Seawater Samples Research Articles

Community Structure of Phytoplankton in The Waters of Gili Trawangan, North Lombok

Gili Trawangan is one of the popular marine tourism destinations and conservation areas in the West Nusa Tenggara Province. Increased human activity in the Gili Trawangan is associated with increased pressure on aquatic ecosystems. Human activity pressure comes from tourism activities and negative impacts due to various community activities around the waters can reduce water quality. Changes to water quality can be seen from the abundance and composition of phytoplankton. This is because phytoplankton plays an important role in a water body, namely as a primary producer in the food chain and has the ability to respond to the changes of the environment factors. This rearch was conducted to determine the abundance and composition of phytoplankton community structure in Gili Trawangan, North Lombok. Seawater samples were taken using a 20 µm plankton net by filtering 100 L of water. The filtered water samples were then preserved using formalin in 4% concentration. Data were analyzed by calculating the abundance of individuals, diversity (H'), uniformity (E), and dominance (D). The results showed that the average abundance of phytoplankton species was 1026.296 Ind/L and 22 genera of phytoplankton were identified. Species diiversity index (H'=2.58) is classified as medium. Species uniformity index (E=0.88) and species dominance index (C=0.10). Based on the results of this research it can be concluded that the waters of Gili Trawangan North Lombok are classified as oligotrophic waters.

Effective Removal of Anthracene from Seawater Samples Using a Thermo-Sensitive Polymer Based on Magnetic Graphene Oxide: Fabrication and Characterization

Effective Removal of Anthracene from Seawater Samples Using a Thermo-Sensitive Polymer Based on Magnetic Graphene Oxide: Fabrication and Characterization

Microbial indicators of coastal water in Velipoja beach, Albania

Abstract The Albanian coastline is about 450 km long, with wide access to the Adriatic and Ionian seas. It has become popular in recent years for its many unexplored rocky and sandy beaches, crystal waters, curative sand rich in iodine, which has given a great impact in tourism and economy. Velipoja beach is located on the northwest of Adriatic Sea. Coastal waters of Velipoja are used for bathing, fishing and tourism, but in recent years these waters are exposed to various sources of pollution, which are related to restaurants and agricultural activities, wastewater discharge, etc. The quality of coastal water in Albania is particularly analysed by the Public Health Institution. It was considered reasonable to monitor the microbiological quality of coastal waters on Velipoja beach through microbiological parameters during summer season. Evaluations of the results were done based on Directive 2006/7/EC for inland waters, coastal and transitional waters. Seawater samples were tested mainly for E. coli, E. faecalis, S. faecalis, heterotrophs in accordance with European Standards using the membrane filtration method. Water samples were taken monthly from May-September 2023. Based on the data received, during the monitoring period the bacterial concentration for E. faecalis varied from 0 CFU /100 ml to 228 CFU/100 ml. The concentration for S. faecalis varied from 0 CFU /100 ml to 128 CFU/100 ml. The concentration for E. coli varied from 0 CFU /100 ml to 134 CFU/100ml. Velipoja Center has the highest concentration of E. coli, E. faecalis. The concentration of bacteria increases during the months of July and August, probably due to the large number of tourists visiting Velipoja beach during this period. According to Directive 2006/7/EC of the European Parliament, the quality of coastal waters of Velipoja during the period of investigation for E. coli is in the category “Excellent quality”. Monitoring for the presence of pathogen bacteria are essential water quality assessment, which directly or indirectly leads to serious problems to human health. Enterococcus faecalis is an indicator of an old faecal pollution (EN ISO 7899-2, 2000). The European Community (2006) recommended the following parameters: Escherichia coli/100 ml (500/1.000), and Intestinal enterococci/100 ml (200/400) categorized in the class A and B. Urban wastewaters are major sources for surface and groundwater pollution in the Shkodra lake basin. Monitoring for the presence of pathogen bacteria are essential water quality assessment, which directly or indirectly leads to serious problems to human health. Enterococcus faecalis is an indicator of an old faecal pollution (EN ISO 7899-2, 2000). The European Community (2006) recommended the following parameters: Escherichia coli/100 ml (500/1.000), and Intestinal enterococci/100 ml (200/400) categorized in the class A and B. Urban wastewaters are major sources for surface and groundwater pollution in the Shkodra lake basin.

