Estuary Area Research Articles

Risk of extinction, variability in fish species composition, and factors influencing fish biodiversity in the Malacca Strait.

Fish biodiversity in Malaysia is under pressure due to overexploitation, pollution, and climatic stressors. Nevertheless, the information on fish biodiversity and species vulnerability status is not well documented in the region. Therefore, a study on fish species composition and abundance in the Malacca Strait of Malaysia has been conducted for the purpose of monitoring biodiversity, determining the risk of species extinction, and identifying factors influencing biodiversity distribution. The sampling was conducted based on a random stratified sampling method from the three zones of sampling locations, i.e., estuary, mangrove, and open sea area of Tanjung Karang and Port Klang of Malacca Strait. Higher species diversity was recorded at Tanjung Karang coastal and mangrove areas (H' = 2.71; H' = 1.64) than Port Klang coastal and mangrove areas (H' = 1.50, H' = 0.29), an indication that the Port Klang area is comparatively more vulnerable. The study also explored sampling location, habitat, and IUCN red list as the influencing factors for fish biodiversity. Applying IUCN red list, this study identified one Endangered and one Vulnerable species with the forecasted increasing landing for both species. Our findings suggest the urgent need for the implementation of conservation measures as well as the continuous monitoring of fish biodiversity in the area.

RESTORASI EKOSISTEM MANGROVE PADA MEDIA BIODEGRADABLE DI PESISIR DESA WAAI

Mangroves are plants that live on the coast and are affected by sea tides. Mangroves play an important role in estuary areas, namely the border between seawater and fresh water because they have ecological, economic and chemical functions to support the life of organisms. Mangrove ecosystems can experience threats from both natural and human factors. Human activities that cause damage to mangroves are due to a lack of public awareness regarding the importance of mangrove ecosystems for organisms. This is the condition that occurs in the mangrove ecosystem in Waai Village, therefore, it is necessary to restore the mangrove ecosystem. Mangrove ecosystem restoration uses one of the potential media, namely BESE-Element, which is a biodegradable material. Community service is carried out in collaboration with the Pattimura University Maritime Center and Wardenburg Ecology International. The community service activities were carried out for two days, 7-8 February 2023. The result of the activity was that mangrove ecosystem restoration was carried out in semi-enclosed areas using 10 BESE-Element. The types of mangrove species planted were Sonneratia alba, Rhizophora stylosa, and Ceriops tagal. Around BESE-Elements planted seedlings and mangrove propagules as a control for mangroves in BESE-Elements. This restoration activity seems to be applicable not only in Waai Village but also in other areas that have experienced degradation of the mangrove ecosystem.

Dissemination of antibiotic resistance genes from the Pearl River Estuary to adjacent coastal areas

The spread of antibiotic resistance genes (ARGs) is a growing concern over the world's various environments. Coastal environments may receive pollutants from land runoffs via estuaries. However, the impact of ARG contamination from estuarine regions to coastal areas is rarely reported. This study used high-throughput quantitative PCR to examine the diversity and abundance of ARGs in Pearl River Estuary (PRE) and adjacent coastal areas. We found that the distribution of ARGs in seawater exhibited the distance-decay phenomenon from the estuary to coastal areas, while the sediment samples did not exhibit an obvious distribution pattern. The estuarine water was found to be the hotspot of ARGs, with 74 ARG species detected and absolute abundance being 5.93 × 105 copies per mL, on average, while less species and lower abundance of ARGs were detected in coastal waters. Ordination analysis showed that estuarine ARG communities were significantly different from coastal ARG communities for water samples. SourceTracker analysis revealed that ARGs from the estuarine environment contributed only a minor fraction of ARG contamination to downstream coastal areas (1.5%–7.4% for water samples, and 0.7–1.8% for sediment samples), indicating the strong dilution effect of seawater. Mantel tests, redundancy analysis and random forest model analysis identified salinity, nutrients, microbial community structure and mobile genetic elements (MGEs) as important factors influencing ARG distribution. Partial least squares-path model revealed that, among all environmental factors, MGEs directly affected the distribution of ARGs, while other factors indirectly contributed by affecting the MGEs assemblage. Our study provides insight into the dissemination of ARGs from the PRE to adjacent coastal areas.

