Introduction. The Southern Ocean has unique environmental conditions compared to other areas of the world, making it a key area for the analysis of future biodiversity changes. The peculiarities of this polar ecosystem have played an important role in structuring marine biodiversity, being characterized by high levels of endemism and ecological and cryptic diversity. The data on benthic communities show their marked sensitivity to anthropogenic and climatic changes, impacting both community and species levels. However, these studies have rarely been conducted with reproducible and standardised techniques, limiting our understanding of these changes in both space and time. Here, we present the application of Autonomous Reef Monitoring Structures (ARMSs) to study pioneer benthic communities' development located near the Italian research station Mario Zucchelli in Terra Nova Bay (Ross Sea).
Methods. Each ARMS consists of 10 stacked PVC plates with a 1 cm space to allow for colonization on both surfaces. These structures are characterized by a simplified design, allowing researchers to use more advanced technologies, such as High Throughput Sequencing and photo-analysis to study colonising organisms. The ARMSs were deployed at 25 metres of depth and recovered after 1, 2, 3 and 5 years, respectively. The panels were disassembled, photographed, and the species were identified to the lowest taxonomic level possible. Each photograph was analysed using photo analysis software, highlighting differences in community composition and structure between increasing years of deployment.
Results. The analysis of the data, from one to five years, showed a difference from the point of view of the composition and structure of the communities. They differed particularly according to growth orientation, creating a well-defined structuring depending on the year.
Conclusion. These structures represent the first of their kind to be deployed in Antarctica, providing a fundamental tool for the study of benthic communities, and establishing a baseline against which future population dynamics can be compared.

The Burdwood Bank (BB) hosts a Marine Protected Area in the SW Atlantic Ocean, situated within the Scotia Arc. Considering that the knowledge regarding sponges (Phylum Porifera) is still limited, in this study we attempt to estimate the richness of sponges of the order Poecilosclerida inhabiting the BB. We also compare these results with the richness recorded in adjacent regions of the Scotia Arc and neighboring areas (Tierra del Fuego, Malvinas, South Georgias, South Orkney and South Sandwich Is.). The studied material came from the Burdwood Bank, and it was collected during two research cruises in 2016 and 2017 onboard the OV "Puerto Deseado". We also compiled previous records from the BB and other regions using the published literature. A checklist of 150 species of poecilosclerid sponges, 39 from the BB (with 22 of them representing new records and probably a couple of them new species for science), 49 from Malvinas Islands, 30 from Tierra del Fuego, 55 from South Georgias, 25 from the South Orkney, and 3 from the South Sandwich Islands. In total, 87% of the species were only recorded in one region. Only Mycale (Aegogropila) magellanica, Iophon proximum, Isodictya setifera, Isodictya verrucosa, Myxilla (Myxilla) mollis, Tedania (Tedaniopsis) massa, and Tedania (Tedaniopsis) mucosa (3.60%) were widely distributed among the studied regions. These preliminary results confirmed that BB sponge richness was previously underestimated. Until the present study, only 18 taxa were known from the BB, and we have doubled the known richness. Our results also suggest that the recorded richness may also constitute an artifact of the sampling effort exerted in each region. These results will be complemented with future studies considering the other orders and classes of the phylum Porifera.

The study of the benthic community associated with the Patagonian scallop fishery (Zygochlamys patagonica) has been carried out periodically by the Benthic Mollusc Fisheries Programme (INIDEP) since the fishery began in 1996. The objective of this study was to provide comparative information on the richness, diversity and biomass of the benthic invertebrate community in two of the main Patagonian scallop fishing grounds (FG_D and FG_E) in Argentina during the period between 2015 and 2022. The study area covers soft bottoms between 41°25'S and 43°02'S. Depths range from 87 to 131 m in the SW Atlantic Ocean. A total of 254 samples were studied from five stock assessment cruises using a non-selective dredge. Each sample analysed consisted of approximately 10 litres of unsorted catch. A total of 90 taxa were recorded in the area. FG_D had a higher biomass of benthic communities and associated fauna than FG_E. Porifera was dominant in FG_D, whereas Ophiuroidea was dominant in FG_E. In addition, the specific richness was significantly higher in FG_D. The asymptotic specific richness was 98 species in FG_D and 74 species in FG_E. The observed and estimated effective numbers of common and dominant species were similar in both FGs. The most conspicuous association of species was formed by the Patagonian scallop Z. patagonica, the brittle stars Ophiosabine vivipara, Ophiactis asperula and Ophiuroglypha lymani, Porifera, the sea urchin Sterechinus agassizii and the cnidarian Alcyonium sp. Although this association showed some differences between years, these were related to variations in the biomass contribution of the main species to the total community. The composition of the benthic community and the species association did not differ from those previously recorded for these FGs in previous years.

