Seawater Samples Research Articles

Structure and assembly process of fungal communities in the Yangtze River Estuary.

Marine fungi are essential for the ecological function of estuarine ecosystems. However, limited studies have reported on the structure and assembly pattern of the fungal communities in estuaries. The purpose of this study is to reveal the structure and the ecological process of the fungal community in the Yangtze River Estuary (YRE) by using the amplicon sequencing method. Phyla of Ascomycota, Basidiomycota, and Chytridiomycota were dominant in the seawater and sediment samples from YRE. The null model analysis, community-neutral community model (NCM), and phylogenetic normalized stochasticity ratio (pNST) showed that the stochastic process dominated the assembly of fungal communities in YRE. Drift and homogeneous dispersal were the predominant stochastic processes for the fungal community assembly in seawater and sediment samples, respectively. The co-occurrence network analysis showed that fungal communities were more complex and closely connected in the sediment than in the seawater samples. Phyla Ascomycota, Basidiomycota, and Mucoromycota were the potential keystone taxa in the network. These findings demonstrated the importance of stochastic processes for the fungal community assembly, thereby widening our knowledge of the community structure and dynamics of fungi for future study and utilization in the YRE ecosystem.

Analysis of Bacterial Communities and Antibiotic Resistance Genes in the Aquaculture Area of Changli County

In order to understand the distribution of microorganisms and various antibiotic resistance genes in the aquaculture area of Changli County, Qinhuangdao, high-throughput sequencing technology was used in this study. We utilized 16S rDNA gene sequencing and metagenome sequencing methods to analyze the seawater, sediment, and gut contents of the local fish Synechogobius hasta in the aquaculture area in spring. The results showed that Proteobacteria, Firmicutes, and Bacteroidota were the dominant bacteria in seawater; and Proteobacteria, Crenarchaeota, Acidobacter, and Actinobaciota were rich in the sediment; whereas Proteobacteria, Cyanobacteria, Firmicutes, and Bacteroidota were in relatively high abundance in fish gut contents. The microbial diversity of sediment samples was the most abundant, followed by seawater samples, and the microbial diversity of fish intestinal contents was the lowest. Moreover, the microbial diversity of similar samples was relatively similar, and the microbial diversity of different types of samples was quite different. For samples at different sites, there were significant differences between seawater samples at each site, and there were small differences between sediment samples at each site, and some sediment sample groups did not have significant differences in microbial composition. In all sample groups, five β-lactam antibiotic resistance genes (blaOXA-325, cepS, blaCARB-20, blaOXA-55, and blaTRU-1) and four aminoglycoside antibiotic resistance genes[aac(6')-IIb, amrA, aac(6')-Ie-aph(2″)-Ia, and aph(3')-Vc] were detected. There was also a certain correlation between antibiotic resistance genes and microbial communities.

A novel electrochemiluminescence biosensor based on Ru(bpy)32+-functionalized MOF composites and cycle amplification technology of DNAzyme walker for ultrasensitive detection of kanamycin

An electrochemiluminescence (ECL) sensing platform for ultrasensitive and highly selective detection of kanamycin (KANA) was developed based on the prepared Ru(bpy)32+-functionalized MOF (Ru@MOF) composites by hydrothermal synthesis and Ag+-dependent DNAzyme. In this sensor, the stem-loop DNA (HP) with the ferrocene (Fc) was used as substrate chain to quench the ECL emission generated by the Ru@MOF. Using the specific recognition effect between KANA and the KANA aptamer (Apt) and the DNAzyme dependence on Ag+, the KANA aptamer as the pendant strand of the DNAzyme was assembled on Ru@MOF/GCE with the aptamer. When both Ag+ and KANA were present simultaneously, KANA specifically was binded to KANA aptamer as a pendant chain. Subsequently, Ag+-dependent DNAzyme walker continuously cleaved the HP chain and released the modified end of Fc to restore the ECL signal of Ru@MOF composites, thus achieving selective and ultrasensitive detection of KANA. The constructed KANA biosensor exhibits a wide detection range (30 pM to 300 μM) accompanied by a low detection limit (13.7 pM). The KANA in seawater and milk samples are determined to evalute the practical application results of the sensor. This ECL detection strategy could be used for detecting other similar analytes and has broad potential application in biological analysis.

