Intertidal Sediments Research Articles

Description of Fuscovulum ytuae sp. nov, a facultative autotroph isolated from the intertidalite of Yangma island, China.

In this study, we reported a Gram-stain-negative, ovoid to rod-shaped, atrichous, and facultative anaerobe bacteria strain named YMD61T, which was isolated from the intertidal sediment of Yangma island, China. Growth of strain YMD61T occurred at 10.0-45.0°C (optimum, 30.0°C), pH 7.0-10.0 (optimum, 8.0) and with 0-3.0% (w/v) NaCl (optimum, 2.0%). Phylogenetic tree analysis based on 16S rRNA gene or genomic sequence indicated that strain YMD61T belonged to the genus Fuscovulum and was closely related to Fuscovulum blasticum ATCC 33,485T (96.6% sequence similarity). Genomic analysis indicated that strain YMD61T contains a circular chromosome of 3,895,730bp with DNA G + C content of 63.3%. The genomic functional analysis indicated that strain YMD61T is a novel sulfur-metabolizing bacteria, which is capable of fixing carbon through an autotrophic pathway by integrating the processes of photosynthesis and sulfur oxidation. The predominant respiratory quinone of YMD61T was ubiquinone-10 (Q-10). The polar lipids of YMD61T contained phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, five unidentified lipids, unidentified aminolipid and unidentified aminophospholipid. The major fatty acids of strain YMD61T contained C18:1ω7c 11-methyl and summed feature 8 (C18:1 ω 7c or/and C18:1 ω 6c). Phylogenetic, physiological, biochemical and morphological analyses suggested that strain YMD61T represents a novel species of the genus Fuscovulum, and the name Fuscovulum ytuae sp. nov. is proposed. The type strain is YMD61T (= MCCC 1K08483T = KCTC 43,537T).

TENet: A Texture-Enhanced Network for Intertidal Sediment and Habitat Classification in Multiband PolSAR Images

This paper proposes a texture-enhanced network (TENet) for intertidal sediment and habitat classification using multiband multipolarization synthetic aperture radar (SAR) images. The architecture introduces the texture enhancement module (TEM) into the UNet framework to explicitly learn global texture information from SAR images. The study sites are chosen from the northern part of the intertidal zones in the German Wadden Sea. Results show that the presented TENet model is able to detail the intertidal surface types, including land, seagrass, bivalves, bright sands/beach, water, sediments, and thin coverage of vegetation or bivalves. To further assess its performance, we quantitatively compared our results from the TENet model with different instance segmentation models for the same areas of interest. The TENet model gives finer classification accuracies and shows great potential in providing more precise locations.

Employing a triple metabarcoding approach to differentiate active, dormant and dead microeukaryotes in sediments.

Microbial communities are commonly characterised through the metabarcoding of environmental DNA. This DNA originates from both viable (including dormant and active) and dead organisms, leading to recent efforts to distinguish between these states. In this study, we further these approaches by distinguishing not only between viable and dead cells but also between dormant and actively growing cells. This is achieved by sequencing both rRNA and rDNA, in conjunction with propidium monoazide cross-linked rDNA, to partition the active, dormant and relic fractions in environmental samples. We apply this method to characterise the diversity and assemblage structure of these fractions of microeukaryotes in intertidal sediments during a wet-dry-rewet incubation cycle. Our findings indicate that a significant proportion of microeukaryotic phylotypes detected in the total rDNA pools originate from dormant and relic microeukaryotes in the sediments, both in terms of richness (dormant, 13 ± 2%; relic, 47 ± 5%) and read abundance (dormant, 20 ± 7%; relic, 14 ± 5%). The richness and sequence proportion of dormant microeukaryotes notably increase during the transition from wet to dry conditions. Statistical analyses suggest that the dynamics of diversity and assemblage structure across different activity fractions are influenced by various environmental drivers. Our strategy offers a versatile approach that can be adapted to characterise other microbes in a wide range of environments.

