Gordonia aquimaris sp. nov., a novel marine actinobacterium isolated from seawater in the upper gulf of Thailand.

An actinobacterium strain, SW21T, was isolated from seawater collected in the upper Gulf of Thailand. Cells were Gram-stain-positive, aerobic and rod-shaped. Growth was observed from 15 to 37 °C and at pH 6-8. Maximum NaCl for growth was 14 % (w/v). meso-Diaminopimelic acid, arabinose, galactose, glucose, rhamnose and ribose were detected in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside were detected as the phospholipids in the cells. The major menaquinones were MK-9(H2) and MK-7(H2). The major cellular fatty acids were C16 : 0, C18 : 1 ω9c, C18 : 0 and C18 : 010-methyl (TBSA). The 16S rRNA gene sequence data supported the assignment of strain SW21T to the genus Gordonia and showed that Gordonia mangrovi KCTC 49383T (98.7 %) was the closest relative. Moreover, the average nucleotide identity-blast (85.5 %) and digital DNA-DNA hybridization (30.7 %) values between strain SW21T and its closest neighbour were below the threshold values for delineation of a novel species. The combination of genotypic and phenotypic data indicated that strain SW21T is representative of novel species of the genus Gordonia. The name Gordonia aquimaris sp. nov. is proposed for strain SW21T. The type strain is SW21T (=TBRC 15691T=NBRC 115558T).

Preindustrial levels and temporal enrichment trends of mercury in sediment cores from the Gulf of Thailand.

Four sediment cores in the middle of Gulf of Thailand (GOT) and one core close to Bang Pakong River mouth were examined for total mercury (T-Hg) using direct thermal decomposition coupled with the atomic absorption spectrometry (DTD-AAS) method and acid digestion (acid-CVAAS) method, and sediment chronologies using 210Pb dating. T-Hg in the river mouth core ranged 44.49-52.76 µg/kg and higher than the cores from the middle of GOT (18.26-36.68 µg/kg). The age span obtained from the cores dated back to the 1940s with the sediment accumulation rates of 0.15-0.76 cm/year. The preindustrial levels of T-Hg showed an initial slow increase followed by a rapid elevation since the 1960s which marked the start of the industrialized period in the country. To this end, we posit that T-Hg in the GOT sediment can be attributed to not only land-based sources but also offshore activities including petroleum exploration and frequent accidental oil spills.

Feeding habits and seasonal trophic guilds structuring fish community in the bay mouth region of a tropical estuarine habitat.

Understanding trophic relationships of fish in estuarine ecosystem is an important element for sustainable resource management. This study examined the feeding habits of 29 dominant fish species, characterized the trophic guilds, assessed the impact of season and clarified the role of diets in structuring the fish community in the mouth region of Pattani Bay, Thailand. Samples of 5792 fishes collected monthly by gillnets from March 2019 to February 2020 were used for stomach content analyses. It was found that the number of food types and fullness index differed between fish taxa (P < 0.001). Most fishes were specialist feeders feeding on specific food components and were categorized into five trophic guilds: piscivore, shrimp-fish feeder, polychaete feeder, zooplanktivore and planktivore. Six species were piscivorous, considered as apex predators, that fed almost entirely on fishes. High diet overlaps among some species (>0.6) were recorded. Not much variation in seasonal guilds was observed: four guilds in the dry season, three in the moderate rainy season and four in the rainy season. Some species remained in the same guild the whole year round, but some fishes changed seasonally. Two fish communities from different regions of the bay were segregated based on feeding habits. The inner bay community comprised mainly copepod and plankton feeders, but there were more piscivores in the deeper bay mouth area. Results from this study help us to understand the feeding habits and trophic guilds of dominant fish species at the mouth of this tropical estuarine bay.

Marine bacterial communities in the upper gulf of Thailand assessed by Illumina next-generation sequencing platform.

