ABSTRACT FROM AUTHOR]

Ocean warming endangers coastal ecosystems through increased risk of infectious disease, yet detection, surveillance, and forecasting of marine diseases remain limited. Eelgrass (Zostera marina) meadows provide essential coastal habitat and are vulnerable to a temperature‐sensitive wasting disease caused by the protist Labyrinthula zosterae. We assessed wasting disease sensitivity to warming temperatures across a 3500 km study range by combining long‐term satellite remote sensing of ocean temperature with field surveys from 32 meadows along the Pacific coast of North America in 2019. Between 11% and 99% of plants were infected in individual meadows, with up to 35% of plant tissue damaged. Disease prevalence was 3× higher in locations with warm temperature anomalies in summer, indicating that the risk of wasting disease will increase with climate warming throughout the geographic range for eelgrass. Large‐scale surveys were made possible for the first time by the Eelgrass Lesion Image Segmentation Application, an artificial intelligence (AI) system that quantifies eelgrass wasting disease 5000× faster and with comparable accuracy to a human expert. This study highlights the value of AI in marine biological observing specifically for detecting widespread climate‐driven disease outbreaks. [ABSTRACT FROM AUTHOR]

One objective of eco‐evolutionary dynamics is to understand how the interplay between ecology and evolution on contemporary timescales contributes to the maintenance of biodiversity. Disturbance is an ecological process that can alter species diversity through both ecological and evolutionary effects on colonization and extinction dynamics. While analogous mechanisms likely operate among genotypes within a population, empirical evidence demonstrating the relationship between disturbance and genotypic diversity remains limited. We experimentally tested how disturbance altered the colonization (gain) and extinction (loss) of genets within a population of the marine angiosperm Zostera marina (eelgrass). In a 2‐year field experiment conducted in northern California, we mimicked grazing disturbance by migratory geese by clipping leaves at varying frequencies during the winter months. Surprisingly, we found the greatest rates of new colonization in the absence of disturbance and that clipping had negligible effects on extinction. We hypothesize that genet extinction was not driven by selective mortality from clipping or from any stochastic loss resulting from the reduced shoot densities in clipped plots. We also hypothesize that increased flowering effort and facilitation within and among clones drove the increased colonization of new genets in the undisturbed treatment. This balance between colonization and extinction resulted in a negative relationship between clipping frequency and net changes in genotypic richness. We interpret our results in light of prior work showing that genotypic diversity increased resistance to grazing disturbance. We suggest that both directions of a feedback between disturbance and diversity occur in this system with consequences for the maintenance of eelgrass genotypic diversity. [ABSTRACT FROM AUTHOR]

Seed size can have an impact on angiosperm reproductive fitness. Ecological theory predicts plants that will produce larger seeds in stressful environments to increase the chances of seedling survival and numerous small seeds in favourable conditions to increase the number of recruits. We measured seed morphology of the seagrass Heterozostera nigricaulis from four populations under differing environmental conditions in South East Australia. Seed size and mass among sites showed consistent differences over four flowering seasons. Seeds from exposed, ephemeral meadows (Blairgowrie, Edwards Point) were 19%–53% heavier than those from larger, stable meadows at more sheltered sites (Swan Bay, Point Henry). Overall, heavier seeds from exposed sites performed better in germination experiments and persisted (remained viable) longer compared to small seeds from sheltered sites. Seeds from sheltered sites showed contrasting levels of seed performance. Small seeds from Swan Bay had the lowest germination but the proportion of viable seeds after 12 months were much higher (41%) than similar sized seeds from Point Henry (0%). There are clear life history benefits of large seeds that facilitate seed persistence and germination at exposed sites; however, the performance of smaller seeds varied between sites and may be a function of other site-specific advantages. [ABSTRACT FROM AUTHOR]

Seagrass meadows are productive ecosystems and many animal species are dependent on them, including a wide diversity of invertebrates. This study aims to explore spatial diversity patterns of benthic invertebrates associated with Zostera noltei. Three areas with Z. noltei meadows were sampled along the Mira Channel (Ria de Aveiro). At each area, two sites were selected and four cores were taken at each site. Fauna was sorted, counted, and identified to the lowest taxonomical level. Results showed significant differences in the number of taxa among meadows. It was also observed that some taxa presented differences in the abundance among meadows. [ABSTRACT FROM AUTHOR]

Plant invasion can alter soil organic matter composition and indirectly impact estuary ecology; therefore, it is paramount to understand how plant invasion influences the bacterial community. Here, we present an absolute quantification 16S rRNA gene sequencing to investigate the bacterial communities that were collected from Zostera japonica and Spartina alterniflora covered areas and Z. japonica degradation areas in the Yellow River Estuary. Our data revealed that the absolute quantity of bacteria in the surface layer was significantly (p <.05) higher than that in the bottom and degradation areas. Following the invasion of S. alterniflora, the abundances of Bacteroidia, Acidimicrobiaceae, and Dehalococcoidaceaewere enriched in the S. alterniflora sediment. In addition, variations in the composition of sediment bacterial communities at the phylum level were the most intimately related to total organic carbon (TOC), and the content of heavy metals could reduce the abundance of bacteria. This study provided some information to understand the effects of S. alterniflora invasion on Z. japonica from the perspective of microbiome level. [ABSTRACT FROM AUTHOR]