First report on BTEX leaching from waterpipe tobacco wastes (WTWs) into aquatic environment

Waterpipe tobacco wastes (WTWs) may contain considerable levels of hazardous contaminants such as BTEX (benzene, toluene, ethylbenzene, o-xylene, and m/p-xylene). However, no research has been carried out on BTEX levels in WTWs and the release of these pollutants into the water environment. This research examined the levels of BTEX in WTWs of flavored/local tobacco and also the release rate of these toxins into three kinds of water, including seawater (SW), tap water (TW), and distilled water (DW) with different leaching times (15, 30 min, 1.2, 4, 8 h, and 1, 2, and 4 days). The mean contents of BTEX in WTW samples of Al-Mahmoud, Al-Fakher, Mazaya, Al-Ayan brands, and local tobacco samples were 17.0 ± 4.14, 19.1 ± 4.65, 19.6 ± 4.19, 18.8 ± 4.14, and 3.16 ± 0.63 μg/kg, respectively. The mean BTEX levels in flavored tobacco samples were considerably greater than that of local tobacco (p < 0.05). The WTWs leaching experiments showed that the levels of BTEX ranged from 5.26 to 6.12, 5.02–5.60, and 3.83–5.46 μg/L in DW, TW, and SW, respectively. All target compounds were found for all exposure times in DW, TW, and SW samples. After adding sodium azide as an antibacterial agent to water samples (simulating biodegradation processes), higher levels of BTEX compounds were detected in SW. Further research is needed to address the potential environmental hazards due to WTWs leaching into aquatic environments.

Accessing the intrinsic factors of carbonyl index of microplastics: Physical and spectral properties, baseline correction, calculation methods, and their interdependence

Carbonyl index (CI) is a measure of the degradation status of microplastics. While many studies address environmental factors of microplastic degradation, intrinsic factors like physical properties, spectral properties, baseline correction, and CI calculation methods are less explored. This research focused on these aspects using surface seawater samples. We found that color and shape have limited dependence on particle size or signal-to-noise ratio (SNR). Baseline correction can significantly alter CI values, with the direction of the shift depending on the methods used. Additionally, most CI values before and after baseline correction and those calculated using different methods tend to be strongly correlated. Using the selected CI calculation methods, we found that CI values varied significantly by shape and color. CI's relation to the similarity between the sample and its pristine form suggests an alternative degradation measure. Our findings emphasize the need for standardized CI calculation methods.

Saxitoxin hazard! Detection of toxic algae in molluscs breeding areas in North-Western Adriatic Sea

Abstract Background Saxitoxin (SXT) can cause the paralytic shellfish poisoning (PSP) with severe impacts on both human health and marine ecosystems. Dinoflagellates are the major marine producers of STX and other variety of secondary toxic metabolites that can gather in molluscs becoming a risk for consumers’ poisoning. The aim of this work was to investigate the presence of the main algal species producing SXT in an area intended for molluscs breeding. Methods During 2020-2023, 40 seawater samples were collected from two macro-areas in the Adriatic Sea (North-Western) at different distances from the coast. After water filtration, DNA was extracted (DNeasy PLANT Mini Kit) and analysed with Real Time PCR for Alexandrium minutum and Gymnodinium catenatum detection. The possible ability to produce SXT was confirmed by sxt4A gene detection. Molecular results were compared with the microscopy gold-standard method. Results A. minutum was detected in 62.5% (CI 95% 0.47-0.75) of the samples, with 84% (CI 95% 0.65-0.94) of them possibly producing SXT. G. catenatum was found in 95% (CI 95% 0.83-0.99) of samples, with 73.7% (CI 95% 0.58-0.85) of them presenting STX gene. By microscopy, only Alexandrium spp. were identified without successful species identification. No other saxitoxin-producing genera or species were observed. Conclusions Our results underlined that A. minutum and G. catenatum can play an important role in the production of SXT, confirming their harmful presence in the areas intended for molluscs breeding. Microscopic identification can lead to an underestimation of the presence of potentially toxic algal species, stressing the relevance of improving molecular tools also in this field. These findings highlighted the importance of reporting and monitoring toxic algae presence, given the saxitoxin impact for food safety, and its significance for public health. Key messages • Saxitoxin-producing algae detection through molecular methods in molluscs breeding areas may represent an early warning useful to improve food safety and human health. • Harmful algal monitoring can improve water management in a One Health perspective.