ESTIMATION OF CARBON RESERVES IN SEDIMENTS IN THE MANGROVE ECOSYSTEM OF BUKIT BATU VILLAGE, BENGKALIS REGENCY, RIAU

This research was carried out in December 2021. Sampling and water quality measurements were carried out in the Bukit Batu Muara River, Bengkalis Regency, Riau Province. Sample analysis was continued at the Marine Chemistry Laboratory, Department of Marine Science, Faculty of Fisheries and Marine, Universitas Riau. The purpose of this study was to determine the estimation of carbon stocks in sediments, the comparison of carbon stocks between transects, and the relationship between density and carbon stocks in the Muara Sungai Bukit Batu mangrove area, Bengkalis Regency, Riau Province. The method used in this study is a survey method. Parameters measured included mangrove density (Ind/Ha), organic matter content, and carbon stock in sediments. In addition, water quality was also measured in the form of temperature, salinity, and degree of acidity. Analysis of carbon stock using the loss on ignition method. The result of the average density of mangroves throughout the transect is 3733.33 (Ind/Ha). The lowest carbon stock value in sediments is in transect 2 with medium mangrove density with a value of 29.26 tons/ha, while the highest carbon stock value is in transect 3 with high-density mangrove areas with a value of 36.15 tons/ha. The results of a simple linear regression to determine the relationship between mangrove density and carbon stock show a coefficient of determination R² = 0.023, which means that 2.3% of total carbon stock is affected by density, while 97.7% is influenced by other factors. The value of R = 0.152, which means that the relationship between density and carbon stock in the Bukit Batu River estuary area, Bengkalis Regency, is low.

Potential risks of climate change and tropical storms on ecosystem and clams culture activities in Giao Thuy, Nam Dinh, Vietnam

Ecosystem and aquaculture in estuary areas are sensitive to climate change and severe climatic events. In this study, three environmental monitoring events were carried out on a 1800-ha clam culture area in Giao Thuy district, Nam Dinh province, Vietnam. The first monitoring was carried out in fair weather. The second and 3rd monitorings were conducted two days after the Ma On and Noru storms, respectively. The variation of water and sediment physicochemical variables, zoobenthos and plankton composition and density, and clam pathogen were investigated at five locations. In addition, long-term variations of temperature, rainfall, and sunshine duration in the area were investigated. The results illustrated the increased temperature, rainfall, and sunshine duration tendency. The clam-cultured species and activities had substantially changed. Ma On and Noru negatively impacted water quality by decreasing the water quality index by 39% and 30%, respectively. Storms decreased water salinity, alkalinity, and sediment’s phosphorus, iron, lead. However, they increased water’s nitrite, phosphorus, total suspended solid, phytoplankton, zooplankton density, and sediment’s total nitrogen, cadimium. The total Vibrio spp. density in clam highly fluctuated between the two storm events. The effect of storm varied according to site location. Shallow and domestic wastewater adjacent sites suffered high risks of extreme temperature, salinity variation, and organic pollution.

Shoreline change detection along North Sebou–Moulay Bousselham, based on remote sensing analysis