Biogeochemical evidence of flow re-entrainment on the main fringing reef of La Reunion Island

Understanding factors influencing seawater chemistry variability in coral reef environments is a major challenge to improve predictions of their evolution in the context of ocean acidification. In this study, autonomous sensors for current speed and direction, photosynthetically active radiation (PAR), temperature, salinity, dissolved oxygen (DO) and pHT were deployed three times between 2021 and 2022 offshore and on three reef flat sites of the main fringing reef of La Reunion Island. Discrete sampling of seawater for DO, pHT and total alkalinity (TA) at different times of the day complemented the monitoring. Diurnal variation of those variables on the reef flat was mainly driven by benthic community metabolism but hydrodynamics and reef geomorphology played also a key role. DO and pHT variations were decoupled in time, especially at night when we observed DO rebounds while pHT values were stationary. The reef flat was also largely TA depleted compared to offshore waters. We hypothesize that the strong offshore-alongshore current redirected TA depleted water exiting from reef channels into the reef flat. This seawater re-entrainment could also explain specific variations of DO and pHT values. This result highlights the important role of reef geomorphology in modulating changes in seawater chemistry. Neglecting this phenomenon could lead to substantial errors in the estimation of carbonate budgets when using the Eulerian approach.

Low-level tritium measurements in freshwater and seawater samples

AbstractThe aim of this study was to test two potential tritium determination methods (with and without electrolysis enrichment) suitable for low-level measurements. Both methodologies were applied to water samples from the Baltic Sea and ten Polish rivers providing new data on tritium activity concentration. Optimization steps carried out to the standard method lowered minimum detectable activity concentration (MDC) from 3.1 to 1.8 Bq L–1 (at 95% confidence level) enabling to apply it to environmental water samples. However, electrolytic enrichment method of MDC of 0.20 Bq L–1 provided more accurate results for tritium activity concentration in surface waters.

Tracing the fate of seabird‐derived nitrogen in a coral reef using nitrate and coral skeleton nitrogen isotopes

AbstractSeabirds transfer nutrients from the ocean to their nesting island, potentially altering nitrogen (N) cycling within adjacent terrestrial and marine ecosystems. Yet, the processes involved in seabird‐N transfer along the land–sea continuum remain elusive. Using δ15N and δ18O measurements of groundwater nitrate, we demonstrate the role of brackish groundwater located within a coral island's landmass as a major reservoir of nitrate (at millimolar levels). Nearly all of the total dissolved seabird‐derived N leaching into the groundwater (mostly ammonium and uric acid) is converted to nitrate by nitrification, as supported by the relatively low δ18O of the groundwater nitrate (3.97‰ ± 0.30‰). Comparison of nitrate δ15N and δ18O suggests that little denitrification takes place within the groundwater lens, implying that the high δ15N of groundwater nitrate (13.73‰ ± 0.05‰) derives from the high trophic position of seabirds and postdepositional processes that increase the δ15N of seabird excreta. Seawater and coral skeleton samples from a reef flat exposed to groundwater had higher δ15N values than at sites devoid of groundwater influence, indicating that the main source of N at the latter site was the Subtropical Upper Water, while the groundwater nitrate dominated the exposed reef flat N pool up to 200 m from shore. In addition, these results indicate that coral‐bound δ15N can detect seabird‐derived nitrate δ15N, raising opportunities to reconstruct historical seabird‐N inputs to coral reefs in relation to climatic and other changes, such as the introduction of invasive species.

Deep eutectic solvent-doped graphite as an efficient adsorbent for pipette tip micro-solid phase extraction of mitoxantrone from seawater, drug, urine and blood samples prior to its spectrophotometric determination

Deep eutectic solvent-doped graphite as an efficient adsorbent for pipette tip micro-solid phase extraction of mitoxantrone from seawater, drug, urine and blood samples prior to its spectrophotometric determination

Recommendations for best practice for iron speciation by competitive ligand exchange adsorptive cathodic stripping voltammetry with salicylaldoxime