BACKGROUND: The total bacterial community plays an important role in aquatic ecosystems. In this study, bacterial communities and diversity along the shores of the Upper Gulf of Thailand were first characterized. The association between bacterial communities and types of land use was also evaluated. RESULTS: The bacterial communities and diversity of seawater in the Upper Gulf of Thailand, with regard to types of land use, were first revealed by using Illumina next-generation sequencing. A total of 4953 OTUs were observed from all samples in which 554 OTUs were common. The bacterial communities in sampling sites were significantly different from each other. The run-off water from three types of land use significantly affected the community richness and diversity of marine bacteria. Aquaculture sites contained the highest levels of community richness and diversity, followed by mangrove forests and tourist sites. Seawater physicochemical parameters including salinity, turbidity, TSS, total N, and BOD5, were significantly different when grouped by land use. The bacterial communities were mainly determined by salinity, total N, and total P. The species richness estimators and OTUs were positively correlated with turbidity. The top ten most abundant phyla and genera as well as the distribution of bacterial classes were characterized. The Proteobacteria constituted the largest proportions in all sampling sites, ranging between 67.31 and 78.80%. The numbers of the Marinobacterium, Neptuniibacter, Synechococcus, Candidatus Thiobios, hgcI clade (Actinobacteria), and Candidatus Pelagibacter were significantly different when grouped by land use. CONCLUSIONS: Type of land use significantly affected bacterial communities and diversity along the Upper Gulf of Thailand. Turbidity was the most influential parameter affecting the variation in bacterial community composition. Salinity, total N, and P were the ones of the important factors that shaped the bacterial communities. In addition, the variations of bacterial communities from site-to-site were greater than within-site. The Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Verrucomicrobia, Euryarchaeota, Planctomycetes, Firmicutes, Deep Sea DHVEG-6, and Marinimicrobia were the most and common phyla distributed across the Upper Gulf of Thailand.

Genetic structure and diversity of green turtle (Chelonia mydas) in the Gulf of Thailand.

Background and Aim: The International Union for the Conservation of Nature and Natural Resources lists the green turtle as endangered. Green turtle nesting behavior in the Gulf of Thailand has decreased to <50% of the 1995 level. The population structure of green turtles in the Gulf of Thailand has not yet been studied. This study aimed to characterize the genetic diversity of green turtles in the Gulf of Thailand based on comparisons of mitochondrial DNA (mtDNA) control region with sequences of Indo-Pacific management units (MUs) and rookeries, to investigate population structures, and to explore phylogeographic relationships. Materials and Methods: Blood samples (1 mL each) from 91 stranded green turtles were collected from four parts of the Gulf of Thailand (eastern, upper, central, and lower). The control mtDNA region was amplified by polymerase chain reaction using LCM15382 and H950 primer. The obtained 384-bp or 770-bp sequences were analyzed for haplotype, clade, and haplotype and nucleotide diversities and were used to construct a phylogenetic tree and haplotype network diagram, respectively. In addition, we analyzed genetic differentiation within and among populations of green turtles in the Gulf of Thailand and between green turtles in the Gulf of Thailand and other Indo-Pacific MUs and rookeries. Results: In total, 12 (based on 384 bp) or 13 (based on 770 bp) haplotypes and two clades (clades VII and VIII) were identified, with nine or 10 haplotypes belonging to clade VIII and three haplotypes belonging to clade VII. Of the new haplotypes, four or five were identified and classified as clade VII (two haplotypes, for both fragment lengths) and clade VIII (two or three haplotypes, for 384 bp or 770 bp fragments, respectively). The overall haplotype and nucleotide diversity of green turtles in the Gulf of Thailand were high (0.755 ± 0.039 and 0.01146 ± 0.00248, respectively). Based on the analysis of molecular variance, green turtles in the Gulf of Thailand could be divided into two subpopulations (UC-Eastern Gulf of Thailand [UC-EGT] and lower Gulf of Thailand [LGT]). Comparisons with other MUs and rookeries in the Indo-Pacific showed that UC-EGT was not genetically different from the Peninsular Malaysia and Eastern Taiwan (Lanyu) MUs and the Terrangganu and Mersing rookeries, and LGT were not genetically different from Peninsular Malaysia, Sipadan, Brunei Bay, Eastern Taiwan (Lanyu), Scott Reef and Browse Island, and Gulf of Carpentaria MUs and the Perak, Perhentain Island, Redang, Pahang, and Vietnam rookeries. Conclusion: To the best of our knowledge, this is the first report to identify the haplotypes and clades of green turtles in the Gulf of Thailand and to show that the populations in the Gulf of Thailand not only present high genetic diversity but also have haplotypic endemism. Longer mtDNA fragments (770 bp) increased the resolution of the stock structure. Clade VII is a unique clade not only for Japan but also for Thailand and Malaysia, and CmP82 is a unique haplotype for both the Gulf of Thailand and Malaysia. Conservation and management of these populations are important to preserve the genetic diversity, biological diversity, and evolutionary potential of green turtles in the Gulf of Thailand.

