Seagrass morphometrics and meiofauna composition: A comparative study in South Andaman’s waters

Zonation and structuring factors of meiofauna communities in a tropical seagrass bed (Gazi Bay, Kenya)

We studied spatial variation in seagrass communities in the Andaman and Nicobar archipelago (ANI), India using latitude as a surrogate variable. We classified the ANI into five latitudinally distinct island groups: North & Middle Andaman, Ritchie's archipelago, South Andaman, Little Andaman, and the Nicobar archipelago. We evaluated the Importance Value Index (IVI) for species to determine the ecologically dominant seagrasses within each Island group. Later, we related our findings to investigate the three decadal pre- and post-tsunami status of seagrass habitats in the ANI which were severely impacted by the Indian Ocean tsunami of 2004. Six of the 11 observed species, such as Halophila ovalis, Halophila beccarii, Halophila minor, Halodule pinifolia, Thalassia hemprichii, and Cymodocea rotundata, dominated the seagrass population among all island groups. Seagrass composition significantly varied across the five investigated latitudinal gradients. Seagrass communities in 'Ritchie's Archipelago and Nicobar' and 'South Andaman and Little Andaman' revealed the highest and lowest variation. Further, Ritchie's Archipelago and Nicobar had the highest species richness (n = 10), followed by North & Middle Andaman (n = 8), and the lowest in South and Little Andaman (n = 6). Despite similar species richness and composition, Nicobar contributed to the highest seagrass coverage compared to the lowest recorded in the Ritchie's Archipelago. Our observations on the re-colonization of disturbed areas by early successional and historical species suggest recovery of the seagrass population in the ANI post-disturbance. Lastly, co-variates associated with latitude as a surrogate warrant further investigation.

Relationship between seagrass community structure and carbon stocks on the coasts of Karimunjawa Marine National Park, Indonesia

Detailed petrographical and geochemical investigations of the Andaman Flysch provide distinct yet contrasting provenance and tectonic setting in different parts of the arc-parallel, uplifted subduction complex. Petrographical and geochemical data from multiple sections in North, Middle and South Andaman Islands highlight the spatial variation in the composition of sediments from north to south. While lithic wacke dominates North and Middle Andaman Islands, the composition of sandstone varies from lithic wacke to quartz wacke in the South Andaman Islands. The QFR data corresponds to the dissected arc origin of samples. Flysch sediments of North Andaman Islands exhibit a moderate to high Al2O3/SiO2, variable K2O/Na2O ratios and high Fe2O3+MgO contents, while those in South Andaman Islands show a low to moderate Al2O3/SiO2, high K2O/Na2O ratios and high TiO2. Flysch sediments of South and Middle Andaman Islands bear the signature of active continental margin to continental island arc system while those of the North Andaman Islands bear oceanic island signature. The REE data indicates the predominance of felsic source of the South Andaman Island samples. The combined petrographical and geochemical study suggests the derivation of sediments in the North Andaman Islands possibly from the Irrawaddy delta, while Andaman Flysch in Middle and South Andaman Islands possibly sourced from rocks occurring to the east and northeast direction.

The Biodiversity Assessment of Seagrass Ecosystem in Orwer and Ambroben Waters, Biak Numfor Regency, Papua Province is very important for a baseline study of the ecosystem health of seagrass beds. The ecological function of seagrass ecosystems is to stabilize the seabed, provide food and habitat for other marine life, and maintain water quality. The research conducted aims to (1) determine the types of seagrasses, density, and percentage of seagrass cover in Orwer and Ambroben waters, and (2) find out the characteristics of aquatic environmental parameters that play an important role in determining the health status of seagrass meadow ecosystems. Based on the results of the research has been found as many as four types of seagrasses are in Orwer waters, namely Halodule pinifolia, Cymodocea rotundata, Thalassia hemprichii, and Halophila ovalis. In Ambroben waters have been found as many as 7 types of seagrass, namely Halodule pinifolia, Halodule uninervis, Cymodocea rotundata, Syringodium isoetifolium, Enhalus acoroides, Thalassia hemprichii and Halophila ovalis. The average density per seagrass species in Orwer waters is higher (2101 ind/m2) compared to Ambroben waters (1553 ind/m2). The percentage of seagrass ecosystem cover in Orwer is higher (94.44%) than in Ambroben waters (91.53%). The characteristics of aquatic health indicators for seagrass ecosystems in Orwer and Ambroben waters show almost the same range of values, namely temperatures ranging from 29.47-29.97, salinity 33.27-33.97 oo/oo, and pH 7.57-8.46, the dissolved oxygen parameter shows different values between the two waters. Oxygen levels in Orwer waters are 10.47-14.37 mg / L, while Oxygen levels in Ambroben waters are 7.47-11.10 mg / L. Based on these results, it shows that both waters are still included in the category of healthy waters and meet the quality standard criteria for life requirements for seagrass ecosystems.

