Distribution Of Seagrass Species Research Articles

Mechanism and threshold of environmental stressors on seagrass in high-turbidity estuary: case of Zostera japonica in Yellow River Estuary, China

Zostera japonica (Z. japonica), the most widely distributed seagrass species in temperate estuaries, has experienced a dramatic decline of nearly 75% over the past decade. While previous research has investigated the adaptation of seagrass individuals and populations to single stress factors, the molecular mechanisms underlying the interaction of multiple stressors remain poorly understood. This study conducted laboratory experiments to examine the response of Z. japonica at different life stages to environmental pressures, specifically salinity and turbidity, as indicated by changes in free amino acids (FAAs). The results demonstrate that Z. japonica exhibits stronger adaptability to high salinity environments but displays weaker adaptability to freshwater conditions. Through single stress experiments, the salinity and turbidity thresholds for FAA homeostatic disturbance in Z. japonica were determined at seedling, juvenile, and mature stages. As Z. japonica matures, its metabolic pathways expand and diversify, allowing the regulation of key FAAs to enhance stress resistance. Turbidity stress exerts a more pronounced negative impact on the cellular homeostasis of Z. japonica compared to salinity stress, and when turbidity levels exceed 150 NTU, they significantly intensify the negative effects of salinity stress on the seagrass. Furthermore, under strong salinity-turbidity interactions, the concentration of key FAAs generally decreases by 20-30%, indicating inhibition of growth and development in Z. japonica. These findings have important implications for the conservation of intertidal seagrass beds and estuarine ecosystems in the face of multiple human activities and environmental stressors. The study provides valuable insights into the molecular mechanisms underlying Z. japonica’s adaptations to salinity and turbidity stress, contributing to the development of targeted strategies to mitigate the impacts of environmental pressures on seagrass populations and promote the resilience of these critical marine ecosystems.

Halophilomyces hongkongensis, a Novel Species and Genus in the Lulworthiaceae with Antibacterial Potential, Colonizing the Roots and Rhizomes of the Seagrass Halophila ovalis.

Seagrass serves as a quintessential reservoir for obligate marine Lulworthiaceae fungi. Our current knowledge of the mycological diversity associated with seagrass in Hong Kong remains poor. We analyzed the diversity of fungi associated with the most widely distributed seagrass species in Hong Kong Halophila ovalis (Hydrocharitaceae), using a combination of culture-based methods and high-throughput amplicon sequencing. Halophilomyces hongkongensis, a novel fungal species in a newly proposed genus within the Lulworthiaceae family, was isolated from H. ovalis roots and rhizomes. The novel fungus showed distinct morphological characteristics, while both combined 18S-28S and internal transcribed spacer (ITS) phylogenetic trees based on maximum likelihood and Bayesian methods supported its discrimination from other existing Lulworthiaceae members. The ITS2 region in the Illumina sequencing results of multiple H. ovalis compartments, water, and adjacent non-seagrass sediments revealed continuous recruitment of H. hongkongensis by H. ovalis throughout the year despite dramatically fluctuating environmental conditions, with remarkably high proportions of this taxon found in root and rhizome internal tissues, possibly indicating a strong and specialized relationship established between the Lulworthiaceae fungal partner and its seagrass host. The inhibitory abilities exhibited by H. hongkongensis against Staphylococcus aureus SA29213 and ATCC 43300 (methicillin-resistant) may imply its capacity in producing (novel) antibacterial compounds. The discovery of H. hongkongensis as the first novel Lulworthiaceae taxon in Hong Kong, along with its distributional pattern in the seagrass meadow, provides valuable insights into the systematics and ecology of this strictly marine fungal family.