Sustainable management of the shoreline is crucial. Shoreline mapping is very essential to investigate the impact of the dynamic nature of the coastal area over a certain period. Coastal zone at the north Sebou estuary experience some issues as shoreline retreats as well as shoreline advancement in some locations. Shoreline mapping along the northern area of Sebou estuary was implemented by applying remote sensing technology to detect and analyze shoreline changes.Multi-temporal satellite images with different periods during the last 37 years (1984–2021) were used to detect changes as well as analyze shoreline change rates. Landsat images (Landsat 5–TM, Thematic Mapper TM, Landsat7 ETM+, Landsat 8 OLI_TIRS) were corrected from geometric and radiometric perspectives, then classified by assigning six different classes for analyzing the evolution of the coastal zone from 1984 to 2021. To detect changes in both land use and land cover, the Support Vector Machine algorithm supervised classification was executed to classify the images. As a powerful statistical analysis tool, DSAS was used to assess the rate of shoreline change by EPR technique and to anticipate the required coastal protection measures along the coastline.The classification results show that agricultural land, bare land, and sand-dune beaches have decreased by −8.26%, −5.92%, and −4.53% respectively. On the other hand, statistical analysis of DSAS shows that the northern area of Sebou estuary experienced an average accretion rate of (+0.96 m/yr) while erosion rates achieved an average of (−1.04 m/yr). A drastic erosion was noticeable at the right side of the estuary with (−3.1 m/yr). The decision matrix by EPR method has been developed. It illustrates the evolution, risk level, and proposed decision at each sector along the shorelines during the preceding three decades. The final goal of this study is to support decision-makers in implementing preventive management techniques in the most vulnerable locations.

Spatio-temporal dynamic diversity of bacterial alkaline phosphatase phoD gene and its environmental drivers in sediments during algal blooms: A case study of shallow Lake Taihu

Bacterial alkaline phosphatase encoded by the phoD gene is essential for phosphorus (P) cycling in ecosystems. Until now, knowledge of the phoD gene diversity in shallow lake sediments is still lacking. In this study, from early to late stage of cyanobacterial blooms, we investigated the dynamic changes of the abundance of phoD gene (hereafter phoD abundance) and phoD-harboring bacterial community composition (hereafter phoD-harboring BCC) in sediments from different ecological regions of Lake Taihu, the third-largest shallow freshwater lake in China, as well as explored their environmental driving factors. Results showed that phoD abundance in the sediments of Lake Taihu showed spatiotemporal heterogeneity. The highest abundance was found in macrophyte-dominated area (mean 3.25*106copies/g DW), where Haliangium and Aeromicrobium were identified as the major contributors. Due to the negative impact of Microcystis species, phoD abundance decreased significantly (by 40.28% on average) during cyanobacterial blooms in all other regions except the estuary area. The phoD abundance in sediment was positively correlated with total organic carbon (TOC) and total nitrogen (TN). However, the relationship between phoD abundance and alkaline phosphatase activity (APA) varied with time, showing positive correlation (R2 = 0.763, P < 0.01) in the early stage of cyanobacterial blooms, but not (R2 = −0.052, P = 0.838) in the later stage. The predominant phoD-harboring genera in sediments were Kribbella, Streptomyces and Lentzea, all of which belong to Actinobacteria. Non-metric multidimensional scaling (NMDS) analysis revealed that the spatial heterogeneity of phoD-harboring BCC in the sediments of Lake Taihu was significantly higher than the temporal heterogeneity. TP and sand were the principle environmental factors affecting the phoD-harboring BCC in the sediments of the estuary area, while DO, pH, organic phosphorus (Po) and diester phosphorus were the key driving factors for other lake regions. We concluded that the C, N, and P cycles in sediments might work in concert. This study extends the understanding of the phoD gene diversity in shallow lake sediments.

DISTRIBUTION OF SIBOGLINIDS (ANNELIDA, SIBOGLINIDAE) IN THE LAPTEV SEA AND ADJACENT AREAS OF THE ARCTIC BASIN

The purpose of the article is to assess the biodiversity of gutless marine worms of the family Siboglinidae (Annelida), whose metabolism is provided by symbiotic bacteria that oxidize hydrogen sulfide and methane. Within the geographical boundaries of the Laptev Sea, 7 species of siboglinids were found, another 1 species was found in the adjacent sector of the Arctic basin. The largest number of finds and the greatest biological diversity of siboglinids were found in the eastern part of the Laptev Sea in the field of numerous methane. One find was noted in the estuary area of the Lena River at a depth of 25 m. The possible connection of siboglinids with methane seepage areas is discussed.

