Seagrasses are essential blue carbon ecosystems that are increasingly threatened by the accumulation of emerging global pollutants, such as microplastics (MPs). However, in regions like Sri Lanka, MP contamination within seagrass beds remains critically understudied. This study investigated MP abundance in seagrass blades (Thalassia hemprichii), sediments, surface water, and sea cucumbers (Holothuria atra) and characteristics of isolated MPs from six selected sites along the Southern and Eastern coastlines of Sri Lanka (Indian Ocean). The average abundances of MPs in seagrass blades, Holothuria atra, surface water, vegetated sediments, and non-vegetated sediments were 1.59 ± 0.11 items/blade, 177.19 ± 53.28 items/kg, 9.60 ± 0.97 items/m3, 69.72 ± 8.38 items/kg, and 33.61 ± 2.15 items/kg, respectively. In this study, fibers were the most prevalent morphological type of MPs, while blue was the most dominant color. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the predominant presence of low-density polyethylene (LDPE) in all types of samples, followed by polyethylene terephthalate (PET), high-density polyethylene (HDPE), polypropylene (PP), and polyamide or commonly known as nylon (PA) in variable amounts. A strong positive correlation between MPs on seagrass blades and those in sediments and surface water suggests that MPs from both water column and seabed contribute to their accumulation on seagrass. Furthermore, the ingestion of MPs by sea cucumbers indicates the potential for fragmentation and trophic transfer within the seagrass ecosystem, enabling MPs to enter and move through the marine food chain.

Conservation efforts have led to substantial recovery of green turtle (Chelonia mydas) populations globally, yet over- or intensive grazing by these megaherbivores is now degrading seagrass ecosystems. We assessed the impacts of turtle-driven grazing and its feedback on turtle nutritional status and growth at Kume Island, Japan, through a comprehensive study conducted between autumn 2023 and spring 2025. Our approach combined seagrass surveys, drone-based density estimation, capture–recapture studies, and stomach content analysis. The surveys revealed a 50.6% reduction in seagrass area since the 1990s, alongside a species shift from mid-sized, long-lived taxa (Thalassia hemprichii) to small, fast-growing species (Halophila ovalis). This species shift was consistent with changes observed in the turtles’ diet composition. The foraging aggregation was dominated by immature turtles, with turtle densities reaching 452.6 individuals per km2, among the highest reported. Body condition indices from 342 captured turtles revealed temporal fluctuations, with severe emaciation in autumn 2023 and spring 2025. The mean growth rate in straight carapace length was only 0.31 ± 1.57 cm/year, substantially lower than other foraging populations. Collectively, our findings demonstrate that intensive grazing by green turtles has fundamentally altered the structure of seagrass habitats, with direct negative feedbacks on turtle nutritional status and growth performance.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-026-49615-8.

This research work reports about the eco-friendly synthesis of cobalt oxide nanoparticles (Co₃O₄ NPs) with excessive reduction potential from marine seagrass, Thalassia hemprichii, possessing plenty of bioactive constituents. The green synthetic strategies for producing environment-friendly nanomaterials and nanomaterial-based biomedical devices is the core objective. FTIR, XRD, TEM and SEM were used to characterize the synthesized Co₃O₄ NPs for their structural and morphological properties. FTIR spectra indicated functional groups of Co₃O₄ NPs interacting with metal–oxygen bonds, validating successful nanoparticle formation. XRD confirmed the crystalline cubic spinel structure of Co₃O₄ nanoparticles with an average crystallite size of ~20–40 nm. The crystalline structure was confirmed, and the average particle size was found to be in the range of 45–52 nm. The in vitro bioactivities of the nanoparticles were evaluated, and the nanoparticles showed strongly dose-dependent free radical-scavenging activity as evidenced by DPPH and nitric oxide (NO) scavenging activities. Co₃O₄ NPs showed 89% DPPH scavenging at 100 µg/mL with IC₅₀ = 42.93 µg/mL, comparable to seagrass extract (76.9%, IC₅₀ = 42.40 µg/mL) and BHT (IC₅₀ = 42.38 µg/mL). In nitric oxide assays, the NPs displayed dose-dependent inhibition, confirming effective free-radical scavenging capacity. The antibacterial activity of Co₃O₄ NPs was also assessed by the well diffusion method against pathogenic bacteria Streptococcus mutans, Pseudomonas aeruginosa, Bacillus subtilis, and Escherichia coli. Co₃O₄ NPs showed strong antibacterial activity with larger inhibition zones against both E. coli and B. subtilis. and strains compared to the seagrass extract. The enhanced efficacy highlights the potential of NPs as effective antimicrobial agents. This research emphasizes the novelty of marine plant extracts for the use as sustainable reducing and stabilizing agents in the synthesis of nanoparticles with respect to environmentally-friendly chemical routes. These results proposed that as-prepared green-synthesized Co₃O₄ NPs can be as potent antioxidants and antibacterial agents for biomedical and environmental uses.