The method of competitive ligand exchange followed by adsorptive cathodic stripping voltammetry (CLE-AdCSV) allows for the determination of dissolved iron (DFe) organic speciation parameters, i.e., ligand concentration (LFe) and conditional stability constant (log KFe′Lcond). Investigation of DFe organic speciation by CLE-AdCSV has been conducted in a wide range of marine systems, but aspects of its application pose challenges that have yet to be explicitly addressed. Here, we present a set of observations and recommendations to work toward establishing best practice for DFe organic speciation measurements using the added ligand salicylaldoxime (SA). We detail conditioning procedures to ensure a stable AdCSV signal and discuss the processes at play during conditioning. We also present step-by-step guidelines to simplify CLE-AdCSV data treatment and interpretation using the softwares ECDSoft and ProMCC and a custom spreadsheet. We validate our application and interpretation methodology with the model siderophore deferoxamine B (DFO-B) in a natural seawater sample. The reproducibility of our application and interpretation methodology was evaluated by running duplicate titrations on 19 samples, many of which had been refrozen prior to the duplicate analysis. Nevertheless, 50% of the duplicate analyses agreed within 10% of their relative standard deviation (RSD), and up to 80% within 25% RSD, for both LFe and log KFe′Lcond. Finally, we compared the sequential addition and equilibration of DFe and SA with overnight equilibration after simultaneous addition of DFe and SA on 24 samples. We found a rather good agreement between both procedures, with 60% of samples within 25% RSD for LFe (and 43% of samples for log KFe′Lcond), and it was not possible to predict differences in LFe or log KFe′Lcond based on the method applied, suggesting specific association/dissociation kinetics for different ligand assemblages. Further investigation of the equilibration kinetics against SA may be helpful as a potential way to distinguish natural ligand assemblages.

Assessment of Trace Metal Contamination in Bivalve, Mytilus galloprovincialis, By Bioconcentration Factor (BCF) in the Moroccan Mediterranean Coast Environment

This study investigates the pollution of Morocco’s Mediterranean coastal zones by trace metals, highlighting its significance due to detrimental impacts on marine ecosystems and potential health risks through the food chain, exacerbated by the expansion of coastal areas in recent years. It focuses on measuring concentrations of trace metals such as copper, cadmium, lead, and chromium in the bivalve Mytilus galloprovincialis and surrounding seawater across three sites along the northern Moroccan Mediterranean coast. This research aims to evaluate metal bioaccumulation levels using the Biota Concentration Factor (BCF). Seawater samples were examined using both flame and graphite furnace atomic absorption spectrophotometry, while bivalve tissue samples underwent analysis through Inductively Coupled Plasma Optical Emission Spectrometry. Findings indicate that M. galloprovincialis significantly accumulates trace metals, with concentrations in descending order: Pb, Zn, Cr, Cu, and Cd. Conversely, the seawater metal concentration sequence was Zn, Cu, Cr, Cd, and Pb. The study applied BCF thresholds from Regulation (EC) No 1907/2006 (REACH) and the US EPA’s Toxic Substances Control Act (TSCA), categorizing metals as “bioaccumulative” (BCF between 1000 and 5000) and “very bioaccumulative” (BCF over 5000). This distribution provides insights into the toxicity and bioaccumulation of metals, underscoring the environmental and health implications for the marine ecosystem and species like M. galloprovincialis.

Fish and coral assemblages of a highly isolated oceanic island: The first eDNA survey of the Ogasawara Islands

AbstractThe Ogasawara Islands are a highly isolated oceanic archipelago in the Pacific Ocean that possess unique faunal and floral biodiversity with a high level of endemism. As historically more focus has been put on the terrestrial realm in examining diversification and evolutionary processes on oceanic islands, publicly accessible and spatially resolved data of marine reef ecosystems remain scarce. To address this issue, we conducted the first environmental DNA (eDNA) metabarcoding surveys of the actinopterygian (ray‐finned) and elasmobranch fishes and of Scleractinia coral assemblages in the waters of the Ogasawara Islands. We detected a total of 124 unique taxa of fish and 38 unique taxa of scleractinian corals. Overall, our eDNA results confirmed that the Ogasawara Islands host a rich variety of coral and fish fauna and underline the strength of eDNA surveys in rapidly obtaining targeted multi‐taxa data using seawater samples, requiring comparatively little effort and a lack of requirement for in situ taxonomic expertise. We anticipate that continued biomonitoring using eDNA with high sampling effort will add to and complement the body of knowledge regarding species distributions, invasive species, and biodiversity hotspots within oceanic archipelagos.