Lead and Copper Heavy Metal Content in the Morosari Waters, Demak Region

The utilization of river bodies as waste disposal has an impact on the entry of heavy metals into the sea. The Morosari estuary area is an estuary area, which consists of mangrove areas, tourist areas, and several industrial activities, both large-scale and household. This condition causes the entry of waste containing heavy metals lead (Pb) and copper (Cu) into the estuary area. This study aims to determine the content of heavy metals Pb and Cu in the estuary of the Morosari River. This research was conducted in April - June 2009 and took place in the Morosari River estuary, Demak Region. The research method used was a descriptive exploratory method, while the sampling was purposive. random sampling, to 3 stations. Water samples are taken every 2 weeks, and followed by an analysis carried out at the Growth Center Laboratory, Kopertis Region IV, Semarang. The data obtained were analyzed descriptively. Analysis results for Pb content in water: 0.039 - 0.089 and Cu content in water 0.024 - 0.055 mg/l. The value of heavy metal content in the water has exceeded the threshold.

Investigation of Microplastics in Surface Water and Estuarine Mullet Mugil cephalus from 23 Estuary Areas, South China

Microplastics, which are defined as small plastic particles smaller than 5 mm, have been found in various aquatic environments all over the world. In this study, we investigated the level of microplastics in the surface water and estuarine mullet Mugil cephalus from 23 estuary areas in the south of China. M. cephalus, due to its wide distribution and high tolerance, was selected as a candidate fish species for monitoring the ingestion of marine microplastics. The size, color, and type of all microplastics were recorded from the water and fish samples by stereomicroscope. The average abundance of microplastics was 18,261 items/m3 in the surface water, and 7.2 items/individual in fish. These alarming numbers revealed significant pollution due to microplastics in the environment. Fragments and minute-sized particles were the most common features found in both the water and the fish samples. Some impurities in the water sample were easily confused with microplastics, but regular forms on the surface of the impurity could be distinguished by using scanning electron microscopy (SEM). The shape, color, and size of the microplastics in the fish and water samples were similar, which suggested that the microplastics in the water might enter the organisms’ body, thereby affecting the health of aquatic species and even humans. Based on these findings, it is highly recommended that the monitoring and managing of pollution due to microplastics be addressed in the estuaries.

Spatiotemporal variations and the ecological risks of organophosphate esters in Laizhou Bay waters between 2019 and 2021: Implying the impacts of the COVID-19 pandemic

Organophosphate esters (OPEs) are a group of synthetic chemicals used in numerous consumer products such as plastics and furniture. The Coronavirus Disease 2019 (COVID-19) pandemic significantly slowed anthropogenic activities and reduced the emissions of pollutants. Meanwhile, the mismanagement of large quantities of disposable plastic facemasks intensified the problems of plastic pollution and leachable pollutants in coastal waters. In this study, the joint effects of the COVID-19 outbreak on the occurrence of 12 targeted OPEs in the waters of Laizhou Bay (LZB) were investigated. The results showed that the median total OPE concentrations were 725, 363, and 109 ng L−1 in the sewage treatment plant effluent, river water, and bay water in 2021, decreased significantly (p < 0.05) by 67%, 68%, and 70%, respectively, compared with those before the COVID-19 outbreak. The release potential of targeted OPEs from disposable surgical masks in the LZB area was ∼0.24 kg yr−1, which was insufficient to increase the OPE concentration in the LZB waters. The concentrations of most individual OPEs significantly decreased in LZB waters from 2019 to 2021, except for TBOEP and TNBP. Spatially, a lower concentration of OPEs was found in the Yellow River estuary area in 2021 compared with that before the COVID-19 pandemic due to the high content of suspended particulate matter in the YR. A higher total OPE concentration was observed along the northeastern coast of LZB, mainly owing to the construction of an artificial island since 2020. The ecological risks of the OPE mixture in LZB waters were lower than those before the COVID-19 outbreak. However, TCEP, TNBP, and BDP should receive continuous attention because of their potential ecological risks to aquatic organisms.