Decadal change (2015-2025) in seagrass cover, species composition and ecosystem quality in eastern Bintan marine protected area, Indonesia.

The coastal waters of West Sekotong possess significant potential in fisheries and marine resources. Seagrass is one of the key biotas contributing nutrients to support the fertility of surrounding waters. This study, conducted from May to July 2021 aimed to identify seagrass species and assess the health status of seagrass bed based on percentage cover and ecological indices. The research method used was purposive sampling with three research stations and systematic random sampling with transects. Based on the research that has been conducted, the following results were obtained seven seagrass species from two families. Hydrocharitaceae families (Enhalus acoroides, Thalassia hemprichii, Halophila ovalis, Halophila minor) and Cymodoceaceae families (Cymodocea rotundata, Cymodocea serrulata, Halodule pinifolia). The highest species density was H. pinifolia (119.47 ind/m²), with the highest important value index at station 1 (H. pinifolia 89%), station 2 (T. hemprichii 205%), and station 3 (E. acoroides 300%). Station 1 had the highest diversity and uninformity index, while station 3 was dominated by single species. Seagrass cover ranged from 31–48.33%, indicating unhealthy conditions, although environmental parameters remained within suitable ranges for seagrass growth.

Seagrass ecosystems play a crucial role in maintaining coastal environmental stability, yet their presence in Pahawang Island shows a declining trend due to human activity pressures and changes in aquatic conditions. This study aims to describe the structure of the seagrass community and analyze its correlation with environmental parameters at four stations with different characteristics. Seagrass data collection was conducted using the transect-quadrant method to measure coverage, density, and species composition, while environmental parameters observed included temperature, salinity, pH, dissolved oxygen (DO), current, and water clarity. The results showed the presence of three seagrass species, namely Enhalus acoroides, Thalassia hemprichii, and Halodule uninervis, with varying coverage and density across locations; the best condition was found at the natural station and the lowest at the pier area. The diversity index was classified as low, while uniformity and dominance varied according to human activity levels around the water. PCA analysis indicated that salinity, current, clarity, DO, pH, and temperature contribute differently at each station and collectively influence the variation in the seagrass community. These findings emphasize that differences in environmental quality and the intensity of anthropogenic disturbances are key factors determining the condition of the seagrass beds in Pahawang Island. Keywords: Seagrass, Water Quality, Community Structure, PCA, Pahawang Island

Abstract. Tebaiy S, Manan J, Manangkalangi E, Suruan SS, Mampioper DC, Musyeri P, Manuputty A, Sawaki D. 2025. Seagrass ecosystems as habitats for target fish (Siganidae and Lethrinidae) in the waters of the Aruri Islands, Papua Province, Indonesia. Biodiversitas 26: 5726-5736. This study aimed to identify seagrass species, analyze their composition, percentage, and average cover, and determine the distribution and composition of fish species within seagrass ecosystems. Additionally, the relationships among various species and the presence of target fish, namely Siganidae and Lethrinidae, were examined. The research was conducted from November to December 2022 at three locations: Rayori Village, Nyambarai Village, and Munsaki Island in the Aruri Islands, Supiori District, Papua Province, Indonesia. Seagrass sampling employed the quadrat transect method modified from the Seagrass Watch protocol, while fish samples were collected using gill nets with the circle method. The results revealed the presence of six seagrass species in the study area, namely Cymodocea rotundata, Enhalus acoroides, Halodule pinifolia, Halophila ovalis, Oceana serrulata, and Thalassia hemprichii. Target fish, Siganus sp. and Lethrinus sp. were found at all observation sites, with 139 and 9 individuals, respectively. Furthermore, T. hemprichii showed a clear relationship with the presence of Siganus sp. and Lethrinus sp. indicating its essential role in seagrass ecosystems as a habitat for these target fish species. This study's findings underscore the crucial role of T. hemprichii in seagrass ecosystems and its implications for the conservation of these vital habitats in the Supiori District.

