Abstract The study of benthic meiofauna has been undertaken in Latin America since the beginning of the 20th century, recently gaining attention due to its recognized role on the ecological functioning of meiofauna assemblages. Bibliometric data provide information regarding research results, explain the degree to which a subject has advanced, and identify its major strengths and weaknesses. In Latin American countries, this type of review is scarce for meiofauna communities. This study analyzes knowledge of marine meiofauna by focusing on the documents Latin American authors published from 1990 to 2021. Documents from three bibliographic databases were analyzed to obtain the most relevant bibliometric indicators. Moreover, the interrelationships between authors, countries, and concepts were analyzed using science mapping techniques. Latin American research on marine meiofauna has increased since the 1990s, producing a total of 399 documents over three decades by almost 1,000 authors. Brazil produced the majority of these documents (predominantly published by Brazilian authors and institutions). The number of documents by country was associated with five development indicators. Their main sources and keywords indicate that ecology, oceanography, and biogeography were the main addressed topics, especially on deep marine environments. Most productive authors were clustered into main research groups with varying degrees of links. We conclude that research efforts on marine meiofauna are gaining importance despite the small number of documents by a relatively low number of research groups. We found a high centralization of documents by countries and a relation with four indicators, such as country size and research spending. Greater regional collaboration could further expand the knowledge of marine meiofauna in Latin America.

Abstract The exploited mangrove crab Ucides cordatus, an important ecosystem engineer in South American mangroves, has a biphasic lifecycle with pelagic larvae developing offshore. Megalopae return to the mangrove forest to settle, i.e., metamorphose into benthic juveniles but its environmental drivers remain poorly understood. We postulate that conspecific crabs facilitate recruitment. In the field, we investigated whether the number of recruits is higher near conspecific burrows than in areas without conspecific bioturbation. Recruit sampling was conducted monthly from April 2008 to May 2009 along an environmental gradient. First, U. cordatus recruits of that year emerged from March to July. Intraspecific facilitation was indicated by significantly higher recruit numbers in bioturbated than in non-bioturbated substrates. Recruits were most abundant in zones with intermediate conditions of inundation, leaf litter standing stock, sediment consistency, luminosity, temperature, salinity, and pH. Avoidance of more inundated zones likely reduces predation by fishes and of less inundated zones helps individuals escape more stressful, drier environmental conditions. The observed habitat-specific recruitment pattern must be considered when designing field assessments of the population structure of U. cordatus (which should include sampling recruits) and enhancing stocks by releasing laboratory-cultivated larvae and first juveniles into the wild.

Abstract Reviews can be useful to provide an overview of specific knowledge areas to facilitate research guidelines and the comparison of study results. Therefore, we aimed to detect regions, environments, and taxonomic groups of elasmobranch that lack information on their feeding ecology and consequently need further attention. Using specific keywords on diet and feeding studies, we searched for articles on the trophic and feeding ecology of elasmobranchs. We found an increase in studies over the last 24 years, with an emphasis on stomach contents and stable isotopes. The USA, Australia, Mexico, Argentina, and Brazil were the countries with the highest number of published articles. Australia, the USA, Argentina, Brazil, Mexico, South Africa, Spain, Uruguay and India were the countries with the highest number of species studied. Estuarine and freshwater environments seem to need more attention, since studies on species in these environments were scarce (~3%). The total number of shark and ray species studied showed no significant differences (164 and 186, respectively), but most of the articles reviewed concerned sharks (67.5%). The larger elasmobranch families also need more attention, especially demersal species such as Rajidae, Dasyatidae, Arhynchobatidae, and Sycliorhinidae. Feeding studies only analyze some of the data deficient (DD) species (~7%) included in the IUCN Red List, pointing to the need to obtain more information about them.

