Search Results (75)

This study provides the first comprehensive characterization of benthic macrofaunal communities in the Loukkos estuary, highlighting their spatial and seasonal variability and the environmental factors shaping their structure. A total of 47 species were identified across 12 site–season combinations, dominated by molluscs (47%), polychaetes (23%), and crustaceans (21%). Species richness varied considerably along the estuarine gradient, ranging from fewer than five species in the upstream sector to up to 30 species downstream. Overall, higher diversity was observed in the downstream areas and during the dry season. Macrofaunal density also exhibited substantial variability, ranging from 95 ind.m⁻² to 14,852 ind.m⁻², with a mean density of 2535 ± 4058 ind.m⁻². Multivariate analyses identified four distinct benthic assemblages structured primarily by spatial factors (ANOSIM R = 0.86, p = 0.002), with negligible seasonal effect (R = −0.03, p = 0.6). Assemblages ranged from marine-influenced communities at the estuary mouth dominated by Cerastoderma edule, through rich and diverse seagrass-associated communities in the lower estuary dominated by Bittium reticulatum, and moderately enriched mid-estuary communities characterized by Scrobicularia plana and Hediste diversicolor, to species-poor upstream communities dominated by the tolerant species H. diversicolor. Canonical analysis showed that salinity and vegetation explain nearly 40% of the variation in benthic assemblages, highlighting the key role of Zostera seagrass beds as structuring habitats. Moreover, upstream anthropogenic pressures alter environmental conditions, reducing benthic diversity and favoring tolerant species. Full article

To accurately assess the water quality, ecosystem status, distribution of large benthic organisms, and ecological restoration under human intervention, an analysis of benthic organisms on Caofeidian in September and November 2023 and January and May of the following year was conducted in this work. By performing CCA (canonical correspondence analysis) and cluster and correlation coefficient (Pearson) analyses, the temporal variation characteristics of benthic abundance, dominant species, community structure and biodiversity were analyzed. A total of 79 species of macro-benthic animals were found in four months, including 32 species of polychaetes, cnidarians, 1 species of Nemertean, 19 species of crustaceans, and 24 species of molluscs. The use of conventional grab-type mud collectors revealed that the Musculus senhousei dominated the survey (Y > 0.02). While only a small number of Ruditapes philippinarum were collected from bottom-dwelling species, a certain number of bottom-dwelling species (Ruditapes philippinarum and Scapharca subcrenata) were also collected during the trawl survey. Additionally, a significant population of Rapana venosa was found in the area. It is speculated that the dual effects of predation and competition are likely the primary reasons for the relatively low abundance of bottom-dwelling species. The density and biomass of macro-benthos were consistent over time, which was the highest in May, the second highest in January, and the lowest in September and November. The main environmental factors affecting the large benthic communities in the surveyed sea areas were pH, DO, NO₂⁻-N, T, SAL and PO₄³⁻-P. Combined with historical data, it was found that although the environmental condition in the Caofeidian sea area has improved, the Musculus senhousei has been dominant. In addition, the abundance of other species is much less than that of the Musculus senhousei, and the diversity of the benthic community is still reduced. Our work provides valuable data support for the management and improvement of bottom Marine pasture and promotes the transformation of Marine resources from resource plunder to a sustainable resource. Full article

The study of the impact of anthropogenic and natural pollution on living organisms has become a major social issue. In this context, the objective of this work is to assess the use of the polychaete annelid Hediste diversicolor as a bioindicator organism for the quality of the marine environment. The concentration of four heavy metals (lead, copper, zinc, and cadmium) was determined in natural populations of H. diversicolor captured from four locations along the Tunisian coast using atomic absorption spectroscopy. Concentration ranges (µg/g dry weight) across all sites were as follows: Cd (0.12–0.43), Cu (3.80–6.45), Zn (18.35–42.78), and Pb (22.64–63.91). Statistical analysis confirmed significant spatial variation (Pb: F = 12.15, p < 0.001; Zn: F = 3.32, p = 0.04; Cd: F = 48.66, p < 0.001; Cu: F = 9.08, p < 0.001), with peak Pb in Bizerte and Cu in Sfax. These results highlight the influence of local environmental factors, such as industrial and urban pollution on metal accumulation in Hediste diversicolor. In this study, the accumulation of the analyzed elements in the tissues of H. diversicolor follows an increasing order as follows: Cd < Cu < Zn < Pb. Additionally, lead metal concentrations were higher than those of cadmium, zinc, and copper for all four studied locations. To our knowledge, this is the first study in Tunisia to assess heavy metal accumulation in H. diversicolor. The recorded levels were similar to, or lower than, those reported in other studies worldwide. These findings underscore the potential of H. diversicolor as a sensitive and effective bioindicator for monitoring coastal contamination and guiding environmental management strategies in Tunisia. Full article