Migration and Transformation of Heavy Metal and Its Fate in Intertidal Sediments: A Review

Intertidal sediments are rich in biological resources, which are important for material circulation and energy exchange. Meanwhile, these areas can be treated as sinks as well as sources of coastal heavy metal pollutants. Due to the influence of the tide, the intertidal sediments are in a state of periodic flooding and exposure, and environmental factors such as dissolved oxygen, salinity and overlying water pressure are changeable. Heavy metals in sediments are prone to migration and transformation with the dynamic effects of tidal water and the changes in the environment factors, which increase the bioavailability of heavy metals. In this review, the characteristics of distribution and the bioavailability of heavy metals in intertidal sediments are described; the migration and transformation behavior of heavy metals and its influencing factors under tidal conditions are analyzed; and the mechanisms of heavy metal’s migration and transformation in the intertidal zone are summarized. Moreover, the bioaccumulation of heavy metal by organisms and the remediation techniques are discussed. Therefore, this review systematically summarizes the states of existence, the transport mechanisms, and the fate of heavy metals in the intertidal sediment, fills in the research gap of the cycling of heavy metal in the intertidal zone, and provides a theoretical basis for the control of heavy metal pollution.

Distribution characteristics and ecological risk assessment of microplastics in intertidal sediments near coastal water

Plastic products are widely distributed worldwide and continue to have a negative impact on the environment and organisms. Intertidal regions, which interface between upland and marine ecosystems, are regions of high ecological importance and serve as repositories for a variety of plastic wastes. However, ecological risk assessments of microplastics (MPs) in these transitional environments are still scarce. In this study, the morphological characteristics and spatial distribution of MPs in the intertidal surface sediments of Haizhou Bay were analyzed, and an ecological risk assessment framework for MPs was developed. Overall, the average abundance of MPs in the sediments was 2.31 ± 1.35 pieces/g dw. The size of the MPs was mainly less than 1 mm, and the main shape, color and polymer type of the MPs were mainly fibrous (58%), blue (30%), and PVC (22%), respectively. Cluster analyses showed that the sites could be well distinguished by size and polymer type but not by MP shape and color. According to the hazard scores, most of the sites in this area belonged to a risk level of IV, while the pollution loading index (PLI) showed that most of the sites belonged to a risk level of II. The ecological toxicity risk from the species–sensitive distribution (SSD) model showed that one–third of the sites had ecological MPs toxicity risks to marine organisms. We believe that normalized and standardized assessment methods should be implemented to monitor and manage the risk of MPs in the intertidal sediments. Particularly, the multiple dimensions, standard abundance of MPs, as well as MPs ingestion in the intertidal organisms, should be fully considered in the next step.

Large‐scale sedimentary shift induced by a mega‐dam in deltaic flats

ABSTRACTDeltas are crucial for land building and ecological services due to their ability to store mineral sediment, carbon and potential pollutants. A decline in suspended sediment discharge in large rivers caused by the construction of mega‐dams might imperil deltaic flats and wetlands. However, there has not been clear evidence of a sedimentary shift in the downstream tidal flats that feed coastal wetlands and the intertidal zone with sediments. Here, integrated intertidal/subaqueous sediment samples, multi‐year bathymetries, fluvial and deltaic hydrological and sediment transport data in the Nanhui tidal flats and Nanhui Shoal in the Changjiang (Yangtze) Delta, one of the largest mega‐deltas in the world, were analysed to discern how sedimentary environments changed in response to the operations of the Three Gorges Dam. Results reveal that the coarser sediment fractions of surficial sediments in the subaqueous Nanhui Shoal increased between 2004 to 2021, and the overall grain size coarsened from 18.5 to 27.3 μm. Moreover, intertidal sediments in cores coarsened by 25% after the 1990s. During that period, the northern part of the Nanhui Shoal suffered large‐scale erosion, while the southern part accreted in recent decades. Reduced suspended sediment discharge of the Changjiang River combined with local resuspension of fine‐grained sediments are responsible for tidal flat erosion. This study found that the spatial pattern of grain‐size parameters has shifted from crossing the bathymetric isobaths to being parallel to them. Higher tide level and tidal range induced by sea‐level rise, an upstream increase in bed shear stress and larger waves likely further exacerbated erosion and sediment coarsening in deltaic flats. As a result, this sediment‐starved estuary coupled with sea‐level rise and artificial reclamations have enhanced the vulnerability of tidal flats in Changjiang Delta, this research is informative to the sedimentary shift of worldwide mega‐deltas.