ABSTRACT Knowledge of coastal hydrodynamics is essential for understanding the processes of transport of dissolved or particulate material since in these areas there are large ports and the vessel traffic with a greater possibility of accidents. Studies related to currents are of fundamental importance to support decision-making to mitigate environmental impacts. The present work aims to test the technique of measuring currents through drones, as it has the advantage of a quick response in obtaining and analyzing data. For this study, a field survey was carried out in the region of the mouth of Lagoa dos Patos, RS, Brazil. The method's validation was done through the use of a colored tracer in which it was used to measure the surface current velocities simultaneously with the vectors generated by the drone. The results obtained a percentage difference between the methods of 10%, both for speed and for current direction, showing to be very promising for the use of drones to obtain surface current fields. In this way, it opens a new perspective in carrying out field experiments, so new experiments will be carried out to verify the feasibility of using this technique in different conditions, such as in the surf zone and areas with the presence of density fronts.

Abstract Marginal reefs can provide meaningful information about the structure and dynamics of ecosystems under suboptimal environmental conditions. In addition to their different characteristics, these environments can also occur in urbanized areas. In this note, we characterize marine animal forests (MAFs) on turbid-zone reefs on an urban coast in the equatorial southwestern Atlantic. Overall, the sandstone ferruginous reefs (6-10 m depth) exhibited a flat topography and gentle slope (1-2 m above the seabed). Benthic cover is composed mainly of sponge gardens and ascidians. In addition, we found a low-relief coral carpet with only one massive reef-building coral (Siderastrea stellata) and Zoantharia. The ascidians and sponges had a higher diversity (at least 15 species) than the cnidarians (two species) in these forests. The main animals forming this seascape are weedy and stress-tolerant species adapted to challenging environmental conditions, such as swell waves, mesotidal regimes, moderate turbidity waters, and periodic burial. In this regard, these conditions and human impacts have shaped a unique MAF. Remarkably, the studied formations seem similar to high-latitude marginal reefs or low-latitude reefs under the influence of upwelling, which sustains soft corals and non-framework building coral communities along with sponges and ascidians. In particular, the shallow MAFs along the semi-arid coast of Brazil seem to lack some of the characteristics of low-latitude reefs under high sedimentation, whose structure was described as coral rubble within sedimentary matrices. This suggests that factors other than periodic burials and low light availability affected these MAFs. These overlooked forests are widespread in this area and have been neglected in studies, despite their richness (> 31 taxa) and valuable ecosystem goods and services. In the context of urbanized areas subject to climate change and pollution impacts, jetties, and dredging activities, it is necessary to consider these lush forests in impact assessments and conservation policies.

Abstract The Santos Basin in eastern Brazil is adjacent to the largest human populations in the southwestern Atlantic Ocean, with several potential threats to marine vertebrates. In this study, we provided a systematic bibliographic review and integrated unpublished primary datasets to provide an overview on species, research topics and gaps, and threats to seabirds in the Santos Basin. Bibliographical sources were used for species recorded within the limits of the basin, while species census data were obtained through research and monitoring projects. We analyzed 156 studies from 1914 to 2021. An increase in the number of publications was observed from the 2000s onward (> 80%), with the state of Santa Catarina showing the highest number of publications (56%) on seabirds. Notes and Records (27%), Population and Community Structure (22%), and Fishing (11%) were the main subjects studied. Among the 76 seabird species reported in the Santos Basin (~2/3 of the species reported in Brazil), Procellariiformes was the most prevalent order (51%), including 14 species listed as threatened, either globally or nationally. Resident (28%) and long-distance migratory species, such as visitors from the Southern (39%) and Northern (17%) Hemispheres and Europe (12%), were widely recorded in the region, as well as vagrant species. The inclusion of different data sources allowed broadening the geographic cover used by species to consider both coastal (predominating in previous studies) and offshore areas. The association of seabird distribution with oceanographic and meteorological features should be addressed in future studies, as should studies on the impact of fishing and pollution on a range of common species.

