Storage and dynamics of soil organic carbon in allochthonous-dominated and nitrogen-limited natural and planted mangrove forests in southern Thailand.

Mangrove forests can help to mitigate climate change by storing a significant amount of carbon (C) in soils. Planted mangrove forests have been established to combat anthropogenic threats posed by climate change. However, the efficiency of planted forests in terms of soil organic carbon (SOC) storage and dynamics relative to that of natural forests is unclear. We assessed SOC and nutrient storage, SOC sources and drivers in a natural and a planted forest in southern Thailand. Although the planted forest stored more C and nutrients than the natural forest, the early-stage planted forest was not a strong sink relative to mudflat. Both forests were predominated by allochthonous organic C and nitrogen limited, with total nitrogen being a major driver of SOC in both cases. SOC showed a significant decline along land-to-sea and depth gradients as a result of soil texture, nutrient availability, and pH in the natural forest.

Identification of anthropogenic debris in the stomach and intestines of giant freshwater prawns from the Trang River in southern Thailand.

Background: Anthropogenic waste, especially microplastics, is becoming more prevalent in the environment and marine ecosystems, where it has the potential to spread through food chains and be consumed by humans. Southeast Asian countries are home to giant freshwater prawns, a common freshwater species that is eaten around the world. Microplastic pollution in river water, sediment, and commercially significant aquatic species such as fish and mollusks has been observed, yet few studies have been conducted on giant freshwater prawns in the rivers of southern Thailand, where microplastics may contaminate prawns via the food they ingest. The purpose of this research was to investigate the accumulation of anthropogenic material in the organs of river prawns (Macrobrachium rosenbergii). Methods: Microplastics in the stomachs and intestines of giant freshwater prawns were the focus of this study. Samples were digested with 30 ml of 10% potassium hydroxide (KOH), heated for 5 min at 60 °C, and then digested at room temperature. The quantity, color, and appearance of microplastics were assessed using a stereomicroscope after 12 h. Furthermore, polymers were examined using a Fourier transform infrared spectrophotometer (FTIR). Microplastic counts were compared between sexes. A T-test was used to compare male and female microplastic counts in the stomach and intestine, and the Pearson correlation was used to compare the association between microplastic counts in the stomach and intestine and carapace length (CL), length of abdomen (LA), and body weight (BW) of male and female giant freshwater prawns. The threshold of significance was fixed at p < 0.05. Results: Based on the study results, a total of 370 pieces of anthropogenic debris were discovered in the stomachs and intestines of both female and male prawns. The average number of microplastics per individual was 4.87 ±  0.72 in female stomachs and 3.03 ± 0.58 in male stomachs, and 1.73 ± 0.36 in female intestines and 2.70 ± 0.57 in male intestines. The majority of microplastics found in females were within the <100 µm range, while males contained microplastics in the range of 100-500 µm. Both male and female prawns contained fibers (72.70%) and fragments (27.30%). Various polymers were identified, including cotton, rayon, and polyvinyl chloride (PVC). The study also explored the relationship between carapace length, length of abdomen, body weight, stomach weight, and the number of microplastics. The findings reveal a significant association between the number of microplastics and stomach weight in male prawns (R = 0.495; p = 0.005). These findings provide alarming evidence of anthropogenic debris ingestion in prawns and raise concerns about the future effects of anthropogenic pollution on giant freshwater prawns.

Occurrence of microplastics in freshwater gastropods from a tropical river U-Taphao, southern Thailand.

Background: Microplastics (MPs) are pollutants in rivers and marine environments. Rivers can be sources and sinks of MPs that enter the biota. Previous studies focusing on freshwater species are quite limited, especially for gastropods. Freshwater gastropods are essential to aquatic ecosystems because they are food to other aquatic animals, such as fish, shrimp, and crabs. They are a crucial link in the food chain between water resources and human food. Therefore, this study aimed to investigate MP accumulation in freshwater gastropods, commonly known as snails (Filopaludina sumatrensis speciosa and Pomacea canaliculata), in a river flowing into a shallow coastal lagoon. Method: In this study, snail tissue samples were digested with 30% hydrogen peroxide. The mixture was heated at 60 °C for 24 h. MP particles were identified, counted, and characterized (shape, size, and color) by visual identification under a stereomicroscope. Furthermore, polymer-type identification was performed using Fourier transform infrared spectroscopy (FTIR). Analysis of variance (ANOVA) was applied for the statistical analysis. Results: The MPs found were as follows: 4.76 particles/individual were found in F. sumatrensis speciosa upstream, 5.20 particles/individual were found in F. sumatrensis speciosa downstream, 7.28 particles/individual were found in P. canaliculata upstream, and 4.00 particles/individual were found in P. canaliculata downstream. It was found in the two-way ANOVA that the accumulation of MPs in gastropods was affected by species and study sites (upstream and downstream). There was a significant difference in the amount of MPs in P. canaliculata between upstream and downstream sites (p = 0.003). Fibers were the most common MPs in both species. Moreover, P. canaliculata upstream had the most significant amount of MPs. The smallest amount of MPs was recorded for P. canaliculata downstream, but there was great diversity in shape, size, and polymer type. MPs sized 500 µm-1 mm were the most common in both species. Fourier transform infrared spectroscopy revealed six polymers: poly (ethylene terephthalate), polypropylene, rayon, polyethyleneimine, polyamine, and poly (propylene: ethylene). The occurrence of MPs in gastropods is alarming for food security in Thailand. The results of this study can be used to support baseline data on MP accumulation among freshwater gastropods.

The application of chemometrics in metals source of identification in Brunei Bay surface sediment.