Sediment temperature characteristics and their relation to distribution patterns of two sentinel crab species in intertidal flats in western Japan

In the context of global climate change, monitoring focused on temperature and benthic animals in intertidal flats and the development of metrics to assess climate change and ecosystem responses are essential for a sustainable society. However, few studies have assessed the relationship between intertidal sediment temperature and the distribution of benthic animals. To address this gap, in the present study, intertidal sediment temperatures were observed in 12 intertidal flats in 11 survey areas over 335 days, from October 2, 2019, to August 31, 2020, using water temperature data loggers. The characteristics of intertidal sediment temperatures were variable among the survey areas, and a correlation analysis suggested that such characteristics are possibly influenced by various spatial-scale factors, such as geographical, basin, and habitat scales. Furthermore, two sentinel crab species, Macrophthalmus japonicus and Macrophthalmus banzai were collected, and the number of wintering individuals of each species was estimated based on their carapace width to analyze the changes in abundances of the two species in each survey area. The results show that the number of days with daily minimum temperature ≥ 19 °C was the factor that influenced the abundance rate, suggesting that M. japonicus and M. banzai populations may decrease and increase, respectively, according to future climate change in Japan. Our findings emphasize the importance of long-term monitoring of sediment temperatures and benthic animals in intertidal flats to evaluate the influence of future climate change.

Bacterial community composition in the Northern Gulf of Mexico intertidal sediment bioturbated by the ghost shrimp Lepidophthalmus louisianensis.

Bioturbation plays an important role in structuring microbial communities in coastal sediments. This study investigates the bacterial community composition in sediment associated with the ghost shrimp Lepidophthalmus louisianensis at two locations in the Northern Gulf of Mexico (Bay St. Louis, MS, and Choctawhatchee Bay, FL). Bacteria were analysed for shrimp burrows and for three different depths of bioturbated intertidal sediment, using second-generation sequencing of the 16S rRNA gene. Burrow walls held a unique bacterial community, which was significantly different from those in the surrounding sediment communities. Communities in burrow walls and surrounding sediment communities also differed between the two geographic locations. The burrow wall communities from both locations were more similar to each other than to sediment communities from same location. Alpha- and Gammaproteobacteria were more abundant in burrows and surface sediment than in the subsurface, whereas Deltaproteobacteria were more abundant in burrows and subsurface sediment, suggesting sediment mixing by the bioturbator. However, abundance of individual ASVs was geographic location-specific for all samples. Therefore, it is suggested that the geographic location plays an important role in regional microbial communities distinctiveness. Bioturbation appears to be an important environmental driver in structuring the community around burrows. Sampling was conducted during times of the year and water salinity, tidal regime and temperature were variable, nevertheless the structure microbial communities appeared to remain realatively stable suggesting that these environmental variable played only a minor role.

Radioactivity concentration and risk indices in intertidal sediments of the Red River Delta, Vietnam

Radioactivity concentration and risk indices in intertidal sediments of the Red River Delta, Vietnam

Marine microdebris pollution in sediments from three environmental coastal areas in the southwestern Argentine Atlantic

Microplastics (MPs) and antifouling paint particles (APPs) are important components of marine microdebris (MDs), which constitute a potential environmental risk. This study analyzed baseline contamination levels of MDs and mesodebris (MesDs) in intertidal sediments at different depths, exploring the geomorphological influence in three Argentine coastal environments: Bahía Blanca Estuary (BBE), Los Pocitos (LP) and Puerto Madryn (PM). The MDs and MesDs samples were characterized by μ-FTIR, SEM/EDX and XRD. The abundance of MPs and APPs in sediments, range between 19.78 and 1087.19 and between 0 and 172.93 items/kg d.w., respectively. Despite variations in population and industrial developments in these areas, MPs abundance shows no significant differences in low and high intertidal zones. However, mean MPs concentrations were higher in the surface layer (0–5 cm) compared to the deeper sediments (5–10 cm), indicating recent MPs deposition. Chemical characterization evidenced the presence of cellulose (CE) and denser polymers as acrylonitrile butadiene styrene (ABS) and polyacrylics (PAN), APPs, metallic and black MDs. Surface degradation and heavy metals (Zn, Cr, and Ba) were also detected in APPs and other MDs, either as additives or adhered to their surfaces. Changes in crystallinity were also observed on the MesDs due to weathering. The calculated polymer hazard index (PHI) and the presence of hazardous polymers such as ABS and PAN indicated an increased risk of MPs pollution on the BBE and PM coasts. The pollution load index (PLI) values (from 4.63 to 5.34) suggested unpolluted to moderately polluted levels. These findings offer insights into potential risks associated with MDs in Argentine intertidal sediments, underscoring the critical need to comprehend the geomorphology and the influence of coastal dynamics. This is crucial for effectively addressing challenges linked to MDs pollution guiding the development of robust management and mitigation strategies.