Development of a dispersive liquid-liquid microextraction method for the determination of plastic additives in seawater.

A method using dispersive liquid-liquid microextraction (DLLME) prior to high performance liquid chromatography-diode array detection (HPLC-DAD) was developed to determine seven additives from the plastics industry (butylated hydroxytoluene, diisodecyl phthalate, irgafos 168, lawsone, quercetin, triclosan and vitamin E) in seawater samples. These compounds can reach seawater due to direct discharge from wastewater treatment plants and leaching from plastics and microplastics. The extraction was performed using 25 mL of seawater, 500 μL of 1-octanol (extraction solvent) and a stirring step instead of dispersive solvent. Additive concentrations were determined by LC-DAD on a C18 column with a mobile phase of acetonitrile and phosphoric acid aqueous solution (pH 3.5) by gradient elution. The analytical recoveries ranged from 82 to 93% for all compounds, except for lawsone (60%). Repeatability and intermediate precision were adequate with RSD < calculated values following the Horwitz equation at the concentration levels evaluated (0.06 and 0.24 mg L-1). All additives exhibited linear matrix calibration curves (R2 > 0.99). Detection limits ranged from 0.009 to 0.028 mg L-1 and quantification limits ranged from 0.027 to 0.084 mg L-1. Finally, the application of the method to real samples verified the method as accurate and applicable to seawater.

Diel Patterns in the Composition and Activity of Planktonic Microbes in a Subtropical Bay

Planktonic microbes play a crucial role in the matter transformation and energy transfer of marine ecosystems. Marine microbial communities are profoundly influenced by various environmental factors, and their variations are typically investigated in a time-dependent manner. However, studies conducted on a monthly or annual basis do not offer sufficient temporal resolution to reveal changes that can occur on an hourly basis. We conducted a high-resolution time-series study using amplicon sequencing on seawater samples taken at 2-h intervals over a 3-d period from the subtropical Daya Bay to investigate changes in the microbial community composition and activity. The results showed that 46.8% of the microbial rRNA sequences exhibited circadian rhythms, including phytoplankton (e.g., Bacillariophyta, Cryptophyta, and Dinophyceae), heterotrophic bacteria (e.g., Actinomarinaceae, Flavobacteriaceae, and SAR11_clade), and zooplankton (e.g., Bestiolina and Phyllopharyngea). The genera of Bacillariophyta (e.g., Chaetoceros and Pseudo-nitzschia ) exhibited higher activity than those of Chlorophyta (e.g., Micromonas ). A similar trend was observed for zooplankton, where Choanozoa (e.g., Copepoda ) showed a strong circadian rhythm in abundance whereas Ciliophora (e.g., Pithites ) were more active. Light intensity and tides were identified as the driving factors behind the periodic succession and activity of the heterotrophic bacteria and phytoplankton with the exception of picocyanobacteria, which were mainly influenced by fluctuations in temperature, nutrients, and salinity. These high-resolution time-dependent observations showed that, despite the dynamic coastal environment, the periodic changes in the microbial community and activity were distinct and phylogenetically conserved. The findings may help in the development of ecosystem models for predicting microbial abundance and activity in rapidly changing coastal and estuary environments.

Legacy and emerging per- and polyfluoroalkyl substances in the Shuidong bay of South China: Occurrence, partitioning behavior, and ecological risks

