Presence Of Seagrass Research Articles

The contribution of seasonal variations and Zostera marina presence to the bacterial community assembly of seagrass bed sediments

BackgroundMicroorganisms play pivotal roles in seagrass ecosystems by facilitating material and elemental cycling as well as energy flux. However, our understanding of how seasonal factors and seagrass presence influence the assembly of bacterial communities in seagrass bed sediments is limited. Employing high-throughput sequencing techniques, this study investigates and characterizes bacterial communities in the rhizosphere of eelgrass (Zostera marina) and the bulk sediments across different seasons. The research elucidates information on the significance of seasonal variations and seagrass presence in impacting the microbial communities associated with Zostera marina.ResultsThe results indicate that seasonal variations have a more significant impact on the bacterial community in seagrass bed sediments than the presence of seagrass. We observed that the assembly of bacterial communities in bulk sediments primarily occurs through stochastic processes. However, the presence of seagrass leading to a transition from stochastic to deterministic processes in bacterial community assembly. This shift further impacts the complexity and stability of the bacterial co-occurrence network. Through LEfSe analysis, different candidate biomarkers were identified in the bacterial communities of rhizosphere sediments in different seasons, indicating that seagrass may possess adaptive capabilities to the environment during different stages of growth and development.ConclusionsSeasonal variations play a significant role in shaping these communities, while seagrass presence influences the assembly processes and stability of the bacterial community. These insights will provide valuable information for the ecological conservation of seagrass beds.

Spatial prioritization of dugong habitats in India can contribute towards achieving the 30 × 30 global biodiversity target

Indian coastal waters are critical for dugong populations in the western Indian Ocean. Systematic spatial planning of dugong habitats can help to achieve biodiversity conservation and area-based protection targets in the region. In this study, we employed environmental niche modelling to predict suitable dugong habitats and identify influencing factors along its entire distribution range in Indian waters. We examined data on fishing pressures collected through systematic interview surveys, citizen-science data, and field surveys to demarcate dugong habitats with varying risks. Seagrass presence was the primary factor in determining dugong habitat suitability across the study sites. Other variables such as depth, bathymetric slope, and Euclidean distance from the shore were significant factors, particularly in predicting seasonal suitability. Predicted suitable habitats showed a remarkable shift from pre-monsoon in Palk Bay to post-monsoon in the Gulf of Mannar, indicating the potential of seasonal dugong movement. The entire coastline along the Palk Bay-Gulf of Mannar region was observed to be at high to moderate risk, including the Gulf of Mannar Marine National Park, a high-risk area. The Andaman Islands exhibited high suitability during pre- and post-monsoon season, whereas the Nicobar Islands were highly suitable for monsoon season. Risk assessment of modelled suitable areas revealed that < 15% of high-risk areas across Andaman and Nicobar Islands and Palk Bay and Gulf of Mannar, Tamil Nadu, fall within the existing protected areas. A few offshore reef islands are identified under high-risk zones in the Gulf of Kutch, Gujarat. We highlight the utility of citizen science and secondary data in performing large-scale spatial ecological analysis. Overall, identifying synoptic scale ‘Critical Dugong Habitats’ has positive implications for the country's progress towards achieving the global 30 × 30 target through systematic conservation planning.

Seagrass recovery trajectories and recovery potential in relation to nutrient reduction

