Search Results (52)

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

In some estuaries, low inflow and/or isolation from the ocean can result in evapoconcentration and hypersalinity (≥40 ppt). This can create osmoregulatory and energetic challenges for the faunal community, leading to reductions in diversity as more species pass their thresholds. As climate change is increasing the magnitude and duration of hypersaline conditions, we used benthic macroinvertebrate data from 12 estuaries across a Mediterranean climatic region (southwestern Australia) to assess the influence of salinity (0–122 ppt) on the invertebrate fauna. Taxa richness and diversity were highest in salinities between 0 and 39 ppt, peaking at salinities closest to seawater, while total density peaked at 40–49 ppt. Beyond 50 ppt, these measures declined significantly. Community composition changed markedly along the salinity gradient. In lower salinities, communities were diverse, comprising polychaetes, malacostracans, hexapods, ostracods, bivalves, and gastropods. However, in salinities ≥50 ppt, many taxa declined, leading to communities dominated by polychaetes (mainly Capitella spp.) and hexapods (mostly larval chironomids). At 90 ppt, only polychaetes and hexapods remained, and at ≥110 ppt, only the latter taxon persisted. This faunal shift towards insect dominance in hypersaline conditions mirrors observations in other Mediterranean and arid/semi-arid regions, with the resulting communities resembling saline wetlands or salt lakes. This loss of invertebrates can substantially impact ecosystem functioning and trophic pathways, and the findings of this study provide a basis for predicting how these communities will respond to increasing hypersalinity driven by climate change. 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

This study investigates the effects on hard-bottom macro-zoobenthic communities of converting a mariculture plant into an Integrated Multi-Trophic Aquaculture (IMTA) system. This study was conducted from 2018 to 2021 in the semi-enclosed Mar Grande basin of Taranto (northern Ionian Sea), on a facility located 600 m off the coastline, with a production capacity of 100 tons per year of seabass (Dicentrarchus labrax) and seabream (Sparus aurata). The results from seasonal sampling performed in a treatment site, where bioremediators (filter-feeding invertebrates such as sponges, polychaetes, mussels, and macroalgae) were deployed, and a control site without bioremediators were compared. Before the IMTA installation, the hard substrates under the cages were sparsely inhabited, with significant sediment coverage. By 2021, the treatment site exhibited revitalized and more diverse macro-zoobenthic communities, with species richness increasing from 83 taxa in 2018 to 104 taxa, including notable growth in sponges, annelids, mollusks, and bryozoans. In contrast, the control site showed no substantial changes in biodiversity over the same period. Biodiversity indices, including Shannon and Margalef indices, improved significantly at the treatment site, particularly during summer months, highlighting a more resilient and balanced benthic environment. Taxonomic distinctness (delta+) and multivariate analyses (PERMANOVA, PCO) confirmed significant spatial and temporal shifts in community structure at the treatment site, driven by IMTA implementation. SIMPER analysis identified key taxa contributing to these changes, which played a pivotal role in structuring the community. The emergence of filter feeders, predators, and omnivores at the treatment site suggests enhanced nutrient cycling and trophic complexity, while the decline in opportunistic species further supports improved environmental conditions. These findings demonstrate the potential of IMTA to promote recovery and sustainable mariculture practices, also offering a comprehensive understanding of its positive effects on hard-bottom benthic community dynamics. 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

Fine-grained organic-rich sediments (FGORSs) from anthropogenic impacts are a growing concern for bays and estuaries around the world. This study explores the relationships of infaunal community diversity and species abundances with FGORSs in the Indian River Lagoon and its tributaries. To examine these potential relationships, infauna was collected monthly using a Petite Ponar grab at 16 stations in the central Indian River Lagoon from October 2015 to August 2016. Abundant taxa in these sediments include polychaete worms (e.g., the polychaete Nereis succinea), mollusks (e.g., clam Parastarte triquetra), and arthropods (e.g., the tanaid Leptochelia dubia), with densities as high as 5.3 × 10⁴ m⁻² (L. dubia in July 2016). Increasing organic matter (OM) in the sediments was inversely correlated with species richness (R² = 0.75; p-value < 0.001), densities (R² = 0.69; p-value < 0.001), and diversity (R² = 0.37; p-value < 0.001). Other infaunal community and population data showed similar relationships with silt–clay (%), sediment porosity, and dissolved oxygen (mg L⁻¹). Two thresholds of OM and correlated environmental parameters are discussed: an impairment threshold at 2% OM, above which infauna decreases precipitously, and a critical threshold at 10% OM, above which infauna is generally absent. Full article

Predicting which non-indigenous species (NISs) will establish persistent invasive populations and cause significant ecosystem changes remains an important environmental challenge. We analyzed the spatial and temporal dynamics of the entire zoobenthos and the biomass of Marenzelleria spp., one of the most successful invaders in the Baltic Sea, in the Neva estuary in 2014–2023. A considerable decrease in Marenzelleria biomass was observed in the second half of the study period, which was accompanied by a sharp increase in the dominance of opportunistic oligochaete and chironomid species. Our one-way analysis of variance showed that communities with high Marenzelleria biomass had significantly higher diversity and biomass of native benthic crustaceans compared to communities with low alien polychaetes biomass. A high biomass of Marenzelleria was observed in biotopes characterized by low temperatures, high salinity, low plankton primary production and chlorophyll concentration. The results of PCA and one-way ANOVA indicated that these factors significantly influenced the spatial and temporal dynamics of the polychaete biomass. More detailed studies of the responses of NISs to environmental variables are needed to better understand and anticipate their dynamics in different regions of the Baltic Sea in relation to climate warming and anthropogenic impacts. Full article