With the phase-out of legacy per- and polyfluoroalkyl substances (PFASs), PFAS alternatives have been increasingly used in industrial production and daily life. However, available information on the occurrence of PFASs and PFAS alternatives in semi-enclosed bays remains limited. As a representative semi-enclosed bay in Guangdong Province, China, Shuidong Bay has experienced severe anthropogenic pollution (industrial, shipping, cultural, and domestic) in recent decades. Water pollution in Shuidong Bay has worsened, and PFASs have been identified as ubiquitous environmental pollutants in this bay. In this study, 23 PFASs, including 5 emerging PFASs, were analyzed in water, suspended particulate matter (SPM), and sediment samples collected from Shuidong Bay. We determined that perfluorobutanoic acid (PFBA) was the predominant PFAS compound in seawater, whereas 6:2 fluorotelomer sulfonic acid (FTS) and perfluorooctane sulfonamide acetate (FOSAA) were dominant in SPM and sediment, respectively. The sediment–water partitioning coefficients were greatly dependent on the perfluorinated carbon chain length. Chlorophyll a concentration had a significant effect on the dissolved concentrations of PFASs in seawater. The ecological risk assessment indicated that the PFASs detected in the seawater and sediment samples posed no considerable risks to aquatic organisms. This study provides a valuable reference for evaluating PFAS contamination in Shuidong Bay and conducting ecological risk assessments for aquatic organisms.

A two-year monitoring of Cryptosporidium spp. oocysts and Giardia spp. cysts in freshwater and seawater: A complementary strategy for measuring sanitary patterns of recreational tropical coastal areas from Brazil

Primary contact recreation is an important transmission route of gastroenteric protozoa such as Cryptosporidium and Giardia. However, data on the environmental epidemiology of both protozoa in Brazilian coastal areas still need to be available. The main goal of this study was to perform environmental monitoring and quantify the concentration of Cryptosporidium oocysts and Giardia cysts on the main beaches of the state of Paraná, Brazil, as a complementary tool for measuring the sanitary quality of bathing waters for two years. A total of 144 water samples were harvested monthly for two years from Guaratuba, Caiobá and Matinhos beaches (72 samples of seawater and 72 of freshwater) to search for pathogenic protozoa. Protozoa were concentrated by the membrane filtration technique and visualized by direct immunofluorescence assay (IFA). All positive samples by IFA were submitted for DNA extraction for PCR analysis. Fecal indicator bacteria (FIB) were enumerated by conventional microbiological techniques. Both protozoa were detected on all beaches during the two-year monitoring period. At least one protozoa were detected in 58.3% (n = 14) months of sampling, totaling 24 positive samples. Guaratuba was the most contaminated beach followed by Caiobá and Matinhos. Giardia spp. was detected in 15, Cryptosporidium spp. in seven and both parasites in two samples. Giardia DNA was confirmed on two beaches, and Cryptosporidium was detected for the first time through molecular assays in a coastal area of Brazil. An essential impact of FIB was observed in the first year and a reduction in contamination rates in the second year of monitoring. This is the first study conducted in the country in different environments that composes coastal areas to monitor together parasitological and microbiological quality for extended periods. The monitoring of coastal waters can guide environmental agencies aiming to improve the sanitary quality of beaches and safeguard public health.

Microbiome pattern and diversity of an anadromous fish, hilsa shad (Tenualosa ilisha).

The host-microbe interactions are complex, dynamic and context-dependent. In this regard, migratory fish species like hilsa shad (Tenualosa ilisha), which migrates from seawater to freshwater for spawning, provides a unique system for investigating the microbiome under an additional change in fish's habitat. This work was undertaken to detect taxonomic variation of microbiome and their function in the migration of hilsa. The study employed 16S rRNA amplicon-based metagenomic analysis to scrutinize bacterial diversity in hilsa gut, skin mucus and water. Thus, a total of 284 operational taxonomic units (OTUs), 9 phyla, 35 orders and 121 genera were identified in all samples. More than 60% of the identified bacteria were Proteobacteria with modest abundance (> 5%) of Firmicutes, Bacteroidetes and Actinobacteria. Leucobacter in gut and Serratia in skin mucus were the core bacterial genera, while Acinetobacter, Pseudomonas and Psychrobacter exhibited differential compositions in gut, skin mucus and water. Representative fresh-, brackish- and seawater samples of hilsa habitats were primarily composed of Vibrio, Serratia and Psychrobacter, and their diversity in seawater was significantly higher (P < 0.05) than freshwater. Overall, salinity and water microbiota had an influence on the microbial composition of hilsa shad, contributing to host metabolism and adaptation processes. This pioneer exploration of hilsa gut and skin mucus bacteria across habitats will advance our insights into microbiome assembly in migratory fish populations.