Biomonitoring by using Rapid-Read Pathogenic Bacteria Indicator in Sediments and Bivalve Mollusks: Southern Gulf of Thailand, a Mangrove Area Case Study

Pathogenic bacteria groups can be applied to be rapid bioindicator for environmental assessment. The objective of study was to monitor 5 groups of indicator and pathogenic bacteria (Escherichia coli/ total coliform, Salmonella spp., Vibrio spp., Bacillus spp. and Clostridium spp.) in surface water sediments collected before monsoon and after monsoon season from 6 areas located in a Thepha District, Songkhla province mangrove closed to Southern gulf of Thailand. Each collected area were selected in criteria of totally different in environment parameter and tide. The relative levels of total coliforms, and E. coli, were typically increased in rainy season (July) compared with winter and summer at most sites. In parallel, the highest number of Vibrio spp. was found in summer (April). The highest number of E. coli and Coliform were detected during rainy season at the estuary area with low oxygen dissolved, the average numbers were 6.6×103 and 3.8×105 CFU/g, respectively. Coliform number shows negative correlate with dissolved oxygen (r2 = 0.756, p &lt; 0.05). In addition, total coliform, Bacillus spp. and Clostridium spp. were found in bivalve mollusks during rainy season but the total was not over standard. A very strong positive correlation was found between the temperature and the number of Vibrio spp. and Bacillus spp. The number presence of Vibrio spp. has a strong positive correlation with pH, the number of Bacillus spp. and number of Clostridium spp. In contrast, Vibrio spp. number was strongly negative correlated with water salinity (r2 = 0.632, p &lt; 0.05). Salmonella species were detected only 2 area around shrimp farm in between December of a year-round. In this study area, there are no evidence that the number of Salmonella and Clostridium species founded related to changing of season. This is the first baseline data as an alternative guide concept for the determination of bacterial indicators. Pathogenic bacteria number can be applied to be a key factors for a rapid health assessment for villager around study area that related to EIA in the near future. HIGHLIGHTS The common problem in biomonitoring process in environment are limit of biological indicator and less data collected to establish relative between bioindicator and environmental parameters Key pathogenic bacteria groups were selected and analyzed conducted in order to find the rapid-read method for biomonitoring and assessment This is the first baseline data as an alternative guide concept for the determination of bacterial indicators. Pathogenic bacteria number can be applied to be a key factors for a rapid health assessment for villager around study area that related to EIA in the near future GRAPHICAL ABSTRACT

Long chain fatty acids analysis of intertidal biofilm by direct injection liquid chromatography time of flight mass spectrometry

The critical importance of mono- and polyunsaturated fatty acids (FAs) in a variety of biological functions, including animal nutrition and as an environmental stress monitor, is well recognized. However, while methods exist for monitoring of fatty acids, few are specific either to the profile of a microphytobenthos matrix or practical in application to multiple, diverse intertidal biofilm sample sets. In the current study, a sensitive liquid chromatography (LC) quadrupole time of flight mass spectrometry (QTOF) method was developed for the quantitative analysis of 31 FAs specific to intertidal biofilm, a thin mucilaginous layer of microalgae, bacteria, and other organisms on the surface of coastal mudflats, which provide a rich source of FAs for migratory birds. Preliminary screening of diverse biofilm samples collected from shorebird feeding grounds highlighted eight saturated (SFA), seven monounsaturated (MUFA), and sixteen polyunsaturated FAs (PUFA) that were selected for analysis. Improved method detection limits in the range 0.3–2.6 ngmL−1 were achieved, excepting for stearic acid at 10.6 ngmL−1. These excellent results were obtained without use of complex sample extraction and clean-up procedures undertaken by other published methods. An alkaline matrix of dilute aqueous ammonium hydroxide with methanol was shown to be selective for extraction and stability of the more hydrophilic fatty acid components. The direct injection method showed excellent precision and accuracy both during validation and application to hundreds of real-world intertidal biofilm samples from the Fraser River estuary (British Columbia, Canada) and other areas of the region frequented by shoreline birds.

