Search Results (61)

Dugongs (Dugong dugon), classified as vulnerable marine mammals, are increasingly impacted by infectious diseases, yet the role of septicemia and disseminated intravascular coagulation (DIC) in their mortality remains uncharacterized. This study aimed to investigate the pathological and microbiological features associated with an acute mortality event in a juvenile dugong during rehabilitation in southern Thailand. Comprehensive histopathological and microbiological analyses were conducted on tissue samples collected postmortem. Bacterial isolation and identification were performed using standard culture techniques and the VITEK-2 system. Histological examination revealed multisystemic lesions, including fibrin thrombi, hemorrhage, hepatocellular degeneration, pancreatic necrosis, lymphoid depletion, and neuronal damage. Oxidative stress and DNA damage were confirmed in brain tissues through immunofluorescence detection of 4-hydroxynonenal (4-HNE) and 8-hydroxy-2′-deoxyguanosine (8-oxodG). Achromobacter xylosoxidans, an opportunistic pathogen, was isolated from multiple organs, consistent with acute systemic infection. These findings represent the first evidence of septicemia-associated DIC in dugongs caused by A. xylosoxidans, highlighting a previously undocumented cause of mortality in dugongs. The results emphasize the role of opportunistic bacteria in triggering oxidative damage and coagulopathy and underscore the importance of early detection and targeted therapeutic strategies to improve survival in stranded or rehabilitated dugongs. Full article

The accurate prediction of water quality parameters is essential for effective pollution control and resource management. This study presents a hybrid AI-remote sensing framework for forecasting water quality in the Gulf of Thailand, which combines Sentinel-2 imagery with Support Vector Machine (SVM) and Autoregressive Integrated Moving Average (ARIMA) models. Our approach achieves a 5.4× increase in data coverage over traditional methods, demonstrating the effectiveness of machine learning in environmental monitoring. Predictive accuracy was evaluated across Support Vector Machine (SVM), ARIMA, and Amazon Forecast models. Results indicate that SVM, optimised through RBF kernel and grid search, outperforms other models for Chlorophyll-a (RMSE: 1.8), while ARIMA exhibits superior performance for Secchi Depth (RMSE: 0.2) and Trophic State Index (RMSE: 0.8). The study also introduces Aqua Sight, a web-based visualisation tool built on Google Earth Engine, enabling stakeholders to access real-time water quality forecasts. These findings highlight the potential of integrating satellite-derived data with machine learning to enhance early warning systems and support environmental decision making in coastal ecosystems. Full article

The degradation of marine and coastal resources, caused mainly by human activities, underscores the urgent need for conservation. In waters around the Sichang Islands, the Bryde’s whale is listed as an endangered marine species. The extensive human activities in this area have raised serious concerns about the possible negative influence on this species. To conserve the species effectively and efficiently, we need to understand where it distributes and how human activities influence its distribution. For this purpose, we use spatial modeling techniques alongside diverse databases encompassing various spatial and ecological factors to analyze the distribution of, and human activities’ impact on, the Bryde’s whale (Balaenoptera edeni) in the Sichang Islands, Thailand. We also use the MaxEnt model to predict habitat suitability and the result reveals key factors influencing whale occurrence across seasons. During the dry season, TSS (32.8%), chlorophyll-a (20.1%), and DO (15.9%) levels play significant roles, while DO (29.9%), NH₃ (29.4%), and distance to shore (13.3%) are crucial in the wet season. Furthermore, the Species Risk Assessment (SRA) model indicates the mooring area (14.95%) is the high-risk area for the Bryde’s Whale, particularly during the wet season. In contrast, moderate risks are observed during the dry season, notably in fishing zones (99.68%) and mooring areas (99.28%). The study also highlights that the factors mentioned above influence prey availability and habitat suitability for the Bryde’s whale and identifies potential threats posed by human activities, such as fishing and other maritime operations, that are likely to decrease water quality and prey abundance. These results are useful information for identifying sensitive areas and measures for risk mitigation, thus supporting the development of MSP or MPA plans. Full article