The study determined the carbon sequestered by seagrasses from the three (3) coastal sites of Don Marcelino, namely Talagutong, Kinanga, and Lawa. The study employed one-shot sampling as part of a preliminary survey visit at the study sites. The survey was conducted during the lowest tide of the day, and the observation of seagrass species was limited to a depth of 0–3 meters. A total of four species of seagrasses were identified using taxonomic field guides. The species Halodule pinifolia, Thalassia hemprichii, and Cymodocea rotundata were present in Talagutong, while Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, and Halodule pinifolia were recorded in Kinanga and Lawa. Thalassia hemprichii is the most dominant seagrass species and has the highest percent cover, followed by Cymodocea rotundata. Moreover, Thalassia hemprichii is more dominant in the study area, which also obtained the highest shoot density, followed by Cymodocea rotundata. Cymodocea rotundata obtained the highest sequestered total carbon from Lawa compared to the other two (2) sites. The carbon sequestered by Thalassia hemprichii in Talagutong and Lawa is significantly higher compared to Kinanga. Furthermore, the carbon sequestered by Halophila sp. in Lawa and Kinanga is significantly higher (21.56 and 18.56 (g/m²) than in Talagutong. It is highly recommended to the local government units to include seagrass areas of Don Marcelino into marine protected areas as a part of the implementation of proactive climate change mitigation.

Although spectrally different, seagrass species may not be able to be mapped from multispectral remote sensing images due to the limitation of their spectral resolution. Therefore, it is important to quantitatively assess the possibility of mapping seagrass species using multispectral images by resampling seagrass species spectra to multispectral bands. Seagrass species spectra were measured on harvested seagrass leaves. Spectral resolution of multispectral images used in this research was adopted from WorldView-2, Quickbird, Sentinel-2A, ASTER VNIR, and Landsat 8 OLI. These images are widely available and can be a good representative and baseline for previous or future remote sensing images. Seagrass species considered in this research are Enhalus acoroides (Ea), Thalassodendron ciliatum (Tc), Thalassia hemprichii (Th), Cymodocea rotundata (Cr), Cymodocea serrulata (Cs), Halodule uninervis (Hu), Halodule pinifolia (Hp), Syringodum isoetifolium (Si), Halophila ovalis (Ho), and Halophila minor (Hm). Multispectral resampling analysis indicate that the resampled spectra exhibit similar shape and pattern with the original spectra but less precise, and they lose the unique absorption feature of seagrass species. Relying on spectral bands alone, multispectral image is not effective in mapping these seagrass species individually, which is shown by the poor and inconsistent result of Spectral Angle Mapper (SAM) classification technique in classifying seagrass species using seagrass species spectra as pure endmember. Only Sentinel-2A produced acceptable classification result using SAM.

Sea grass is one component of biodiversity in marine waters composed of many species with various morphological characters. The aim of this study was to obtain the morphological data of seagrass species on the East and West Coasts in Nature Reserve of Pangandaran. The method used was survey method and line transect as far as 200 meters with random sampling technique. Measurements were made for each species of seagrass in the leaf length, leaf width, leaf thickness, stem length and rhizomes length and root length. The results showed that on the East Coast founded three species of seagrass were Cymodocea rotundata, Thalassia hemprichii and Halodule pinifolia, while on the West Coast founded one species of seagrass was Thalassia hemprichii. Cymodocea rotundata has characteristic rounded edges with slight curvature in the middle, Thalassia hemprichii has rounded, brown tip and a brown patterned rhizome, and Halodule pinifolia has side toothed leaf tip with part of the middle there are brown leaf veins Key words: sea grass, morphology, Pangandaran Nature Reserve

Fitrian T, Kusnadi A, Persilette RN. 2017. Seagrass community structure of Tayando-Tam Island, Southeast Moluccas, Indonesia. Biodiversitas 18: 788-794. Seagrass bed is one of the marine ecosystem that having the highest productivity that could sustain coastal resources. The research purposes of this paper is to determine the community structure of seagrass at Tayando-Tam Island, Southeast Moluccas, Indonesia. The method of observation of seagrass bed using a line transect, transect ran perpendicular to the shore line for 100 meters. The field of observations include identification of seagrass species, counting the number of shoots and percentage (%) of seagrass cover. Seven species of seagrass had been found in Tayando-Tam island, i.e. Enhalus acoroides, Thalassia hemprichii, Cymodocea serrulata, Cymodocea rotundata, Halodule pinifolia, Halophila ovalis, Syringodium isoetifolium. Halodule pinifolia had the highest density in Tam Island with the number of 684.18 shoots/m2. The coverage in this area was between 4.64-43.1 %. Based on the number of species, diversity index and dominance index Tam Island had the most stable seagrass communities, with moderate value of diversity index (H'=1.26), high evenness Index (E=1.63), and low value of dominance index (D=0.34). Seagrass resources in the Tayando-Tam islands is good and the potential for biota the association, which is supported by the quality of water is good for the growth of seagrass.