Ecological Response to the Diluted Water in Guangxi during the Spring Monsoon Transition in 2021

Based on the field survey data of the Guangxi offshore voyage in May 2021, the distribution characteristics of the wind field during the spring monsoon transition period, the temporal and spatial changes in the diluted water path, and the corresponding ecological responses were analyzed. The results show the following: the core region of diluted water is located along the coast of Guangxi, and the diluted water expands to the east and west at the same time, where the thickness of the diluted water reaches 20 m. Under the combined action of the easterly wind and westward current, the westward expansion trend was stronger than the eastward expansion trend. The surface distribution of suspended solids, chlorophyll a, dissolved oxygen, and active silicon is similar to the dispersion range of the diluted water, and the high-value areas all appear near the estuary, which is basically consistent with the salinity distribution in the core region of the diluted water. Under the mixing caused by the wind and tide in the estuary area, the difference in dissolved oxygen between the surface and bottom layer is small, while in the nearshore area, the stratification of seawater hinders the dissolved oxygen’s downward transmission, resulting in a large difference in dissolved oxygen between the bottom and the surface.

Analysis of Total Organic Matter, Total Nitrogen, and Total Phosphorus in the Estuary Waters of Maros as a Source of Brackish Water for Fish Ponds Aquaculture

Indonesia is a tropical area with high rainfall, the area on land is connected by around 472 large and small rivers that flow into the sea. The estuary area is the meeting area of ​​rivers or fresh water streams with the ocean. Transportation of organic matter, minerals and sediments from upstream to the estuary and from the sea containing minerals, hence estuarine waters are more fertile than other areas. In addition, estuary areas are important habitats for several types of marine and freshwater organisms to fulfill their life cycles, which are used as spawning, foraging, and nursery grounds.&#x0D; This study aimed to determine the total organic contents, total Nitrogen, and Phosphorus in the estuary waters of Maros as a source of brackish water for fish pond aquaculture in Maros Regency. The research was conducted in the estuary waters of Maros for three months from September to November 2020. Sampling was conducted four times with an interval of once every 15 days. Sampling was carried out at five stations based on water movements to the estuary, station A was located at the seawater, station B was located in the pond wastewater locations, station C was water sources from residential waste, station D was located in the river, and station E was the estuarine water. The results showed that the dominant water quality parameters affecting estuarine water quality were salinity, total organic matter, nitrogen content, either in the form of ammonia, nitrate, or nitrite, and phosphorus content, especially phosphate. Water entering the estuary has an impact on high concentrations of total organic matter, increased concentrations of Total N, and phosphorus. The results of water quality analysis in estuaries showed that salinity, organic matter, ammonia, nitrite and nitrate, and phosphate exceed the standard threshold for water quality standards for fish pond aquaculture. Thus, the waters of the Maros estuary are not suitable for aquaculture, especially for the 5 observed stations (A, B, C, D and E).

Population density and distribution patterns of Austruca annulipes (Ring-legged fiddler crab) in the mangrove of Bogowonto Estuary, Kulon Progo, Yogyakarta, Indonesia