Plastic ingestion by three species of Scylla (Brachyura) from the coastal areas of Thailand.

This study marked the first investigation into the presence of plastic particles in the stomachs of three mud crab species (Scylla olivacea, S. paramamosain and S. tranquebarica) collected across the Andaman Sea and the Gulf of Thailand. The highest number of plastic particles in the stomach of crab samples was polyethylene (PE) that contributed 88.5 %; while green was the predominant colour (60.3 %). Ingested particles recovered from the stomachs of crabs differed significantly between species and sites (p < 0.001). The average number of plastic particles per individual was 2.3 ± 8.6 in Scylla olivacea, 7.2 ± 16.9 in S. paramamosain, and 13.5 ± 48.9 in S. tranquebarica. Satun, revealed the highest number of plastic particles recovered from mud crabs, while the lowest number of plastic particles were from Pattani. To conclude, species of crab and site of collection plays a crucial factor in the propensity of plastic particles ingested by the genus Scylla mud crabs.

Population genetic structure and demographic history of short mackerel, Rastrelliger brachysoma, in the Gulf of Thailand.

The short mackerel Rastrelliger brachysoma (Bleeker 1851) is an important fish in the Gulf of Thailand (GoT). The biology of this species has been intensively studied, but its genetic diversity is little known. The genetic diversity, population genetic structure, and demographic history of this species in the GoT were studied using complete mt control region sequences. The CR sequences of 455 mackerel samples collected from 23 localities at four fishing grounds revealed 333 haplotypes with haplotype diversity (h) per population, ranging between 0.8933 and 1.000, with an average of 0.9781. In turn, the nucleotide diversity (µ) ranged between 0.0119 ± 0.0060 and 0.0333 ± 0.0174, with an average of 0.0220 ± 0.00059.A haplotype network analysis showed that all sequences segregated into two subgroups named, clade I and clade II. Two clades were separated by 26 mutational steps. Each clade formed star-like clusters with many haplotypes derived from a common haplotype. Moreover, an analysis of molecular variance (AMOVA) revealed no significant differences among the studied localities, suggesting the presence of a single population in the GoT. Pairwise differences between samples from different fishing regions also indicated no population structure. Both Tajima's D and Fu's FS statistics were highly significant for the two clades but nonsignificant for the entire population according to a mismatch distribution analysis. These results confirmed that both clades experienced demographic expansion. The estimated expansion times for clade I and clade II were 1,542.307 years (1.5423 ka BP) and 7,602.541 (7.6025 ka BP) years, respectively.

Increasing marine heatwaves in the Gulf of Thailand after the global warming hiatus.

Marine heatwaves (MHWs) have been reported often throughout the world, producing severe effects on marine ecosystems. However, the spatial pattern and trend of MHWs in the Gulf of Thailand (GOT) is still unknown. Based on high-resolution daily satellite data over a 40-year period from 1982 to 2021, changes in annual mean SST and MHW occurrences across the GOT are explored here. The results demonstrate that during a warming hiatus (1998-2009), annual mean SST in the GOT encountered a dropping trend, followed by an increasing trend during a warming reacceleration period (2010-2021). Although a warming hiatus and a warming reacceleration occurred in the annual mean SST after 1998, regional averaged SSTs were still 0.18 °C-0.42 °C higher than that for 1982-1997. Statistical distributions reveal that there was a significant shift in both annual mean SSTs and annual extreme hot SSTs. These changes have the potential to increase the frequency of MHWs. Further analysis reveals that MHW frequency has increased at a rate of 1.11 events per decade from 1982 to 2021, which is 2.5 times the global mean rate. For the period 2010-2021, the frequency and intensity of MHWs in the GOT have never dropped, but have instead been more frequent, longer lasting and extreme than those metrics of MHWs between 1982 and 2009. Furthermore, the findings highlight significant changes in the SST over the GOT that may lead us to change or modify the reference period of the MHW definition. The findings also suggest that heat transport and redistribution mechanisms in the GOT sea are changing. This study contributes to our understanding of MHW features in the GOT and the implications for marine ecosystems.

Occurrence of microplastics and ecological risk assessment during tidal changes in the Chao Phraya River estuary, Thailand.