Abstract Seagrass recovery has been reported across the globe where previously eutrophied waters have become less nutrient‐rich. In the European Wadden Sea, different recovery trajectories were found after riverine nutrient loads decreased, namely full, temporary and no recovery. We compiled intertidal seagrass presence (Zostera noltei and Z. marina) and eutrophication data for 1930–2020, to relate the seagrass trajectories and regional eutrophication differences to riverine nutrient loads, and inferred prospects for seagrass recovery. Seagrass fully recovered in the less eutrophic North Frisian region. The recovery trajectory was tightly coupled to riverine nutrient load reduction. Relative seagrass area (meadow area/region area) dropped from 10% prior to eutrophication to 2% during the eutrophication peak, increased to 7% during the nutrient reduction period and subsequently expanded to 13%. Colonization of marginal habitats was observed, indicating propagule spillover from neighbouring meadows. The more eutrophic southern regions showed no or only temporary seagrass recovery. Prospects for (limited) recovery are good in only two out of four southern regions, provided that riverine nutrient loads are further reduced by ~40% (reference: 2010–2017). Without this reduction, seagrasses may only temporarily recover and will remain vulnerable to erratic disturbances like macroalgae accumulation or storms. Historical evidence and application of habitat suitability models suggest that the potential relative seagrass area in the southern regions is low: less than 0.2% in the western Dutch region and maximum 2.4% in the Ems‐Jade region. Synthesis and applications. Within a large seascape (15,000 km2) the least eutrophicated region showed seagrass recovery upon nutrient reduction. We translated the critical riverine nutrient loads for this recovery, via regional eutrophication indicators, to loads that may enable a sustained recovery in the other regions. This technique is applicable in other complex systems, provided sufficient historical data are available. Propagule spillover exerts a positive feedback at metapopulation scale leading to acceleration of recovery. Occupied and potential seagrass habitat (e.g. assessed by the maximum recorded area in the past) are thus important landscape selection criteria for restoration, particularly when eutrophication is not yet sufficiently reduced.

Adapting Methods For Bed Level Assessment In And Around Submerged Vegetation

Coastal vegetation has the capacity to reduce flow and orbital velocities near the bed and stabilize the sediment with its root network. As a result it has an effect on sediment dynamics which gains increasing attention as ecosystem service in coastal protection. To quantify and predict this ecosystem service, laboratory experiments with live or artificial vegetation are often conducted. During these experiments the assessment of bed level change is challenged by the presence of the vegetation. Standard optical and acoustic measurement techniques cannot obtain data below vegetation canopies. Especially for submerged flexible vegetation like seagrass, this challenge is aggravated for airborne methods that require flume drainage (e.g. terrestrial laser scanning) (Follett and Nepf, 2012). Flexible blades will spread on the ground during drainage, potentially covering meadow edges and thus excluding areas of interest from the bed level analysis. Moreover, live aquatic vegetation may be stressed by air exposure, if the facility is drained for bed level measurements. This potentially leads to different, non-natural behaviour in consecutive experiments. And finally, draining and refilling the facility is time consuming, especially as it needs to be done very carefully as not to disturb any generated bedforms. This time aspect hampers the collection of time series and thus the assessment of the development of bed level changes with airborne methods. Underwater technology like sonar and echo sounder avoid shading of areas by spread-out vegetation, but are equally not capable of obtaining data below vegetation canopies. Moreover, instruments that can obtain spatially resolved data underwater often require a minimum water depth which may exceed the water depth relevant for experiments with vegetation. In intertidal areas (e.g. salt marshes) the challenge of obtaining bed level data below vegetation canopies is overcome by the use of a sediment-erosion-bar (SEB) (Cahoon et al., 2002). For this method a horizontal bar is installed at a fixed height above the ground and the distance between this bar and the ground is measured at defined locations along the bar and set time intervals to obtain information on the bed level change. SEBs have successfully been adapted to laboratory settings in the past (Spencer et al., 2016), but still required flume drainage. We applied this method in an undrained flume to assess sediment dynamics in and around an artificial seagrass meadow. Additionally, we tested underwater photogrammetry to obtain 3D-spatial information (e.g., 3D models) on bed level and bedforms at and near the vegetation edges. Photogrammetry has been successfully applied to obtain bedform information in the presence of seagrass stands, but to date still required the drainage of the facility (Meysick et al., 2022).

Community Structure Of Seagrass In Southeast Waters Cempedak Island West Kalimantan

Cempedak Island is one of the Coastal and Small Islands Conservation Areas (KKP3K) in West Kalimantan has various marine biological resources and important ecosystems, including seagrass. Seagrass is used as the main food source for dugong, potential habitat for various types of organisms, and potential to be developed as marine ecotourism. On the other hand, seagrass ecosystems faced threats, such as high sedimentation and the influence of anthropogenic activities. It is unknown about the current status of seagrass on Cempedak Island. This research aimed to analyze the structure of seagrass in the southeastern waters of Cempedak Island. Seagrass data collection was carried out in the tidal zone using line transect of 70 m and a quadratic transect of 1x1 m2. Data collection on seagrass and water parameters was carried out in October 2023. Determination of research sites was done using an explorative method based on the presence of seagrass. The seagrass found consisted of 4 species, namely Enhalus acoroides, Cymodocea rotundata, Halodule pinifolia, and Halophila ovalis. Seagrass cover ranged from 9.17–16.74%, with an abundance of 1.4–373.3 ind/m2. The diversity index (H') is in the low to medium category, the uniformity index (E) is in the medium category and the dominance index (C) is in the low category. Conditions of water quality parameters were into the optimal range to support seagrass life.