Abstract. Fadilah RN, Yulia IT, Alfitra ZS, Armadhan WS, Widyaningtyas R, Rahmayani D, Permatasari DP, Igustita, Kusuma D, Prambudi SA, Berlin GE, Triyanto A, Sutarno, Indrawan M, Dadiono MS, Rahim KABA, Setyawan AD. 2023. Population density and distribution patterns of Austruca annulipes (Ring-legged fiddler crab) in the mangrove of Bogowonto Estuary, Kulon Progo, Yogyakarta, Indonesia. Intl J Bonorowo Wetlands 13: 1-8. The mangrove forest ecosystem is a forest with coastal plant characteristics that are influenced by tides and tolerate high salt levels. Mangrove forests in Indonesia contain about 89 species of flora, and around 18% of their fauna are keystone species. Keystone species are species that play an important role in maintaining the balance of the ecosystem. Austruca annulipes (H. Milne-Edwards, 1837), or Ring-legged fiddler crab is one of the fauna species in the mangrove ecosystem, which has an important role in maintaining the balance of the food chain and nitrogen cycle, so the study of this species is very important for the sustainability of the ecosystem in mangrove area. This study aimed to determine the population density and distribution patterns of A. annulipes in the Mangrove Bogowonto Estuary Area, Kulon Progo, Yogyakarta, Indonesia. The research method was purposive random sampling using a 10m x 10m square plot. Furthermore, the identification of morphology and documentation of the activities of A. annulipes was carried out, and data were examined using calculations of crab density. Based on the research finding, the population density of A. annulipes is 0.9975 individuals/m2. Calculating the Morisita Index of A. annulipes obtained a value of 1.38 with the category of clumped distribution patterns. Various factors influence this distribution, including abiotic factors such as soil moisture, temperature, air, salinity, and pH. In addition, the presence of vegetation has also affected the density of A. annulipes because it is used as a shelter and foraging among its roots.

Characterization and Expression Analysis of Four Cadmium-Tolerance-Associated Genes of Avicennia marina (Forsk.).

Mangroves colonize the intertidal area of estuaries (e.g., Pichavaram, Payardia, and Mai Po) with remarkable cadmium (Cd) pollution. A study on the mechanism of mangrove plant response to Cd pollution can help to understand the adaptive characteristics of plants under Cd stress. This study explored the roles of peroxidase (PRX), pectate lyase (PL), and phytosulfokine (PSK) genes in cadmium tolerance of mangrove Avicennia marina. Full-length sequences of four genes (i.e., AmPRX1, AmPRX2, AmPL, and AmPSK) associated with metal tolerance were identified with suppression subtractive hybridization and rapid amplification of cDNA ends. These genes showed the characteristic features of the respective protein family, indicating functions similar to other plant proteins. Real-time quantitative PCR analysis demonstrated that cadmium exposure resulted in differences in expression patterns among the tissues. Our findings emphasize the complex regulatory mechanism of these four genes in response to trace metal pollution and reveal their functions in metabolic signaling during the stress response.

Extensive assessment of climate change impacts on coastal zone paddy growth using multispectral analysis and hydrodynamic modeling

Global warming has led to sea levels raise (SLRs) and Malaysia is no exception to this problem. Especially for low-lying coastal areas including the Kuala Kedah area which is active in agricultural and fisheries activities. Farmers have had to bear up to 75 % of yield losses due to seawater breaches since 2016. Therefore, this study is designed to assess the impact of seawater encroachment on water quality through spatial technology approaches and hydrodynamic modeling related to the growth of paddy trees. The study was conducted during two different paddy cultivation seasons namely Season 1–2019 and Season 2–2019 which take place in the southwest and northeast monsoon in Kuala Kedah, Malaysia. The study involved three phases, which are the assessment of salinity and pH concentration levels, the assessment of the health of paddy crops through multispectral image analysis involving three plant indices (VI), namely Normalized Difference Vegetation Index (NDVI), Blue Normalized Difference Vegetation Index (BNDVI) and Normalized Difference Red Edge (NDRE), and finally, the assessment of the impact of SLR through the numerical method in MIKE 21 for hydrodynamic modeling considering two conditions that are without mitigation factor (K1) and with existing mitigating factor (K2). According to the findings, the salinity concentration trend is decreasing across the growth stage during Season 1–2019, whereas it is the contrary during Season 2–2019. It was discovered that during the study period for both tidal events, 73 % of the 44 sampling points in Season 1–2019, as opposed to just 3 % in Season 2–2019, were categorized as Class 4 and Class 5. Even though there were fluctuations throughout the observation, the pH reading is still within the allowed range of 6.5 to 9.0 for the estuary area. Following that, the ANOVA analysis proved that salinity concentration a statistically significant difference with tidal variations and pH levels. Moreover, the multispectral image analysis findings revealed that the VI value was correlated with both the yield and the health of the rice crop, with R-square values of 0.842 compared to 0.706 and 0.575 for NDVI and BNDVI values, respectively. It confirmed that NDRE granted a more accurate and reliable measurements. Additionally, the hydrodynamic simulation results demonstrated that, if the mitigation factors were considered in the modeling, overflow seawater to the mainland could be reduced by up to 20 %, reducing the impact of coastal flooding on the local area as well as the nearby rice cultivation area. Ultimately, these three elements—water quality, vegetation index, and hydrodynamic modeling—can assist in identifying the underlying cause of the problem and develop short and long-term solutions.