Analyzing seagrass species and distribution for sustainable management of coastal areas and small islands: A case study of Java Island, Indonesia

Seagrass beds are essential components of coastal communities globally, as they support productive fisheries and coastline stabilization. In view of its numerous ecosystem services, the coverage of seagrass is an important indicator of ecosystem health. However, there are conflicting data regarding Indonesia’s seagrass coverage. Some research indicates that seagrass bed areas have declined, with significant damage observed on Java Island. The objective of this study are to provide an inventory of the various species of seagrass found; present their distribution on a map; and assess the extent of seagrass cover. This seagrass study was conducted from 2014 to 2021 on the java Coast. Data were collected using a systematic literature review. The distribution of seagrass species was processed using QGIS. The coverage of seagrass analysis was conducted descriptively by considering the categories listed in the Decree of the Minister of Environment of the Republic of Indonesia 200/2004. There are 11 types of seagrass found in 13 districts along the Java Coast. Seagrass coverage are varies 3% to 80%. The health status of seagrass beds on the north coast of Java is moderate to good, while the condition of seagrass beds on the south coast is poor to moderate.

Spatial diversity and habitat characteristics of seagrass meadows with management recommendations in the Andaman and Nicobar Islands, India

The Andaman and Nicobar Islands, India, a geographically remote region, harbor a diverse island ecosystem. Limited exploration has hindered our understanding of marine floral biodiversity in this area. To address this gap, we investigated seagrass meadows in the Andaman and Nicobar Islands to understand their spatial distribution, species composition, and habitat characteristics. We assessed 66 seagrass meadows, including 32 newly discovered ones, filling data gaps in the region’s seagrass coldspots. Seagrasses were found across a wide range of depths, with the majority occurring in shallow subtidal waters (< 8 m). Large-sized species such as Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, Cymodocea serrulata, and Syringodium isoetifolium dominated the littoral and shallow subtidal zones, while smaller species such as Halophila spp. and Halodule spp. exhibited broader depth distributions. H. beccarii and H. decipiens were strictly intertidal and subtidal species, respectively. Water depth significantly influenced seagrass occurrence (p < 0.0001), cover (β = -0.2759; SE = 0.02471; p < 0.0001), shoot densities (β = -0.3556; SE = 0.1231; p = 0.005), and biomass (β = -0.3526; SE = 0.1159; p = 0.003). Sand availability emerged as the second significant predictor of seagrass distribution, cover, and biomass (p values < 2e-16, < 2e-16, and 0.01, respectively). Habitat heterogeneity decreased with increasing water depth, and seagrass species exhibited strong preferences for specific substrata, resulting in spatial niche partitioning. Our study provides novel insights into the seagrass spatial diversity, habitat characteristics, and seagrass-environment relationship in the Andaman and Nicobar Islands. Further, it highlights the importance of water depth, habitat characteristics, and substratum heterogeneity in seagrass distribution and growth. Lastly, our findings imply that any change to the benthic profile of the meadows will influence the seagrass species distribution and growth. Understanding these factors is crucial for seagrass conservation and management in the region, aiding the development of targeted strategies to protect these valuable marine habitats and associated biodiversity.

Species‐specific acclimatization capacity of key traits explains global vertical distribution of seagrass species

AbstractAimThe global vertical depth distribution of seagrass species remains poorly understood. Locally, the abundance and distribution of seagrasses is determined by light penetration, but at global levels each seagrass species has very distinct maximum distributional depth ranges, indicating that plant‐associated traits must also influence their specific depth ranges. Seagrass‐specific attributes, such as plant size or architecture, growth or reproductive strategy and their physiological and/or morphological acclimatization potential, have been suggested to be responsible for this variety of vertical distributions. We investigate here whether these species‐specific traits drive differences in the global maximum vertical distribution of seagrasses.LocationGlobal.Time periodPublications between 1982 and 2020.Major taxa studiedSeagrasses (order Alismatales).MethodsWe tested whether the species‐specific maximum vertical distribution of seagrasses can be predicted by (1) their rhizome diameter (a proxy for plant size); (2) their functional resilience (growth/reproductive strategy); or (3) their acclimatization capacity. For the last aspect, we used a systematic review followed by meta‐analytical approaches to select key seagrass traits that could potentially acclimatize to extreme light ranges across different seagrasses.ResultsWe found that vertical distribution is best explained by the species‐specific acclimatization capacity of various seagrass traits, including saturation irradiance (physiological trait), leaves per shoot (morphological trait) and above‐ground biomass (structural trait). In contrast, our results indicate no predictive power of seagrass size or growth/reproductive strategy on the vertical distribution of seagrasses.Main conclusionsAcross the globe, the ability of seagrass species to thrive at a wide range of depths is strongly linked to the species‐specific acclimatization capacity of key traits at different organizational levels.

