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Deep-sea chemosynthesis-based ecosystems support unique biological communities, but human impacts are an increasing threat. Understanding the life-history traits of species from deep-sea chemosynthesis-based ecosystems can help to develop adequate management strategies, as these can have impacts on ecological responses to changes in the environment. Here we examined the occurrence of sexual dimorphism in the yeti crab Kiwa puravida , an endemic species from the Costa Rican Pacific margin that aggregates at active methane seeps and depends on chemosynthetic bacteria for nutrition. The two morphological features examined included the claws, suspected to be under sexual selection and used for defense, and the carpus of the second pereopod not suspected to be under sexual selection. A total of 258 specimens, 161 males, 81 females, 16 juveniles, were collected from Mound 12 at 1,000-1,040 m depth in 2017 and 2018 and analyzed. We found that males have larger and wider claws than females, while there were no differences in carpus length. These results suggest that claw weaponry is under sexual selection in K . puravida , which is probably related to the mating system of this deep-sea species. This is the first attempt to study the reproductive biology of K . puravida , and additional observations will be necessary to shed more light on this matter. 

As biodiversity loss accelerates globally, understanding environmental influence over biodiversity–ecosystem functioning (BEF) relationships becomes crucial for ecosystem management. Theory suggests that resource supply affects the shape of BEF relationships, but this awaits detailed investigation in marine ecosystems. Here, we use deep-sea chemosynthetic methane seeps and surrounding sediments as natural laboratories in which to contrast relationships between BEF proxies along with a gradient of trophic resource availability (higher resource methane seep, to lower resource photosynthetically fuelled deep-sea habitats). We determined sediment fauna taxonomic and functional trait biodiversity, and quantified bioturbation potential (BPc), calcification degree, standing stock and density as ecosystem functioning proxies. Relationships were strongly unimodal in chemosynthetic seep habitats, but were undetectable in transitional ‘chemotone’ habitats and photosynthetically dependent deep-sea habitats. In seep habitats, ecosystem functioning proxies peaked below maximum biodiversity, perhaps suggesting that a small number of specialized species are important in shaping this relationship. This suggests that absolute biodiversity is not a good metric of ecosystem ‘value’ at methane seeps, and that these deep-sea environments may require special management to maintain ecosystem functioning under human disturbance. We promote further investigation of BEF relationships in non-traditional resource environments and emphasize that deep-sea conservation should consider ‘functioning hotspots' alongside biodiversity hotspots. 

Exploration of the deep sea off the Pacific margin of Costa Rica has resulted in the discovery of a number of new species and reports for the region. Here, we report on the occurrence of the octocoral genus Swiftia, and describe a new species collected by the Alvin submersible off the Pacific coast of Costa Rica. The new species has been observed at around 1000 m depth, growing on authigenic carbonates near methane seeps. Swiftia sahlingi sp. nov. is characterised by having bright red colonies that are with limited branching, with slightly raised polyp-mounds, thin coenenchyme mainly composed of long warty spindles, and conspicuous plates. A molecular phylogenetic analysis supports the differences between this new taxon and the closest Swiftia species. The new species represents the first record of the genus from Costa Rica and in fact for the Eastern Tropical Pacific. 

Deep-sea cold seeps are dynamic sources of methane release and unique habitats supporting ocean biodiversity and productivity. Here, we describe newly discovered animal-bacterial symbioses fueled by methane, between two species of annelid (a serpulid Laminatubus and sabellid Bispira ) and distinct aerobic methane-oxidizing bacteria belonging to the Methylococcales, localized to the host respiratory crown. Worm tissue δ 13 C of −44 to −58‰ are consistent with methane-fueled nutrition for both species, and shipboard stable isotope labeling experiments revealed active assimilation of 13 C-labeled methane into animal biomass, which occurs via the engulfment of methanotrophic bacteria across the crown epidermal surface. These worms represent a new addition to the few animals known to intimately associate with methane-oxidizing bacteria and may further explain their enigmatic mass occurrence at 150–million year–old fossil seeps. High-resolution seafloor surveys document significant coverage by these symbioses, beyond typical obligate seep fauna. These findings uncover novel consumers of methane in the deep sea and, by expanding the known spatial extent of methane seeps, may have important implications for deep-sea conservation. 

