Astartids are a major component in marine ecosystems, playing important roles in trophic networks. At the southern Southwest Atlantic, Astarte longirostra lives partially buried in the sediment. Muricid and naticid gastropods feed on clams, drilling a hole on their valves. Drillholes made by predatory gastropods are useful tools for evolutionary and ecological studies, since they provide direct, preservable evidences of predation. The aim of this study was to analyse the community structure of and predation pressure on A. longirostra from the continental shelf off Tierra del Fuego (Southwest Atlantic), covering an area of 120 km². Bottom samples were collected with a 13.94 dm² Van Veen grab during July 2014. Complete valves were separated from the sediment under a stereomicroscope. The valve length and drillhole diameter were measured with a micrometer eyepiece. Astarte longirostra valves occurred from 42 to 92 m. Predation pressure was assessed in 12 samples with at least 20 valves each, which were collected from 74 to 92 m, as clams were less frequent at shallower depths. The densities of this clam were variable (14–409 ind.m^-2). Of the 4,292 disarticulated valves analysed, 959 had drillhole marks. Due to their irregular shape, 11.6% of the drillholes could not be attributed to predatory gastropods. The remaining 88.4% had rounded drillholes attributable to muricids and naticids, which exert strong predation pressure on clams. The predation rate was high (34.2% to 68.2%; pooled rate=44.4%). Predation did not differ between left and right valves (Fisher´s Test, p=0.67). The correlation between drillhole diameter and valve length was positive and highly significant, meaning that larger predators prefer larger clams. The size of the valves ranged from 0.62 to 5.85 mm. The size--frequency distribution was bimodal, with modes in 2–2.49 mm and 3.5–3.99 mm, suggesting the existence of two cohorts. Drillholes were significantly more frequent in the central sector of the valves. Of the seven species of predatory gastropods found, the naticid Falsilunatia patagonica was the most frequent.

Background: "Crassostrea virginica belongs to a class of bivalve mollusks that play vital roles in the marine ecosystem. This species holds economic and biological significance, making it a key species in the Atlantic, Caribbean, and Gulf of Mexico. This study aimed to understand the genetic diversity of virginica by barcoding techniques and if the distribution of oysters in the Atlantic Ocean is known, it would indicate which areas require further study.
Methods: Two thousand and eight sequences of virginica COI gene were downloaded from BOLD, aligned, and trimmed using BioEdit and ClustalW. For the haplotypes and their networks, MJN used Network and PopArt. DnaSP was used for sequence grouping and population genetic analysis. The p-Distance and Tajima-Nei values were obtained by Mega v11 software. Finally, to generate the phylogenetic tree, IQTree using maximum likelihood and FigTree were utilized.

Results: The three most abundant haplotypes were AY5422 (58.937%), GB8915 (9.661%), and GB1513 (5.314%). Four sets of sequences have been generated by the origin of capture: 176 for the United States, 9 for Canada, 17 for Cuba, and 4 for Panama. The results revealed two haplotype networks based on region and frequency. A total of 42 different haplotypes. The haplotype network showed that they were grouped by regions, with Canada and the US mixed, as well as Cuba and Panama. Genetic diversity values were nearly zero for individuals within the same geographic populations, while there were higher values among the four regions described (0.01 < FST < 0.9). The Tajima-Nei analysis revealed values ranging from approximately 0.001 to 0.029 within regions and between regions, respectively.

Conclusions: This study revealed that among the 4 regions examined, there were significant genetic differences, indicating the need to explore additional regions in the Gulf of Mexico to develop conservation and commercialization initiatives for virginica.