A comprehensive assessment of seagrass morphometry and associated meiofaunal communities was conducted in South Andaman Island from January to March 2020. Three seagrass species, Thalassia hemprichii, Halophila ovalis, and Halodule pinifolia, were sampled fortnightly at two sites. Morphometric analysis indicated broad similarity among species, except for leaf length, which varied significantly. Halophila ovalis supported the highest meiofaunal abundance(191 individuals), followed by T. hemprichii (176) and H. pinifolia (104). Meiofauna were distributed across the root, stipe, and leaf regions of all species, with nematodes and harpacticoid copepods dominating the communities. Key taxa such as Robertsonia robusta, Elphidium sp., Calcarina sp., and Sorites sp. occurred consistently across all seagrasses. Statistical analyses revealed no significant differences in meiofaunal community composition among the three species, suggesting a relatively uniform distribution. However, strong correlations (r = 0.98) indicated subtle variations in community structure. Environmental variables exerted differential influences on meiofaunal groups: air temperature showed strong positive associations with Oligochaeta and Foraminifera, whereas dissolved oxygen exhibited strong negative correlations with several taxa, particularly Polychaeta and Tanaidacea. This study highlights the complex interactions between seagrass morphometry, environmental factors, and meiofaunal assemblages in South Andaman Island. Although overall community composition appeared uniform, the subtle species-specific associations observed here emphasize the need for broader spatial and temporal investigations to better understand the ecological processes shaping these critical marine habitats.

Abstract. Tebaiy S, Manan J, Manangkalangi E, Suruan SS, Mampioper DC, Musyeri P, Manuputty A, Sawaki D. 2025. Seagrass ecosystems as habitats for target fish (Siganidae and Lethrinidae) in the waters of the Aruri Islands, Papua Province, Indonesia. Biodiversitas 26: 5726-5736. This study aimed to identify seagrass species, analyze their composition, percentage, and average cover, and determine the distribution and composition of fish species within seagrass ecosystems. Additionally, the relationships among various species and the presence of target fish, namely Siganidae and Lethrinidae, were examined. The research was conducted from November to December 2022 at three locations: Rayori Village, Nyambarai Village, and Munsaki Island in the Aruri Islands, Supiori District, Papua Province, Indonesia. Seagrass sampling employed the quadrat transect method modified from the Seagrass Watch protocol, while fish samples were collected using gill nets with the circle method. The results revealed the presence of six seagrass species in the study area, namely Cymodocea rotundata, Enhalus acoroides, Halodule pinifolia, Halophila ovalis, Oceana serrulata, and Thalassia hemprichii. Target fish, Siganus sp. and Lethrinus sp. were found at all observation sites, with 139 and 9 individuals, respectively. Furthermore, T. hemprichii showed a clear relationship with the presence of Siganus sp. and Lethrinus sp. indicating its essential role in seagrass ecosystems as a habitat for these target fish species. This study's findings underscore the crucial role of T. hemprichii in seagrass ecosystems and its implications for the conservation of these vital habitats in the Supiori District.