The ocean plays a crucial role in the functioning of the Earth System and in the provision of vital goods and services. The United Nations (UN) declared 2021–2030 as the UN Decade of Ocean Science for Sustainable Development. The Roadmap for the Ocean Decade aims to achieve six critical societal outcomes (SOs) by 2030, through the pursuit of four objectives (Os). It specifically recognizes the scarcity of biological data for deep-sea biomes, and challenges the global scientific community to conduct research to advance understanding of deep-sea ecosystems to inform sustainable management. In this paper, we map four key scientific questions identified by the academic community to the Ocean Decade SOs: (i) What is the diversity of life in the deep ocean? (ii) How are populations and habitats connected? (iii) What is the role of living organisms in ecosystem function and service provision? and (iv) How do species, communities, and ecosystems respond to disturbance? We then consider the design of a global-scale program to address these questions by reviewing key drivers of ecological pattern and process. We recommend using the following criteria to stratify a global survey design: biogeographic region, depth, horizontal distance, substrate type, high and low climate hazard, fished/unfished, near/far from sources of pollution, licensed/protected from industry activities. We consider both spatial and temporal surveys, and emphasize new biological data collection that prioritizes southern and polar latitudes, deeper (> 2000 m) depths, and midwater environments. We provide guidance on observational, experimental, and monitoring needs for different benthic and pelagic ecosystems. We then review recent efforts to standardize biological data and specimen collection and archiving, making “sampling design to knowledge application” recommendations in the context of a new global program. We also review and comment on needs, and recommend actions, to develop capacity in deep-sea research; and the role of inclusivity - from accessing indigenous and local knowledge to the sharing of technologies - as part of such a global program. We discuss the concept of a new global deep-sea biological research program ‘ Challenger 150 ,’ highlighting what it could deliver for the Ocean Decade and UN Sustainable Development Goal 14. 

Methane seeps are highly productive deep‐sea ecosystems reliant on chemosynthetic primary production. They are increasingly affected by direct human activities that threaten key ecosystem services. Methane seepage often generates precipitation of authigenic carbonate rocks, which host diverse microbes, and a dynamic invertebrate community. By providing hard substrate, even after seepage ceases, these rocks may promote a long‐lasting ecological interaction between seep and background communities. We analyzed community composition, density, and trophic structure of invertebrates on authigenic carbonates at Mound 12, a seep on the Pacific margin of Costa Rica, using one mensurative and two manipulative experiments. We asked whether carbonate macrofaunal communities are able to survive, adapt, and recover from changes in environmental factors (i.e., seepage activity, chemosynthetic production, and food availability), and we hypothesized a key role for seepage activity in defining these communities and responses. Communities onin situcarbonates under different seepage activities showed declining density with increasing distance from the seep and a shift in composition from gastropod dominance in areas of active seepage to more annelids and peracarid crustaceans that are less dependent on chemosynthetic production under lesser seepage. Response to changing environmental context was evident from altered community composition following (1) a natural decline in seepage over successive years, (2) transplanting of carbonates to different seepage conditions for 17 months, and (3) defaunated carbonate deployments under different seepage regimes over 7.4 yr. Seep faunas on transplants to lesser seepage emerge and recover faster than transition fauna (characterized by native seep and background faunas, respectively) and are able to persist by adapting their diets or by retaining their symbiotic bacteria. The macrofaunal community colonizing defaunated carbonates deployed for 7.4 yr developed communities with a similar successional stage asin siturocks, although trophic structure was not fully recovered. Thus, macrofaunal successional dynamics are affected by habitat complexity and the availability of microbial chemosynthetic productivity. This multi‐experiment study highlights the interaction between biotic and abiotic factors at methane seeps at different time scales along a spatial gradient connecting seep and surrounding deep‐sea communities and offers insight on the resilience of deep‐sea macrofaunal communities.