The Barents Sea region is influenced by an increased inflow of warm Atlantic water, which impacts all components of the local ecosystem. Information on the state of benthic communities is required to predict alterations in the food web’s structure and functioning. The spatial distribution of polychaete communities was investigated in relation to environmental conditions at nine stations along the Kola Transect (70°00′–74°00′ N, 33°30′ E) in April 2019. A taxonomically diverse fauna containing 114 taxa was found, with 95 identified at the species level. The fauna was composed predominantly of boreo-Arctic species (63%), followed by boreal (22%) and Arctic species (13%). The polychaete abundance and biomass exhibited considerable variability, ranging from 910 to 3546 ind. m⁻² and from 3.4 to 72.7 g m⁻², with average values of 1900 ind. m⁻² and 18.7 g m⁻², respectively. Cluster analysis revealed three distinct polychaete communities differing in dominant species composition, abundance, and biomass. The southern region featured the most abundant community, the middle part exhibited the highest diversity, and the northern area presented the community with the highest biomass. These spatial variations in community structure corresponded closely to the distribution and properties of water masses within the study area. Multivariate analysis identified depth as the primary driver of diversity indices, with higher values observed at shallow water sites. Salinity and water temperature together explained 46% of the variation in abundance, reflecting warming effects and showing positive or negative effects, depending on the taxa. Furthermore, an increase in water temperature had a positive impact on the contribution of boreal species to the total material, while exerting a strong negative effect on the overall community biomass, underscoring the potential of polychaetes in biological indication. Full article

We used lipid, fatty acid, and stable isotope analyses to investigate variation, over nine months, in the trophodynamics of 10 dominant cryptofaunal, macroalgal/algal, and environmental components from two sites within a rhodolith (Lithothamnion glaciale) bed in southeastern Newfoundland (Canada). There was an overall shift from a diatom-based food web following the spring phytoplankton bloom to a kelp/algae-based food web during fall, accompanied by preferred use of EPA (20:5ω3) over DHA (22:6ω3) in most cryptofauna. The food web contained three trophic levels that encompassed: (1) direct feeding relationships from primary producers (e.g., rhodoliths, macroalgae) to second-order consumers (e.g., sea stars, polychaetes); (2) trophic subsidy from within and outside the rhodolith bed via settlement, resuspension, and consumption of macroalgal fragments and other detrital organic matter; and (3) strong pelagic/benthic coupling. Riverine input did not affect cryptofaunal diets, as shown by the lack of terrestrial biomarkers at the study site nearest to the riverine input, and there were minor differences in trophodynamics between both study sites. The present study’s findings, applicable to relatively broad spatial and temporal domains, as well as those of complementary studies of the same rhodolith bed, uncover high spatio-temporal stability of the rhodolith bed framework and of resident cryptofaunal abundance, diversity, and trophodynamics. 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

The Amapá margin, part of the Brazilian Equatorial Margin (BEM), is a key region that plays a strategic role in the global climate balance between the North and South Atlantic Ocean as it is strictly tied to equatorial heat conveyance and the fresh/salt water equilibrium with the Amazon River. We performed a new scientific expedition on the Amapá continental shelf (ACS, northern part of the Amazon continental platform) collecting sediment and using instrumental observation at an unstudied site. We show here the preliminary outcomes following the applied methodologies for investigation. Geophysical, geological, and biological surveys were carried out within the ACS to (1) perform bathymetric and sonographic mapping, high-resolution sub-surface geophysical characterization of the deep environment of the margin of the continental platform, (2) characterize the habitats and benthic communities through underwater images and biological sampling, (3) collect benthic organisms for ecological and taxonomic studies, (4) define the mineralogical and (5) elemental components of sediments from the study region, and (6) identify their provenance. The geophysical data collection included the use of bathymetry, a sub-bottom profiler, side scan sonar, bathythermograph acquisition, moving vessel profiler, and a thermosalinograph. The geological data were obtained through mineralogical, elemental, and grain size analysis. The biological investigation involved epifauna/infauna characterization, microbial analysis, and eDNA analysis. The preliminary results of the geophysical mapping, shallow seismic, and ultrasonographic surveys endorsed the identification of a hard substrate in a mesophotic environment. The preliminary geological data allowed the identification of amphibole, feldspar, biotite, as well as other minerals (e.g., calcite, quartz, goethite, ilmenite) present in the substrata of the Amapá continental shelf. Silicon, iron, calcium, and aluminum composes ~85% of sediments from the ACS. Sand and clay are the main fraction from these sediments. Within the sediments, Polychaeta (Annelida) dominated, followed by Crustacea (Arthropoda), and Ophiuroidea (Echinodermata). Through TowCam videos, 35 taxons with diverse epifauna were recorded, including polychaetes, hydroids, algae, gastropods, anemones, cephalopods, crustaceans, fishes, and sea stars. Full article