Myctophids (Family Myctophidae) are among the most common and abundant mesopelagic fishes in the world’s oceans, characterized by ca. 250 species grouped by 33 genera. Despite their globally recognized ecological relevance due to their role in pelagic trophic webs, in the Southwest Atlantic Ocean off of Argentina (33º S - 56º S), myctophids are still understudied, and the available information about these fishes is scarce and fragmented.

During the second half of the last century, a series of surveys was conducted by foreign research and fishing vessels along the continental shelf off of Argentina and its adjacent waters, driven with the aim of studying the main pelagic and demersal resources of the Argentine Sea. Some of these cruises have been pivotal in addressing the first assessments of myctophids’ species diversity and distribution patterns in the region. In the past decades, myctophids have been captured mainly as by-catch aboard fishing and research vessels; nonetheless, there is currently a lack of ecological studies that specifically target these mesopelagic species.

The aim of this study was to provide a comprehensive review of current knowledge of the Family Myctophidae in the Southwestern Atlantic. We analyzed myctophids’ diversity patterns in the region, updating with non-published data and new records from 1,248 fishing trawls collected during 10 cruises (1978-2023) along the Argentine continental shelf, the shelf break, and part of the oceanic domain between 33º and 56º S.

A total of 79 myctophid species belonging to 24 genera were identified, with distinct distribution patterns: 22 tropical, 13 subtropical, 4 temperate, 13 subtropical convergence, 15 subantarctic, 7 antarctic, and 5 widespread. Based on the new data, our results revealed that myctophids’ species-richness is higher in the oceanic zone north of 40° S (Brazil--Malvinas Confluence zone) and lower at the shelf break, with no species present on most of the continental shelf.

Artificial structures such as marinas have increased in recent years due to the growing demand of recreational boating. Marinas modify the original environmental conditions and are thus considered a great stressor to native communities. Nevertheless, piles and floating pontoons provide new habitats that are prone to be colonized by fouling species. Bryozoans and entoprocts are common members of fouling communities that are frequently overlooked given their small size, particularly in the case of entoprocts. Furthermore, little is known about the influence of salinity on the assemblage structure of these two phyla. To improve this knowledge gap, as part of the project ‘Marina-Forests’ (http://doi.org/10.54499/2022.06806.PTDC), fouling animals associated with floating pontoons were studied in 6 recreational (3 coastal and 3 estuarine) marinas of North Portugal. At each marina, 3 sites were haphazardly selected and the fouling community of 4 random 10×10 cm grids per site was scrapped. Collected animals were washed through a 0.5 mm mesh sieve, fixed in a 4% formaldehyde solution, bryozoans and entoprocts were sorted and identified to the lowest level possible. PERMANOVA test was conducted to explore the effect of salinity on the assemblage structure of bryozoans and entoprocts and SIMPER routine to determine the species responsible for differences.

A total of 15 bryozoan species (621 colonies) and 7 entoproct species (1443 colonies) were found. Results showed that the assemblage structure of bryozoans and entoprocts was significantly different between coastal and estuarine marinas. The most important taxa responsible for differences were more abundant on coastal marinas except for the entoproct Barentsia benedeni and the bryozoans Amathia imbricata and Conopeum seurati that were more abundant in estuarine marinas.

Results of this study show that salinity is an important driver of fouling assemblages. In view of many fouling species are invasive, our data also provide useful information to support decision-makers.