A new approach for the determination of As, Cu, and Pb in seawater samples using manganese oxide octahedral molecular sieve as a sorbent for dispersive solid-phase microextraction

This study introduces a novel method for preconcentrating As, Cu, and Pb from seawater samples using manganese oxide octahedral molecular sieve (OMS-2), as a sorbent, and the analysis by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The OMS-2 nanomaterial was synthesized and characterized using X-ray diffraction and scanning electron microscopy, revealing a crystallite size of 20.9 nm and a typical needle-like morphology of cryptomelane structure. To optimize the ICP-OES operating conditions and the preconcentration process, a central composite design was used. The optimal conditions for ICP-OES analyses were 1200 W and 0.7 L min−1 for the levels of the radio frequency potential (RF) and nebulization gas flow rate, respectively. The optimal conditions for the adsorption process were achieved at a pH of 6.5, 30 mg of OMS-2, and 35 min of stirring time, in the presence of the sample matrix. The enrichment factors obtained were 66, 45, and 21, and a limit of detection of 0.3, 0.1, and 2.1 μg L−1 for As, Cu, and Pb, respectively. The recovery tests ranged from 80 % to 120 %. The method was successfully applied to determine As, Cu, and Pb in seawater samples.

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in water-sediment system of southern Mediterranean: Concentration, source and ecological risk assessment

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were studied in the Nile Delta area of Egypt's southern Mediterranean for their environmental impacts, probable sources, and ecological risk assessment. Using the Gas Chromatography Triple Quadrupole technique, the residues of 16 OCPs and 18 PCBs were determined. The total OCPs content in the seawater and sediment samples ranged from 0.108 to 10.97 μg/L and 0.301 to 5.268 ng/g, respectively, while the PCBs residues had values between 0.808 and 1069.75 μg/L in seawater and between not detected and 575.50 ng/g in sediment samples. The findings of the risk evaluation showed that, except for endosulfan-I, OCPs caused little harm in seawater. However, PCB180, PCB153, PCB156, PCB126 and PCB138 posed a comparatively significant risk. The concentration of DDTs was higher than the effect range low and threshold effect level but remained below the effect range median and probable effect level, posing a minimal ecological concern.

Nucleus-forming vibriophage cocktail reduces shrimp mortality in the presence of pathogenic bacteria

The global aquaculture industry has suffered significant losses due to the outbreak of Acute Hepatopancreatic Necrosis Disease (AHPND) caused by Vibrio parahaemolyticus. Since the use of antibiotics as control agents has not been shown to be effective, an alternative anti-infective regimen, such as phage therapy, has been proposed. Here, we employed high-throughput screening for potential phages from 98 seawater samples and obtained 14 phages exhibiting diverse host specificity patterns against pathogenic VPAHPND strains. Among others, two Chimallinviridae phages, designated Eric and Ariel, exhibited the widest host spectrum against vibrios. In vitro and in vivo studies revealed that a cocktail derived from these two nucleus-forming vibriophages prolonged the bacterial regrowth of various pathogenic VPAHPND strains and reduced shrimp mortality from VPAHPND infection. This research highlights the use of high-throughput phage screening that leads to the formulation of a nucleus-forming phage cocktail applicable for bacterial infection treatment in aquaculture.