Brunei Bay is a unique ecosystem which offers a vast biodiversity. This study was carried out to define the source of metals in the surface sediment of Brunei Bay to ensure the bay's health. The secondary data were analysed using chemometrics analysis to verify the possible factors that influence metals distribution in Brunei Bay sediment. Samples were collected several times during 2013 to 2014 using Ponar grab at 16 stations within the bay. Samples were then dried, pre-treated, digested and analysed using Inductively Coupled Plasma Mass Spectrometry (ICPMS) in the laboratory. Overall, the mean concentration of metal, sediment pH and clay fraction were significantly changed during different sampling periods, as the changes were presumed affected by seasonal changes. The Pearson correlation has pointed that metals were dominantly derived by natural input; however, the total organic carbon was proven to be derived by anthropogenic sources. Moreover, the principal component analysis has verified that the distribution of metals in the bay's sediment was dominantly influenced by natural processes. However, the utilization and manipulation of marine resources are slightly affecting the bay's ecosystem which may deteriorate the ecosystem health soon.

Invasion of African Clarias gariepinus Drives Genetic Erosion of the Indigenous C. batrachus in Bangladesh.

The African catfish Clarias gariepinus has been introduced for aquaculture in Bangladesh due to the scarcity of indigenous C. batrachus fingerlings. However, the government of Bangladesh has banned the farming of C. gariepinus due to the carnivorous nature of this species. Recently C. gariepinus has been reported by fish farmers and consumers in Bangladesh, and unplanned hybridization between native and exotic species has been suspected. This study attempts to know the purity of C. batrachus by analyzing mitochondrial genes. Both directly sequenced and retrieved Cytochrome C Oxidase subunit I (COI) and cytochrome b (Cytb) genes from C. gareipinus and C. batrachus were analyzed by MEGA software. The morphologically dissimilar C. batrachus showed the least genetic distance (0.295) from C. gariepinus, which provided evidence of hybridization between the two species. Maximum likelihood (ML) phylogenetic trees showed that C. batrachus from Bangladesh did not cluster with C. batrachus of other countries, instead C. batrachus clustered with the exotic C. gariepinus. The suspected hybrid formed sister taxa with the exotic C. gariepinus. The study corroborates the genetic deterioration of C. batrachus by unplanned hybridization with the invasive C. gariepinus. Unplanned hybridization has deleterious consequences; therefore, immediate action is necessary for aquaculture sustainability and biodiversity conservation in Bangladesh.

Feeding Habits and the Occurrence of Anthropogenic Debris in the Stomach Content of Marine Fish from Pattani Bay, Gulf of Thailand.

This study assessed the feeding habits and ingestion of anthropogenic debris in 34 marine fish species from the southern Gulf of Thailand. A total of 5478 fish samples of 12 families were categorised into seven groups: planktivore, Lucifer feeder, fish feeder, Acetes feeder, shrimp feeder, piscivore, and zoobenthivore fish. A total of 2477 anthropogenic debris items were extracted from 12 fish species by visual inspection. Their ingestion of anthropogenic debris was influenced by season (p < 0.0001), with the highest ingestion during the northeast monsoon season. Furthermore, planktivorous fish displayed more ingested anthropogenic debris than the other investigated species (p = 0.022). Blue-coloured anthropogenic debris was commonly detected in the stomachs of fish and significantly differed between species (p > 0.001). Water depth and season significantly influenced the availability of food types (AF) for fish (p < 0.001). These findings provide evidence of the ingestion of anthropogenic debris by fish inhabiting a natural bay and signal the future anthropogenic pollution of marine fish.

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.

Data on dissolved metals in Terengganu waters of South China Sea during pre-, post-, and Northeast Monsoon season.

Metals are natural elements existed in the environment. However, due to the rapid development of urbanisation and economic, high content of anthropogenic metals are being perceived in polluting the environment. The oceans are known to be a part of the sinking basin for anthropogenic metals ends. Dataset provided is purposely to give an overview of dissolved metals spatial distribution in the South China Sea off the east Peninsular of Malaysia during the pre-, post- and Northeast (NE) Monsoon period. Seawater samples were collected in a grid of 18 stations at 3 different water depth. Dissolved metals were pre-concentrated on-board ship using Chelex-100 resin and analysed using Inductively Coupled Plasma Mass Spectrophotometry (ICPMS). The dataset shows the effect of NE Monsoon on dissolved metals spatial distribution mainly at the area closer to the land. Therefore, this dataset could reveal the past information on anthropogenic metals intrusion in the South China Sea, since Terengganu state was recently pointed to be one of the Malaysian waterfront city. Additionally, this dataset also could help in studying the cycle of metals in the southern South China Sea waters.

Accumulation of Trace Metals in Anadara granosa and Anadara inaequivalvis from Pattani Bay and the Setiu Wetlands.

This study was undertaken to assess the levels of trace metals (As, Cd, Cu, Pb, and Zn) in two common species of cockles (Anadara granosa and Anadara inaequivalvis) from two coastal areas in Thailand (Pattani Bay) and Malaysia (the Setiu Wetlands). A total of 350 cockles were collected in February and September 2014. Trace metals were determined by Inductively Coupled Plasma Mass Spectrometry. We observed that cockles in both areas had a higher accumulation of metals in September. Notably, the biota-sediment accumulation (BSAF) of Cd was highest in both areas. A strong positive correlation of Cd with the length of the cockles at Pattani Bay (r(2) = 0.597) and the Setiu Wetlands (r(2) = 0.675) was noted. It was suggested that As could be a limiting element (BSAF < 1) of cockles obtained from Pattani Bay. In comparison with the permissible limits set by the Thailand Ministry of Public Health and the Malaysia Food Regulations, mean values of As, Cd, Cu, Pb, and Zn were within acceptable limits, but the maximum values of Cd and Pb exceeded the limits for both areas. Regular monitoring of trace metals in cockles from both areas is suggested for more definitive contamination determination.