Clupeiform fishes are represented by a high diversity of species among commercial marine landings on the Kerala coast. They are a globally distributed clade with nearly 400 marine, freshwater, and diadromous species that form large schools and occupy a diverse array of trophic guilds and habitats. However, during this ground-level approach to exploring clupeid fishes on the Malabar Coast, thirteen species belonging to three families were recovered. Among the clupeid fishes recovered during the study period, members of the family Engraulidae were most abundant, followed by Pristigasteridae and Clupeidae. Meanwhile, with respect to the population size, engraulids and cluepeids were more abundant. Regarding oil sardine, Sardinella longiceps is the most abundant clupeiform fish along the Kerala coast, and it supports the state's economy through a single-species fishery. Out of the 112 fish collected during the study period, 83 were found to be members of the order Clupeiformes, belonging to three families: Engraulidae, Clupeidae and Pristigasteridae. Six species of Engraulidae, four species of Pristigasteridae and three species of Clupeidae were identified, but the population size of Engraulidae (48%) was highest, followed by Clupeidae (40%) and Pristigasteridae (12%). An examination of ectoparasitic infestation among these fishes was also thoroughly studied. Two parasitic crustaceans belonging to the two groups Isopoda and Copepoda were found to be infesting the body surface, buccal cavity, opercular cavity, and gills of the clupeid fishes.

Marine environments harbour a wealth of diverse and underexplored microbiota, including species from the actinobacterial genus Streptomyces (Actinomycetota)― remarkably prolific producers of a wide array of natural products with unique bioactivities and high potential for drug discovery and other applications.

In our study, we explored liquid culture supernatants from various Streptomyces strains sourced from deep-sea environments, corresponding to different species, aiming to uncover their chemical diversity and potentially identify valuable natural products. To achieve this, we followed a multi-step extraction procedure involving liquid–liquid and sorbent-assisted extraction steps. Leveraging a high-throughput ultra-high-performance liquid chromatography‒electrospray ionisation‒high-resolution mass spectrometry (UPLC‒ESI‒HRMS) dereplication workflow, we employed molecular networking (MN) and cheminformatic approaches to obtain insights from complex spectral datasets. Our dual focus was to identify known compounds (chemical dereplication) and highlight potentially novel ones within the extracts' "chemical spaces". We further fractionated the extracts, performed general and targeted thin-layer chromatography (TLC) assays, and purified the fractions for structural elucidation using UPLC‒ESI‒HRMS and nuclear magnetic resonance (NMR) spectroscopy, guided by the dereplication.

The investigated strains of marine-derived Streptomyces displayed diverse and intriguing chemical profiles both within and between species. The primary dereplicated compounds included linear and cyclic hydroxamate siderophores from the “ferrioxamine family” and autoregulatory inhibitors of spore germination from the “germicidin family”. Additionally, other natural products, such as carboxylic acid derivatives, dipeptides, and nucleosides, were annotated, all of which with significant application potential.

The described analytical workflow fortified by state-of-the-art cheminformatic approaches allowed us to gain insights into the chemical spaces of the extracts and distinguish potential compounds of interest. The data from MNs are crucial for guided purification during extract fractionation, complementing classical techniques for efficient compound identification and, ultimately, NMR structural elucidation.

Funding: SECRETed project—European Union’s Horizon 2020 research and innovation programme; Grant Agreement No. 101000794.

Introduction
The Eastern Mediterranean Sea (EMS) presents unique environmental traits and complex oceanic processes that affect microbial communities and influence their role in maintaining vital ecosystem functions and services. Despite the heavy anthropogenic stress and predictions of climate change impact, microbial ecology studies in the EMS are limited.

Methods
Two sampling expeditions were conducted in offshore areas south of Crete in August 2019 and February 2020. A total of 14 seawater samples were collected across depths up to 1000 m, from all three EMS water masses. Those underwent DNA extraction and a high-throughput sequencing of their 16S and 18S rRNA genes for bacterial and unicellular eukaryotic analysis, respectively. Moreover, differences between interspecies microbial associations were also evaluated between the top and bottom water masses.

Results
CTD profiling indicated that winter mixing affected the upper 300 m of the water column, with uniform deep waters across sampling seasons. Bacterial and unicellular eukaryotes varied significantly by water mass of origin, with seasonal species fluctuations recorded in the surface layer. Moreover, eukaryotic diversity was higher in all water masses, especially in the intermediate layer, during winter. Photosynthetic taxa were more abundant in winter, while heterotrophs and grazers dominated the deepest waters. Finally, microbial associations were five times higher in the surface network, indicating numerous ecological niches.