The tubes of polychaetes of the genus Chaetopterus (Annelida: Chaetopteridae) provide habitat for cryptic, symbiotic organisms that are often overlooked when examining diversity. Our study employed molecular phylogenetics to examine the diversity of symbiont species associated with Chaetopterus djiboutiensis stat. nov., collected from the Gulf of Tadjoura, Djibouti. A total of 15 Chaetopterus hosts and their associated symbionts were collected from nine coastal sites. Four genetic regions were targeted for PCR amplification: the mitochondrial cytochrome oxidase subunit I and 16S rDNA and the nuclear 18S rDNA and Histone H3. Chaetopterus djiboutiensis was redescribed from topotypic material and elevated to species rank, and a neotype specimen was designated. Phylogenetic and morphological analysis confirmed five species associated with C. djiboutiensis in Djibouti: two porcelain crabs, Polyonyx pedalis and Polyonyx socialis; one nudibranch, Tenellia chaetopterana; one fish, Onuxodon sp.; and one amphipod, Leucothoe sp. A. As only the fourth comprehensive study on Chaetopterus symbionts, our study highlights the diversity and community patterns of symbionts associated with these unique tubicolous marine polychaetes. Full article

Polychaetes are important marine invertebrates that contribute to sediment bioturbation, nutrient recycling, and food web dynamics. This study examines the diversity and structure of the polychaete assemblages associated with the red algae Corallina officinalis in areas with different levels of anthropogenic pressures of the Northeastern Adriatic Sea. Sampling was performed in the intertidal zones. Altogether, 54 species from 13 families were found, with Syllidae being the most abundant. Polychaete richness, relative abundance and diversity at sampling locations with and without anthropogenic pressures showed no significant difference. Multivariate analyses revealed significant differences in species composition between sites under anthropogenic pressures and those without, with key species such as Sphaerosyllis pirifera, Syllis rosea, Syllis prolifera, Syllis gerundensis, and Platynereis dumerilii playing significant roles. Syllis rosea was the most abundant in locations without anthropogenic pressures, while S. pirifera was the most abundant in locations under anthropogenic pressures. These results suggest that while polychaete communities are resilient, anthropogenic pressures are causing shifts in species composition. This pattern is consistent with the results of related studies, indicating a broader ecological trend. The shifts observed here should raise concern among conservation ecologists, underscoring the importance of long-term monitoring to understand and mitigate the impacts of human activities on coastal ecosystems. Full article

The Humboldt Current System (HCS) off southwest America is known for its strong upwelling and the resulting high primary production and associated oxygen minimum zones (OMZs). Macrozoobenthic species represent a group of organisms that are affected by the low oxygen concentrations in the OMZ. In January 2023, benthic diversity was investigated at 8 stations on a transect off Concepción, central Chile (in the centre of the OMZ) in a water depth range from 56 to 912 m. The measured oxygen values ranged from 0 µmol/L in the OMZ to 144.64 µmol/L outside the OMZ. At each station, 3 van Veen grabs were taken, the species identified, counted and weighed. The mean abundance, biomass and diversity were calculated for each station. This analysis provided an overview of the changes in the species communities at different oxygen concentrations. The species communities at the stations with low oxygen levels differed greatly from those with higher oxygen levels. Species diversity at the stations increased during the transition from low (<2 µmol/L) to higher oxygen levels (>100 µmol/L). In contrast, species abundance and, to a lesser extent, biomass tended to be higher at low oxygen concentrations. The species composition at the various stations showed a high occurrence of polychaetes. The spionid polychaete Paraprionospio pinnata played an important role as a central key species within the OMZ. In addition to Paraprionospio, Ampelisca araucana, Magelona phyllisae, Nephtys ferruginea and Cossura chilensis were found in high abundance in the oxygen minimum zone (50–200 m water depth). At the edge and presumably below the oxygen minimum zone (300–912 m), where the oxygen concentration rises again, the dominance of individual species decreased, and the total number of species increased. In addition, the species composition changed and the abundance of other polychaete families (Cirratulidae, Amphinomidae, Oweniidae and Capitellidae) amplified. The proportion of polychaetes in the total abundance decreased from almost 100% at the low-oxygen stations to around 60% at the stations below the oxygen minimum zone. Bivalvia of the families Thyasiridae, Nuculidae and Yoldiidae were of particular importance at the deeper stations with a share of up to 20% of the total abundance. The study of benthic communities is of central importance to better understand the future changes in the structure and function of marine ecosystems in hypoxic waters. Full article