Comparison of methods to determine extraction efficiencies of Ra isotopes and 227Ac from large volume seawater samples

Radium isotopes, other than 226Ra, and 227Ac are typically present at low activities in the open ocean. The analysis of these isotopes thus requires the collection of large volumes of seawater and high sensitivity, low background instruments. To obtain the required large volumes (hundreds to thousands of liters), these radionuclides are typically preconcentrated on cartridge-style filters impregnated with MnO2 (Mn-cartridges) deployed on in-situ pumps. This technique, however, requires the determination of the extraction efficiency of the Mn-cartridges for the radionuclides of interest. For Ra isotopes, we used two methods to estimate the extraction efficiency of these Mn-cartridges at two stations on the South-West Indian Ridge in the Southern Ocean (GEOTRACES GS02). Method (1) compares the 226Ra activities recovered on the Mn-cartridges versus the activities determined in Mn-fibers, through which seawater was passed at a flow rate < 1 L min−1 to quantitatively sorb Ra (Mn-fiber method) while method (2) combines the 226Ra activities determined from two Mn-cartridges placed in series on in-situ pumps (A-B method). The second method is also applied to determine the 227Ac extraction efficiency. We find a relatively wide-range of Ra and 227Ac extraction efficiencies across the dataset (from 44.8% to 99.6% for Ra, and from 23.7% to 77.5% for 227Ac). Overall, the yield of 227Ac extraction is lower than that of Ra (mean value of 49.3 ± 19.0% for 227Ac, n = 10, mean value of 79.2 ± 10.3% for Ra, n = 13, using the Mn-fiber method; and a mean value of 63.9 ± 12.5%, n = 11 using the A-B method). Our dataset suggests that the Ra extraction efficiencies using either the A-B method or the Mn-fiber method are in relatively good agreement. Consequently, the 223Raex, 224Raex and 228Ra activities determined from the Mn-cartridges by applying the two Ra extraction yields are similar. We also show that the 227Ac extraction efficiency can be estimated from the Ra extraction efficiency allowing the use of a single Mn-cartridge. Finally, we recommend to determine the Ra and 227Ac extraction efficiencies in each individual Mn-cartridge, rather than applying a single extraction efficiency to all the Mn-cartridges, since a significant variability in the extraction efficiencies was observed between the different Mn-cartridges.

Vertical dynamics of free-living and particle-associated vibrio communities in the eastern tropical Indian Ocean

Members of the family Vibrionaceae (vibrios) are widely distributed in estuarine, offshore, and marginal seas and perform an important ecological role in the marine organic carbon cycle. Nevertheless, there is little knowledge about whether vibrios play ecological roles in the oligotrophic pelagic area, which occupies a larger water volume. In this study, we investigated the abundance, diversity, and composition of free-living and particle-associated vibrios and their relationships with environmental factors along the water depth in the eastern tropical Indian Ocean (ETIO). The abundance of vibrios in free-living fractions was significantly higher than that of particle-associated fractions on the surface. Still, both were similar at the bottom, indicating that vibrios may shift from free-living lifestyles on the surface to mixed lifestyles at the bottom. Vibrio-specific 16S rRNA gene amplicon sequencing revealed that Paraphotobacterium marinum and Vibrio rotiferianus were dominant species in the water column, and Vibrio parahaemolyticus (a clinically important pathogen) was recorded in 102 samples of 111 seawater samples in 10 sites, which showed significant difference from the marginal seas. The community composition also shifted, corresponding to different depths in the water column. Paraphotobacterium marinum decreased with depth, and V. rotiferianus OTU1528 was mainly distributed in deeper water, which significantly correlated with the alteration of environmental factors (e.g., temperature, salinity, and dissolved oxygen). In addition to temperature and salinity, dissolved oxygen (DO) was an important factor that affected the composition and abundance of Vibrio communities in the ETIO. Our study revealed the vertical dynamics and preferential lifestyles of vibrios in the ETIO, helping to fill a knowledge gap on their ecological distribution in oligotrophic pelagic areas and fully understanding the response of vibrios in a global warming environment.