Improving accuracy and efficiency in seagrass detection using state-of-the-art AI techniques

Seagrasses provide a wide range of ecosystem services in coastal marine environments. Despite their ecological and economic importance, these species are declining because of human impact. This decline has driven the need for monitoring and mapping to estimate the overall health and dynamics of seagrasses in coastal environments, often based on underwater images. However, seagrass detection from underwater digital images is not a trivial task; it requires taxonomic expertise and is time-consuming and expensive. Recently automatic approaches based on deep learning have revolutionised object detection performance in many computer vision applications, and there has been interest in applying this to automated seagrass detection from imagery. Deep learning–based techniques reduce the need for hardcore feature extraction by domain experts which is required in machine learning-based techniques. This study presents a YOLOv5-based one-stage detector and an EfficientDetD7–based two-stage detector for detecting seagrass, in this case, Halophila ovalis, one of the most widely distributed seagrass species. The EfficientDet-D7–based seagrass detector achieves the highest mAP of 0.484 on the ECUHO-2 dataset and mAP of 0.354 on the ECUHO-1 dataset, which are about 7% and 5% better than the state-of-the-art Halophila ovalis detection performance on those datasets, respectively. The proposed YOLOv5-based detector achieves an average inference time of 0.077 s and 0.043 s respectively which are much lower than the state-of-the-art approach on the same datasets.

Developing seagrass index for long term monitoring of Zostera japonica seagrass bed: A case study in Yellow River Delta, China

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.

Effects of nutrients on the utilization pattern of photosynthetic inorganic carbon of the tropical <italic>Thalassia hemprichii</italic>

<p indent="0mm">Studies on the utilization strategy of photosynthetic inorganic carbon of seagrass can reveal its ecological adaptation mechanism. <italic>Thalassia hemprichii</italic>, a widely distributed seagrass species in the Indo-Pacific and Atlantic coastal seas, needs to evolve several utilization patterns of inorganic carbon to adapt different environments and meet its growth, development and reproduction. However, the effect of nutrient on the photosynthetic inorganic carbon utilization strategy in seagrass is still unknown and further research is urgently needed. Therefore, using oxygen electrode technology, chlorophyll fluorescence technology, and non-invasive micro-test technology, this study examined the similarity and difference in the utilization patterns of photosynthetic inorganic carbon of <italic>T</italic>.<italic> hemprichii </italic>from two typical tropical seagrass beds (Tanmen, Hainan Island, and Yongxing Island, Xisha), that were affected by varying degrees of human activity. Experiments showed that the photosynthetic oxygen release rate, maximum relative electron transfer rate, and half-saturated light intensity of <italic>T</italic>.<italic> hemprichii</italic> in Yongxing Island waters were 24.95%, 24.54%, and 28.73% higher than the corresponding in Tanmen, Hainan Island. This indicated that the growth status of <italic>T</italic>.<italic> hemprichii</italic> in the waters of Yongxing Island was better with higher photosynthetic efficiency. The addition of acetazolamide (AZ) and ethoxyzolamide (EZ) significantly reduced the photosynthetic oxygen release rate of <italic>T</italic>.<italic> hemprichii</italic>, with an insignificant difference in the inhibition between AZ and EZ. This indicated that it mainly absorbed HCO₃⁻ via extracellular carbonic anhydrase catalysis. Meanwhile, hydroxymethyl (Tris) inhibited the photosynthetic oxygen release of <italic>T</italic>.<italic> hemprichii</italic> in Tanmen by up to 100% and decreased the maximum relative electron transfer rate and the H⁺ inward flow rate, implying a synergistic H⁺/HCO₃⁻ transport mode. On the other hand, the rate of photosynthetic oxygen release and the maximum electron transfer rate of <italic>T</italic>.<italic> hemprichii</italic> in Xisha did not change significantly with the addition of AZ and EZ, while Tris buffer inhibited photosynthetic oxygen release by up to 100% and significantly reduced the maximum electron transfer rate. This suggested <italic>T</italic>.<italic> hemprichii </italic>in Xisha mainly relied on the H⁺/HCO₃⁻ synergistic transport. Therefore, <italic>T</italic>.<italic> hemprichii </italic>could uptake inorganic carbon in an environment with greater anthropogenic activity, larger nutrient load and lower light availability on Hainan Island by catalyzing HCO₃⁻ into CO₂ with extracellular carbonic anhydrase and the H⁺/HCO₃⁻ synergistic transport. In contrast, <italic>T</italic>.<italic> hemprichii</italic> in an environment with less anthropogenic activity, lower nutrient loading, and greater light availability, relied chiefly on H⁺/HCO₃⁻ synergistic transport. Facing a relatively unfavorable high-nutrient and low-light growth environment, <italic>T</italic>.<italic> hemprichii</italic> could increase the photosynthetic inorganic carbon utilization strategy (such as the activity of extracellular carbonic anhydrase) to improve its utilization ability of inorganic carbon to overcome stress and growth limitation. This suggested that <italic>T</italic>.<italic> hemprichii</italic> could adjust its inorganic carbon utilization patterns according to its geographical environment. With the continuous development of technology, it is urgent to study the utilization mechanism of inorganic carbon of seagrass by applying seagrass omics technology and stable isotope tracing to deepen the understanding of the carbon sink function of seagrass.