Seagrasses can grow and develop well in shallow reef environments, on muddy substrates to coral rubble, and in clear and calm waters. Seagrass beds have important roles and functions from both ecological and economic aspects. The ecological aspect is the main source of organic matter production, habitat for various biota, nurseries, spawning grounds, a food source for rare biota, and supporting the biodiversity of marine biota, as well as the economic value of seagrass ecosystem services. Increased development and community activities in coastal areas are believed to have led to a decline in the condition of seagrass beds. Currently, there are no ongoing studies on the condition of seagrass beds, especially on small islands. This study is a monitoring effort for coral reefs and related ecosystems (mangroves and seagrasses) conducted from 2015-2019. The objective of this study is to obtain information on the condition of seagrass beds on small islands and in the eastern waters of Bintan Island. Data collection on species diversity and density was done using transects perpendicular to the coast. Species identification and percent cover analysis were conducted using the Guidelines for Monitoring Seagrass Meadows in Indonesia and the KMNLH (2004) classification of seagrass conditions. The results of the 2015-2019 surveys revealed a diversity of nine seagrass species, including Thalassia hemprichii (Th), Cymodocea rotundata (Cr), Enhalus acoroides (Ea), Syringodium isoetifolium (Si), Halodule uninervis (Hu), Halophila ovalis (Ho), Halodule pinifolia (Hp), Cymodocea serrulate (Cs), and Thalasodendron ciliatum (Tc). Of the nine dominant species found namely, Thalassia hemprichii dan Enhalus acoroides, while species are rarely found namely Halodule pinifolia (Hp) and Thalasodendron ciliatum (Tc). The density of the Enhalus acoroides species did not show any change during 2015-2019. Overall, from 2015 to 2019 the seagrass condition at each monitoring station declined and was categorized as unhealthy.

Revised ranges of seagrass species in the Myeik Archipelago, Myanmar

Seagrasses are vital to the health of coastal marine ecosystems and are threatened with habitat destruction as well as other anthropogenic pressures, but their diversity and taxonomy remain poorly studied. Seagrasses can exhibit large morphological variation in response to environmental variables, resulting in field observations being unreliable for identification. Therefore, molecular phylogenetic approaches can be informative in delimiting and identifying seagrass species. In this study, molecular phylogenetic analyses and morphological examinations of nearly 100 seagrasses collected from six sites distributed across Singapore’s northern and southern coasts were integrated to assess their diversity and phylogeny. The nuclear ITS and plastid matK loci were amplified and sequenced for phylogenetic analyses. Our analyses and morphological examinations recovered 10 well-supported lineages corresponding to 10 seagrass species in Singapore (Thalassia hemprichii, Enhalus acoroides, Halophila beccarii, Halophila spinulosa, Halophila major, Halophila ovalis, Halodule uninervis, Oceana serrulata, Syingrodium isoetifolium, and Cymodocea rotundata), including one new local record of Halophila major. Although Halophila ovata, Halodule pinifolia and Halophila decipiens are reflected in historical local records, they were not found in the field, hence raising the possibility that these species could have been locally extirpated. The molecular markers used here, ITS and matK, could clearly delineate most seagrass species but some species-level clades within Halodule and Halophila remain unresolved. Continued work on seagrass phylogenetics will help resolve species complexes and provide more precise species richness estimates, which are critical for seagrass meadow conservation and management.