Diversity and distribution of foraminifera and tintinnids (bio‐indicators) from Pulicat Lake, India

AbstractThe foraminifera and tintinnids are essential indicators of the health status of marine and estuarine ecosystems, both past and present, and can be used for monitoring purposes in the future. Tintinnids are known to group among ciliates possessing hard loricate to be considered by hydrogeologists as one of the bio‐indicator species, exhibiting a strong positive correlation with phytoplankton. Pulicat Lake is a marginal marine environment present near the south coast of India. Intertidal sediment samples were collected from September 2013 to August 2014 and were subjected to isolate the foraminiferans and tintinnids by adopting standard methods. In all, twenty‐one genera and 24 species of foraminifera have been identified from the stream, where Quinquelina seminulum was found to be abundant. Contrary to this, a minimum number of species was present in the freshwater inflow zone, mainly Amomalinula glabrata, Haplophragmoides kirki, Natlandia secasensi and Valvulineria candeiana. Tintinnopsis are recorded in the sampling sites, belonging to 5 families and 6 genera, and 12 species have been identified, and among these Favella campanula species was found to be abundant in the study area. From our results, the recorded species in terms of numerical abundance of foraminiferans appeared predominant over the tintinnids. The dominant role of foraminiferans may be a significant contribution to the carbon cycle of marine/estuarine ecosystems proved elsewhere in turn responsible for the substantial uptake of phytodetritus deposition. Based on these findings, our preliminary study may be useful to explore the carbon sequestration process in the Pulicat Lake ecosystem.

Identification of microbial exopolymer producers in sandy and muddy intertidal sediments by compound-specific isotope analysis

Identification of microbial exopolymer producers in sandy and muddy intertidal sediments by compound-specific isotope analysis

Characterization of Maribacter polysaccharolyticus sp. nov., Maribacter huludaoensis sp. nov., and Maribacter zhoushanensis sp. nov. and illumination of the distinct adaptative strategies of the genus Maribacter

Polysaccharides are complex carbohydrates and are abundant in the marine environment. Microbes degrade and utilize them using Carbohydrate-active enzymes (CAZymes), which mediate polysaccharides into the marine carbon cycle. With the continued supply of polysaccharides from the marine environment, tidal flats are also abundant in polysaccharides, resulting in an abundance of marine polysaccharide degrading strains. In this study, three novel strains, designated as D37T, M208T, and SA7T, were isolated from the intertidal sediment samples located in Zhoushan, Zhejiang and Huludao, Liaoning, PR China. The phylogenetic trees using the 16S rRNA gene and genome sequences showed that the three novel strains belonged to the genus Maribacter. The highest 16S rRNA gene sequence similarities between the three novel strains and other strains of the genus Maribacter were 98.7%, 99.2%, and 98.8%, respectively, while the ANI, AAI, and dDDH values between the three strains and the other strains of the genus Maribacter were 70-86%, 67-91%, and 17-30%, respectively, supporting their affiliation as novel species. Combined with other phenotypic and genotypic characterization in this study, three novel species are proposed as Maribacter polysaccharolyticus sp. nov., Maribacter huludaoensis sp. nov., and Maribacter zhoushanensis sp. nov., respectively, for the three strains. Furthermore, we compared all available genomes of Maribacter representatives and found that Maribacter strains could be divided into two groups (A and B). The two groups are different in genome size and G + C content and gene densities of CAZyme, peptidase, and sulfatase. Group A possesses more CAZymes which are related to degrading laminarin, fucoidan, mannan, xylose, and xylan. This result suggests that the two groups may have different niche adaptation strategies. Our study contributes to a better understanding of the role of marine flavobacteria in biogeochemical cycles and niche specialization.