Mapping the distribution and occurrence of four newly recorded species of seagrasses in the North-West Arabian Gulf

For a long time the Iraqi regional waters of north-west Arabian Gulf were classified as free of seagrasses due to the absence of the information concerning these important angiosperms. During the survey carried out by scientist of the Marine Science Center and German divers in 2013-2014 to study the Coral reefs distribution and occurrence in this area, the divers with the help of underwater camera caught photos indicates the existence of seagrass meadows in different places of the north-west Arabian Gulf, so the efforts were made to examine this issue and a work were carried out in April 2017 to study the existence, species composition, occurrences and distribution of seagrass species in the Iraqi marine waters of the north-west Arabian Gulf for the first time. Six sites were chosen distributed along the north-west of Arabian Gulf where the depth was ranging from 0.5 to 15.0 m. Six meadows of seagrass were identified, classified, mapped and seagrass diversity and abundance were investigated. Four species of seagrass namely Halophila stipulacea (Forsskal) Ascherson, Halophila ovalis (R. Brown) Hooker f., Halophila decipiens Ostenfeld and Halodule uninervis (Forsskal) were recorded for the first time in Iraq. Halophila decipiens Ostenfeld was recorded as a new to the whole area of the Arabian Gulf and the Iraqi marine waters and found at a depth of 12-15 m. Halodule uninervis was found to be the most dominant species at all the studied sites followed by Halophila stipulacea. The total seagrass area estimated at all the stations was about 678 hectare fluctuated at different stations. Higher Seagrass total coverage area (240 ha) was found at shallower waters (0.5-3.0 m) compared with 60 ha at deeper waters (12-15 m). The exposed locations showed low seagrass coverage of 35 % comparing with sheltered sites (65 %). The relationship between depth and total coverage of seagrass was significant, while it was not significant with sites. Highest richness value was found in the Alkheran area (Khor Al-Zubair) at a depth of 0.5 m. The relative evenness of the seagrasses species, with different depths showed that the depth 0-3 m has the highest value. The distribution of seagrasses in Khor Al-Zubair and Khor Abdullah down to the open area of Khor Al-Omaya was mapped by using the GIS and Arc Map version 10.5 applications.