River estuaries are specific transition zones that connect coastal and terrestrial environments and are recognized as primary conveyors for land-derived plastics to open oceans. The present study is the first to investigate tidal effects on microplastics (MPs) in the Chao Phraya River estuary. MPs (16-5000 µm) were collected from the water column during the changes in tidal current in order to analyze abundance, characteristics, and ecological risk. The abundance of MPs varied from 1.37 to 4.51 pieces/L and an average of 4.0 ± 3.8 pieces/L were found during the tidal cycle, which implied moderate to relatively high contamination when compared to other estuaries. Moreover, the average abundance of MPs during the low tide period was comparatively higher than that in other tidal phenomena. Morphological characteristics revealed that shape of fragments, shade of blue, size of 16-100 µm and PTFE is dominant in the MPs. The pollution load index (PLICPRE) was 5.98, which denoted that the Chao Phraya River estuary is polluted with MPs at a low contamination level. In contrast, the risk index (RICPRE) of MPs in the water column during the tidal cycle was 318.8, which indicated that the estuarine ecosystem of the Chao Phraya River is under considerable risk. In the present study, an ecological risk assessment was conducted for the Chao Phraya River estuary, which provides basic reference data for the management of pollution control related to MPs in the Chao Phraya River basin.

Investigation of the marine bacterial community along the coastline of the Gulf of Thailand.

The Gulf of Thailand provides many services to the Thai population, and human activities may influence the diversity of microorganisms in the seawater. Information of the microorganisms' profile which inhabit the coastline can be used to monitor the water quality. This study aimed to investigate the bacterial community in the waters along the coastline provinces, including Rayong, Chonburi, Prachuap Kiri Khan, and Nakhon Sri Thammarat. Seawater samples were collected at each site, and the conductivity, pH, salinity, temperature, and turbidity were measured. The samples were subjected to whole DNA extraction, 16S rRNA amplification, next-generation sequencing, and statistical analysis to identify the bacterial diversity and analyse the effects of water parameters on the bacterial community. The dominant bacterial phyla found were Proteobacteria, Bacteroidota, and Cyanobacteria. Spearman rank correlation analysis revealed a high correlation of Pseudoalteromonas, the NS5 marine group, Lachnospiraceae, Marinobacterium, Mariviven, and Vibrio with the seawater parameters. The predatory bacteria Peredibacter and Halobacteriovorax were reported among these bacterial communities for the first time in the Gulf of Thailand. Interestingly, Akkermansia, a novel candidate for next-generation probiotics to improve human health, was also found in the sample from Nakhon Sri Thammarat Province. Although the rich-ness and diversity of the bacterial communities differed among sampling sites, it is a possible source of many valuable bacteria for future use.

Effect of tidal current on the settling and accumulation of microplastics in the Chao Phraya River estuary, Thailand.

The deposition of MPs in a water column and surface sediment during a mixed spring tidal cycle of the Chao Phraya River estuary was investigated. The settling MPs during flood and ebb tides were collected by deploying traps at 3 m below the surface, while the settled MPs throughout the tidal cycle were collected by deploying traps at 1 m above the bottom. The settling rate of MPs was 2168 pieces/m2/h during highest to low tide, and 639 pieces/m2/h during high to lowest tide. The deposition rate of MPs after the end of the tidal cycle was 3172 pieces/m2/day, while the accumulation rate of MPs in the surface sediment was 1515 pieces/m2/day. The settling MPs tended to decrease inversely to the suspended solids and salinity. The major types of the deposited MPs were polyethylene (36 %) and polyamide (33 %), while that of the surface sediment was epoxy resin (80 %).

Species-specific eDNA assay development for enhanced box jellyfish risk management in coastal environments.