ABSTRACT The ocean bottom morphology, depth, sediment grain size, sediment sorting, carbonate content, and water depth are used to compose seafloor maps as support for biological studies. Sediments are reworked by waves and currents and accumulate according to the hydrodynamic level on the continental shelf. In contrast, sediments are accumulated by pelagic settling, mass wasting, turbidity flows, and boundary currents on the slope. Sea level oscillations during the Quaternary also played an important role in modifying the shelf seabed's morphology and sedimentary mosaic composition. The work addresses these topics in the Santos Basin based on extensive bathymetric data, shallow seismic records, and stratified bottom sediment samples in water depths ranging from 25 to 2,400m, as part of The Santos Basin Regional Environmental Characterization Project (PCR-BS). The main objective is to provide broad background information on the sedimentology and morphology of Santos Basin, focusing on the continental shelf. The morphology, sediment supply, shelf orientation, and ocean climate imprint the Santos Basin's characteristics. The Northern shelf sector is the most dynamic because of the narrow shelf, steep gradient, and East-West shoreline orientation, providing conditions for storm waves to approach and mobilize sediment in the ocean bottom shallow than 50 m water depth. The Southern sector of the shelf is much broader than the Northern sector; it displays a gentler gradient, and its orientation is Northeast-Southwest; therefore, less subject to storm waves than the Northern sector.

Abstract This study describes the hydrography and water masses of the Santos Basin Continental Shelf (SBCS) during two hydrographic campaigns (SANAGU, SANSED) in 2019. Coastal Water (CW) is the dominant water mass in the southern portion of the SBCS, with relatively low salinity values (S<35.5 g kg–1), and satellite data show that local precipitation and river discharge could not account for the low salinity observed during the cruises in the southern region of the domain. The low salinity observed is explained by the transport from the south influenced by Subtropical Shelf Water (STSW), which was influenced by the La Plata River discharge. In the northern region of the SBCS, the South Atlantic Central Water (SACW) dominates the bottom layers of the water column, with the wind playing a major role in the uplift of this water mass, as evidenced by a wind impulse analysis. In this part of the shelf, Tropical Water (TW) was the second water mass in volume and occupied the surface layers and offshore the shelf. CW is restricted to a thin surface layer, which reaches distances of a few kilometers from the coast. Our analysis show the differences in the hydrographic structure of the SBCS and suggests that the SBCS can be divided in two regions with distinct characteristics: 1) the area southwest of São Sebastião, where the hydrographic parameters were modulated by the presence of the Subtropical Shelf Water (STSW); 2) the area northeast of São Sebastião, where the uplifting of SACW was the dominant process.

Abstract The degradation of tropical coastal lagoon systems in urban areas of the least developed countries has been associated with an increase in impermeable areas and poor domestic sewage treatment, increasing land-based runoff of nutrients and suspended solids from catchments. This study aimed to assess the biogeochemical changes caused by human interventions through the analysis of the spatial distribution of sedimentary phosphorus (P) and its mass balance in the Itaipu lagoon, located on the east coast of the state of Rio de Janeiro. Human intervention in the Itaipu lagoon system has caused severe imbalances in biogeochemical cycles over the past decades. Watercourses have been channeled to normalize the hydrological regime and increase hydraulic energy, improving sediment transport capacity. In this context, the increase in runoff from the coastal urban basin into the Itaipu lagoon has buried an increasing amount of phosphorus in the sediment. Recently, a regional increase in storm events caused a series of landslides and floods, which have been reported as possible consequences of global climate change. In recent decades, the synergy between landslides and river channeling has increased TP loads, accelerating phosphorus settling and changing P spatial distribution in surface sediments. This has accelerated siltation of the lagoon with an accumulation of nutrients and organic matter, leading in some cases to sediment anoxia. The lagoon has undergone strong eutrophication, changing its trophic state from meso- to hypertrophic in less than 30 years, even though P loads are not as high as in other coastal lagoons. Our findings confirm that human intervention impacts nutrient loads, which in turn disrupt the balance of biogeochemical cycles, compromising coastal water resources. This leads to the collapse of ecosystem services, another step towards degrading planetary boundaries.