Nation-wide hierarchical and spatially-explicit framework to characterize seagrass meadows in New-Caledonia, and its potential application to the Indo-Pacific

Despite their ecological role and multiple contributions to human societies, the distribution of Indo-Pacific seagrasses remains poorly known in many places. Herein, we outline a hierarchical spatially-explicit assessment framework to derive nation-wide synoptic knowledge of the distribution of seagrass species and communities. We applied the framework to New Caledonia (southwest Pacific Ocean) and its 36,200 km2 of reefs and lagoons. The framework is primarily field-based but can leverage various habitat maps derived from remote sensing. Field data collection can be stratified by map products and retrospectively contribute to developing new seagrass distribution maps. Airborne and satellite remote sensing alone do not allow for the spatial generalisation of the finest attributes (species distribution and types of seagrass beds), but staged stratified field sampling provides synoptic views of these attributes. Using three examples, we discuss how the hierarchical and spatial information generated from this framework's application can inform conservation and management objectives.

Aquaculture and eelgrass Zostera marina interactions in temperate ecosystems

This paper reviews the impacts of shellfish and finfish aquaculture on eelgrass Zostera marina, the most widely distributed seagrass species in the northern hemisphere. Shellfish aquaculture can have positive, neutral, and negative effects on eelgrass. Positive interactions can be generated by the filtering activity of cultured bivalves, which may improve water quality and reduce epiphyte loads, and shellfish biodeposits may provide more nutrients to eelgrass and other vegetation. However, negative responses are more commonly reported and can be caused by shading and sedimentation. These negative effects tend to occur directly under and immediately surrounding shellfish farms and rapidly diminish with increasing distance. In contrast to shellfish aquaculture, only one field study has investigated the effects of finfish aquaculture on eelgrass in a temperate setting, and the results were inconclusive. However, many studies have investigated the effects of Mediterranean finfish farms on 2 other species of seagrass (Posidonia oceanica and Cymodocea nodosa). These studies reported clear negative interactions, which have been linked to increased nutrient concentrations, sulphides, sedimentation, epiphyte loads, and grazing pressure. It is unknown if these studies are relevant for finfish aquaculture in temperate regions due to differences in environmental conditions, and because the studies focused on different species of seagrass. Thus, further study in a temperate setting is warranted. We conclude by highlighting key research gaps that could help regulators establish unambiguous operational and siting guidelines that minimize the potential for negative interactions between aquaculture and eelgrass.

Sonar and in situ surveys of eelgrass distribution, reproductive effort, and sexual recruitment contribution in a eutrophic bay with intensive human activities: Implication for seagrass conservation

Seagrass beds are recognized as pivotal and among the most vulnerable coastal marine ecosystems globally. The eelgrass Zostera marina L. is the most widely distributed seagrass species and dominates the temperate northern hemisphere. However, an alarming decline in seagrass has been occurring worldwide due to multiple stressors. Seagrass meadow degradation is particularly serious in the Bohai Sea, in temperate China; however, large areas (> 500 ha) of seagrass meadows and population recruitment have rarely been reported in this area. In the present study, we report on a large eelgrass bed in a eutrophic bay of the Bohai Sea. Sonar and field survey methods were used to investigate the distribution of seagrass and its population recruitment. We also analyzed the major threats to this large seagrass bed. Results showed that a large Z. marina bed with an area of 694.36 ha occurred in this area of the Bohai Sea, with a peripheral area of ~25 km2. Seagrass canopy height and plant coverage had a significant correlation with water depth. Asexual reproduction principally occurred in autumn and played a dominant role in population recruitment in vegetated areas, where no seedlings successfully colonized. In contrast, a considerable number of seedlings survived in the seagrass meadow gaps, and thus played a critical role in the recruitment in these areas. The maximum reproductive shoot densities were about 100 and 70 shoots m−2 at sampling site (S)-1 and S-2 in 2018, respectively, which was about two times more than in 2019 (50 and 20 reproductive shoots m−2 at S-1 and S-2, respectively). The potential seed output per unit area in 2019 was about 1020 seeds m−2 at S-1 and 830 seeds m−2 at S-2, and the seed output in the study area was at a low level compared with global values. Overall, high spring and summer water temperature appeared to induce sexual reproduction of Z. marina in the study area, including reproductive effort, reproductive investment, and seedling development. Furthermore, eelgrass height, aboveground biomass, and density were significantly related to water temperature. Among the potential threatening factors to seagrass in this area, the activities of clam harvesting were intense with daily clam catches >2000 kg, leading to patchy seagrass meadows, especially in the fringe areas. The seagrass bed was also threatened by marine pollution (nutrient loading) and land reclamation. Therefore, the protection and restoration of this seagrass bed are strongly recommended. Our study will provide fundamental information for the conservation and management strategies of large eelgrass beds in the Bohai Sea.