Conclusions
To our knowledge, this is the first study that has applied molecular biology tools to examine the ecology and networking of both planktic prokaryotes and unicellular eukaryotes in the EMS. Distinct taxa were found across the three water layers of the EMS, showing differences in microbial diversity and structure, which, however, require further interseasonal samplings to be statistically verified. Overall, these findings underline the need for further exploration and understanding of microbial ecology in one of the most understudied marine habitats.

Barnacles [Cirripedia: Thecostraca] are among the most biologically diverse and ecologically important marine crustaceans, commonly encountered in the inter-tidal and benthic habitats. Adult barnacles are sessile and can either be epibionts or foulers. The marine fauna of Goa, a coastal state on the west coast of India, is not well represented in general. Of the ca. 144 species of barnacles, distributed among 75 genera and 19 families, reported to be present on the coasts of India, only five species from Goa have been identified so far.
The paucity of information and the dearth of data pertaining to the diversity and distribution of barnacles propelled the current study, which aimed at providing a preliminary account of barnacles along the Goan coast. Species diagnosis was mainly based on arthropodal characterization. A total of six cirripedes distributed among three families (Lepadidae, Chthamalidae, and Balanidae) and four genera arereported in the present study. Among these, three species constitute the first records from Goa. The only gooseneck barnacle recorded in the present study was found to be attached to the washed ashore debris on a sandy coastline. All acorn barnacles were recorded in rocky inter-tidal habitats, and a few individuals were found to colonize plastics lodged in rock crevices.

Environmental characteristics such as depth, turbulence, and substrate composition influence the structure and dynamics of benthic communities in marine ecosystems. This study examines the biological descriptors (α- and β-diversity, abundance, and biomass) and functional traits (mobility, feeding mechanism, and diet) of benthic communities across a depth gradient from the surf zone (SZ) to shallow subtidal zones (SSZs) on an exposed sandy shore of a small tourist beach (38°59′S, 61°18′W, Argentina). Samples were collected in spring 2018 and autumn 2019 from three depths (1m, 5m, and 14m) using a benthic sledge (500μm mesh size). Overall, 10,055 individuals from 132 taxa were identified, with Arthropoda, Annelida, and Mollusca being the most represented groups. Arthropods were the most abundant at 1m, while mollusks and annelids dominated at 5m and 14m, respectively. The maximum abundance and biomass were recorded at 14m depth (1450.54 ind/100m², 264.72 g/100m²), while α-diversity was higher at 5m depth (93±15.40). β-diversity indicated high species turnover across the gradient (β_SOR=0.72; β_SIM=0.55), especially between 1m and 14m depths. More mobile, deposit-feeding, and detritivore organisms were found at 1m, while sedentary, filter-feeding, and omnivore organisms were more abundant at 5m and 14m. The results indicate that biological descriptors and functional traits differed significantly across depths. At 1m depth (SZ), the lowest abundance, richness, and diversity suggested that fewer species are adapted to this area, where higher mobility is advantageous to cope with the turbulence generated by continuous wave action. At 5m and 14m (SSZ), where environmental conditions are more stable, sedentary species prevail. Significant differences in diet could be related to the main food sources available in each zone. These findings suggest the existence of distinct benthic assemblages at variable depths. The heterogeneity of the marine benthic environment increases diversity and influences ecosystem functioning.