Unraveling the Complexities of Groundwater Salinization in Coastal Environments: Insights from Laizhou Bay’s Eastern Coast, China

Coastal areas have made substantial contributions to global economic development but are plagued by challenges such as groundwater salinization. Groundwater serves as the primary source for drinking, industrial, and domestic purposes in these coastal areas. Therefore, understanding the causes and processes of groundwater salinization holds paramount significance for effective groundwater management. The coastal area of Laizhou Bay in northern China serves as a quintessential example of such a scenario. With substantial groundwater extraction and severe groundwater salinization issues, it exacerbates the disparity between water-resource supply and demand. Currently, our understanding of the processes and influencing factors related to groundwater salinization in this region remains limited. In this study, employing hydrochemical and stable chlorine isotope analyses on 35 groundwater and seawater samples, an in-depth investigation into the complex mechanisms underlying groundwater salinization in the Quaternary aquifers of the eastern coastal plain of Laizhou Bay was conducted. The test results of the samples indicate that brine and saline groundwater are primarily of the Na-Cl type, exhibiting a hydrochemical composition similar to that of seawater. Brackish groundwater exhibits a diverse hydrochemical composition. The hydrogen and oxygen isotope characteristics of brackish and fresh groundwater resemble atmospheric precipitation, while brine, seawater, and saline groundwater show hydrogen and oxygen isotope depletion. Compared to seawater, brine exhibits significant δ37Cl depletion. The analysis of the test results reveals that the formation of brine aquifers results from a complex interplay of climate change, tectonic movements, and sea–land evolution, involving lagoon development during seawater regression, salt concentration through evaporation, and subsequent water–rock interactions. The genesis of saline groundwater involves a complex interplay of brine–seawater mixing, significant evaporation, and potential input of fresh groundwater from atmospheric precipitation and river sources. The formation of brackish groundwater is predominantly influenced by atmospheric precipitation, and agricultural activities, with significant variations in NO3− concentrations attributed to varying intensities of fertilizer application in the northern plain area. These insights contribute to a deeper understanding of the origins of groundwater and can inform the development of policies for groundwater protection in this area.

Seasonal and Spatial Dynamics of Fungal Diversity and Communities in the Intertidal Zones of Qingdao, China.

Intertidal zones comprise diverse habitats and directly suffer from the influences of human activities. Nevertheless, the seasonal fluctuations in fungal diversity and community structure in these areas are not well comprehended. To address this gap, samples of seawater and sediment were collected seasonally from the estuary and swimming beaches of Qingdao's intertidal areas in China and were analyzed using a metabarcoding approach targeting ITS2 rDNA regions. Compared to the seawater community dominated by Ciliophora and Agaricomycetes, the sediment community was rather dominated by Dothideomycetes and Eurotiomycetes. Furthermore, the seawater community shifted with the seasons but not with the locations, while the sediment community shifted seasonally and spatially, with a specific trend showing that Cladosporium, Alternaria, and Aureobasidium occurred predominantly in the estuarine habitats during winter and in the beach habitats during spring. These spatiotemporal shifts in fungal communities' composition were supported by the PERMANOVA test and could be explained partially by the environmental variables checked, including temperature, salinity, and total organic carbon. Unexpectedly, the lowest fungal richness was observed in the summer sediments from two swimming beaches which were attracting a high influx of tourists during summer, leading to a significant anthropogenic influence. Predicted trophic modes of fungal taxa exhibited a seasonal pattern with an abundance of saprotrophic fungi in the summer sediments, positively correlating to the temperature, while the taxa affiliated with symbiotroph and pathotroph-saprotroph occurred abundantly in the winter and spring sediments, respectively. Our results demonstrate the space-time shifts in terms of the fungal community, as well as the trophic modes in the intertidal region, providing in-depth insights into the potential influence of environmental factors and human activity on intertidal mycobiomes.