Variation in Seagrass Carbon Stocks Between Tropical Estuarine and Marine Mangrove-Fringed Creeks

Seagrass and associated blue carbon ecosystems are important carbon sinks and hence understanding their spatial and temporal variability is vital in appreciating their potential roles in climate change mitigation and adaptation. Indo-Pacific region has the highest seagrass biodiversity yet little focus has been made to compare seagrass habitat extent and carbon dynamics with their temperate counterparts. The present study assessed habitat characteristics and seagrass species distribution, diversity and carbon storage in Eastern (marine) and Western (estuarine), mangrove fringed creeks of Gazi Bay, Kenya. Data on species composition, canopy cover, biomass and sediment organic carbon were collected in 80 plots of 0.25m by 0.25m laid along transects established perpendicular to the waterline. Five species formation viz; Thalassia hemprichii, Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, and Thalassidendron ciliatum were encountered as either single or mixed stands. There was a significant difference in total seagrass biomass between creeks (p < 0.01) with Eastern creek recording a mean of 10.2 ± 0.6 Mg C ha-1 while Western creek recorded 4.3 ± 0.3 Mg C ha-1. In addition, sediment carbon to 1 m depth varied significantly (p < 0.01) between species in the two creeks and ranged from 98 – 302 Mg C ha-1, with the Eastern and Western creeks recording means of 258 ± 90 and 107 ± 21 Mg C ha-1 respectively. The total carbon stocks from 50 ha of seagrasses in Eastern creek was 13,420 Mg C; whereas in the 70 ha of Western creek, it was 7,769 Mg C. The study shows that seagrass community attributes such as species composition and productivity can vary dramatically over small spatial extent due to differences in biophysical conditions and cautions estimation of site-specific carbon stocks using generalized global values.

Overexpression of Seagrass Nucleotide Exchange Factor Gene ZjFes1 Enhances Heat Tolerance in Transgenic Arabidopsis

ABSTRACT Nucleotide exchange factors (NEFs) play an important role in plant abiotic stress response, but their characteristics and functions in seagrass have not been studied. Zostera japonica (Z. japonica) is one of the most widely distributed seagrass species in China and are distributed in subtropical and temperate coastal areas. Z. japonica is intertidal seagrass, which often undergoes heat stress during summer when the tide ebbs. Overexpression of ZjFes1 in Arabidopsis results in an increase in heat tolerance. We found that ZjFes1 associates with ZjHsp70 in vivo by yeast two-hybrid and bimolecular fluorescence complementarity (BiFC). Overexpression of ZjFes1 leads to selective reduction of Hsp70 transcription and an increase in Hsp101. In conclusion, our results suggest that ZjFes1 may be an active regulator of heat tolerance.