The Effect of Location, Time, and Environmental Conditions on Fish Use of Southern Temperate Saltmarshes

Fish use of saltmarsh varies spatially, temporally, and with environmental conditions. The specific impact of these effects on fish assemblages in southern temperate Tasmania, Australia—the only mangrove-free Australian state—is as yet largely unknown. Seasonal variation in fish abundance, richness, diversity, and size was investigated in succulent saltmarshes in three estuaries (Marion Bay, Barilla Bay, and Ralphs Bay) in south-eastern Tasmania. All parameters varied between sampling locations. Greater numbers of fish were recorded at two sites (Marion Bay, mean density and standard error of 396.9 ± 71.3 individuals per 100 m2; Barilla Bay, mean density and standard error of 94.1 ± 30.1 individuals per 100 m2) than have been previously reported in Australian saltmarshes. Fish abundance was greatest in July–August (mean density and standard error of 200.2 ± 49.7 individuals per 100 m2) reflecting the breeding patterns of the numerically dominant Atherinosoma microstoma. Both abundance and species richness responded positively to water temperature in ordinal logistic regression models, and species richness and diversity increased with water depth in the models. It is likely that the strong differences between sampling locations are partly related to differences in water depth and water temperature between the estuaries. They may be also related to the habitat context of each estuary, especially the presence or absence of seagrass. The greater numbers of fish found in the present study relative to abundances reported in mainland Australia may relate to the absence of mangroves and the consequent differences in seascape habitat context, including greater water depths in marshes. Importantly, these results demonstrate that temperate southern hemisphere saltmarshes are year-round habitat for fish, thus emphasising their importance as a fish habitat.

Investigation of the Growth and Mortality of Bacteria and Synechococcus spp. in Unvegetated and Seagrass Habitats

There is no doubt that seagrass beds constitute one of the most productive ecosystems in shallow coastal waters. Despite this, picoplankton in seagrass ecosystems has received relatively little attention. The purpose of this study was to compare picoplankton growth and mortality rates between seagrass and unvegetated habitats using chamber incubations. We tested two main hypotheses: (i) incubation with seagrass would result in higher bacterial growth rates due to increased DOM release from seagrass photosynthesis, and (ii) Synechococcus spp. would be lower in the presence of seagrass due to competition for inorganic nutrients. Bacterial growth rates were higher in seagrass chambers (2.44 d–1) than in non-seagrass chambers (2.31 d−1), respectively, suggesting that organic carbon coming from the seagrass community may support bacterial production. Furthermore, the growth rate of Synechococcus spp. was significantly lower in the seagrass treatment than in the non-seagrass treatment, likely reflecting nutrient competition with the seagrass. Small-scale chambers proved to be a useful tool for studying the factors controlling spatial and temporal patterns of picoplankton across different habitats. Furthermore, future studies should examine picoplankton growth over a wider range of spatial scales in seagrass beds and adjacent unvegetated sediment.

Rapid sea level rise causes loss of seagrass meadows

As global declines in seagrass populations continue to cause great concern, long-term assessment of seagrass meadows show promise in furnishing valuable clues into fundamental causes of seagrass loss and drivers of environmental change. Here we report two long-term records of seagrass presence in western Gulf of Mexico coastal waters (Laguna Madre) that provided insight into their rapid decline in a relatively pristine ecosystem. Coincident with unprecedented increases in water depth starting in 2014 (14–25 mm y−1), monthly measurements at a deep edge fixed station revealed that two ubiquitous seagrass species (Halodule wrightii and Syringodium filiforme) vanished altogether in just five years; a subsequent basin-wide assessment revealed that seagrasses disappeared at 23% of 144 sentinel stations. Models that incorporate differing sea level rise scenarios and water depth thresholds reveal potential global losses of seagrass habitat (14,000 km2), with expansion into newly created shallow habitats constrained by altered natural shorelines.