Impact of domestic and industrial effluent on marine environment at Karachi Port Trust (KPT) coastal area, Pakistan.

The extent of aquatic pollution of Karachi Port Trust (KPT) coastal area located at the south of Pakistan coast has increased considerably in the last few decades due to unrestricted discharge of sanitary waste. The current study lays emphasis on the identification of vulnerable zones severely impacted by pollution in the KPT coastal area using laboratory monitoring, geospatial techniques, and statistical analysis. During 2019, sampling was conducted along the KPT coastal area, and 54 samples of seawater were collected during pre- and post-monsoon seasons. The outcomes of physical and chemical analysis revealed that the concentrations of BOD (biochemical oxygen demand), COD (chemical oxygen demand), nitrate, phosphate, phenol, cyanide, and oil and grease frequently exceeded the permitted limit of international norms and reached much greater levels. The levels of perilous metals in the seawater samples were in the order Ni>Cr>Cu>Pb>Cd>As in both phases and also reached to elevated levels as a consequence of the indiscriminate discharge of untreated industrial and domestic wastewater. Based on detailed examination during pre- and post-monsoon, six sites near KPT, Lyari River outfall, and Karachi Harbour were identified as highly polluted zones due to heavy discharge of sanitary effluents at these sites. In particular, the industrial zones present in the formal and informal sectors of Karachi are responsible for the deterioration of the KPT coastal area. Therefore, it is advised to design and build a submerged drainage system to transport and distribute massive amounts of treated municipal and industrial waste to the deep open sea in order to minimize the high pollutant levels in these locations.

Highly Blue-fluorescent Carbon Quantum Dots Obtained from Medlar Seed for Hg2+ Determination in Real Water Samples.

The carbon quantum dots (CQDs) have been prepared from medlar seeds with pyrolysis method in an oven at 300°C. UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR) spectroscopy, x-ray diffraction (XRD) technique, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used in the characterization of CQDs. CQDs, give a strong blue fluorescence under UV lamp (at 365nm), have a quantum yield of 12.2%. The influence of metal ions such as K+, Mg2+, Ca2+, Be2+, Cr3+, Mn2+, Ni2+, Ag+, Hg2+, and Al3+ on the fluorescence properties of the CQDs was investigated by means of emission spectrophotometry. CQDs altering fluorescence characteristics depending on the excitation wavelength show selectivity for Hg2+ ions with outstanding fluorescence quenching among the tested metal ions. Based on these results, a new fluorimetric method has been developed for the determination of Hg2+ in real water samples. The linear range of method is 1.0 to 5.0 mgL- 1. Limit of detection and limit of quantification are 0.26 and 0.79 mgL- 1, respectively. The proposed method has been successfully used in determination of Hg2+ ions in tap, sea, and stream water samples with application of addition-recovery experiments.

First pelagic fish biodiversity assessment of Cosmonaut Sea based on environmental DNA