Relationship of Distribution Seagrass Species with Dugong (&lt;i&gt;Dugong dugon&lt;/i&gt;) Sighting at Liki Island-Papua

Dugong dugon is a herbivorous marine mammal. One of Dugong's favorite foods is seagrass. This study examines the distribution of seagrass species to dugong sighting in Liki Island. The study was conducted in November 2018. Observation of seagrass conditions was carried out using a line transect method and a 50x50 cm transect with a distance interval between 10 m plots. Interviews were also conducted with the community to find out the location of Dugong presence in Liki Island. There are seven species of seagrass found in Liki Island :Enhalus acoroides, Cymodocea rotundata, Thalassia hemprichii, Halophila ovalis, Halodule uninervis, Halodule pnifolia and Syringodium isoetifolium spread over four observation stations. The results showed that Dugong in Liki Island is often found during the eastern season, they often appear in seagrass ecosystem area to do eating activities. Dugong is often found in the eastern part of Liki Island (Station 4) and sometimes also found in the western part of Liki Island (Station 3).Keywords:biodiversity,Dugong dugon, liki, papua, seagrass

Propagule risk in a marine foundation species: Seascape effects on Zostera marina seed predation

Abstract Both biotic and abiotic factors can affect whether seagrass meadows establish as large, continuous features or as a mosaic of smaller patches, and these processes act across multiple spatial scales. Of these processes, sexual recruitment is considered vital for the recovery and resilience of seagrass meadows. Because numerous estuarine fauna can impact sexual recruitment by consuming seeds, it is important to understand variation in seed consumption throughout the seascape. We sought to determine how cross‐scale processes affected seed consumption of Zostera marina, a widely distributed seagrass species. We deployed seed predation units (SPU) within patches ranging in size from 0.28 to 28.48 m2, and on unvegetated, sandy bottom. Seed consumption was analysed across patch sizes, at patch centres and edges and within the context of total seagrass cover within buffer zones surrounding SPU locations. Using structural equation modelling, we found that measured seascape parameters explained 34% of the observed variation in seed consumption. Specifically, we found that seagrass presence had the strongest effect on seed predation followed by a negative effect of patch size on seed consumption. Although there was no direct effect of percent seagrass cover (within a 4‐m buffer of the SPU) on seed predation, percent seagrass cover had a negative indirect effect through its positive correlation with patch size. However, we found that once variation due to patch size and areal cover were accounted for, seeds placed at patch interiors actually experienced greater consumption rates. We did not find similar relationships with our potential seed consumers, although our snapshot sampling likely obscured transient effects. We argue that seagrass recruitment could be affected by seed predation, which is influenced by multiple processes, including predator dispersal, behaviour and aggregation. Since seed‐based restoration is becoming more common, and the role of sexual recruitment in meadow maintenance appears to be increasingly important for seagrass resilience, our results demonstrate that for current management strategies to be successful, there is a need to better understand seed predation in seagrass‐dominated seascapes. Synthesis. Factors that influence propagule supply and recruitment success of seagrass operate and interact across multiple spatial scales, which can have implications for management.

A Comparative Study on the Diversity of Seagrass Species in Selected Areas of Puttalam Lagoon in Sri Lanka

Seagrasses are aquatic angiosperms located in shallow marine and brackish water environments and considered as a key environmental resource. Seagrasses are not only important as primary producers in aquatic environment but also they are important to protect coastal environment from erosion and provide environment to large number of species. This study was carried out to investigate the distribution of seagrass species in selected areas of Puttalam lagoon. Point transect method was used for data collection. Sites were randomly selected and three lines transects, perpendicular to shore were laid. Water quality parameters including water temperature (°C), pH, salinity (ppt), conductivity (mS/cm) and dissolved oxygen (mg/L) were also measured. Shannon-Wiener diversity index was used and Minitab14 statistical software is performed for data analysis. There was a significant relationship between relative abundance of Halodule uninervis (Narrow) and Syringodium isoetifolium with water temperature respectively. Shannon-Wiener diversity index values indicated that diversity of Kalpitiya region and Kuringipitiya region was closely related whereas diversity of Paliwasalthurai was closely related to the diversity of Kandakuda. Zero diversity was recorded in Palavi which is composed of only Halophila ovalis. Moreover, it has been shown a relationship between of water quality and distribution of the seagrass species.

