Gonzalo Bravo

Rhodolith/maërl beds are biogenic habitats formed by free-living coralline algae, recognized for their ecological importance and global distribution. Along the Argentine coastline, the published literature lacks visual field documentation of rhodolith/maërl beds, despite historical reports of rhodolith-forming species. Here, we present visual records of a rhodolith/maërl bed in the Argentine Beagle Channel, associated with an extensive Macrocystis pyrifera kelp forest (~150 m from shore). Two perpendicular swimming transects allowed confirmation of a minimum spatial extent exceeding 40 × 40 m (>1600 m²). Underwater imagery reveals continuous rhodolith cover over unconsolidated sediments, highlighting a knowledge gap in the regional distribution of these habitats in southern South America.

Soft-sediment benthic habitats are shaped by interactions between physical forcing and biological processes, yet their relative roles under low anthropogenic disturbance remain unclear. We tested whether the hydrodynamic regime acts as a primary driver of taxonomic and functional structure across a depth gradient (20–70 m) in Nuevo Gulf, a trawl-free marine protected area in northern Patagonia. Between April 2023 and February 2024, 601 non-destructive video quadrats (1012.6 m2) were collected using the towed quadrat system Toki in zones of contrasting tidal current intensity. Hydrodynamic regimes were validated through in situ measurements and Regional Ocean Modelling System outputs. Assemblage structure was analyzed using richness estimators, PERMANOVA, nMDS ordination, indicator species analysis, and species co-occurrence networks. Thirty-five taxa were recorded. High-current environments supported higher cumulative richness, greater evenness, and assemblages dominated by suspension feeders and structure-forming taxa. In contrast, low-current areas were strongly dominated by the squat lobster Grimothea gregaria (~85% of total abundance), resulting in reduced evenness and simplified association patterns. Both the current regime and depth significantly influenced community composition, with hydrodynamic effects intensifying at greater depths. Network analyses revealed higher connectivity and recurrent positive associations under high-current conditions, consistent with increased structural complexity and functional integration. Our results demonstrate that hydrodynamic forcing modulates depth-related patterns and governs both composition and species associations in temperate sublittoral soft sediments, providing a robust ecological baseline for predictive habitat mapping and conservation planning in temperate sublittoral ecosystems of the southwestern Atlantic.

The Marine Biodiversity Observation Network Pole to Pole of the Americas (MBON Pole to Pole) brought together 30 participants from 10 countries in Patagonia, Argentina, to strengthen observing capacity of coastal biodiversity across the Americas. The network held a five-day workshop focused on three core components: standardized rocky intertidal photo-quadrat surveys, low-cost environmental DNA (eDNA) sampling, and affordable plankton imaging tools. Participants included researchers, park rangers, and conservation practitioners fostering a collaborative and inclusive environment. Key outcomes included field validation of protocols, identification of context-specific methodological adaptations (e.g., for low tidal amplitude areas), adoption of novel tools for monitoring marine life, and strategies for broader participation and data harmonization. The workshop highlighted the potential of simple, replicable methods to support long-term monitoring, and emphasized the value of shared protocols, tools, and open data for building a more connected and resilient regional observation network.

Artificial reefs are submerged human-made objects. In particular, the artificial wrecks are intentionally submerged obsolete ships. Once deployed, these wrecks are rapidly colonized by diverse benthic communities. Currently, this effect is positively valued by the recreational diving industry, which uses this colonization effect as one of the main arguments to promote the deployment of artificial wrecks. However, there is increasing evidence that artificial wrecks are not a substitute for natural reefs and may alter complex ecological processes such as food web structure and increase the likelihood of invasive species establishment and spread. Here, we discuss our main concerns related to the unintended socioecological consequences of the creation of artificial wrecks, problematizing the paradigm that this practice favours marine conservation. Although we recognize that artificial wrecks have positive economic, social and even some environmental outcomes, we argue that the benefits are often usufructed by only a portion of society and that this practice requires a broader discussion. Finally, we also discuss the management implications of these concerns and propose alternatives to encourage recreational diving through the adoption of more environmentally sustainable and socially participative approaches. Hopefully, this will lead to better and more consensual practices for the management of coastal areas.

Marine Protected Areas (MPAs) require efficient monitoring tools to assess habitats and biodiversity, particularly in remote or understudied regions. This study demonstrates the utility of the towed video-diver technique combined with high-resolution video for rapidly surveying benthic habitats and associated taxa. Applied in Arredondo, a shallow bay within an MPA in Atlantic Patagonia, the method covered 14,000 m² through eight transects, utilizing just 180 min of dive time and ~300 min of video analysis. Substrate types and their associated taxa were classified using the CATAMI framework, yielding a list of 28 taxa and density estimates of mobile organisms. Additionally, the percentage cover of Gracilaria sp.—a commercially valuable macroalga historically overexploited in the region—was estimated for the bay. The invasive crab Carcinus maenas was found across all substrate types on the bay, underscoring its ecological tolerance and the need for ongoing monitoring. This cost-effective, rapid methodology is highly effective for detecting and describing areas of ecological or conservation interest, providing critical baseline data for targeted, detailed studies. Its simplicity and efficiency make it ideal for initial surveys in remote regions, supporting the conservation and management of MPAs.