The Cosmonaut Sea is a typical marginal sea in East Antarctica that has not yet been greatly impacted by climate change. As one of the least explored areas in the Southern Ocean, our knowledge regarding its fish taxonomy and diversity has been sparse. eDNA metabarcoding, as an emerging and promising tool for marine biodiversity research and monitoring, has been widely used across taxa and habitats. During the 38th Chinese Antarctic Research Expedition (CHINARE-38), we collected seawater and surface sediment samples from 38 stations in the Cosmonaut Sea and performed the first, to our knowledge, eDNA analysis of fish biodiversity in the Southern Ocean based on the molecular markers of 12S rRNA and 16S rRNA. There were 48 fish species detected by the two markers in total, with 30 and 34 species detected by the 12S rRNA and 16S rRNA marker, respectively. This was more than the trawling results (19 species) and historical survey records (16 species, “BROKE-West” cruise). With some nonsignificant differences between the Gunnerus Ridge and the Oceanic Area of Enderby Land, the Cosmonaut Sea had a richer fish biodiversity in this research compared with previous studies, and its overall composition and distribution patterns were consistent with what we know in East Antarctica. We also found that the eDNA composition of fish in the Cosmonaut Sea might be related to some environmental factors. Our study demonstrated that the use of the eDNA technique for Antarctic fish biodiversity research is likely to yield more information with less sampling effort than traditional methods. In the context of climate change, the eDNA approach will provide a novel and powerful tool that is complementary to traditional methods for polar ecology research.

Simultaneous Measurement of Trace Levels of Hg, As, Sb, and Bi in Coastal Seawater with a Multichannel Chemical Vapor Generation Atomic Fluorescence Spectrometer.

Trace levels of Hg, As, Sb, and Bi in coastal seawater have been simultaneously detected by a laboratory-built multichannel chemical vapor generation coupled to an atomic fluorescence spectrometer. The system was configured with a built-in electrochemical H2 generator as the fuel supplier to replace chemical H2 produced by the oxidation of potassium borohydride under acidic conditions in traditional instruments. The electrochemical H2 generator not only isolated the atomization process from the chemical vapor injection process but also improved the stability of atomization, excitation, and fluorescence emission in the hydrogen flame, making it easier to optimize conditions for CVG while introducing evaporating multielement vapors. Calibrations were obtained using a mixed standard solution of Hg(II), As(III), Sb(III), and Bi(III). The addition of KBr to a 3% (v/v) HCl solution was selected as the preservative to ensure the stability of 0.10 μg/L Hg(II) in a multielement standard solution for at least 15 days while also preserving μg/L levels of As(III), Sb(III), and Bi(III) stable. The method detection limits (LOD, 3σ) were 0.001, 0.015, 0.010, and 0.005 μg/L for Hg, As, Sb, and Bi, respectively. The relative standard deviations (RSD, n = 7) of the standard spiked seawater samples were 3.2% (0.020 μg/L Hg), 1.2% (0.50 μg/L As), 1.0% (0.50 μg/L Sb), and 3.5% (0.050 μg/L Bi), respectively. The recoveries of seawater samples spiked with different salinities were in the range of 84.5%(Sb)-114%(Hg). The system has been successfully applied to the simultaneous analysis of the four elements in the seawater samples collected from Xiamen Bay, Southeast China.

Comparative analyses of eight primer sets commonly used to target the bacterial 16S rRNA gene for marine metabarcoding-based studies

Next-generation sequencing (NGS), especially metabarcoding, is commonly used to study the diversity and distribution of microbes in diverse ecosystems. The choice of primer set is critical, given the drawbacks of short amplicons and amplicon sequencing bias inherent to metabarcoding. However, comparative analyses of primer sets have rarely been conducted using field samples. In this study, we compared eight commonly used primer sets, all targeting hypervariable regions in the bacterial 16S rRNA gene: 27F/338R (V1–V2), V2f/V3r (V2–V3), PRK341F/PRK806R (V3–V4), 341F/785R (V3–V4), 515F/806RB (V4), 515F/806R (V4), 515F-Y/926R (V4–V5), and B969F/BA1406R (V6–V8). We conducted NGS in triplicate, with &amp;gt;0.8 billion bases in total using coastal seawater samples. The representation of bacterial community composition varied significantly across the eight primer sets, despite being from the same sample. The 27F/338R primer set showed the highest number of operational taxonomic units (OTUs) and read counts, and accounted for 68% of all the order-level taxa found. Remarkably, a novel complementary combination of two primer sets, 27F/338R and 515F/806RB, covered 89% of all the orders that were present. Compared to other primer sets, this combination detected more OTUs of the orders Pelagibacterales and Rhodobacterales, which are ubiquitous in the oceans. As such, use of this combination in future studies may help to reduce diversity bias in ocean-derived samples, in particular temperate coastal samples.