Biomonitoring and environmental impact assessment of marine ecosystems are important for the effective management of petroleum platform activity. Eukaryote biodiversity in water and sediment near petroleum platforms in the Gulf of Thailand was surveyed using environmental DNA (eDNA) based on 18S ribosomal DNA variable region 4 (18S rDNA-V4), the full-length 18S rDNA gene (18S rDNA-FL), and cytochrome c oxidase subunit 1 (COI). Water and sediment samples were collected from three platforms. The water sample was also collected from a reference site located farther south, away from the platforms. Both 18S rDNA markers outperformed COI. A total of 1144 and 889 species were found in water and sediment when analyzed by 18S rDNA-V4, and 519 species were found in sediment when analyzed by 18S rDNA-FL. Only 99 species were found in water samples when analyzed by COI. Alpha-diversity (Shannon and Simpson Evenness) indices were significantly different in water (p < 0.05), but not in sediment (p > 0.05). Beta-diversity (PCoA and NDMS) revealed significant species components between different petroleum platforms (p < 0.01). Species distribution revealed biological connectivity between eukaryotes from different platforms suggesting the importance of platforms on ecological impacts. This study also illustrates the possible application of eDNA for monitoring ecological toxicity around petroleum platforms. Full article

High-resolution (2 km), high-frequency (hourly) SST data of the Advanced Himawari Imager (AHI) flown onboard the Japanese Himawari-8 geostationary satellite were used to derive the monthly climatology of temperature fronts in the South China Sea. The SST data from 2015 to 2022 were processed with the Belkin–O’Reilly algorithm to generate maps of SST gradient magnitude GM. The GM maps were log-transformed to enhance contrasts in digital maps and reveal additional features (fronts). The combination of high-resolution, cloud-free, four-day-composite SST imagery from AHI, the advanced front-preserving gradient algorithm BOA, and digital contrast enhancement with the log-transformation of SST gradients allowed us to identify numerous mesoscale/submesoscale fronts (including a few fronts that have never been reported) and document their month-to-month variability and spatial patterns. The spatiotemporal variability of SST fronts was analyzed in detail in five regions: (1) In the Taiwan Strait, six fronts were identified: the China Coastal Front, Taiwan Bank Front, Changyun Ridge Front, East Penghu Channel Front, and Eastern/Western Penghu Islands fronts; (2) the Guangdong Shelf is dominated by the China Coastal Front in winter, with the eastern and western Guangdong fronts separated by the Pearl River outflow in summer; (3) Hainan Island is surrounded by upwelling fronts of various nature (wind-driven coastal and topographic) and tidal mixing fronts; in the western Beibu Gulf, the Red River Outflow Front extends southward as the Vietnam Coastal Front, while the northern Beibu Gulf features a tidal mixing front off the Guangxi coast; (4) Off SE Vietnam, the 11°N coastal upwelling gives rise to a summertime front, while the Mekong Outflow and associated front extend seasonally toward Cape Camau, close to the Gulf of Thailand Entrance Front; (5) In the Luzon Strait, the Kuroshio Front manifests as a chain of three fronts across the Babuyan Islands, while west of Luzon Island a broad offshore frontal zone persists in winter. The summertime eastward jet (SEJ) off SE Vietnam is documented from five-day mean SST data. The SEJ emerges in June–September off the 11°N coastal upwelling center and extends up to 114°E. The zonally oriented SEJ is observed to be located between two large gyres, each about 300 km in diameter. Full article