The detection, observation, recognition, and statistics of marine plankton are the basis of marine ecological research. In recent years, digital holography has been widely applied to plankton detection and recognition. However, the recording and reconstruction of digital holography require a strictly controlled laboratory environment and time-consuming iterative computation, respectively, which impede its application in marine plankton imaging. In this paper, an intelligent method designed with digital holography and deep learning algorithms is proposed to detect and recognize marine plankton (IDRMP). An accurate integrated A-Unet network is established under the principle of deep learning and trained by digital holograms recorded with publicly available plankton datasets. This method can complete the work of reconstructing and recognizing a variety of plankton organisms stably and efficiently by a single hologram, and a system interface of YOLOv5 that can realize the task of the end-to-end detection of plankton by a single frame is provided. The structural similarities of the images reconstructed by IDRMP are all higher than 0.97, and the average accuracy of the detection of four plankton species, namely, Appendicularian, Chaetognath, Echinoderm and Hydromedusae,, reaches 91.0% after using YOLOv5. In optical experiments, typical marine plankton collected from Weifang, China, are employed as samples. For randomly selected samples of Copepods, Tunicates and Polychaetes, the results are ideal and acceptable, and a batch detection function is developed for the learning of the system. Our test and experiment results demonstrate that this method is efficient and accurate for the detection and recognition of numerous plankton within a certain volume of space after they are recorded by digital holography. Full article

Various types of tidal barriers are used in estuaries to reduce saltwater intrusion and regulate freshwater discharge, but they often alter the physicochemical environment and faunal composition. With the use of these structures expected to increase due to climate change, there is a need to understand their impacts. A tidal exclusion barrier in the Ramsar-listed Vasse–Wonnerup Estuary (Australia) was found to act as an ecotone, fragmenting the estuarine gradient into two distinct components, a relatively stable marine-like environment downstream and a highly variable oligohaline to hypersaline (~0 to >100 ppt) environment upstream. The downstream regions contained a speciose and functionally rich estuarine fauna, comprising mainly polychaetes and bivalves. The upstream regions were taxonomically and functionally depauperate, containing insects, gastropods, and ostracods typically found in saline wetlands. The fragmentation of the estuary has likely impacted the provision of ecosystem services, with the fauna downstream mainly comprising burrowing species that bioturbate and, thus, aid in nutrient cycling. In contrast, the environmental conditions caused by the barrier and the resultant epifaunal invertebrate assemblages upstream aid little in bioturbation, but provide nutrition for avian fauna. These results may help in understanding the impacts of constructing new barriers in coastal ecosystems in response to climate change. Full article

Two novel strains, CB1-14^T and CB2-10, were isolated from the marine polychaetes Chaetopterus cautus from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus Vibrio, sharing 98.96% identity with Vibrio hangzhouensis CN 83^T. MLSA using five protein-coding genes (ftsZ, gyrA, gyrB, mreB, and rpoA) showed that CB1-14^T and CB2-10 are closely related to the members of the Mediterranei clade, namely Vibrio mediterranei CECT 621^T, Vibrio barjaei 3062^T, Vibrio thalassae CECT 8203^T, Vibrio hangzhouensis CGMCC 1.7062^T, Vibrio maritimus CAIM 1455^T, and Vibrio variabilis CAIM 1454^T. Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by V. maritimus CAIM 1455^T and V. variabilis CAIM 1454^T. Both new strains CB1-14^T and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with V. variabilis CAIM 1454^T and 90.3%/93.1% with V. maritimus CAIM 1455^T. The dDDH values between strain CB1-14^T and the members of the Mediterranei clade ranged from 20.9% to 45.7%. Major fatty acids were C_16:1ω9c, C_16:1ω7c, and C_18:1ω9c, followed by C_16:0 and C_18:1ω7c. The genome of CB1-14^T is 5,591,686 bp in size, with DNA G+C content of 46.1%. It consists of two circular chromosomes (3,497,892 and 1,804,652 bp) and one plasmid (241,015 bp) and comprises 4782 protein-coding genes and 10 rrn operons. The CB1-14^T and CB2-10 genomes were enriched in CAZyme-encoding genes of the following families: GH1, GH3, GH13, GH23, GH43, GH94, PL17, and CE4, indicating the potential to catabolize alginate, xylan, and chitin, common polysaccharides in marine ecosystems. Based on the combined phylogenomic analyses and phenotypic properties, a new species, Vibrio chaetopteri sp. nov., is proposed, with CB1-14^T = (KMM 8419^T = KCTC 92790^T) as the type strain. Full article