Potential ecological risk assessment of microplastics in coastal sediments: Their metal accumulation and interaction with sedimentary metal concentration

Metal pollution in sediments has long been recognized, while sediments are also a long-term sink for microplastics (MPs). MPs may also adsorb environmental pollutants, including metals, as well as leaching polymer components and chemicals used during production. A comprehensive survey of 21 locations around Qatari coastline investigated abundance of MPs in high-shore intertidal sediments and concentration of metals both on MPs and sediment particles. MPs abundance ranged from 3 to 156 MPs particles·kg−1 (12–624 MPs particles·m−2) with polyethylene being the most abundant (27.4 %). MPs showed physical morphologies, with 76 % displayed signs of chemical degradation as confirmed by the carbonyl absorption peak profile, possibly due to exposure to harsh environmental conditions on the Arabian Gulf shores. Most metals analyzed were found at higher concentrations in sediments than the same metals adsorbed to MPs. The average metal concentration ranged from 0.26 (Cd) to 3122.62 μg∙g−1 (Sr) in sediments while 0.22 (Mo) to 30.26 μg∙g−1 (Sr) in MPs. The calculated metal Pollution Load Index (Sed PLI, range 0.57–2.38) for sediments indicates unpolluted to moderately polluted levels, while the Potential Ecological Risk Index (Sed PERI, range 6.9–2220) indicates a relatively considerable ecological risk for metal pollution in sediments in some of the coastal areas surveyed. PLI values calculated for metals associated with MPs (MPs PLI, range 1.1–7.5), suggests relatively moderate pollution, while the PERI for metals in MPs (MPs PERI, range 25.2–1811) has similar ecological risk in terms of metal pollutants in MPs as for sediments. This may be effective in providing relative spatial indices of pollution load and risk for metals associated with MPs, which could potentially inform establishment of an appropriate assessment framework, where MPs are increasingly abundant in coastal sediments. However, this does not account for the relatively lower abundance of MPs compared to sediments.

Winogradskyella vincentii sp. nov. and Winogradskyella alexanderae sp. nov., two novel bacteria isolated from intertidal sediment.

Two novel Gram-stain-negative, facultative anaerobic, chemoheterotrophic, non-motile and rod-shaped strains were isolated from intertidal sediment sampled at Xiaoshi Island, Weihai, PR China. Full sequence analysis of the 16S rRNA genes showed that the two strains were closely related to members of the genus Winogradskyella and the phylogenetic similarities to their closest relative, Winogradskyella aquimaris, were 96.7 and 95.8 %, respectively. The DNA G+C contents of strains 2Y89T and D23T were 33.3 and 35.1 mol%, respectively. The respiratory quinone detected in both strains was MK-6. The major fatty acids detected in strain 2Y89T were iso-C15 : 0 and iso-C15 : 1G, and in strain D23T they were iso-C15 : 1G, iso-C15 : 0 and iso-C17 : 03-OH. The principal polar lipids of strain 2Y89T mainly included phosphatidylethanolamine, aminoglycolipids, unidentified aminolipids, unidentified glycolipids and unidentified lipids; strain D23T was the same as strain 2Y89T except that it did not contain aminoglycolipids. Based on the phenotypic, chemical taxonomic, genotypic and phylogenetic features established in this study, we suggest that the new strains represent two novel species of the genus Winogradskyella, for which the names Winogradskyella vincentii sp. nov. (type strain 2Y89T=MCCC 1H00477T=KCTC 92034T) and Winogradskyella alexanderae sp. nov. (type strain D23T=MCCC 1H00462T=KCTC 92023T) are proposed.

Kaistella polysaccharea sp. nov., isolated from Antarctic intertidal sediment produces a novel extracellular polymeric substance.