Reconstruction of Daily MODIS/Aqua Chlorophyll-a Concentration in Turbid Estuarine Waters Based on Attention U-NET

An attention U-Net was proposed to reconstruct the missing chlorophyll-a concentration (Cchla) data. The U-Net is a lightweight full convolution neural network architecture consisting of an enccoder-decoder (i.e., down-sampling and up-sampling). The attention gates (AGs) were integrated into the U-Net. Training the U-Net with AGs could implicitly teach it to suppress irrelevant areas and highlight the salient features in the missing data areas, which would increase the network sensitivity and reconstruction accuracy. The neural network uses the satellite-derived Cchla anomalies and its variance as the input, and the reconstructed fields along with their variances as outputs. The trained network was applied to long-term daily MODIS/Aqua Cchla products in the Pearl River estuary (PRE) and adjacent continental shelf area. The model performance was evaluated by using an independent test dataset from both satellite-derived and in-situ measurements. The results showed that the proposed neural network not only had good performance in the reconstruction of valid pixels, but also provided a more reasonable reconstruction compared to the standard U-Net without AGs. This study provided a feasible method for the reconstruction task in the field of ocean color, which should be helpful in producing a creditable dataset to study the ecological effects of extreme weather conditions such as typhoons on the upper ocean in the PRE waters. Based on the reconstructed Cchla products, the footprints of the typhoons were studied. An increase in surface Cchla near the typhoons’ track and a decrease in estuary were found. The composite results illustrated that the Cchla increases occurred for almost the entire area within a radius of 100 km. The time series analysis showed that the Cchla peak appeared on the fifth day after the typhoon’s passage.

Use of 210Pb dating models for estimating sedimentation rate of a typical sediment core taken in the Ba Lat coastal area (Red River)

Sediment cores were taken in the coastal area of Ba Lat estuary (Red River), in the Xuan Thuy national park. Each core was cut into slices of 4 cm in thickness, numbered from top to bottom and then analyzing for radionuclides (226Ra, 137Cs and 210Pb). Computational dating models were used to determine the age and sedimentation rate for each sediment core. This report presents the results of applying computational models to the sediment core BL13 that could provide a general methodology for determining the age and the sedimentation rate of the sediment cores taken in the coastal area of Ba Lat estuary. Results show that Constant rate of supply (CRS) model is probably the best model for determining the sedimentation rate. For the sediment core BL13, the use of the Composite model by adjusting the results of the CRS model in combination with the time marker of August 1971 (the time of the historical flood event on the Red River) seems to give the most reasonable results. The average sedimentation rate at the BL13 site before 1960 was about 0.5 cm/year. The rate had increased significantly from 1960, up to the highest value of 1.5 cm year-1 in the 1970s and then decreased to about 1.0 to 1.2 cm/year from the 1980s to the present. The change in the sedimentation rate could be caused by the main flow changes and large floods of the Red River from 1960 to 1980.