Coastal erosion is a critical environmental challenge in the Upper Gulf of Thailand, driven by both natural processes and human activities. This study analyzes 35 years (1988–2023) of shoreline changes using geoinformatics, machine learning algorithms (Random Forest, Support Vector Machine, Maximum Likelihood, Minimum Distance), and the Digital Shoreline Analysis System (DSAS). The results show that the Random Forest algorithm, utilizing spectral bands and indices (NDVI, NDWI, MNDWI, SAVI), achieved the highest classification accuracy (98.17%) and a Kappa coefficient of 0.9432, enabling reliable delineation of land and water boundaries. The extracted annual shorelines were validated with high accuracy, yielding RMSE values of 13.59 m (2018) and 8.90 m (2023). The DSAS analysis identified significant spatial and temporal variations in shoreline erosion and accretion. Between 1988 and 2006, the most intense erosion occurred in regions 4 and 5, influenced by sea-level rise, strong monsoonal currents, and human activities. However, from 2006 to 2018, erosion rates declined significantly, attributed to coastal protection structures and mangrove restoration. The period 2018–2023 exhibited a combination of erosion and accretion, reflecting dynamic sediment transport processes and the impact of coastal management measures. Over time, erosion rates declined due to the implementation of protective structures (e.g., bamboo fences, rock revetments) and the natural expansion of mangrove forests. However, localized erosion remains persistent in low-lying, vulnerable areas, exacerbated by tidal forces, rising sea levels, and seasonal monsoons. Anthropogenic activities, including urban development, mangrove deforestation, and aquaculture expansion, continue to destabilize shorelines. The findings underscore the importance of sustainable coastal management strategies, such as mangrove restoration, soft engineering coastal protection, and integrated land-use planning. This study demonstrates the effectiveness of combining machine learning and geoinformatics for shoreline monitoring and provides valuable insights for coastal erosion mitigation and enhancing coastal resilience in the Upper Gulf of Thailand. Full article

The multiple-tentacle box jellyfish, Chironex indrasaksajiae (Sucharitakul, 2017) and Chiropsoides buitendijki (Horst, 1907), are venomous species found in Thai waters. They are responsible for numerous envenomations through their stinging organelles, nematocysts. These specialized microscopic structures discharge venom, yet detailed knowledge of their types and morphology in these species remains limited. This study updates the characterization of nematocyst types and features in C. indrasaksajiae and C. buitendijki using light and scanning electron microscopy for detailed examination. Four distinct nematocyst types were identified: banana-shaped microbasic p-mastigophores, oval-shaped microbasic p-rhopaloids, sub-spherical microbasic p-rhopaloids, and rod-shaped isorhizas. In C. indrasaksajiae, banana-shaped microbasic p-mastigophores exhibited significant intraspecific variability, ranging from 30.26 µm to 102.56 µm in length and 6.42 µm to 17.01 µm in width. Conversely, C. buitendijki showed a narrower size range, 72.17 µm to 98.37 µm in length and 10.73 µm to 16.48 µm in width, based on multiple individuals. The size ranges for the other nematocyst types were consistent across both species. This study enhances the understanding of nematocyst morphology in these box jellyfish, providing a foundation for further research on venom delivery mechanisms and improved management of jellyfish envenomations in Thai waters. Full article

Marine debris (MD) causes significant threats to marine ecosystems. However, limited research addresses its transport of MD in tropical shallow semi-enclosed seas. This study applied a validated 3D hydrodynamic model and a particle tracking model to simulate the seasonal distribution of floating marine debris (FMD) originating from major river mouths in the vicinity of the Gulf of Thailand (GoT). The aim was to examine seasonal distribution patterns and variations influenced by sea surface circulation. Simulated particles were released every six hours from 12 river mouths and tracked over three years. Results revealed that seasonal currents drive the distribution of debris between the eastern and western regions, as well as its export and import across the gulf. The upper Gulf of Thailand (UGoT) exhibited the highest concentration of debris, with around 50% of the total released particles ending up onshore across the GoT, varying seasonally. An analysis showed that 74% of the debris released within the gulf remains there. Additionally, the GoT receives approximately 10% of the debris from rivers located outside its boundaries. Findings from this study suggest that the GoT, as an example of a tropical semi-enclosed sea, functions as both a sink and a source for FMD. These results could support the development of strategic seasonal cleanup frameworks, optimizing efforts during peak debris accumulation periods to enhance management efficiency. In addition, the mapping of debris distribution provides critical data for assessing and mitigating marine environmental impacts in the GoT. Full article