Galbibacter pacificus sp. nov., isolated from surface seawater of the western Pacific Ocean and transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. and emended description of the genus Galbibacter.

Two Gram-stain-negative, non-motile, non-spore-forming, strictly aerobic and rod-shaped bacterial strains, CMA-7T and CAA-3, were isolated from surface seawater samples collected from the western Pacific Ocean. Phylogeny of 16S rRNA gene sequences indicated they were related to the genera Galbibacter and Joostella and shared 95.1, 90.9 and 90.8% sequence similarity with G. mesophilus Mok-17T, J. marina DSM 19592T and G. marinus ck-I2-15T, respectively. Phylogenomic analysis showed that the two strains, together with the members of the genera Galbibacter and Joostella, formed a monophyletic clade that could also be considered a monophyletic taxon. This distinctiveness was supported by amino acid identity and percentage of conserved proteins indices, phenotypic and chemotaxonomic characteristics and comparative genomics analysis. Digital DNA‒DNA hybridization values and average nucleotide identities between the two strains and their closest relatives were 18.0-20.8 % and 77.7-79.3 %, respectively. The principal fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G, Summed Feature 3 (C16 : 1 ω7c/C16 : 1 ω6c or C16 : 1 ω6c/C16 : 1 ω7c), Summed Feature 9 (iso-C17 : 1 ω9c or C16 : 0 10-methyl), and C15 : 0 3-OH. The predominant respiratory quinone was MK-6. The polar lipids were phosphatidylethanolamine, aminolipid, aminophospholipid, phospholipid, phosphoglycolipid, glycolipid and unknown polar lipid. The genomic DNA G+C content of strains CMA-7T and CAA-3 was both 38.4 mol%. Genomic analysis indicated they have the potential to degrade cellulose and chitin. Based on the polyphasic evidence presented in this study, the two strains represent a novel species within the genus Galbibacter, for which the name Galbibacter pacificus sp. nov. is proposed. The type strain is CMA-7T (=MCCC M28999T = KCTC 92588T). Moreover, the transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. (type strain En5T = KCTC 12518T = DSM 19592T=CGMCC 1.6973T) is also proposed.

Occurrence and pathways of microplastics, quantification protocol and adverse effects of microplastics towards freshwater and seawater biota

Plastic has become one of the major contributors to the world’s pollution. As it may degrade into smaller particles known as microplastics (&lt;5 mm), which has become a new threat towards marine ecosystems. Due to their size, microplastics can easily enter the food chain due to seafood consumption, entering the digestive system. Moreover, microplastics also bring negative impact towards freshwater biota and sea life. Despite the extensive studies on microplastic contamination in the marine environment, research on microplastic in seafood and freshwater environments, specifically regarding ingestion and effect of microplastics in aquatic organisms, freshwater biota as well as human health along the supply chain are still scarce. Microplastic ingestion in aquatic animals causes health hazards such as leaking gut, transferring pathogenic bacteria into the blood and increasing toxic levels in the body. This scenario could potentially introduce similar hazards to human health if consumed. This paper reviewed the sources, detection method, allocation and adverse effects of microplastics contamination in seafood and freshwater ecosystems. The focus of this review is on biota which includes samples of aquatic animals as well as seawater samples from various sources including riverine (river), lacustrine (lake) and wastewater treatment plants (WWTPs) throughout the world. Since microplastics are related to synthetic substances from waste, there is an alarming concern regarding their physical and chemical compounds that might be present in the aquatic life and food supply chain. Therefore, recommendations and improvements on future studies of microplastic contamination in marine ecosystems regarding identification and quantification protocol along with the study on microplastics towards the freshwater organism also are addressed in this paper.