Microbiome profile of the Antarctic clam Laternula elliptica.

The filter feeder clam Laternula elliptica is a key species in the Antarctic ecosystem. As a stenothermal benthic species, it has a poor capacity for adaptation to small temperature variations. Despite their ecological importance and sensitivity to climate change, studies on their microbiomes are lacking. The goal of this study was to characterize the bacterial communities of L. elliptica and the tissues variability of this microbiome to provide an initial insight of host-microbiota interactions. We investigated the diversity and taxonomic composition of bacterial communities of L. elliptica from five regions of the body using high-throughput 16S rRNA gene sequencing. The results showed that the microbiome of L. elliptica tended to differ from that of the surrounding seawater samples. However, there were no significant differences in the microbial composition between the body sites, and only two OTUs were present in all samples, being considered core microbiome (genus Moritella and Polaribacter). No significant differences were detected in diversity indexes among tissues (mean 626.85 for observed OTUs, 628.89 Chao1, 5.42 Shannon, and 0.87 Simpson). Rarefaction analysis revealed that most tissues reached a plateau of OTU number according to sample increase, with the exception of Siphon samples. Psychromonas and Psychrilyobacter were particularly abundant in L. elliptica whereas Fluviicola dominated seawater and siphons. Typical polar bacteria were Polaribacter, Shewanella, Colwellia, and Moritella. We detected the prevalence of pathogenic bacterial sequences, particularly in the family Arcobacteraceae, Pseudomonadaceae, and Mycoplasmataceae. The prokaryotic diversity was similar among tissues, as well as their taxonomic composition, suggesting a homogeneity of the microbiome along L. elliptica body.The Antarctic clam population can be used to monitor the impact of human activity in areas near Antarctic stations that discharge wastewater.

Distribution characteristics and migration trends of hexabromocyclododecanes between seawater-sediment system in different seasons of fishing grounds along the Yellow sea and East China sea coasts

Pollutants in the ecological environment of fishery seawater are harmful to the survival and reproduction of aquatic organisms. Hexabromocyclododecanes (HBCDs) were 42.9% detected within ND-48.89 ng/L in 177 seawater samples and 30.7% within ND-1.07 ng/g dw in 88 sediment samples of the fisheries in the Yellow Sea and East China Sea, respectively. γ-HBCD accounted for 65% of seawater and 89% of sediment samples. HBCDs in seawater in winter (ND-48.89 ng/L) were significantly higher than in summer (ND-4.99 ng/L), possibly because the re-suspension caused by winds and waves could re-migrate HBCDs from the sediment to the seawater in winter. However, seasonal differences of HBCDs in sediment were not significant. The fugacities indicated HBCDs’ migrating trend from seawater to sediment due to their hydrophobic nature. There is almost no terrestrial input of HBCDs from the Yangtze and Yellow Rivers, and currently used fishery materials in marine may compose long-lasting sources of HBCDs.

Phenol Biodegradation by Free and Immobilized Acinetobacter calcoaceticus K5 and Candida tropicalis YM2 Isolated from Persian Gulf

Phenols exhibit high solubility in water, leading to their potential to contaminate significant volumes of freshwater, wastewater, groundwater, oceans, and soil. The primary objective of this study is to isolate and identify bacterial and yeast isolates with optimal phenol degradation capabilities from Persian Gulf. Sea water and sediment samples were collected to isolate bacterial and yeast isolates, which were then evaluated for their ability to degrade phenol both in their single-cell form and when encapsulated in chitosan and alginate. The phenol-degrading strains were quantified using colony-forming unit (CFU) and most probable number (MPN) methods. The most promising microorganisms were selected and identified using phenotypic and polymerase chain reaction techniques. The selected isolates were immobilized in alginate and chitosan carriers, and their bioremediation potential was assessed at different phenol concentrations. The removal of phenol by the isolates was confirmed using Gas Chromatography. Through molecular techniques, Acinetobacter calcoaceticus K5 and Candida tropicalis YM2 were identified as the most efficient phenol-degrading strains. Acinetobacter calcoaceticus K5 exhibited the highest growth at phenol concentrations of 200 and 300 ppm, while Candida tropicalis YM2 showed optimal growth at a concentration of 700 pp. In case of Acinetobacter calcoaceticus, chitosan immobilization and a phenol concentration of 500 ppm proved to be the best conditions for phenol bioremediation. In the case of Candida tropicalis YM2, the highest percentage of phenol removal was achieved using the chitosan carrier at a concentration of 1000 ppm. Comparing the immobilized strains to their free counterparts, it was observed that the stabilized bacteria exhibited greater phenol removal efficiency, particularly at a concentration of 500 ppm, with a significant difference between the two conditions. This study demonstrates that the novel strains Acinetobacter calcoaceticus K5 and Candida tropicalis YM2 are efficient strains for the bioremediation of various phenol-contaminated seawater and this is the first report to show such rapid phenol degradation by these organisms isolated from sediment and seawater samples collected from Persian Gulf.