Nematocysts, specialized stinging cells in cnidarians, play a crucial role in both defense and prey capture, containing venomous, coiled tubes within a capsule. While box jellyfish are recognized as a medical threat, information on the nematocysts of species like Gershwinia thailandensis and Morbakka sp. from Thai waters remains sparse. This study explores the types and morphology of nematocysts found in the tentacles of these species using light and scanning electron microscopy. We identified three nematocyst types: club-shaped microbasic p-mastigophores, oval isorhizas, and oval microbasic p-rhopaloids. Notably, significant differences in capsule sizes were observed, especially in the microbasic p-mastigophores and isorhizas. The discharge tubules tapered from the proximal to the distal ends, featuring arrow-shaped spines in a helical pattern. A distinct lancet structure was present in both microbasic p-mastigophores and p-rhopaloids. These findings suggest that variations in nematocyst size and morphology may be linked to evolutionary adaptations, functional roles, and venom toxicity. Further research into venom discharge mechanisms could offer valuable insights into the ecological and medical importance of these cnidarians. Full article

We used NASA’s high-resolution (1/48° or 2.3 km, hourly) Estimating the Circulation and Climate of the Ocean (ECCO) estimates of salinity at a 1 m depth from November 2011 to October 2012 to detect semi-diurnal and diurnal internal tides (ITs) in the Andaman Sea and determine their characteristics in three 2° × 2° boxes off the Myanmar coast (box A), central Andaman Sea (box B), and off the Thailand coast (box C). We also used observed salinity and temperature data for the above period at the BD12-moored buoy in the central Andaman Sea. ECCO salinity data were bandpass-filtered with 11–14 h and 22–26 h periods. Large variations in filtered ECCO salinity (~0.1 psu) in the boxes corresponded with near-surface imprints of propagating ITs. Observed data from the box B domain reveals strong salinity stratification (halocline) in the upper 40 m. Our analyses reveal that the shallow halocline affects the signatures of propagating semi-diurnal ITs reaching the surface, but diurnal ITs propagating in the halocline reach up to the surface and bring variability in ECCO salinity. In box A, the semi-diurnal IT characteristics are higher speeds (0.96 m/s) with larger wavelengths (45 km), that are closer to theoretical mode 2 estimates, but the diurnal ITs propagating in the box A domain, with a possible source over the shelf of Gulf of Martaban, attain lower values (0.45 m/s, 38 km). In box B, the propagation speed is lower (higher) for semi-diurnal (diurnal) ITs. Estimates for box C are closer to those for box A. Full article

Family Parvoviridae consists of small, non-enveloped viruses with linear, single-stranded DNA genomes of approximately 4-6 kilobases, subdivided into three subfamilies, Parvovirinae, Densovirinae, and Hamaparvovirinae, and unassigned genus Metalloincertoparvovirus. Parvoviruses of aquatic animals infect crustaceans, mollusks, and finfish. This review describes these parvoviruses, which are highly host-specific and associated with mass morbidity and mortality in both farmed and wild aquatic animals. They include Cherax quadricarinatus densovirus (CqDV) in freshwater crayfish in Queensland, Australia; sea star-associated densovirus (SSaDV) in sunflower sea star on the Northeastern Pacific Coast; Clinch densovirus 1 in freshwater mussels in the Clinch River, Virginia, and Tennessee, USA, in subfamily Densovirinae; hepatopancreatic parvovirus (HPV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV) in farmed shrimp worldwide; Syngnathid ichthamaparvovirus 1 in gulf pipefish in the Gulf of Mexico and parts of South America; tilapia parvovirus (TiPV) in farmed tilapia in China, Thailand, and India, in the subfamily Hamaparvovirinae; and Penaeus monodon metallodensovirus (PmMDV) in Vietnamese P. monodon, in unassigned genus Metalloincertoparvovirus. Also included in the family Parvoviridae are novel parvoviruses detected in both diseased and healthy animals using metagenomic sequencing, such as zander parvovirus from zander in Hungary and salmon parvovirus from sockeye salmon smolts in British Columbia, Canada. Full article