Human interaction with marine creatures holds both positive and negative dimensions. Coastal communities benefit from marine environments, relying on them for sustenance and livelihoods. Fishing activities support economies, and marine biodiversity contributes to overall ecosystem health. However, challenges like overfishing, habitat destruction, and pollution pose threats to both marine life and human communities. Recently, there has been widespread concern regarding the potential increase in jellyfish populations across global marine ecosystems, attributed mainly to environmental factors such as climate drivers and anthropogenic forces, or their complex interactions. Encounters with hazardous marine species, such as box jellyfish, exemplify the dangers associated with coastal activities. Unintended interactions may lead to stings, injuries, and even fatalities, necessitating proactive measures and advanced technologies. This study addresses the inadequacies of existing measures in preventing box jellyfish incidents by introducing environmental DNA (eDNA) assays for detecting the deadly Chiropsoides buitendijki and focuses on developing qPCR and dPCR-based eDNA assays. Emphasising prevention over treatment, the study establishes a proactive system to assess C. buitendijki distribution across 63 tourist beaches in the Gulf of Thailand. Comparative analysis highlights the superior performance of dPCR over qPCR and traditional surveys. The dPCR experiment yielded positive results for all eDNA samples collected at sites where C. buitendijki had previously been identified. Remarkably, the eDNA testing also detected positive results in 16 additional sample locations where no physical specimens were collected, despite reported jellyfish stings at some of these sites. These findings underscore the precision and efficacy of the proposed eDNA detection technology in the early detection and assessment of box jellyfish distribution. This advancement therefore not only aids ecological research but also serves as a valuable tool for safeguarding public health, providing an early warning system for potential jellyfish encounters. Balancing positive human-marine interactions with effective risk mitigation strategies is crucial for sustainable coexistence, the preservation of marine ecosystems, and human well-being.

Unraveling the physiological responses of morphologically distinct corals to low oxygen.

Background: Low oxygen in marine environments, intensified by climate change and local pollution, poses a substantial threat to global marine ecosystems, especially impacting vulnerable coral reefs and causing metabolic crises and bleaching-induced mortality. Yet, our understanding of the potential impacts in tropical regions is incomplete. Furthermore, uncertainty surrounds the physiological responses of corals to hypoxia and anoxia conditions. Methods: We initially monitored in situ dissolved oxygen (DO) levels at Kham Island in the lower Gulf of Thailand. Subsequently, we conducted a 72-hour experimental exposure of corals with different morphologies-Pocillopora acuta, Porites lutea, and Turbinaria mesenterina-to low oxygen conditions, while following a 12/12-hour dark/light cycle. Three distinct DO conditions were employed: ambient (DO 6.0 ± 0.5 mg L-1), hypoxia (DO 2.0 ± 0.5 mg L-1), and anoxia (DO < 0.5 mg L-1). We measured and compared photosynthetic efficiency, Symbiodiniaceae density, chlorophyll concentration, respiratory rates, primary production, and calcification across the various treatments. Results: Persistent hypoxia was observed at the study site. Subsequent experiments revealed that low oxygen levels led to a notable decrease in the maximum quantum yield over time in all the species tested, accompanied by declining rates of respiration and calcification. Our findings reveal the sensitivity of corals to both hypoxia and anoxia, particularly affecting processes crucial to energy balance and structural integrity. Notably, P. lutea and T. mesenterina exhibited no mortality over the 72-hour period under hypoxia and anoxia conditions, while P. acuta, exposed to anoxia, experienced mortality with tissue loss within 24 hours. This study underscores species-specific variations in susceptibility associated with different morphologies under low oxygen conditions. The results demonstrate the substantial impact of deoxygenation on coral growth and health, with the compounded challenges of climate change and coastal pollution exacerbating oxygen availability, leading to increasingly significant implications for coral ecosystems.

Hydrogeological environments and radon activities of saline geothermal hot spring sites located along eastern and western coastlines of southern Thailand.

Hydrogeological settings and natural radionuclides of saline geothermal fields along the coastlines of the Gulf of Thailand and Andaman Sea in Southern Thailand are currently not fully understood. Six saline geothermal springs have been discovered in Surat Thani Province (Southern Thailand's east coast); SR2, SR3, and SR7 sites; Krabi Province (Southern Thailand's west coast); KB2, KB3, and KB4 sites. Based on total dissolved solid contents, we divided the saline geothermal springs into three categories: a) slightly saline geothermal spring had only SR7 (1828 mg/L), b) moderately saline geothermal spring consisted of SR2 (10,196 mg/L) and KB3 (3448 mg/L), and c) very saline geothermal spring comprised SR3 (11,856 mg/L), KB2 (17,014 mg/L) and KB4 (18,070 mg/L). The major ions in the saline geothermal groundwater represent decreasing trends with the distance from the coastline. Stable isotope signatures (δ18O and δ2H) relative to the VSMOW plotted in comparison with the global meteoric water line and local meteoric water line are presumably of meteoric origin and influenced by seawater/brackish water. However, the SR7 and KB3 sites indicated that the isotopic signatures were mainly recharged by rainwater. Significantly, the Na-K-Ca-Mg geothermometer can reasonably estimate the reservoir temperatures for the five saline geothermal springs to be in the range of 120 °C (KB3) to 169 °C (SR2). While the SR7, the silica-quartz geothermometer is proposed of approximately 115 °C. However, the silica-chalcedony and other cation geothermometers fail to estimate suitable reservoir temperatures. On the other hand, the radon concentrations in the saline geothermal groundwater along the Gulf of Thailand and Andaman Sea were assessed by RAD7-H2O, which varied from 18.64 ± 0.96 kBq/m3 (KB2; Andaman Sea side) to 8507.48 ± 1.06 kBq/m3 (SR7; Gulf of Thailand side). A comparison of radon activity with the saltwater intrusion showed that the saline geothermal groundwater on the Gulf of Thailand side had higher levels than that at the Andaman Sea side. The deposition of Quaternary sediments combined with significant saltwater inflow enriched with radon resulted from the decay of uranium from both non-marine and coastal deposits related to granitic mountain weathering along the Gulf of Thailand. Radon concentrations in the geothermal groundwater were highly influenced by the local geological environment and coastal sediments.