An exopolysaccharide-producing bacterial strain GW4-15T, belonging to the genus Kaistella, was isolated from intertidal sediment from King George Island, Antarctic. The strain was Gram-stain-negative, aerobic, rod-shaped, non-motile and yellow-pigmented. The strain was able to grow in the presence of 0-2 % (w/v) NaCl (optimum, 0 %), at 4-30 °C (optimum, 20-28 °C) and at pH 5.0-10.0 (optimum, pH 8.0). A phylogenetic tree based on 16S rRNA gene sequences showed that strain GW4-15T formed a lineage within the genus Kaistella with the closest phylogenetic neighbours Kaistella carnis NCTC 13525T (98.3 %), Kaistella gelatinilytica G5-32T (97.7 %), Kaistella antarctica LMG 24720T (97.4 %) and Kaistella yonginensis HMD1043T (96.9 %). Digital DNA-DNA hybridization values of strain GW4-15T with K. carnis NCTC 13525T, K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 22.8, 22.0, 21.7 and 21.6 %, respectively. The average nucleotide identity values between strain GW4-15T and K. carnis NCTC 13525T , K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 79.3, 78.6, 77.5 and 77.2 %, respectively. The G+C content of the genome was 36.2 mol%. The major phospholipids were phosphatidylethanolamine and aminophospholipid. The predominant menaquinone was MK-6. The major fatty acids were anteiso-C15 : 0 (28.7 %), iso-C16 : 0 3-OH (15.7 %), iso-C16 : 0 H (10.0 %), iso-C16 : 0 (5.4 %), summed feature 9 (comprising iso-C17 : 1 ω9c and/or 10-methyl C16 : 0; 5.2 %) and iso-C15 : 0 (5.1 %). The monosaccharide composition of the new type of extracellular polymeric of GW4-15T was Glc, GalN, GlcN, Rha, Man and Gal with a molar ratio of 3.14 : 3.83 : 8.38 : 5.16 : 1 : 2.82. Based on phenotypic, phylogenetic and genotypic data, a novel species, Kaistella polysaccharea sp. nov., is proposed with the type strain GW4-15T (=CGMCC 1.19368T=KCTC 92753T).

Polychlorinated biphenyls (PCBs) in intertidal sediment and water from Lagos lagoon: Baseline report on occurrence, distribution and ecotoxicological risk assessment

To assess the occurrence and potential ecological risk associated with organic micropollutants in Lagos lagoon, 27 polychlorinated biphenyls (PCBs) were analysed in sediments and surface water. Sediment samples were obtained from 18 designated sites (SD1 – SD18) using a Van Veen grab sampler and extracted following standard procedures. Cleaned extracts were analysed using gas chromatography with electron capture detector (ECD). The concentration of ∑PCBs in sediment samples ranged between 6757.61 and 273.46 µg/kg. The PCB homologues distribution patterns in sediments indicated that the low-chlorinated (∑di-PCB - ∑penta-PCB) PCBs were more dominant with 61.1 % occurrence than the high-chlorinated ((∑hexa-PCB - ∑nona-PCB) PCBs with 38.9 % relative abundance. The following is the decreasing order of the average homologue composition of PCBs in sediment samples: ∑tetra-PCB (24.6%) > ∑octa-PCB (21 %) > ∑hexa-PCB (13.8 %) > ∑penta-PCB (12.8) > ∑tri-PCB (11.4 %) > ∑hepta-PCB (7.8 %) > ∑nona-PCB (4.9 %) > ∑di-PCB (2.9 %). More so, the ∑PCBs in surface water samples ranged from 69.28 to 440.90 ng/L, with the mean ranging between 7.21 and 16.33 ng/L. The class distribution of PCB homologue profiles in water samples indicated that highly-chlorinated (∑hexa-PCB to ∑nona-PCB) PCBs were the dominant homologues, with 94.4 % occurrence, compared to the very low occurrence rate (5.6 %) of the low-chlorinated (∑di-PCB to ∑penta-PCB) PCBs. Hexa-PCBs (PCB-138 and PCB-153) were the dominant congeners in most water samples. The concentrations of ∑PCBs in sediments and surface water were unprecedentedly high at almost all locations. The total toxicity equivalent concentrations (TTECs) of dioxin-like PCBs for the sediment samples ranged from 0.001 to 2.43 µg/kg, with an average of 0.34 µg/kg. These findings suggest that PCB congeners are pervasive from anthropogenic point sources of pollution. Intensive site-specific monitoring and remediation are recommended.