Through the integration of high-resolution hydrodynamic modeling and comprehensive field measurements, this study elucidates the intricate three-dimensional hydrographic characteristics of the eastern Gulf of Thailand (eGOT). In addition to the prevalent tidal currents dictating alternating flow along the northwestern and southeastern axes, our investigation reveals pronounced seasonal variations in mean currents, water temperature, and salinity within the eGOT, closely linked to the dynamics of the Asian–Australian monsoon system. During the southwest monsoon, mean currents exhibit a southeasterly trend, contrasting with a northwesterly pattern during the northeast monsoon. Lowest water temperatures occur during the latter, while the highest levels are observed during the 1st monsoon transition (April–March). Notably, salinity levels reach their lowest levels during the southwest monsoon and the 2nd monsoon transition (October), coinciding with the seasonal stratification of the water column and the emergence of a distinct stable along-the-shore northwesterly current with the average speed of 15 cm/s, defined here as the “Chanthaburi Coastal Current (CCC)”. Model experiments attribute the formation of the CCC to decreased salinity induced by direct rainfall, highlighting the significance of rainfall as a key factor influencing coastal water dynamics in tropical regions or areas experiencing high precipitation. Full article

Climate change is increasingly impacting both environments and human communities. Coastal regions in Thailand are experiencing more severe impacts, which vary based on the unique physical and socio-economic characteristics of each area. To assess the vulnerability of coastal regions in Thailand, this study focused on two provinces, Nakhon Si Thammarat (NST) and Krabi, each representing distinct coastal environments. NST, situated on the Gulf of Thailand’s east coast, has an agriculture-based economy, while Krabi, on the Andaman Sea’s west coast, relies heavily on tourism. The study utilized a multi-criteria decision analysis approach (MCDA) and GIS to analyze the Coastal Vulnerability Index at the sub-district level. The results revealed that, although NST was more vulnerable than Krabi to socio-economic factors such as the poverty rate and the number of fishery households, Krabi was much more vulnerable in the physical environment, including wave height, tidal level, coastal erosion, and slope. However, overall, Krabi exhibited high to the highest levels of coastal vulnerability, while NST displayed moderate to high levels. These findings provide valuable insights for policymakers and government agencies, aiding in the development of strategies to mitigate vulnerability and enhance the quality of life for local residents in both provinces. Full article

The external morphology and morphological variations of Sepiella inermis vary across regions, necessitating investigation. However, the histological information on the subcutaneous gland has been insufficient to describe it. In this study, specimens were systematically collected and characterized from the Gulf of Thailand. Regarding external morphology, female cuttlebones exhibit greater width and more pronounced curves compared to males, while males feature 17–19 white dots along the fin margins. The presence of the subcutaneous gland was discerned during the embryonic stage at stage 19. A histological study of the subcutaneous gland illustrated the structure and development of the gland in both embryonic and adult stages, with four layers of membranes covering the gland. In the adult stage, trabeculae are dispersed throughout the gland, whereas in the embryonic stage, they form four distinct lines. The morphometric analysis revealed significant differences between males and females (p < 0.05) and the morphological variations within both sexes across the seven study areas exhibit significant differences (p < 0.05). According to the discriminant analysis results, there were significant differences (p < 0.05) between the groups in Surat Thani Province. Examining the length–weight relationship between dorsal mantle length and body weight showed significant differences between the sexes, indicating an allometric growth. Full article

The aim of this study was to determine the contamination of lead (Pb), cadmium (Cd) and microplastic (MP)-like particles in bivalves and estimate the exposure of the Thai population to these contaminants due to bivalve consumption. Clams, mussels and cockles were purchased from five wholesale seafood markets located on the upper Gulf of Thailand during the period 2017–2019. Determinations of Cd and Pb in the bivalves were conducted using a graphite furnace atomic absorption spectrometer (GFAAS). Visualization was conducted using a stereomicroscope to investigate the morphology and content of MP-like particles in the bivalve samples. The average Pb contents in clams, mussels and cockles were 112, 64 and 151 µg/kg wet wt., respectively. The average Cd contents were 126, 107 and 457 µg/kg wet wt. for clams, mussels and cockles, respectively. The average number of MP-like particles in bivalve samples varied from not detected to 1.2 items/g wet wt. and not detected to 4.3 items/individual. The exposure to Pb, Cd and MP-like particles due to bivalve consumption varied between 0.005 and 0.29 µg/kg bw/day, 0.017 and 28.9 µg/kg bw/month and 0.015 and 27.5 items/person/day, respectively. There was no potential health risk of exposure to Pb and Cd due to bivalve consumption in any age group. However, a high consumption of cockles with high Cd levels (the worst-case scenario) in children may be of concern. Full article