Eco-friendly synthesis and characterization of copper nanoparticles using Thalassia hemprichii seagrass: Evaluation of antioxidant and antibacterial activities

Fish communities in seagrass ecosystems are known to play a vital role in maintaining coastal biodiversity due to the provision of essential habitat, food, and shelter. This study investigates the structure of fish communities associated with seagrass habitats and evaluates the influence of seagrass density on fish abundance in the coastal waters of Pahawang Island, Lampung. Field surveys were conducted in October 2025 at three purposively selected stations. Fish assemblages were sampled using gill nets, while seagrass density and coverage were quantified along transect–quadrat lines. Three seagrass species Enhalus acoroides, Thalassia hemprichii, and Halodule uninervis were identified, exhibiting spatial variability in coverage ranging from 18% to 44%. A total of 87 individual fishes, comprising nine species, were recorded, with Siganus spp. being the most abundant genus. Diversity, evenness, and dominance indices indicated a stable and well-balanced community structure. Statistical analyses revealed a significant positive relationship between seagrass cover and fish abundance, underscoring the ecological importance of seagrass meadows in supporting coastal fish populations. These findings provide critical insights for enhancing management and conservation strategies in the marine environment of Pahawang Island.

Seagrass beds are coastal ecosystems that have important ecological functions as a provider of habitat, food sources, protection, and reproductive areas for various marine life including Echinoderms. This study aims to analyze the diversity of Echinoderms and their relationship with seagrass distribution in Kiama Beach, Melonguane District, Talaud Islands Regency. The research was conducted in the intertidal zone at three stations using the exploration method with purposive sampling technique. Each station is divided into three plot installation zones measuring 4 × 4 meters, with observations made at low tide. Environmental parameters (temperature and pH), type and number of Echinoderm individuals, and seagrass species were recorded and analyzed using the Shannon-Wiener diversity index and product moment correlations. The results showed that the Echinoderma community consists of two classes and five species: Archaster typicus, Linckia laevigata, Culcita novagueniae, Holothuroidea scabra, and Holothuroidea forskali, with the Asteroidea class dominating (75%). The diversity index (H') value was relatively low at all stations with a range of 0.6261–0.6631. Seagrass beds consist of five species, namely Halophila ovalis, Cymodocea rotundata, Thalassia hemprichii, Halodule uninervis, and Syringodium isoetifolium, with the highest abundance found in Halophila ovalis. Correlation results showed a strong to very strong relationship between the abundance of Echinoderms and certain seagrass types (r = 0.77–0.99) as well as a strong correlation at the overall level of the station (r = 0.74). This study confirms that the presence and abundance of Echinoderms is greatly influenced by the density and composition of seagrass species. These findings provide important baseline data for the management and conservation of seagrass beds as a support for the sustainability of coastal biodiversity.

Seagrasses are important primary producers that support marine life. The litter, or fallen leaves, of seagrasses plays a vital role as a source of nutrients in coastal ecosystems. One of the seagrass ecosystems found in Inner Ambon Bay is located in Tanjung Tiram. Studies on litter production have been extensively conducted in mangrove ecosystems; however, in the Maluku region, only one such study has been reported, and no research on seagrass litter production has yet been documented. Litter production serves as an important indicator for assessing coastal ecosystem functioning and blue carbon stocks. Therefore, this study aimed to analyze the litter production of two seagrass species, Enhalus acoroides and Thalassia hemprichii, in the Tanjung Tiram waters of Inner Ambon Bay. The research was conducted from July to August 2025 in the Tanjung Tiram seagrass ecosystem, Ambon City. Litter production was measured using the cage method, constructed from a 3 mm mesh nylon net with dimensions of 0.5 × 0.5 m. Prior to cage installation, the substrate was cleared of existing litter material and benthic organisms, and seagrass density was subsequently estimated. The study period lasted for 3 × 24 hours, with floating and sunken litter collected every 24 hours. The collected litter was oven-dried and weighed to determine dry biomass. Results showed that both E. acoroides and T. hemprichii produced higher amounts of sunken litter (0.0082 g dry weight/shoot/day and 0.0063 g dry weight/shoot/day, respectively) compared to floating litter (0.0062 g dry weight/shoot/day and 0.0028 g dry weight/shoot/day, respectively). The total litter production of E. acoroides (0.0144 g dry weight/shoot/day) was higher than that of T. hemprichii (0.0091 g dry weight/shoot/day).