Abstract We evaluate how the concentrations of inorganic nutrients and chlorophyll a vary in a heterogeneous area (Equatorial SW Atlantic), covering a gradient from stations closer to the coast to others more distant associated or not with turbid-zone reefs. Vertical temperature (27.9 ± 0.10 °C; mean ± standard deviation) and salinity (36.2 ± 0.14) profles showed that the water column is well mixed (0-30 m depth). The oligotrophic condition was marked by low concentrations of phosphate (0.30 ± 0.22 µM) and dissolved inorganic nitrogen (0.64 ± 0.74 µM). Moreover, dissolved reactive silicon (DSi) was low in most samples (< 2.0 µM), but higher (>10 µM) in nearshore stations, probably related to continental runoff and/or resuspension of the bottom sediments. The pelagic phytoplankton biomass indicated that chlorophyll a (0.25 ± 0.08 µg L-1) was low, positively correlated with light and negatively correlated with nutrients, indicating possible phytoplankton uptake. Chlorophyll a concentrations were lower in stations closer to the coast and higher in some stations near the reefs, indicating that the latter could be more prone to phytoplankton development and depletion of nutrients, especially DSi. Therefore, although oligotrophy is present along this coast, we found some unexpected heterogeneity of nutrient and chlorophyll a distributions, which were probably infuenced by benthic-pelagic coupling due to the presence of extensive reefs, sponge gardens (18-30 m depth), and the proximity to the coast. These results highlight the importance of understanding the heterogeneity of ocean productivity, especially in lesser known low-latitude areas, which showed distinct nutrient and chlorophyll a levels related to the occurrence of tropical reefs that are capable of supporting important fsh stocks and unique biological communities.

Abstract The bearded fireworm Hermodice carunculata is widely distributed across tropical and subtropical Atlantic and Mediterranean Oceans and was previously considered to be mostly associated with shallow reefs. We provide here data on the distribution, abundance and habitat use of H. carunculata across a euphotic-mesophotic gradient (0-90 m) in the Saint Peter and Saint Paul’s Archipelago (SPSPA, Mid Atlantic Ridge, Brazil). Samples were obtained using SCUBA and a Remote Operated Vehicle (ROV). A total of 189 individuals were observed and a sharp increase in abundance with depth was recorded, particularly from 50 m depth onwards. In the mesophotic zone (50-90 m) individuals were closely associated with branching black-corals (Tanacetipathes spp.) and predation over black-corals and the scleractinian Madracis decactis was commonly sighted. A Boosted Regression Tree model indicated black-coral abundance as the main driver of H. carunculata abundance, suggesting that preference for optimal habitats to hide/forage is more important than depth per se on the bathymetric distribution of the fireworm. The high abundances of H. carunculata in the mesophotic zone, and its predation on keystone benthic cnidarians, suggests that this species play important roles in the dynamics of deep reefs.

Abstract Mangrove forests play a critical role in natural disaster resistance and provide meaningful livelihoods for local communities, especially integrated mangrove shrimp farming (IMSF) systems. Organic shrimp certification actually increases the value chains of shrimp farming in addition to ameliorating mangrove–forest management. Identifying technical issues and assessing environmental risks are the leading concerns when considering organic shrimp production certification. In this study, the technical practices of 30 households were investigated, and surface water and sediment samples were collected in the IMSF models and adjacent rivers in the Thua Duc Forest Management Board area, Ben Tre Province. Data collected from shrimp farming ponds and the environmental background were referred to both the Naturland and National Standards. The results showed that the average mangrove forest and shrimp pond ratio was 56.90:42.70 (%). Two technical issues were highlighted: (i) the use of rotenone, known as a toxin to kill undesirable fish before stocking shrimp, and (ii) annual shrimp pond regeneration causing increased pollution. The data showed that higher concentrations of TSS and P-PO4 3- were detected in surrounding rivers, while surface water in either IMSF ponds or adjacent rivers slightly surpassed the permissible levels of total Fe concentration. All parameters—including heavy metals; toxic and persistent parameters; oil and grease and coliforms analysed in surface water, and sediment samples—were lower than the detection and permissible levels. The results provided evidence that the IMSF’s practices and environmental characteristics were suitable for recommending the Naturland Standards. Recommendations and technical interventions for farmers are necessary to help reduce Fe levels and the safe use of rotenone in IMSF systems. An environmental quality monitoring programme at the target area should be applied when launching organic shrimp production.