Hidden cost of pH variability in seagrass beds on marine calcifiers under ocean acidification

Coastal ecosystems experience large environmental variability leading to local adaptation. The key role of variability and adaptation in modulating the biological sensitivity to ocean acidification is increasingly acknowledged. Monitoring and understanding the ecological niche at the right spatio-temporal scale is key to understand the sensitivity of any organism and ecosystems. However, the role of the variability in relevant carbonate chemistry parameters as a driver is often overlooked. For example, the balance between photosynthesis and respiration over the day/night cycle is leading to high pH/pCO2 variability in seagrass beds. We hypothesized that (i) the calcifying larvae of the sea urchin Echinus esculentus exposed to seagrass-driven variability would have some physiological mechanisms to respond to such variability; and (ii) these mechanisms would reach their limit under ocean acidification. We compared the presence and absence of the seagrass Zostera marina in flow through mesocosms fed with seawater with 4 pHs. The carbonate chemistry was monitored and biological response of a sea urchin larvae was documented over 3 weeks. Growth and net calcification rates were measured twice a day to encompass diurnal variability. Our results show that larvae growth rate significantly decreased with decreasing average pHT in both absence and presence of seagrass. Moreover, sea urchin larvae showed a slower growth rate in presence of seagrass, only visible in the lowest pH conditions. In addition, larvae raised in presence of seagrass, maximized calcification during the day, and lower their calcification during the night. In contrast, no significant difference was observed between day and night for the net calcification rate in larvae raised in absence of seagrass. Our results demonstrate the limit of local adaptation to the present range of variability under ocean acidification conditions. It also demonstrates that photosynthetic ecosystems such as seagrass may not play a role of refuge against future ocean acidification.

Restored intertidal eelgrass (Z. marina) supports benthic communities taxonomically and functionally similar to natural seagrasses in the Wadden Sea

Ecological restoration has become an important management-tool to counteract the widespread losses of seagrass meadows and their associated biodiversity. In the Dutch Wadden Sea, long-term restoration efforts have recently led to the successful restoration of annual eelgrass (Zostera marina) at high densities on a local scale. However, it is yet unknown if restored seagrass plants also lead to improved local biodiversity and ecosystem functioning in the intertidal zone. We therefore compared the macrozoobenthos communities of a small-scale restored meadow to 22 naturally occurring intertidal seagrass meadows. Using a taxonomic and trait-based approach we aimed to study 1) how intertidal seagrasses (Zostera marina and Zostera noltii) affect benthic communities and their functional trait distribution and 2) if a restored meadow facilitates benthic communities similar to natural meadows. We found that both natural and restored seagrasses increased abundances of benthic animals and the richness (both taxonomic and functional) of associated benthic communities compared to nearby unvegetated areas. Additionally, the presence of intertidal seagrass shifted benthic community composition both taxonomically and functionally, thus broadening the niche space for species inhabiting tidal flats. Seagrasses especially facilitated epifaunal species and traits associated with these animals. Surprisingly, our results indicate that the mere presence of seagrass aboveground structure is enough to facilitate benthic communities, as neither higher seagrass cover nor biomass increased benthic biodiversity in the intertidal zone. By studying the effect of seagrass restoration on benthic diversity, we found that the restored meadow functioned similarly to the natural meadows after only two years and that the success of our restoration efforts indeed led to local biodiversity enhancements. Our findings contribute to the understanding of the ecological functioning of intertidal seagrasses and can be used to define/refine conservation and restoration goals of these valuable ecosystems.

Preliminary Determination of Organic Carbon Content in Seagrass Bed at Ao Pae, Rayong Province, Thailand

Seagrass meadows play crucial roles in delivering ecosystem services to various organisms and environmental systems, particularly in efficiently capturing and storing carbon. Thus, seagrasses are included in plans to address climate change challenges. However, there is limited data on carbon sequestration by seagrass in Thailand, especially in localized areas. Therefore, this study aimed to assess the carbon storage in both sediments and seagrass at Ao Pae, Rayong Province. The analysis focused on sediment depth and the impact of moisture content. Sediment and seagrass samples were collected during the low tide season during May 2022. The sampling area was divided into two zones: one with seagrass presence (9 stations) and another where seagrass was absent (4 stations). Sediment was collected from a depth of 60 cm, divided into six layers of 10 cm each. Results indicated that the highest organic carbon content was observed in sediment at depths of 0-10 cm (22.82±2.08%). Additionally, the organic carbon content showed a significant correlation with sediment moisture content in the area with seagrass presence (p&lt;0.05). Furthermore, the mean belowground organic carbon (1.93±0.29%) exceeded the aboveground carbon (1.66±0.28%), and sediments from stations with seagrass had higher organic carbon content compared to those without seagrass. These findings underscore the potential role of seagrass as a significant carbon sequester in Ao Pae, Rayong Province.