Amahai and Sehati are located in Central Maluku Regency, Maluku Province, which has a diversity of seagrass species spread across the intertidal and subtidal zones. The purpose of this study was to determine (1) the distribution of seagrass in the intertidal and subtidal zones, (2) the diversity value of seagrass species in the intertidal and subtidal zones. The study was conducted from 8 to 21 December 2024 using the linear quadrat transect method. 3 transects were made in Amahai waters and 5 transects in Sehati waters. Each transect consisted of 10 quadrats measuring 1x1 meter. The study found 3 types of seagrass, namely Cymodocea serrulata, Halodule pinifolia, and Halophila ovalis in the intertidal zone and Enhalus acoroides and Thalassia hemprichii seagrass species were found in the subtidal zone. The Physico-Chemical Factors of Amahai waters in the intertidal zone found seawater temperature of 280C, salinity of 27.40/00, and pH of 7.4. The Physico-Chemical factors of Amahai waters in the subtidal zone are, temperature 280C, salinity 29.10/00, and pH 7.3. The average physico-chemical factors in the tidal zone in Sehati coastal waters are, sea air temperature of 290C, salinity of 26.50/00, and sea air pH of 7.5. The average physico-chemical factors in the subtidal zone of Amahai waters are, temperature 290C, salinity 28.40/00, and pH 7.5. The distribution pattern of seagrass in the intertidal and subtidal zones in Amahai and Sehati waters is relatively even. The value of the seagrass species diversity index in the tidal zone of Amahai (1.487) and Sehati waters (1.359) is classified as moderate. The value of the seagrass species diversity index in the subtidal zone of Amahai (0.675) and Sehati (0.693) is classified as moderate. This research contributes to the coastal ecosystem to improve the welfare of the community around Amahai Village and Sehati Village.

Abstract. Jamil K, Najih MR, Hawati, Suleman Y, Mustafa, Awaluddin, Rahmaniar N, Aisyah N. 2025. Mapping seagrass distribution in Gili Mantra National Conservation Area, Indonesia, using Sentinel 2A imagery. Biodiversitas 26: 4324-4333. Indonesia, an archipelagic country dominated by coastal areas, possesses high biodiversity and abundant natural resources. Among these, seagrass ecosystems play a vital ecological role by providing habitat, supporting marine biodiversity, and stabilizing coastal sediments. Gili Trawangan Island, located in North Lombok District, West Nusa Tenggara Province, Indonesia, is surrounded by extensive seagrass beds. However, increasing anthropogenic activities have altered environmental conditions, leading to reduced water quality and degradation of coastal ecosystems, including seagrass habitats. This study aimed to assess the distribution and composition of seagrass beds on Gili Trawangan Island over the past two years. Field surveys were conducted from January to March 2024 using a quadrat-transect method, with 100 m transect lines laid perpendicular to the coastline and sampling performed with 50×50 cm2 frames at 10 m intervals. Satellite imagery from Sentinel-2A was also processed to complement field observations. Three seagrass species were recorded: Cymodocea rotundata, Thalassia hemprichii, and Halodule pinifolia. Cymodocea rotundata showed the highest density at all four sampling stations, whereas T. hemprichii exhibited the lowest. Seagrass coverage declined markedly from approximately 75 ha in 2022 to 44 ha in 2023. These findings provide essential baseline information for the sustainable conservation and management of seagrass ecosystems in Gili Trawangan.

This study aims to describe the diversity of seagrass species found on the coast of Malanggo Pesisir Village, South Tinombo District, Parigi Moutong Regency. This study used a quantitative descriptive method with a linear quadratic transect technique conducted at three observation stations. Each station was observed to determine the type and number of seagrass individuals found. The data obtained were then analyzed using the Shannon-Wiener diversity index (H’) to determine the level of seagrass species diversity at the study site. The results showed that there were five seagrass species found, namely Enhalus acoroides, Thalassia hemprichii, Halodule pinifolia, Halodule uninervis, and Cymodocea rotundata. The total number of seagrass individuals obtained was 8,548 with a diversity index value (H’) of 1.518 which is classified as moderate. This value indicates that the seagrass ecosystem in the waters of Malanggo Pesisir Village is in a relatively stable condition and is able to support the existence of several seagrass species. However, human activities around the coastal area have the potential to put pressure on the balance of the seagrass ecosystem. Therefore, efforts are needed to manage and preserve seagrass ecosystems sustainably so that their ecological function is maintained.