Using environmental DNA to better inform decision making around decommissioning alternatives for offshore oil and gas infrastructure.

Artificial reefs are being utilised globally to aid in natural resource management, conservation, restoration or the creation of unique marine habitats. There is discussion around the optimal construction materials and designs for artificial reefs, the influences these have on biological communities, and the resulting ecological and social benefits. This discussion also includes the ecological value of repurposed marine infrastructure, such as decommissioned oil and gas platforms. Platforms often have an operational life spanning multiple decades, over which time they can develop extensive and unique community assemblages. The creation of artificial reefs by repurposing oil and gas platforms can have ecological, economic and sociological merit. However, with >12,000 platforms requiring decommissioning globally, there is the need for holistic assessment of biological communities associated with these platforms to inform the potential outcomes of different decommissioning options. We use environmental DNA metabarcoding (eDNA) of water, bio-foul and sediment samples to census broad eukaryotic diversity at eight platforms in the Gulf of Thailand (GoT) and five nearby soft sediment habitat locations. We sampled three target depths at sites (shallow, mid, deep) and detected 430 taxa at platforms, with higher diversity in shallow (near-surface) samples (313 taxa), compared to mid (30 m collection depth; 261 taxa) and deep (50 m; 273 taxa). Three percent of taxa were shared among all depths at platforms with distinct assembles at each depth. Introduced species are an ongoing risk for platforms, however the eDNA detected no known introduced species. While the eDNA data provide broad taxon coverage and significant assemblage patterns, ongoing sampling innovation, assay design and local reference material still require development to obtain the maximum benefit of the technique. This study highlights the versatility and scalability of eDNA metabarcoding to holistically census marine infrastructure and inform the management and potential conservation of extant communities.

Study of trace elements in stranded green turtles (Chelonia mydas), hawksbill turtles (Eretmochelys imbricata), and olive ridley turtles (Lepidochelys olivacea) in Gulf of Thailand and Andaman Sea.

The purpose of this study was to survey and compare the amounts of elements in the serum of stranded sea turtles from the Gulf of Thailand and the Andaman Sea. The sea turtles from the Gulf of Thailand had Ca, Mg, P, S, Se, and Si concentrations significantly higher than those in sea turtles from the Andaman Sea. The Ni and Pb concentrations of sea turtles from the Gulf of Thailand was higher, but not significantly so, than in sea turtles from the Andaman Sea. Rb was detected only in sea turtles from the Gulf of Thailand. This may have been related to the industrial activities in Eastern Thailand. The concentration of Br in the sea turtles from the Andaman Sea were significantly higher than those in sea turtles from the Gulf of Thailand. The higher serum concentration of Cu in hawksbill (H) and olive ridley turtles (O) than in green turtles may be due to hemocyanin, as an important component in the blood of crustaceans. The higher Fe concentration in the serum from green turtles than for H and O may be due to chlorophyll, which is an important component of chloroplasts in eel grass. Co was not found in the serum of green turtles but was found in the serum of H and O. The monitoring of important elements in sea turtles may be used as a tool to assess the levels of pollution in marine ecosystems.

Mercury content and consumption risk of 8 species threadfin bream (Nemipterus spp.) caught along the Gulf of Thailand.

