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With the COVID-19 pandemic came what media has deemed the “port congestion pandemic”. Intensified by the pandemic, the commonplace anchoring of high-tonnage ships causes a substantial geomorphologial footprint on the seabed outside marine ports globally, but isn’t yet quantified. We present the first characterisation of the footprint and extent of anchoring in a low congestion port in New Zealand-Aotearoa, demonstrating that high-tonnage ship anchors excavate the seabed by up to 80 cm, with the impacts preserved for at least 4 years. The calcuated volume of sediment displaced by one high-tonnage ship (> 9000 Gross Tonnage) on anchor can reach 2800 m 3 . Scaled-up globally, this provides the first estimates of the footprint of anchoring to the coastal seabed, worldwide. Seafloor damage due to anchoring has far-reaching implications for already stressed marine ecosystems and carbon cycling. As seaborne trade is projected to quadruple by 2050, the poorly constrained impacts of anchoring must be considered to avoid irreversible damage to marine habitats.

The impacts of large terrestrial volcanic eruptions are apparent from satellite monitoring and direct observations. However, more than three quarters of all volcanic outputs worldwide lie submerged beneath the ocean, and the risks they pose to people, infrastructure, and benthic ecosystems remain poorly understood due to inaccessibility and a lack of detailed observations before and after eruptions. Here, comparing data acquired between 2015 - 2017 and 3 months after the January 2022 eruption of Hunga Volcano, we document the far-reaching and diverse impacts of one of the most explosive volcanic eruptions ever recorded. Almost 10 km 3 of seafloor material was removed during the eruption, most of which we conclude was redeposited within 20 km of the caldera by long run-out seafloor density currents. These powerful currents damaged seafloor cables over a length of >100 km, reshaped the seafloor, and caused mass-mortality of seafloor life. Biological (mega-epifaunal invertebrate) seafloor communities only survived the eruption where local topography provided a physical barrier to density currents (e.g., on nearby seamounts). While the longer-term consequences of such a large eruption for human, ecological and climatic systems are emerging, we expect that these previously-undocumented refugia will play a key role in longer-term ecosystem recovery. During the 2022 Hunga Volcano eruption, 10 km 3 of seafloor material was removed, fueling long-run out seafloor density currents. These powerful currents damaged seafloor cables over a length of >100 km, reshaped the seafloor, and caused mass-mortality of seafloor life.

We report striking discoveries of numerous seafloor seeps of climate-reactive fluid and gases in the coastal Ross Sea, indicating this process may be a common phenomenon in the region. We establish the recent emergence of many of these seep features, based on their discovery in areas routinely surveyed for decades with no previous seep presence. Additionally, we highlight impacts to the local benthic ecosystem correlated to seep presence and discuss potential broader implications. With these discoveries, our understanding of Antarctic seafloor seeps shifts from them being rare phenomenon to seemingly widespread, and an important question is raised about the driver of seep emergence in the region. While the origin and underlying mechanisms of these emerging seep systems remains unknown, similar processes in the paleo-record and the Arctic have been attributed to climate-driven cryospheric change. Such a mechanism may be widespread around the Antarctic Continent, with concerning positive feedbacks that are currently undetermined. Future, internationally coordinated research is required to uncover the causative mechanisms of the seep emergence reported here and reveal potential sensitivities to contemporary climate change and implications for surrounding ecosystems. Researchers reveal widespread, newly formed seafloor seeps along Antarctica’s Ross Sea coast. Methane-rich flows alter local ecosystems and may influence warming. The drivers remain unknown, warranting coordinated study.

Areas covered in compact sea ice were often assumed to prohibit upper-ocean photosynthesis. Yet, under-ice phytoplankton blooms (UIBs) have increasingly been observed in the Arctic, driven by anthropogenic changes to the optical properties of Arctic sea ice. Here, we show evidence that the Southern Ocean may also support widespread UIBs. We compile 77 time series of water column samples from biogeochemical Argo floats that profiled under compact (80%–100% concentration) sea ice in austral spring–summer since 2014. We find that that nearly all (88%) such measurements recorded increasing phytoplankton biomass before the seasonal retreat of sea ice. A significant fraction (26%) met a observationally determined threshold for an under-ice bloom, with an average maximum chlorophyll-a measurement of 1.13 mg/m 3 . We perform a supporting analysis of joint light, sea ice, and ocean conditions from ICESat-2 laser altimetry and climate model contributions to CMIP6, finding that from 3 to 5 million square kilometers of the compact-ice-covered Southern Ocean has sufficient conditions to support light-limited UIBs. Comparisons between the frequency of bloom observations and modeled bloom predictions invite future work into mechanisms sustaining or limiting under-ice phytoplankton blooms in the Southern Hemisphere.