Most deep-sea organisms feed on the organic matter produced in surface waters and settle on the seafloor. In polar regions, sea ice algal detritus and phytoplankton detritus are the main food sources for benthic fauna that reach the seafloor in pulses. Climate change affects the extension and duration of sea ice cover, which may affect the quantity and quality of food reaching the seafloor, resulting in less ice algae and more phytoplankton biomass. We conducted onboard pulse-chase experiments using sediment cores collected from Baffin Bay, Amundsen Gulf, and the Beaufort Sea to study how macroinfaunal communities in the Canadian Arctic use both food sources. Dual-labeled (¹³C and ¹⁵N) diatoms, Thalassiosira nordenskioeldii (phytoplankton treatment) and Synedra hyperborea (ice algae treatment), were used as tracers of food consumption by macroinfaunal groups. Community structure was analyzed in each region and differences were found among sites. The total uptake of both food sources was higher in Baffin Bay; the macroinfaunal biomass was the highest, with facultative filter/surface-deposit feeders accounting for more than 70% of the total biomass. The Baffin Bay station was the only location where there were notable variations in the biomass-specific uptake of ice algae and phytoplankton detritus by the bivalves and polychaetes, as well as by the community as a whole. At the same time, both food sources were consumed in equal quantities at the Amundsen Gulf and Beaufort Sea stations. This suggests that ice algae are not preferentially uptaken, and macroinfaunal communities may be resilient to a decrease in ice algal input to the seafloor inflicted by sea ice reduction.

The Marine Biodiversity Observation Network Pole to Pole of the Americas (MBON Pole to Pole) conducted two workshops on 27-31 March 2023 and 22-26 January 2024 in the Argentinian Patagonia aiming to enhance capacity for long-term monitoring of rocky intertidal communities in Argentina and Chile by applying novel and easy-to-use methods for biodiversity observing. In these workshops, participants received training on the collection and processing of benthic photo-quadrat imagery and their analysis using open-source artificial intelligence applications. Workshop participants included park rangers, undergraduate and graduate students and scientists. These training activities covered theoretical concepts of rocky shore ecology and field exercises. The workshops promoted collaboration and knowledge exchange between users of biodiversity data and ecologists resulting in the development of a standardised biodiversity monitoring protocol for rocky intertidal communities available in the Ocean Best Practices System of the Intergovernmental Oceanographic Commission of UNESCO. Participants learned to identify dominant species and functional groups (e.g. macro-algal taxa, molluscs, barnacles) commonly present in these habitats and their zonation patterns along elevation gradients, capture high-quality benthic photographs using quadrat frames and cameras provided by the MBON Pole to Pole and compute percentage cover estimates of observed taxonomic groups using open-source automated classifiers. Emerging recommendations underscored the importance of actively involving park rangers in survey efforts and facilitating communication with decision-makers managing Marine Protected Areas. These activities were endorsed by the UN Decade as contributions to the Marine Life 2030 programme towards increasing capacity in the implementation of coordinated, standardised and sustained biodiversity observing efforts in the Americas.

Underwater sampling needs to strike a balance between time-efficient and standardized data that allow comparison with different areas and times. The roving diver survey involves divers meandering and actively searching for species and has been useful for producing fish species lists but has seldom been implemented for benthic taxa. In this study, we used this non-destructive technique to register species associated with kelp forests at the sub-Antarctic Bécasses Island (Beagle Channel, Argentina), detecting numerous species while providing the first multi-taxa inventory for the area, including macroalgae, invertebrates, and fish, with supporting photographs of each observation hosted on the citizen science platform iNaturalist. This research established a timely and cost-effective methodology for surveys with scuba diving in cold waters, promoting the obtention of new records, data sharing, and transparency of the taxonomic curation. Overall, 160 taxa were found, including 41 not reported previously for this area and three records of southernmost distribution. Other studies in nearby areas with extensive sampling efforts arrived at similar richness estimations. Our findings reveal that the roving diver survey using photographs is a good approach for creating inventories of marine species, which will serve for a better understanding of underwater biodiversity and future long-term monitoring to assess the health of kelp environments.

Jewel sea anemones constitute a relatively small group of solitary cnidarians, a sister group of scleractinian corals. In the southwest Atlantic Ocean off Argentina, two species of jewel sea anemones have been found: Corynactis carnea and Corallimorphus rigidus. Corynactis carnea is a common and abundant species in shallow water of northern Atlantic Patagonia, but reproductive data on this species is scarce; the species is known to reproduce asexually. During a SCUBA diving survey in an Atlantic rocky reefs (20 m depth) in Patagonia, we observed for the first time specimens of C. carnea releasing sperm, eight days after the full moon and during the summer season while spawning has been previously observed in at least three species of Corynactis, but all were recorded as occurring in winter.