We studied benthic communities with different types of habitats in the Moulay Bousselham lagoon during the winter and summer of 2019. We aimed to investigate biodiversity trends across a scale of seasonal variation. The lowest water temperatures were recorded downstream. This reflects the influence of cold oceanic waters at the lagoon entrance while the salinity shows a decreasing gradient from downstream to upstream. Sediment analyses showed that the lagoon is mainly composed of sandy and silty sediments. In stations with vegetated habitats, the biomass of Zostera noltei seagrass ranged from 0.79 g dry weight (DW) to 46.69 gDW in winter and from 9.34 gDW to 47.67 gDW in summer, while the biomass of Ruppia cirrhosa seagrass ranged from 5.53 gDW to 28.66 gDW in winter and from 14.48 gDW to 34.06 gDW in summer. Apart from water temperature and salinity, environmental variables are not significantly different in winter and summer (ANOVA test: p > 0.05). In the 29 sampled stations we used, we found 42 taxa in winter and 32 taxa in summer with a mean biomass value of 25.10 g AFDW m−2 (winter) and 9.14 g AFDW m−2 (summer). Apart from biomass, which is subject to seasonal variations, diversity parameters are not significantly different from one season to the next (ANOVA test: p > 0.05). Results from DistLM analysis revealed that the diversity and distribution of benthic macrofauna in the Moulay Bousselham lagoon were controlled by a combination of factors: sediment characteristics (mud content, median grain size, total organic matter %, carbon %, CaCO3% and CO2%), water characteristics (temperature and salinity) and habitat type (biomass of Zostera noltei and Ruppia cirrhosa seagrasses). [ABSTRACT FROM AUTHOR]

Background: The polyphyletic group of seagrasses shows an evolutionary history from early monocotyledonous land plants to the marine environment. Seagrasses form important coastal ecosystems worldwide and large amounts of seagrass detritus washed on beaches might also be valuable bioeconomical resources. Despite this importance and potential, little is known about adaptation of these angiosperms to the marine environment and their cell walls. Results: We investigated polysaccharide composition of nine seagrass species from the Mediterranean, Red Sea and eastern Indian Ocean. Sequential extraction revealed a similar seagrass cell wall polysaccharide composition to terrestrial angiosperms: arabinogalactans, pectins and different hemicelluloses, especially xylans and/or xyloglucans. However, the pectic fractions were characterized by the monosaccharide apiose, suggesting unusual apiogalacturonans are a common feature of seagrass cell walls. Detailed analyses of four representative species identified differences between organs and species in their constituent monosaccharide composition and lignin content and structure. Rhizomes were richer in glucosyl units compared to leaves and roots. Enhalus had high apiosyl and arabinosyl abundance, while two Australian species of Amphibolis and Posidonia, were characterized by high amounts of xylosyl residues. Interestingly, the latter two species contained appreciable amounts of lignin, especially in roots and rhizomes whereas Zostera and Enhalus were lignin-free. Lignin structure in Amphibolis was characterized by a higher syringyl content compared to that of Posidonia. Conclusions: Our investigations give a first comprehensive overview on cell wall composition across seagrass families, which will help understanding adaptation to a marine environment in the evolutionary context and evaluating the potential of seagrass in biorefinery incentives. [ABSTRACT FROM AUTHOR]

This document is a correction to a previously published article titled "The stress response of the seagrass Zostera noltei and three commercial clam species to low salinity associated with heavy rainfall." The correction addresses an error in the original manuscript, where the subsection heading "Mortality" was misspelled as "Morality" in the Results section. The publisher apologizes for the mistake and confirms that it has been corrected. [Extracted from the article]

The ecological fabric of coastal zones is intricately linked to the vitality of seagrass meadows, with Zostera caespitosa serving as a foundational species. Integral to biodiversity conservation and the carbon cycle, these ecosystems are facing unprecedented thermal stress due to global warming. Our research delves into the temperature-dependent physiological responses of Z. caespitosa , focusing on growth rates, photosynthetic activity, and nutrient uptake dynamics across varying thermal regimes. We pinpoint an optimal temperature window of 10–20 °C for these critical physiological processes. These findings not only chart a course for the protective measures of seagrass beds but also furnish pivotal data for predictive models assessing the resilience of these ecosystems under climatic fluctuations. The insights gained offer a strategic advantage for the restoration and stewardship of seagrass habitats, informing climate change mitigation strategies, biodiversity preservation, and the sustained provision of ecosystem services along coastal frontiers. This research, by bridging gaps in our ecological understanding, underscores the imperative of nuanced ecosystem management in an era of changing global temperatures. • Critical temperatures impacting Z. caespitosa's photosynthetic physiology and nutrient absorption kinetics are pinpointed. • An optimal temperature range of 10-20 °C was identified for Z. caespitosa 's critical physiological processes. • Elevated temperatures between 25-35 °C led to the degradation or death of Z. caespitosa. • A low temperature range utilized found in this study contributes to extending the survival of Z. caespitosa. • These findings fill a research gap by emphasizing Z. caespitosa's sensitivity to temperature changes. [ABSTRACT FROM AUTHOR]