Abstract Knowledge of the feeding habits of pelagic fishes off the Brazilian coast is scarce, making the analysis of trophic interactions often inaccurate. Here, we investigated the diet and trophic role of 12 pelagic fish species by revisiting samples obtained by the ECOSAR II Program (FURG/IO/IBAMA) between 23°S and 28°40'S, an area also known as South Brazil Bight. In addition, we analyzed their biomass and fisheries landings in order to examine shifts over time. The content of 432 stomachs was analyzed at the lowest taxonomic level possible. The frequencies of occurrence were used to cluster species, revealing three trophic guilds: "Planktivorous Clupeiformes", "Planktivorous Carangiformes", and "Piscivores". Most Carangidae consumed mainly copepods and other small crustaceans, except Selene setapinnis which clustered in the piscivorous guild together with Scombriformes specimens. In terms of biomass, the dominance of Trachurus lathami, Sardinella brasiliensis, and Trichiurus lepturus was evident. The species' trophic levels ranged from 2.98 to 4.5, showing that these fishes occupied intermediate to high trophic position. Comparing fisheries landings in two study periods (1986-2002 and 2003-2019), six species showed a decrease, while three an increase. Correlations between landings of the Brazilian sardine (Sardinella brasiliensis) and other pelagic fishes indicate that when the former's decreases, the catch of alternative species, such as Opisthonema oglinum and Chloroscombrus chrysurus, increases. The intermediate position of small pelagics in the food web may affect the availability of commercial species by controlling the abundance of lower and upper trophic-level organisms. These findings fill essential gaps for ecosystem modeling, suggesting that ecosystembased fisheries management should address multispecies issues of the pelagic realm rather than only singlespecies approaches. Combining past survey data with yield trends provides evidence for both natural and humaninduced ocean changes.

Abstract Studies relating the populational structure of target species to operational and environmental variables contribute directly to the management of the fisheries in these resources. Therefore, this study aimed to provide data on fishing and ecology of the swordfish ( Xiphias gladius) caught by the Brazilian longline fleet operating in the western Atlantic between 2010 and 2016. Generalized additive mixed models were used to evaluate the relationship between explanatory variables and responses based on Catch Per Unit of Effort (CPUE) data. Results show that the Brazilian longline fleet catches the swordfish mostly between latitudes of 5°N to 30°S and longitudes of 20° to 50°W and that the swordfish prefers temperatures under 25°C at depths below 60 meters. The species showed a tendency toward intermediate light intensity, predominating in the crescent moon phase, and a preference for areas with low chlorophyll concentrations. Our findings on operational and environmental interactions with swordfish CPUE suggest areas and times that can be used by fishing fleets and government institutions as a starting point for swordfish management strategies.

Abstract Picoplankton are central global carbon (C) cycling players and often dominate the ocean plankton communities, especially in low latitudes. Therefore, evaluating picoplankton temporal dynamics is critical to understanding microbial stocks and C fluxes in tropical oceans. However, the lack of studies on low-latitude picoplankton communities translates into a common conception that there is an absence of seasonality. Herein, we studied the temporal variation in abundance (measured by flow cytometry), and carbon flux (taking bacterial production and respiration as proxies) of the picoplanktonic community for the first time, as well as their environmental drivers in a low-latitude (05° 59’ 20.7″S 035° 05’ 14.6″W) Atlantic coastal station. We performed monthly samplings between February 2013 and August 2016 in a novel microbial observatory – hereafter called the Equatorial Atlantic Microbial Observatory – established on the northeastern Brazilian Atlantic coast. Our results revealed stability in temporal dynamics of picoplankton, despite a considerable inter-annual variation, with some related to the El Niño (ENSO) event in 2015. However, weak environmental relationships found were not enough to explain the variation in picoplankton’s abundance, which suggests that other factors such as biological interactions may lead to picoplankton abundance variation over time. Heterotrophic bacteria dominated picoplankton during the entire study period and between photosynthetic counterparts, and Synechococcus showed greater relative importance than picoeukaryotes. These results bring a novel perspective that picoplankton may exhibit more pronounced fluctuations in the tropical region when considering inter-annual intervals, and is increasing prokaryotic contribution to carbon cycling towards the equator.