Calcareous sponges are marine animals that play an important role in the ecology of coastal environments by serving as a substrate and shelter for several small invertebrates, as well as being crucial in the uptake of dissolved organic matter in reef systems, making them available in the form of particulate organic matter. Due to the subsampling and the limited number of specialists around the world, understanding the distribution of this class of sponges remains a persistent challenge. Throughout the Western Atlantic, the Caribbean sea, expected as a hotspot region for many marine taxa, is still poorly understood concerning the diversity and distribution of the class Calcarea, with the Brazilian coast being the region with the highest number of described species. Despite this, there are still large areas of the Brazilian coastline that need investigation. In this work, we present preliminary data from our exploration in one such area, where the presence of the invasive Heteropia glomerosa was observed on different beaches along the coastline of São Paulo, including São Sebastião (Toque Toque Pequeno Beach), Ilhabela (Beach of Pedras Miúdas), and Ubatuba (Saco da Ribeira). Notably, a specimen was living associated to a native sea squirt, Phallusia nigra, demonstrating a strong ecological interaction of the invasive sponge to local fauna. All records herein are from previously unrecorded beaches, which is an advancement in understanding the invasion biology of these animals along the Brazilian coastline. Additionally, the sponges were found on natural substrates, which is noteworthy since previous observations indicated colonization most frequently on artificial substrates, such as ropes and docks. These records from São Paulo demonstrate the potential capacity of this species to colonize the southern coastline and the risk of habitat suppression for indigenous sponges. Further investigations are needed to understand the spread and environmental impacts of these animals, including environmental monitoring over time.

The growth of citizen science has revolutionized the knowledge of biological diversity worldwide, improving the knowledge on the species diversity for particular areas and improving the accuracy of known distributional ranges of the species. This study evaluates the current impact of the iNaturalist platform on understanding marine bivalve diversity along the East Pacific coast, from Alaska (71.39°N) to Cape Horn (54.86°S).

All marine bivalve observations along the East Pacific coast (to mid-June 2024) were obtained from the iNaturalist platform. The geographic coverage of these observations, and the accuracy of this set of information, was evaluated, and this information was contrasted with the total diversity currently known about in this area.

At the time of this analysis, a total of 77,207 marine bivalve observations, comprising 572 species and 62 families, was available in iNaturalist. This represents 45.0% of the total number of species and 77.5% of the total number of families known to the area. Most of these observations (80.5%) come from North America, followed by Central America (14.8%), and only 4.7% come from South America. The greater number of these observations (76.7%) appears to be identified at the species level, while the remaining observations refer to a higher taxonomic level (e.g. Genus, Family, or even Class). Observation quality was categorized as follows: 57.7% as "Research Grade", 41.2% as "Needs ID", and 1.1% as "Casual".

Despite the great number of observations of marine bivalves currently available in iNaturalist, the coverage of this platform is still limited. This phenomenon is registered both at a geographic scale, particularly in the case of South America, and a diversity scale, with more than a half of the known species not yet documented therein.

Zooplankton that drift or weakly swim are influenced by water column structure and hydrodynamics. This investigation studied zooplankton communities in the surf zone (SZ) of sandy beaches, characterized by shallow and turbid waters due to wave propagation, and the adjacent shallow subtidal (SSZ), with calmer, deeper waters. This research presents a novel approach by concurrently studying these communities in both zones. Samples were collected bimonthly for a year at Monte Hermoso, Argentina (38°59’S, 61°18’W), using a 200μm mesh zooplankton net by hand-trawl in the SZ and from a vessel in the SSZ. We analyzed species richness, Shannon and Simpson's diversity, β-diversity, taxonomic composition, and spatial variability in abundance between zones. No differences were found between zones in richness, but Shannon and Simpson's diversity werehigher in the SZ. β-diversity reflected species turnover (βsim=0.294, βnes=0.0982), with approximately 40% taxonomic dissimilarity (βsor=0.392) throughout the year. We identified 55 taxa in 15 major groups. Copepoda, Mollusca, Annelida, and Chordata accounted for over 90% of total zooplankton abundance. The results revealed abundance differences, with total abundances in SZ greater than SSZ (p<0.001; SZ=2708ind.m⁻³; SSZ=134ind.m⁻³), driven predominantly by copepods (p<0.001; r=0.96). These differences were reflected in copepod composition, with Acartia tonsa predominating in the SZ, while Paracalanus parvus dominated the SSZ. Both species exhibited similar seasonal patterns, peaking in warmer months for A. tonsa and in winter for P. parvus. In the SSZ, we registered more neritic taxa (e.g., Chaetognatha; Cnidaria, Ctenophora), whereas in the SZ we found more larval stages of benthic organisms from nearby populations (e.g., Echinodermata, Mollusca, Spionidae, Decapoda) and benthic organisms like Cumacea and Amphipoda. The coexistence of estuarine and neritic species highlights the interconnectedness of coastal habitats and provides insights for future ecological studies.