Shoalgrass Halodule wrightii (Ascherson, 1868) meadows in El Salvador: distribution and associated macroinvertebrates at the estuary complex of Bahia de Jiquilisco

Seagrasses are aquatic angiosperms that grow submerged in shallow marine and estuarine environments worldwide. Halodule wrightii is a circumtropically distributed seagrass species found primarily in the Atlantic Ocean, but also in parts of the Indian Ocean and eastern Pacific Ocean. Along the Pacific coast of Central America, large swaths of the reported distribution of H. wrightii are assumptions based on interpolation between known seagrass point locations, and despite confirmation of H. wrightii occurrence in Bahia de Jiquilisco in El Salvador, little is known about its distribution and associated species, which can hamper efforts to conserve this seagrass ecosystem. To address these gaps in data, we provide the first assessment of H. wrightii distribution and associated macroinvertebrate species in Bahia de Jiquilisco. We identified six areas where seagrasses occurred and two of these were selected for monitoring. At the two sampled areas, heterogeneous patches of H. wrightii covered 27.1 km 2 with 22 associated macroinvertebrate species from three taxonomic groups in three phyla. We conclude by discussing local threats to H. wrightii , including implications for endangered hawksbill ( Eretmochelys imbricata and green ( Chelonia mydas agassizii ) turtles that depend on these ecosystems, and describe opportunities for conservation in Bahia de Jiquilisco.

Seagrass species distribution, density and coverage at Panggang Island, Jakarta

This study aimed to assess species distribution, density and coverage of seagrass in Panggang Island, within Kepulauan Seribu Marine National Park, northern Jakarta. Seagrass sampling was conducted between March to April 2016 at three observation stations in the West, East, and South of Panggang Island. A total of 6 seagrass species was recorded during sampling period, including Cymodocea rotundata, C. serulata, Halodule uninervis, Syiringodium isoetifolium, Enhalus acoroides, and Thalassia hempricii. All species were observed in the South station, while in the West and East station found only three species (C. rotundata, E. acoroides, and T. hemprichii). While, C. rotundata and T. hemprichii were observed at all station. The highest density was observed for C. rotundata (520 ind/m2) and for T. hempricii (619 ind/m2) in the West station and South Station, respectively. The lowest density was observed in South Station for C. serulata (18 ind/m2), Halodule uninervis (20 ind/m2), and Syiringodium isoetifolium (15 ind/m2). Seagrass coverage of Thalassia hempricii was the highest (43.60%) and the lowest observed at Syiringodium isoetifolium (0.40%). This could be basic information for the management of seagrass ecosystem in the Kepulauan Seribu Marine National Park.

Using modelling to predict impacts of sea level rise and increased turbidity on seagrass distributions in estuarine embayments

Climate change induced sea level rise will affect shallow estuarine habitats, which are already under threat from multiple anthropogenic stressors. Here, we present the results of modelling to predict potential impacts of climate change associated processes on seagrass distributions. We use a novel application of relative environmental suitability (RES) modelling to examine relationships between variables of physiological importance to seagrasses (light availability, wave exposure, and current flow) and seagrass distributions within 5 estuarine embayments. Models were constructed separately for Posidonia australis and Zostera muelleri subsp. capricorni using seagrass data from Port Stephens estuary, New South Wales, Australia. Subsequent testing of models used independent datasets from four other estuarine embayments (Wallis Lake, Lake Illawarra, Merimbula Lake, and Pambula Lake) distributed along 570 km of the east Australian coast. Relative environmental suitability models provided adequate predictions for seagrass distributions within Port Stephens and the other estuarine embayments, indicating that they may have broad regional application. Under the predictions of RES models, both sea level rise and increased turbidity are predicted to cause substantial seagrass losses in deeper estuarine areas, resulting in a net shoreward movement of seagrass beds. Seagrass species distribution models developed in this study provide a valuable tool to predict future shifts in estuarine seagrass distributions, allowing identification of areas for protection, monitoring and rehabilitation.