Carbon black/acrylonitrile‐butadiene‐styrene composite material incorporated with silver nanoparticles: A new sensitive and cost‐effective electrochemical platform for trace lead detection in seawater samples

AbstractA novel composite material based on acrylonitrile‐butadiene‐styrene (ABS) and carbon black (CB) was proposed here. Different ratios between CB and ABS (40 : 60–60 : 40 %, w/w) were studied to obtain a substrate with improved electrochemical properties. These materials were characterized by techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Raman and Fourier transform infrared (FT‐IR) spectroscopies and scanning electron microscopy (SEM). Under the CB/ABS substrate (50 : 50 %, w/w), a lower charge transfer resistance (854 Ω) and a higher heterogeneous electron transfer constant (K0=1.551×10−3 cm s−1) were found, indicating a kinetically more favorable reaction. To improve the electroanalytical performance of the CB/ABS electrode (50 : 50 %, w/w), silver nanoparticles (AgNPs) were electrodeposited using recycled silver from photographic waste, whose presence was confirmed by SEM imaging and Raman spectra. A method using square wave anodic stripping voltammetry (SWASV) and Pb2+ as model species was developed, where a wider linear working range (4.0 to 40.0 μg L−1) and lower detection limit (0.4 μg L−1) were achieved for the modified electrode. The electrode modification process was highly reproducible (RSD=9.7 %, n=9, inter‐electrode), with precise electrochemical responses (RSD=3.6 %, n=9, intra‐electrode). The applicability was demonstrated in two seawater samples, where recovery levels between 94 and 106 %, as well as statistically similar results to those obtained by atomic absorption spectroscopy, attested to the reliability of the analysis. Furthermore, it is noteworthy that an appropriate selectivity was achieved even in the presence of other metallic species. The proposed composite material is low‐cost, robust, versatile, and can be a promising tool for additive manufacturing of electrochemical sensors.

Monitoring of anthropogenic impact on the Port Qasim coastal area, Karachi, Pakistan

The present study was undertaken to investigate the extent of pollution load at Port Qasim coastal area, the second largest port in the country. The samples of sea water were collected from 23 locations, including the samples from Bundal Island situated in the Port Qasim area. Samples were analyzed for physico-chemical characteristics to determine the extent of pollution load. Samples were also analyzed for heavy metals including As, Cr, Cu, Cd, Pb and Ni. The investigation revealed that the Port Qasim Area is grossly polluted from inorganic and organic loads mainly coming from the nearby industrial setup. Extensively high organic load was found at the site receiving the wastewater from the Landhi Cattle colony. PQ-6 receives untreated wastewater from oil industries as exhibited by its high oil content. PQ-14 is receiving untreated industrial discharges from the nearby chemical industries and represents a very high pollution load. The sites closed to Bundal Island are relatively less polluted. The mangroves in the area are constantly under threat owing to the indiscriminate discharge of both domestic and industrial effluents. The concentration of DO although not on higher side but at least prevents the anoxic condition in the area. Out of all the heavy metals the concentration of Cr and Pb was exceptionally higher. The distribution of heavy metals demonstrated a typical diffusion pattern from the land to the sea. Principal component analysis and cluster analysis of the data showed the major gradients, similarities of localities and the variables of importance in terms of overall variability in the pollution characteristics. It is concluded that the level of pollution is increasing at an alarming rate, which is detrimental to the biodiversity of the coastal area.