Non-indigenous species (NIS) pose significant threats to coastal ecosystems, causing ecological imbalances and biodiversity loss. Effective monitoring and management strategies are essential to mitigate these impacts, particularly in marinas and ports, which are crucial entry points for NIS due to shipping. This study assessed the spatial distribution of marine invertebrate fauna, particularly NIS, in 10 recreational marinas in Portugal (6 on the mainland and 2 each in Madeira and Azores) using DNA metabarcoding. Samples were collected from hard substrates, water and zooplankton in a single time-point survey in June and July 2020. Using the mitochondrial cytochrome c oxidase subunit I (COI) and the small subunit 18S rRNA gene (18S) markers, a total of 645 species, including 38 NIS, were detected. Only 5% of species and 5% of NIS were common to all marinas. The highest species richness was observed in the mainland North marinas, while Madeira exhibited the lowest richness. Ponta Delgada (Azores) recorded the highest number of NIS (15), whereas Madeira’s marinas recorded the lowest (7 and 9). Species richness and taxonomic composition varied with sample type. A Principal Coordinate Analysis (PCoA) revealed three distinct groups: (1) North and Aveiro (mainland); (2) Lisbon (mainland); and (3) Madeira and the Azores. A PERMANOVA supported the theory that both sample type and marina significantly influenced species composition [P(perm) = 0.001]. A comparison of the 38 NIS detected in this study, with the 2020 national NIS lists, revealed regional differences and spotted species that were not previously considered NIS but are now recognized as such: eight NIS in mainland Portugal, two in Madeira and two in Azores. This study provides valuable insights into the distribution of NIS and marine invertebrate fauna in Portuguese recreational marinas, while highlighting the efficacy of DNA metabarcoding for assessing spatial variability in invertebrate communities and supporting NIS surveillance programs.

Zooplankton responds quickly to environmental changes due to its sensitivity to hydrodynamic variations. This study investigates the impact of different wind events on zooplankton communities in the surf zone of a temperate sandy beach. Zooplankton samples were collected before and after each wind event from May 2017 to July 2019 at Pehuen Co sandy beach. High-frequency wind speed data were used to categorize wind events by direction and duration. Physical and biological variables were analyzed using general Linear Models (LMs) and Generalized Linear Models (GLMs). Additionally, the samples were stained with neutral red to distinguish living organisms from dead ones. The study found that wind direction and duration significantly affect the zooplankton community. Short-duration wind events led to an increase in zooplankton abundance, with Acartia tonsa and Paracalanus parvus being predominant. Winds from the west were associated with the presence of inner continental shelf species such as Ctenocalanus vanus and Euterpina acutifrons, and to a lesser extent, Calanoides carinatus and Labidocera fluviatilis, along with typical surf zone copepods. In contrast, long-duration wind events significantly decreased zooplankton abundance, with SE–SW winds linked to adventitious taxa. In all the samples analyzed before/after the storms, mortality varied from 100% to 4% dead organisms after storms, with the highest mortality generally observed after short-duration wind events. Wind events, particularly their direction and duration, play a crucial role in shaping the abundance and composition of zooplankton in the surf zone of temperate sandy beaches. These findings highlight the importance of considering wind patterns in managing and conserving marine biodiversity. This research contributes to our understanding of how abiotic factors like wind influence coastal ecosystems. The results affect biodiversity conservation strategies in marine environments due to climate change.