Mangrove ghost forests provide opportunities for seagrass

Mangrove forests are degraded by extreme climatic events worldwide, often leaving behind dead standing stems called “ghost forests”. Ghost forests may provide opportunities for seagrass colonization but there is limited research into the conditions found within these ecosystems, or whether they provide a suitable habitat for seagrasses. This study aimed to characterize the environmental conditions within mangrove ghost forests, determine whether conditions are suitable for seagrass survival, and identify whether seagrass was present within the ghost forests of Moreton Bay, Queensland. Six study locations within mangrove ghost forests adjacent to live mangrove forests and seagrass meadows were selected and biophysical conditions within these habitats over the six sites were assessed. Two of the six study sites were found to have live seagrass present within the ghost forests (Godwin Beach and South Stradbroke). Suitable water temperature was linked to the presence and abundance of seagrass within mangrove ghost forests. Mangrove characteristics, including canopy cover, diameter at breast height, and stem densities, contributed to variation in the environment among the three habitats, suggesting that light is a key factor limiting seagrass colonization into live or ghost mangrove forests. Overall, these results suggest that ghost forests can provide suitable habitats for seagrasses, and degraded mangroves may transition to seagrass under future sea level rise scenarios.

Impact of Atmospheric Correction on Classification and Quantification of Seagrass Density from WorldView-2 Imagery.

Mapping the seagrass distribution and density in the underwater landscape can improve global Blue Carbon estimates. However, atmospheric absorption and scattering introduce errors in space-based sensors' retrieval of sea surface reflectance, affecting seagrass presence, density, and above-ground carbon () estimates. This study assessed atmospheric correction's impact on mapping seagrass using WorldView-2 satellite imagery from Saint Joseph Bay, Saint George Sound, and Keaton Beach in Florida, USA. Coincident in situ measurements of water-leaving radiance (), optical properties, and seagrass leaf area index (LAI) were collected. Seagrass classification and the retrieval of LAI were compared after empirical line height (ELH) and dark-object subtraction (DOS) methods were used for atmospheric correction. DOS left residual brightness in the blue and green bands but had minimal impact on the seagrass classification accuracy. However, the brighter reflectance values reduced LAI retrievals by up to 50% compared to ELH-corrected images and ground-based observations. This study offers a potential correction for LAI underestimation due to incomplete atmospheric correction, enhancing the retrieval of seagrass density and above-ground Blue Carbon from WorldView-2 imagery without in situ observations for accurate atmospheric interference correction.

Effects of seagrass restoration on coastal fish abundance and diversity.

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.

Variation in nutritional quality of an invasive seagrass does not explain its low palatability to two key herbivores in a Caribbean Bay

The seagrass Halophila stipulacea continues to spread rapidly through the Caribbean. Documenting native herbivore use of this invasive plant is important for understanding its impacts on marine communities and the mechanisms favoring its expansion. This study used observational and experimental data to determine if juvenile green turtles (Chelonia mydas) and long-spine urchins (Diadema antillarum) from the US Virgin Islands consumed H. stipulacea in the presence of native seagrass. Juvenile turtles associated significantly more with beds of native seagrass than mixed (native and invasive), and monospecific H. stipulacea, beds or sand bottoms. When individuals were followed, turtles foraged significantly more within mixed beds, but selectively fed on native species within them and were never observed feeding on monospecific H. stipulacea stands. When offered the native Thalassia testudinum and Syringodium filiforme, along with H. stipulacea, sea urchins significantly preferred S. filiforme over the other two choices. Measurements of fourteen nutritional and chemical parameters in these three seagrasses showed strong interspecific differences, with fewer and less predictable seasonal variations. Expressing these nutritional data by wet mass, rather than dry mass, also decreased the number of significant seasonal contrasts. Despite these differences, no parameters explained low herbivore preference for the invasive seagrass satisfactorily because nutrient values of H. stipulacea were often similar to those of the preferred natives. Our results conflict with recent studies pointing at low nutritional quality aiding against herbivory and suggest other mechanisms, such as herbivore learning and recognition of a novel resource, could be more important than currently appreciated.