Total mercury (T-Hg) was examined in 8 threadfin bream species (Nemipterus spp.) caught in the Gulf of Thailand (GoT). The T-Hg contents ranged from 11.3 to 374 µg kg-1 wet weight, with the lowest in Nemipterus peronii and the highest in Nemipterus nemurus and Nemipterus tambuloides. Accumulation of T-Hg in fish tissue was found to be related to fish size, trophic levels, feeding habits and habitat. Threadfin bream caught in the upper GoT exhibited significantly (p < 0.05) lower T-Hg than those in the middle and lower parts of GoT, which possibly due to local mercury sources e.g., internal anthropogenic activities in the GoT and external from terrestrial input via river discharge. The estimated daily intakes were ranged from 0.03 to 0.07 µg kg-1 bodyweight day-1. All threadfin breams in the GoT have HQ <1. To prevent the associated potential risk, the maximum safe daily consumption is recommended at 95.3 g day-1.

Complementary molecular and visual sampling of fish on oil and gas platforms provides superior biodiversity characterisation.

Offshore oil and gas platforms have the potential to provide complex refugia for fish and benthic colonisers. We compare two methods of biodiversity assessment for fish and elasmobranchs at seven decommissioned oil and gas platforms as well as five sediment sites, located 5 km from platforms, in the Gulf of Thailand. Using surveys from stereo-video ROV transects, and data from Environmental DNA (eDNA) water-column samples, we detected fish and elasmobranch taxa from 39 families and 66 genera across both platform and sediment sites with eDNA, compared with 18 families and 29 genera by stereo-ROV with platforms yielding significantly greater species richness. This study demonstrates that the combination of stereo-video ROV and eDNA provide effective, non-extractive and complementary methods to enhance data capture. This approach sets new benchmarks for evaluating fish assemblages surrounding platforms and will enhance measurements of biota to inform decisions on the fate of oil/gas infrastructure.

Evidence of fish following towed oil and gas platforms to a reefing site and rapid colonisation.

We investigated the composition and abundance of fish assemblages associated with seven offshore oil and gas platform jackets in the Gulf of Thailand before (pre-lift and pre-tow), and immediately after relocation (post-tow and reefed). Jackets were cut, lifted until partly out of the water, and attached to the rear of a heavy lift vessel. They were towed at speeds of 2.7 - 3.3 knots for between 133.9 and 205.4 km before being placed on the seafloor at an artificial reef site. Sixteen species of fish were observed both before and after jacket towing. We believe these species have sought refuge in the complex structures out of the current and have remained with the jackets. Ten species of fish were observed before towing, but not after. A further seven species of fish were only observed after the jackets were relocated onto the seafloor and were assumed to be early colonisers to the structures. The paper provides empirical evidence of a much-discussed paradigm that fish can swim great distances following moved structures, and further evidence of the ability of fish to rapidly colonise reefed structures.

Identification, Characterization, and Virulence Gene Expression of Marine Enterobacteria in the Upper Gulf of Thailand.

Enterobacteria that commonly inhabit marine environments have a great impact on human health. In this study, enterobacteria isolated from seawater in the Upper Gulf of Thailand were identified and characterized. Seawater from nine sampling sites along the Upper Gulf of Thailand contained presumptive enterobacteria that ranged from 0.22 ± 0.44 to 17.00 ± 3.97 CFU/mL. The 101 strains belonged to seven species in which Klebsiella pneumoniae was the majority (47.5% of strains). The highest prevalence was resistant to ampicillin (76.2%) and ticarcillin (72.3%), respectively, whereas none was resistant to imipenem. Forty-five antibiotic resistance patterns were observed and 33.7% exhibited multidrug resistance, emphasizing the concern about public health. Three ß-lactamase genes, including ampC, blaSHV, and blaTEM, were detected at the frequencies of 47.5%, 21.8%, and 11.9%, respectively. Six virulence genes, including csgD, uge, kfu, eaeA, magA, and LTI, were detected at the frequencies of 37.6%, 31.7%, 19.8%, 16.8%, 12.9%, and 5.9%, respectively. The condition of 4% NaCl downregulated the expression of the kfu and uge genes. The 67.3% and 63.4% of strains synthesized silver nanoparticles ranging between 3.04 ± 0.64 and 20.64 ± 0.95 µg/mL and gold nanoparticles ranging between 7.77 ± 0.45 and 57.57 ± 8.00 µg/mL, respectively.