Background: Jeju Island is a world-renowned tourist destination. However, with the increasing intensity of anthropogenic activities, the coastal marine environment of Jeju Island has been negatively affected. Methods and Results: Our study used five benthic indices to assess the ecological quality of the subtidal zone in northern Jeju Island. Our analysis indicated that apart from the benthic polychaetes amphipods index (BPA), other benthic indices assessed the ecological quality of the subtidal zone in northern Jeju Island as high or good. Distance-based redundancy analysis (dbRDA) indicated that pH and salinity primarily influenced macrobenthic communities in 2011 and 2012. According to the Spearman rank correlation analysis, the multivariate AZTI marine biotic Index (M-AMBI) showed stronger correlations with environmental data than other benthic indices. Conclusions: Overall, the averages of the five benthic indices suggested that the benthic ecological quality of the subtidal zone in the northern part of Jeju Island was high or good. Although immediate marine environmental management is not required, long-term monitoring remains essential. M-AMBI outperformed other benthic indices; however, we recommend using multiple benthic indices to assess the benthic ecological quality of Jeju Island due to the complexity of marine ecosystems. Effective support has been provided by our study for the marine environmental conservation along the coast of Jeju Island. Full article

The multifunctional catalytic hemoglobin from the terebellid polychaete Amphitrite ornata, also named dehaloperoxidase (AoDHP), utilizes the typical oxygen transport function in addition to four observed activities involved in substrate oxidation. The multifunctional ability of AoDHP is presently a rare observation, and there exists a limitation for how novel dehaloperoxidases can be identified from macrobenthic infauna. In order to discover more infaunal DHP-bearing candidates, we have devised a facilitated method for an accurate taxonomic identification that places visual and molecular taxonomic approaches in parallel. Traditional visual taxonomic species identification by the non-specialist, at least for A. ornata or even for other marine worms, is a very difficult and time-consuming task since a large diversity is present and the method is restricted to adult worm specimens. The work herein aimed to describe a method that simplifies the taxonomic identification of A. ornata in particular through the assessment of its mitochondrial cytochrome c oxidase subunit I gene by employing the DNA barcoding technique. Furthermore, whole-worm specimens of A. ornata were used to extract and purify AoDHP followed by an H₂O₂-dependent peroxidase activity assay evaluation against substrate 2,4,6-trichlorophenol. AoDHP isoenzyme A was also overexpressed as the recombinant protein in Escherichia coli, and its peroxidase activity parameters were compared to AoDHP from the natural source. The activity assay assessment indicated a tight correlation for all Michaelis–Menten parameters evaluated. We conclude that the method described herein exhibits a streamlined approach to identify the polychaete A. ornata, which can be adopted by the non-specialist, and the full procedure is predicted to facilitate the discovery of novel dehaloperoxidases from other marine invertebrates. Full article

Vibrio sp. KMM 8419 (=CB1-14) is a Gram-negative bacterium isolated from a food-net mucus sample of marine polychaete Chaetopterus cautus collected in the Sea of Japan. Here, we report the structure and biosynthetic gene cluster of the capsular polysaccharide (CPS) from strain KMM 8419. The CPS was isolated and studied by one- and two-dimensional ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The molecular weight of the CPS was about 254 kDa. The CPS consisted of disaccharide repeating units of D-glucose and sulfated and acetylated L-rhamnose established as →2)-α-L-Rhap3S4Ac-(1→6)-α-D-Glcp-(1→. To identify the genes responsible for CPS biosynthesis, whole-genome sequencing of KMM 8419 was carried out. Based on the genome annotations together with the Interproscan, UniProt and AntiSMASH results, a CPS-related gene cluster of 80 genes was found on chromosome 1. This cluster contained sets of genes encoding for the nucleotide sugar biosynthesis (UDP-Glc and dTDP-Rha), assembly (glycosyltransferases (GT)), transport (ABC transporter) and sulfation (PAPS biosynthesis and sulfotransferases) of the sulfated CPS. A hypothetical model for the assembly and transportation of the sulfated CPS was also proposed. In addition, this locus included genes for O-antigen biosynthesis. Further studies of biological activity, the structure–activity relationship in the new sulfated polysaccharide and its biosynthesis are necessary for the development of potent anticancer agents or drug delivery systems. Full article