Disentangling interactions between seagrasses and small-scale fisheries using scientific and local traditional knowledge

Seagrass meadows deliver key ecosystem services in coastal environments worldwide by hosting early and adult life stages of many fish stocks, improving water quality, capturing carbon dioxide (mitigating the effects of global warming), protecting against adverse events and providing leisure opportunities. Shellfishing is often carried out in seagrass meadows, causing alterations derived from harvesting and/or culture processes. While the negative impacts of shellfisheries on seagrass meadows have been well established, the effects of the meadows on shellfishing have not yet been explored. In this study we analyzed the two-way interactions between shellfishing and Zostera spp. beds in north-west Spain and identified gaps in the governance system related to seagrass management. We conducted interviews (with 154 shellfishers) and held workshops (involving 61 shellfishers) to collect and validate information on the perceptions of shellfishers regarding the ecosystem services supplied by seagrass meadows, the interactions with shellfishing activity and how to improve the management of the activity in these key habitats. In general, shellfishers viewed the presence of seagrass negatively because greater physical effort is needed to extract the shellfish from among the plants. The shellfishers also recognized that the plants are easily damaged during their work. Temporal trends were also perceived negatively, as catches have been decreasing over time, while the area occupied by seagrass meadows has increased. However, experienced shellfishers recognized the benefits of the meadows for coastal ecosystems and fisheries (including those that they exploited), such as increased recruitment of the target species, to the extent that they were open to the allocation of areas to seagrass conservation. The compatibility of traditional shellfishing and management of seagrass meadows should be fostered by developing seagrass monitoring programs to develop adaptive fisheries management strategies and ensure conservation of these complex social-ecological systems.

Subtidal seagrass detector: development of a deep learning seagrass detection and classification model for seagrass presence and density in diverse habitats from underwater photoquadrats

This paper presents the development and evaluation of a Subtidal Seagrass Detector (the Detector). Deep learning models were used to detect most forms of seagrass occurring in a diversity of habitats across the northeast Australian seascape from underwater images and classify them based on how much the cover of seagrass was present. Images were collected by scientists and trained contributors undertaking routine monitoring using drop-cameras mounted over a 50 x 50 cm quadrat. The Detector is composed of three separate models able to perform the specific tasks of: detecting the presence of seagrass (Model #1); classify the seagrass present into three broad cover classes (low, medium, high) (Model #2); and classify the substrate or image complexity (simple of complex) (Model #3). We were able to successfully train the three models to achieve high level accuracies with 97%, 80.7% and 97.9%, respectively. With the ability to further refine and train these models with newly acquired images from different locations and from different sources (e.g. Automated Underwater Vehicles), we are confident that our ability to detect seagrass will improve over time. With this Detector we will be able rapidly assess a large number of images collected by a diversity of contributors, and the data will provide invaluable insights about the extent and condition of subtidal seagrass, particularly in data-poor areas.

Where to fish in the forest? Tree characteristics and contiguous seagrass features predict mangrove forest quality for fishes and crustaceans

Abstract Mangroves often support rich fish and crustacean communities, although faunal abundance and diversity show strong spatiotemporal variability. Consistent patterns in mangrove animal communities might be dictated by forest characteristics, by seascape context or by some combination of these factors. Predicting drivers of spatial heterogeneity in mangrove faunal communities can better support the zoning of forests for management purposes, for example by identifying sites important for fisheries nursery provision. We sampled 14 sites within a large (4000 ha) mangrove forest in Kenya, quarterly over a period of 2 years. There were clear and consistent differences in the quality of sites for fish and crustacean abundance and diversity. Forest characteristics (as summarised by the complexity index, CI) and seascape metrics (the presence, area and configuration of contiguous seagrass) were strong predictors of site differences. However, they showed opposite influences on dominant members of the fish and crustacean faunas, with CI correlated negatively with fishes and positively with crustaceans, and seagrass area correlated positively with fishes and negatively with crustaceans. Synthesis and applications. Sites within the same mangrove forest exhibit consistent differences in fish and crustacean abundance. However, the fish and crustacean communities (and particularly dominant species within them) act differently in response to forest and seascape characteristics. Old growth, mature forest, set in a seascape of seagrass patches with bare sediment, was associated with highest crustacean abundance. In contrast, denser smaller trees and seascapes with larger, continuous areas of seagrass correlated better with fish abundance. Zoning for management, as mandated in new Kenyan policy, will need to consider these differences in seascape use between fish and crustaceans.