 

Ecotones have been described as “biodiversity hotspots” from myriad environments, yet have not been studied extensively in the deep ocean. While physiologically challenging, deep‐water methane seeps host highly productive communities fueled predominantly by chemosynthetic pathways. We hypothesized that the biological and geochemical influence of methane seeps extends into background habitats, resulting in the formation of a “chemotone” where chemosynthesis‐based and photosynthesis‐based communities overlap. To investigate this, we analyzed the macrofaunal assemblages and geochemical properties of sediments collected from “active,” “transition” (potential chemotone), and “background” habitats surrounding five Costa Rican methane seeps (depth range 377–1908 m). Sediment geochemistry demonstrated a clear distinction between active and transition habitats, but not between transition and background habitats. In contrast, biological variables confirmed the presence of a chemotone, characterized by intermediate biomass, a distinct species composition (including habitat endemics and species from both active and background habitats), and enhanced variability in species composition among samples. However, chemotone assemblages were not distinct from active and/or background assemblages in terms of faunal density, biological trait composition, or diversity. Biomass and faunal stable isotope data suggest that chemotones are driven by a gradient in food delivery, receiving supplements from chemosynthetic production in addition to available photosynthetic‐based resources. Sediment geochemistry suggests that chemosynthetic food supplements are delivered across the chemotone at least in part through the water column, as opposed to reflecting exclusivelyin situchemosynthetic production in sediments. Management efforts should be cognisant of the ecological attributes and spatial extent of the chemotone that surrounds deep‐sea chemosynthetic environments.

 

While ocean acidification is a global issue, the severity of ecosystem effects is likely to vary considerably at regional scales. The lack of understanding of how biogeographically separated populations will respond to acidification hampers our ability to predict the future of vital ecosystems. Cold‐water corals are important drivers of biodiversity in ocean basins across the world and are considered one of the most vulnerable ecosystems to ocean acidification. We tested the short‐term physiological response of the cold‐water coralLophelia pertusato three pH treatments (pH = 7.9, 7.75 and 7.6) for Gulf of Mexico (USA) and Tisler Reef (Norway) populations, and found that reductions in seawater pH elicited contrasting responses. Gulf of Mexico corals exhibited reductions in net calcification, respiration and prey capture rates with decreasing pH. In contrast, Tisler Reef corals showed only slight reductions in net calcification rates under decreased pH conditions while significantly elevating respiration and capture rates. These differences are likely the result of environmental differences (depth, pH, food supply) between the two regions, invoking the potential for local adaptation or acclimatization to alter their response to global change. However, it is also possible that variations in the methodology used in the experiments contributed to the observed differences. Regardless, these results provide insights into the resilience ofL. pertusato ocean acidification as well as the potential influence of regional differences on the viability of species in future oceans.

 

Traits are increasingly being used to quantify global biodiversity patterns, with trait databases growing in size and number, across diverse taxa. Despite growing interest in a trait‐based approach to the biodiversity of the deep sea, where the impacts of human activities (including seabed mining) accelerate, there is no single repository for species traits for deep‐sea chemosynthesis‐based ecosystems, including hydrothermal vents. Using an international, collaborative approach, we have compiled the first global‐scale trait database for deep‐sea hydrothermal‐vent fauna – sFDvent (sDiv‐funded trait database for theFunctionalDiversity ofvents). We formed a funded working group to select traits appropriate to: (a) capture the performance of vent species and their influence on ecosystem processes, and (b) compare trait‐based diversity in different ecosystems. Forty contributors, representing expertise across most known hydrothermal‐vent systems and taxa, scored species traits using online collaborative tools and shared workspaces. Here, we characterise the sFDvent database, describe our approach, and evaluate its scope. Finally, we compare the sFDvent database to similar databases from shallow‐marine and terrestrial ecosystems to highlight how the sFDvent database can inform cross‐ecosystem comparisons. We also make the sFDvent database publicly available online by assigning a persistent, unique DOI.

Six hundred and forty‐six vent species names, associated location information (33 regions), and scores for 13 traits (in categories: community structure, generalist/specialist, geographic distribution, habitat use, life history, mobility, species associations, symbiont, and trophic structure). Contributor IDs, certainty scores, and references are also provided.

Global coverage (grain size: ocean basin), spanning eight ocean basins, including vents on 12 mid‐ocean ridges and 6 back‐arc spreading centres.

sFDvent includes information on deep‐sea vent species, and associated taxonomic updates, since they were first discovered in 1977. Time is not recorded. The database will be updated every 5 years.

Deep‐sea hydrothermal‐vent fauna with species‐level identification present or in progress.

.csv and MS Excel (.xlsx).