Seagrass are flowering plants (Angiosperms) that are fully adapted to life immersed in the sea. This plant consists of rhizomes, leaves and roots, (Rhizomes are stems that sink and creep horizontally, leave and flower, and grow roots). It is these rhizomes and roots that hold back the waves and currents on seagrass plants. The purpose of this study was to determine seagrass species, species density, relative density, species frequency, relative frequency, species closure, relative closure, important value index, diversity index, domination index and aquatic environmental conditions. There are 4 species of seagrass found in the waters of Poopoh Beach, namely, Thalassia hemprichii, Enhalus acoroides, Halodule pinifolia, Halophila ovalis. The number of stands of seagrass species in the study area ranged from 53-965 individuals, species density (17.67-321.67) individuals/m2, relative density (3.98-72.61%), frequency (0.045-0.90), relative frequency (3.57-71.42%), species closure (0.41-7.31), relative coverage (1.04-78.12%), seagrass importance value index in Poopoh Beach waters shows that Thalassia hemprchii has the highest importance value index among the other 3 seagrass species namely (212.85%), diversity index (0.97), species dominance index (0.11-0.44%/m²). Environmental conditions in the waters of Poopoh Beach, which has a temperature range of 38°C, a salinity of 35‰, has a substrate of sand, sand mixed with mud, muddy and coral fragments. Keywords: Poopoh Beach, Seagrass, Community Structure. Abstrak Lamun adalah tumbuhan berbunga (Angiospermae) yang sepenuhnya menyesuaikan diri dengan hidup terbenam dalam laut. Tumbuhan ini terdiri dari rhizoma, daun dan akar, (Rhizoma adalah batang yang terbenam dan merayap secara mendatar, berdaun dan berbunga, serta tumbuh akar). Rhizoma dan akar inilah yang menahan hempasan ombak dan arus pada tumbuhan lamun. Tujuan penelitian ini adalah untuk mengetahui jenis-jenis lamun, kerapatan spesies, kerapatan relatif, frekuensi jenis, frekuensi relatif, penutupan jenis, penutupan relatif, indeks nilai penting, indeks keanekaragaman, indeks dominasi dan kondisi lingkungan perairan. Spesies lamun yang ditemukan diperairan Pantai Poopoh berjumlah 4 spesies yaitu, Thalassia hemprichii, Enhalus acoroides, Halodule pinifolia, Halophila ovalis. Jumlah tegakan spesies lamun dilokasi penelitian berkisar dari 53-965 individu, kerapatan spesies (17,67-321,67) individu/m2, kerapatan relatif (3,98-72,61%), frekuensi (0,045-0,90), frekuensi relatif (3,57-71,42%), penutupan jenis (0,41-7,31), penutupan relatif (1,04-78,12%), indeks nilai penting lamun diperairan Pantai Poopoh menunjukkan bahwa Thalassia hemprchii memiliki indeks nilai penting paling tinggi diantara ke 3 spesies lamun lainnya yakni (212,85%), indeks keanekaragaman (0,97), indeks dominasi spesies (0,11-0,44%/m²). Kondisi Lingkungan diperairan Pantai Poopoh yakni mamiliki kisaran suhu 28°C, salinitas 30‰, memiliki substrat pasir, pasir campur lumpur, berlumpur dan patahan karang. Kata Kunci: Pantai Poopoh, Lamun, Struktur Komunitas.

Seagrass ecosystems are vital for marine biodiversity, carbon storage, and coastal protection but face threats from human activities and environmental changes. This study examines seagrass diversity, distribution, and ecological conditions at Sire Beach, North Lombok Regency, West Nusa Tenggara. Research conducted from October to December 2024 used transect-quadrat and exploratory methods at three stations. In addition to biotic elements like seagrass species, abiotic variables including temperature, pH, salinity, and dissolved oxygen were simultaneously examined. Eight seagrass species were identified: Halodule pinifolia, Cymodocea serrulata, Syringodium isoetifolium, Cymodocea rotundata, Thalassia hemprichii, Halophila ovalis, Enhalus acoroides, and Halodule uninervis. Enhalus acoroides dominated due to its adaptability and robust root systems. Diversity (H’=1.66), dominance (0.499), and evenness (0.798) indices indicate moderate biodiversity and balanced species distribution. Abiotic factors, including temperature (29–30.5°C) and pH (7.14–7.60), were optimal, though nutrient levels (phosphate 0.10–0.15 mg/L, ammonia 0.02–0.03 mg/L) could affect photosynthesis. Sire Beach's seagrass ecosystem is moderately diverse and stable but affected by anthropogenic pressures. Conservation measures and long-term monitoring are recommended to sustain this critical habitat.

Kastela coastal waters are one of the tourist attractions in the coastal area of ​​Ternate city where seagrass is found. Information related to diversity, density and, the diverse cover is still lacking and has not been supported by previous scientific research, especially in the area of ​​Kastela Beach. Therefore, this study was conducted to determine the diversity, density and, cover of seagrass species on the Kastela coast, South Ternate. Seagrass diversity in Kastela Beach includes 6 types of seagrass, namely: Halodule pinifolia, Halophila ovalis, Thalassia hemprichii, Cymodocea rotundata, Syringodium isoetifolium and, Enhalus acoroides. Based on the Shannon-Wienner index, the diversity of seagrass on the beach is classified as moderate with a value of 1.42 (station 1), 1.46 (station 2), 1.29 (station 3). Seagrass species Thalassia hemprichii has the highest density among seagrass species found on Kastela Beach with a density value of 580.27 individuals/m². At station 1, 358.27 individuals/m². At station 2, and station 3 it was dominated by Halodule pinifolia species as many as 326.53 individuals/m². For total seagrass closure at each station, especially station 1 and station 2, it was classified as rich or healthy (>60 %), where the value of station 1 was 124.16%/m², and station 2 was 95.2%/ m². Station 3 is classified as less healthy or less rich with a value of 59.79%/m².