Providing a framework for seagrass mapping in United States coastal ecosystems using high spatial resolution satellite imagery

Seagrasses have been widely recognized for their ecosystem services, but traditional seagrass monitoring approaches emphasizing ground and aerial observations are costly, time-consuming, and lack standardization across datasets. This study leveraged satellite imagery from Maxar's WorldView-2 and WorldView-3 high spatial resolution, commercial satellite platforms to provide a consistent classification approach for monitoring seagrass at eleven study areas across the continental United States, representing geographically, ecologically, and climatically diverse regions. A single satellite image was selected at each of the eleven study areas to correspond temporally to reference data representing seagrass coverage and was classified into four general classes: land, seagrass, no seagrass, and no data. Satellite-derived seagrass coverage was then compared to reference data using either balanced agreement, the Mann-Whitney U test, or the Kruskal-Wallis test, depending on the format of the reference data used for comparison. Balanced agreement ranged from 58% to 86%, with better agreement between reference- and satellite-indicated seagrass absence (specificity ranged from 88% to 100%) than between reference- and satellite-indicated seagrass presence (sensitivity ranged from 17% to 73%). Results of the Mann-Whitney U and Kruskal-Wallis tests demonstrated that satellite-indicated seagrass percentage cover had moderate to large correlations with reference-indicated seagrass percentage cover, indicative of moderate to strong agreement between datasets. Satellite classification performed best in areas of dense, continuous seagrass compared to areas of sparse, discontinuous seagrass and provided a suitable spatial representation of seagrass distribution within each study area. This study demonstrates that the same methods can be applied across scenes spanning varying seagrass bioregions, atmospheric conditions, and optical water types, which is a significant step toward developing a consistent, operational approach for mapping seagrass coverage at the national and global scales. Accompanying this manuscript are instructional videos describing the processing workflow, including data acquisition, data processing, and satellite image classification. These instructional videos may serve as a management tool to complement field- and aerial-based mapping efforts for monitoring seagrass ecosystems.

Macrozoobenthos as an indicator of habitat suitability for intertidal seagrass

Seagrass meadows form the foundation of many coastal ecosystems, but are rapidly declining on a global scale. To conserve and restore these key-ecosystems, improved understanding of drivers behind seagrass presence and recovery is needed. Many animals are known to both facilitate and inhibit seagrasses, but biotic factors are still rarely used as indicators of seagrass presence. Hence, we investigate if macrozoobenthos could be used as an indicator for intertidal seagrass (Zostera marina and Zostera noltii) habitat suitability in the international Wadden Sea. Additionally, we explore if macrozoobenthos can explain the differing seagrass recovery rates that have been observed between the Northern (Denmark and Schleswig Holstein) and Southern (Lower Saxony and Netherlands) regions of the Wadden Sea. To achieve this, we performed a Wadden Sea-wide survey at 36 intertidal locations, across three countries, and investigated the importance of 21 abiotic and biotic variables in explaining the presence and absence of intertidal seagrasses. Seagrass presence or absence could be reliably predicted (prediction error: 16.7%) with a multivariate logistic regression with only four variables; chlorophyll a, bivalve, ragworm and mudsnail biomass. We also found higher chlorophyll concentrations and ragworm biomass in the South compared to the Northern Wadden Sea, suggesting that eutrophication and associated community shifts might still inhibit seagrass recovery in the South. Our findings highlight the potential of using macrozoobenthos as indicators for seagrass habitat suitability. In areas, like the Dutch Wadden Sea, where macrozoobenthic surveys are common and where benthic data is readily available, our findings can be used to improve the understanding of seagrass recovery dynamics and the selection of suitable seagrass restoration sites.