Distribution of organochlorine pesticides (OCPs) in surface-mixed layer water and intertidal sediments of Lagos lagoon, Gulf of Guinea

Organochlorinated pesticides (OCPs) were analysed in intertidal sediments and surface-mixed layer water of Lagos lagoon in Nigeria in order to elucidate the contamination levels, sources and distribution characteristics, and potential human and ecological health risks associated with exposures to OCPs. The total ∑ OCPs in sediments ranged from 222.35 to 2585.30 μg/kg dw, with a mean concentration range between 13.08 and 172.35 μg/kg dw, respectively. The most dominant OCP compounds in the sediments were dichlorodiphenylethanes (40%), chlors (26%), cyclodienes (17%), HCHs (9%), and endos (8%). The concentration (μg/kg) of individual ∑OCP groups in sediment decreased in the following order: ∑ dichlorodiphenylethanes > ∑ Chlors > ∑ Cyclodienes > ∑ HCHs > ∑ Endos. The ∑ OCPs in water ranged from 23.63 (mean concentration: 1.97 ng/L) to 172.05 ng/L (mean concentration: 13.23 ng/L). Dichlorodiphenylethanes (46%), cyclodienes (21%), chlors (14%), HCHs (12%), and endos (7%) were the most prevalent OCP compounds in investigated water samples. These locations are pollution hotspots for potential wastes arising from industrial effluents, heavy shipping activities, municipal wastes and discharges of transformer oil from abandoned power generation and transmission facilities. The total composition and β-, γ- and δ-HCH isomeric ratios suggest recent anthropogenic introduction of the HCHs into the lagoonal ecosystem compared to historical deposits. Dichlorodiphenylethanes (p,p′-DDD, p,p′-DDE, and methoxychlor) were ubiquitous except p,p′-DDT. Results indicate historical inputs of technical DDT with considerable biodegradation and photochemical transformations. Generally, the ∑ chlors in sediments and surface-mixed layer water samples decreased following heptachlor > heptachlor epoxide > α-Chlordane > γ-Chlordane. The α-chlordane/γ-chlordane ratios indicate a mix of recent commercial and historical chlordane contamination sources. Concentrations of most OCPs significantly exceeded sediment quality guidelines suggesting that toxicity to benthic-dwelling faunas is estimated to be likely.

Extreme rainstorms change organic matter compositions and regulate greenhouse gas production in mangrove sediments

Extreme rainstorms can flush intertidal sediments and drive the transport of large amounts of organic matter from land to sea. Mangrove wetlands, one of the most important “blue carbon” habitats, are located in the intertidal zone and serve as an ecological corridor connecting land and sea. In this study, we investigated the effects of extreme rainstorms on organic carbon compositions, source-sink processes based on the MixSIAR model, and the production of greenhouse gases, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), using mangrove sediments. The results showed that in the intertidal zone, the total contents of sediment organic carbon, mineral-bound, and fine-particle organic carbon, humic acid, and humin were improved by the influence of an extreme rainstorm. The contents of coarse sediment organic carbon (SOCcoarse) and fulvic acid were decreased and were exported from intertidal zone to the sea. In tidal creek zones, extreme rainstorms enhanced the mean production rates of CH4 and CO2 by 817.4% and 34.3%, respectively, owing to the increased terrestrial organic matter, including SOCcoarse and humic acid. The N2O production rate was decreased by 72.2% in the creek zone because of the loss of total nitrogen after an extreme rainstorm. These findings provide new insights into SOC components, mechanisms of greenhouse gas production, and their response to extreme rainstorms, which will be helpful for the management of coastal wetlands and our understanding of how frequent extreme weather controls wetland biogeochemical processes.

Occurrence and spatial distribution of microplastics in the intertidal sediments along the Oman Sea

Microplastics (MPs) have been found in marine systems more frequently. We aim to analyze the MPs abundances, distribution, and characteristics in the intertidal sediments along the Oman Sea. Samples were collected from 7 locations with three replicates. Density separation was used to extract MPs, which were then visually counted and categorized based on their size, shape, and color. MPs abundance ranged between 219.6 ± 38.3 particles.kg−1dw and 617.3 ± 99.9 particles.kg−1dw with a mean abundance of 315.4 ± 24.4 particles.kg−1 dw. Fragments and fibers were the dominant shapes. Red and blue colors were observed in 61.6 % of the collected MPs. In addition, 100–500 μm size range of MPs were more abundant. Micro-Raman spectroscopy analysis revealed polypropylene was the major polymer constituent. The present study revealed the widespread occurrence of MPs as anthropogenic pollutants throughout the Oman Sea and highlighted the urgent need for regulations and policies to reduce the entry of this material into marine environments.