Megagastropoda are well associated with seagrass ecosystems. Megagastropoda play a role in the food chain in seagrass beds as detritus eaters. The purpose of this study was to analyze the relationship between megagastropoda abundance and seagrass density in the seagrass beds of Malahing Village, Bontang City, East Kalimantan. This study was conducted from October 2024 to February 2025. The sampling stations consisted of 4 stations and each station consisted of 3 sub-stations. Sampling used the purposive sampling method. Megagastropoda and seagrass stand sampling used a 50x50 cm square frame. Water parameter measurements were carried out in situ and ex situ and basic substrate sampling used a corer. Megagastropoda data analysis included abundance, relative abundance of species, diversity index, uniformity and dominance. Seagrass data analysis included density and relative density of species. The relationship between megagastropoda abundance and seagrass density used a Pearson's Product Moment correlation test. Megastropoda found as many as 14 species of megagastropoda namely Strombus urceus, Cypraea tigris, Trochus maculatus, Cymbiola innexa, Nassaridus dorsatus, Polinices tumidus, Rhinoclavis vertagus, Natica vitellus, Vasum turbellinus, Scaphander watsoni, Astralium calcar, Conus sp., Cypraea cervinetta, and Strombus gibberulus, and 2 species of seagrass were found namely Enhalus acoroides and Thalassia hemprichii. The relationship between the abundance of megagastropoda and the density of E. acoroides is very strongly positively correlated.

Pillucina vietnamica influence on mitigating nutrients stress in tropical seagrass Thalassia hemprichii.

Dugongs (Dugong dugon) are specialized marine herbivores that primarily feed on seagrass species such as Thalassia hemprichii, Halophila ovalis, and Halodule uninervis. Their feeding behavior, including grazing and excavating, is influenced by seagrass morphology and sediment type. Dugongs exhibit high digestive efficiency (>90%) when consuming low-fiber seagrasses, which support consistent weight gain and health maintenance. While terrestrial forage species like Brachiaria, Pennisetum purpureum, and Leucaena leucocephala are widely used in ruminant nutrition, their suitability for dugongs remains unproven due to significant differences in palatability, digestive physiology, and ecological compatibility. Captive feeding trials have demonstrated dugongs' strong preference for native seagrasses, supported by nutritional analyses indicating high digestibility and adequate protein content. Ethical and ecological concerns further limit the use of non-native diets and domestication practices. Conservation and ex-situ management strategies must prioritize habitat protection, forage availability, and species-specific nutritional requirements. This review underscores the critical role of seagrass ecosystems in dugong survival and cautions against introducing alternative forages without thorough ecological and physiological evaluation.

Penelitian ini bertujuan untuk memetakan sebaran stok karbon pada padang lamun di tiga lokasi berbeda di Teluk Doreri, Kabupaten Manokwari, yaitu Pantai BLK, Pulau Lemon, dan Tanjung Manggewa. Ekosistem lamun berperan penting sebagai penyerap karbon biru (blue carbon), yang menyimpan karbon baik di atas maupun di bawah substrat. Metode yang digunakan dalam penelitian ini meliputi survei langsung, analisis biomassa lamun menggunakan metode Loss on Ignition, serta pemetaan spasial dengan perangkat lunak ArcGIS. Hasil penelitian menunjukkan terdapat tujuh jenis lamun, dengan Cymodocea rotundata dan Thalassia hemprichii sebagai spesies dominan. Stok karbon tertinggi tercatat di Pulau Lemon sebesar 0,61 metrik ton, sementara terendah di Tanjung Manggewa sebesar 0,14 metrik ton. Temuan ini menunjukkan bahwa aktivitas antropogenik yang rendah berdampak positif terhadap kapasitas penyimpanan karbon pada ekosistem lamun. Data ini diharapkan menjadi acuan dalam pengelolaan ekosistem pesisir berbasis konservasi dan mitigasi perubahan iklim.