The surf zone encompasses the region of sandy beaches where waves break along the shore. The benthic invertebrates inhabiting the water/bottom layer in this ecosystem represent a highly abundant and diverse community. Despite some efforts, more information is still needed on inter-annual variability. In this study, we integrate data from two periods, 2009 and 2015, to understand the variability in the biological descriptors of the community on a sandy beach in Argentina (39°00’S, 61°57’W) in the SW Atlantic. Samples (n = 3) were collected seasonally by hand-towing a benthic sledge across transects parallel to the shore. A total of 62 species were collected; arthropods represented 55% and were mainly peracarid crustaceans. Differences in total density were registered between years (p<0.05), with ~39 ind/m² in 2009 (higher density in spring, p<0.05) and ~14500 ind/m² in 2015 (higher density during autumn/winter, p<0.05). These differences were due to dense patches of two mysids, Arthromysis magellanica and Neomysis americana, registered in 2015 during the cold season, which can be explained by their migratory pattern, as they only arrive in the surf zone under certain physical conditions. Differences in species richness were found between years (15 in 2009 and 42 in 2015; p<0.05), with a high dissimilarity (>0.60%), given by both species turnover and nestedness. Changes in species richness were also detected between seasons: higher richness was registered in spring during 2009 (p<0.05), without differences between seasons during 2015 (p>0.05). The dissimilarity between seasons was also high (2009: >0.70%; 2015: >0.60%), mostly explained by the turnover component during both years. Given that the studied beach is subjected to low anthropogenic impact, the significant interannual variability observed in this ecosystem could be explained by its dynamic nature, emphasizing the importance of an extensive dataset to understand the physical and biological factors involved.

The behavioral patterns and feeding strategies of marine organisms represent significant aspects when comprehending the ecology, evolution, and dynamics of species. In addition, studies focusing on feeding habits in marine environments are fundamental for ecological conservation, since they are capable of revealing pollution levels. However, although individuals of the phylum Cnidaria have different life cycles and present a widespread distribution, studies of feeding behavior in anthozoans are scarce. Sea anemones (Cnidaria; Actiniaria) are predatory organisms and perform ecologically significant functions in benthic food webs. In this study, 42 individuals comprising three species, Actinia bermudensis, Anemonia sargassensis, and Bunodosoma caissarum, were collected in Florianópolis, Santa Catarina. The dissected organisms were analyzed internally using DNA metabarcoding techniques with amplification of the mtCOI sector in order to identify and compare their feeding patterns. The morphological analyses comprised an important stage in the partial identification of the fragments found in the gastrovascular cavity of the specimens, despite many of the food items being fragmented and half-digested. The sequencing method, in extension, revealed the identification of a diverse and extensive portion of predated organisms, illustrating the dietary variation in the species, mainly composed of arthropods, such as crustaceans and insects, annelids, and algae classified as ochrophytes.

In this study, we present the contribution of sponges to benthic communities in three different regions of the Argentine continental shelf and slope, between 34º and 55ºS and between 47 and 551 m, according to their richness, occurence frequence, biomass and density from by-catch data of stock assessment cruises performed by the Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP). The invertebrate by-catch was recorded during five stock assessment cruises of the Argentine hake (Merluccius hubbsi) and the longtail hake (Macruronus magellanicus) in 262 hauls. Sponges were recorded as components of the invertebrate’s by-catch in 49% of the studied sites (133 hauls). Their contribution of biomass to the benthic community sampled varied among areas (north, central and south), as well as between sites within the same region. However, on average, sponges constituted 18,01% of the benthic community (47,91 kg/mn², in terms of density), reaching more than 90% of the by-catch and more than 1000 kg/mn² in some particular sites. In total, 34 sponge taxa were recorded. Tedania spp., Clathria (C.) microxa and Callyspongidae (Siphonochalina fortis + Callyspongia sp.) were the only taxa recorded in the three sampled areas, while Mycale (Aegogropila) magellanica, a common species from Argentina, was present only among the North and the South regions. Sixty percent (60%) of the sponge species were recorded in only one or two sites. The North region is probably the better-known region regarding sponge fauna, and it had the most common species. However, the samples of several taxa recorded in the South and Central regions (i.e. Hadromerida, Phakellia spp., Amphilectus sp., Dragmacidon sp., Asbestopluma sp.) will require more detailed taxonomic studies, as these species may contribute to our understanding of Argentina's sponge biodiversity and richness by providing valuable information on rare species or even constituting new species to science.