Antimicrobial resistance is a critical global health issue, with rising resistance among bacteria and fungi. Marine organisms have emerged as promising, but underexplored, sources of new antimicrobial agents. Among them, marine polychaetes, such as Halla parthenopeia, which possess chemical defenses, could attract significant research interest. This study explores the antimicrobial properties of hallachrome, a unique anthraquinone found in the purple mucus of H. parthenopeia, against Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 9027), Gram-positive bacteria (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228), and the most common human fungal pathogen Candida albicans ATCC 10231. Antibacterial susceptibility testing revealed that Gram-negative bacteria were not inhibited by hallachrome at concentrations ≤2 mM. However, Gram-positive bacteria showed significant growth inhibition at 0.12–0.25 mM, while C. albicans was inhibited at 0.06 mM. Time-kill studies demonstrated dose-dependent growth inhibition of susceptible strains by hallachrome, which exerted its effect by altering the membrane permeability of C. albicans, E. faecalis, and S. epidermidis after 6 h and S. aureus after 24 h. Additionally, hallachrome significantly reduced biofilm formation and mature biofilm in S. aureus, E. faecalis, and C. albicans. Additionally, it inhibited hyphal growth in C. albicans. These findings highlight hallachrome’s potential as a novel antimicrobial agent, deserving further exploration for clinical experimentation. Full article

Dokdo Island’s diverse marine ecosystem requires long-term monitoring to understand the effects of rapid environmental changes, such as global warming, on macrobenthos species and communities. Current studies are often short-term and limited, highlighting the need for extended research to predict future changes to ecosystems. This study analyzed the environmental variables influencing macrobenthos through long-term monitoring. In total, 511 species (spp./23.4 m²) were identified with an abundance of 1709.9 individuals/m² and a diversity of 2.9. Since 2020, there has been a decline in both the number of species and diversity, attributed to changes in sediment composition, particularly an increase in gravel and sand. The dominant species include the crustacean Abludomelita denticulata (17.6%), the polychaete Haplosyllis spongiphila (6.8%), the bivalve Glycymeris munda (5.6%), the polychaete Opisthodonta uraga (5.3%), and the bivalve Limatula japonica (3.8%). The macrobenthos community differs each year, as the dominant species G. munda has decreased in abundance since 2022 and L. japonica since 2021. Depth and gravel sediment strongly correlated with community variation. Site-specific analysis also showed significant differences, with depth, bottom temperature, and sediment composition as the influencing factors. These species thrive in cold water but their abundance declines with an increase in temperature. Continuous long-term monitoring is essential to understand and protect the Dokdo ecosystem amid rapid environmental changes. Long-term monitoring studies have revealed more species than have short-term studies, showing annual and site-specific environmental changes, including sediment erosion and bottom temperature increases. These changes have affected macrobenthos diversity, abundance, and community composition, necessitating ongoing research to determine the persistence of these trends and to protect the ecosystem. Full article

The study of ecological connectivity is a global priority due to the important role it plays in the conservation of diversity. However, few studies in this context have focused on marine benthic ecosystems. To address this issue, the present work determines the ecological connectivity between two sub-Antarctic macrobenthic assemblages through assessment of the α-, β-, and functional diversity indices. Samples were collected using a van Veen grab at stations located in Bahia Inútil and Seno Almirantazgo. The ecological analysis was based on a total of 113 invertebrate taxa. The mean abundance values were lower in Bahia Inútil (888.9 ± 26.8 ind m⁻²) than in Seno Almirantazgo (1358.6 ± 43.4 ind m⁻²). While the mean α-diversity values showed significant differences between assemblages, β- and functional diversity indices presented no significant differences. These results indicate that, despite the distance (56 km) separating the two basins from each other, there is a high degree of connectivity at the functional level between the assemblages due to the high number of shared species and their functional traits. The species most responsible for this observation were the polychaetes Capitela capitata and Aricidia (Acmira) finitima, as well as the bivalves Nucula pisum and Yoldiella sp. 1. In terms of functional biodiversity, species characterized as omnivorous and with lecithotrophic larval development were mostly responsible for connectivity between assemblages. These results suggest the importance of including β- and functional diversity indices as criteria in the future planning of marine protected areas for the maintenance of marine ecosystem integrity. Full article