Underwater sediment density currents triggered by marine volcanic eruptions threaten island communities and infrastructure, while their deposits provide archives of past eruptions. Despite their significance, scarce real-time density current observations and concurrent deposit samples limit our understanding of their behaviour and relationship to varying volcanic mechanisms. Using data acquired following the explosive, VEI 6, shallow-submarine eruption of Hunga Volcano in 2022, we show that syn-eruptive delivery of pyroclastic material into the ocean via low-column collapses and fountaining triggered the multidirectional dispersal of highly-concentrated underwater density currents. Rapid supply of > 6.5 km 3 of dense pyroclastic material onto the steep volcanic flanks over minutes-to-hours generated currents that maintain high density and velocity 10-100s of kilometres from the volcano. We outline diagnostic criteria to differentiate deposits of shallow-submarine generated underwater currents from other volcanic processes - enabling better reconstruction of the records of volcanic activity in marine sediments and enhancing hazard assessments in submerged volcanic settings worldwide. Volcanic material emplaced onto the seafloor by powerful underwater sediment flows during the largest eruption of the 21st century, Hunga volcano, 2022, enables deposit-based diagnosis of large explosive shallow-submarine eruptions.

The deep ocean is increasingly featured in climate solution discussions. An emerging narrative suggests that marine carbon dioxide removal (mCDR) is essential to meet global climate targets. The argument made is similar to claims that deep-seabed mining (DSM) is necessary to enable widespread electrification, in that both are framed as helping to address climate change. We compare the structure and history of these narratives, highlighting that while potential negative impacts on marine life have emerged as a central feature in debates about DSM, environmental and social risks associated with mCDR are yet to receive similar recognition. In light of this comparison, we argue that potential harm needs to be further emphasized in considerations of deploying mCDR.

Methane seep habitats are widespread chemosynthesis-based ecosystem that span continental margins and interact with surrounding marine systems. With many of these habitats occurring below 200m, seeps can serve as an important source of nutrients in otherwise food limited deep-sea environments. However, the potential for marauding megafauna to assimilate seep derived nutrition has been difficult to quantify. Here, we provide the first evidence of a commercially harvested species, Chionoecetes tanneri (tanner crab), assimilating chemosynthetic production. Although bulk isotope analysis of C. tanneri tissue indicated no quantifiable incorporation of seep-derived carbon or sulfur (mean δ13C, -18.5‰; mean δ34S, 19.5‰), depletions in 13C (δ13C as light as -38.8 ‰) were noted in fatty acid (FA) compounds. In addition, diagnostic biomarkers for seep bacteria, including 16:16 and 18:18c FA’s, were found to have been assimilated by C. tanneri. Futher supporting a trophic link between the seep and the C. tanneri, seep associated bacteria and archaea were, in certain cases, the dominant taxa in the gut contents of the crab. This work provides the first insights into a link between seep production and deep-sea ecosystem services, specifically fisheries production. In addition, it reveals a methodological bias that could exist in some trophic studies where bulk isotopes under-represent the role of seep nutrition in the diet of marauding animals.

On 21 May 2021, a milestone Pan-Arctic Report: Gender Equality in the Arctic was published in tandem with the Arctic Council’s Ministerial Meeting held in Reykjavík, 19–20 May 2021. This article provides a brief review of the report and its major findings across six chapters that address key themes concerning gender equality in the Arctic: Law and Governance, Security, Gender and Environment, Migration and Mobility, Indigeneity, Gender, Violence, Reconciliation and Empowerment and Fate Control. A major conclusion of the report is that accessible, comparable, gender-disaggregated, and Arctic -specific data is severely lacking. Further, all chapters highlight the importance of gender-based analysis and gender mainstreaming in all decision-making processes at national and regional levels. The varying roles that gender—and its intersections with existing inequalities—plays in mediating the impacts of climate change and other socioeconomic transformations are also discussed throughout the report. The Arctic Council is identified as the main driver for implementing recommendations that were provided and discussed at the Council’s Ministerial Meeting and in the Reykjavík Declaration 2021, where the eight ministers of Arctic states “Emphasize[s] the importance of gender equality and respect for diversity for sustainable development in the Arctic… encourage[s] the mainstreaming of gender-based analysis in the work of the Arctic Council and call[s] for further action to advance gender equality in the Arctic”. This report and its policy relevant highlights, address these priorities and serve as a knowledge base for promoting gender equality and non-discrimination in the Arctic.

Methane seeps are highly abundant marine habitats that contribute sources of chemosynthetic primary production to marine ecosystems. Seeps also factor into the global budget of methane, a potent greenhouse gas. Because of these factors, methane seeps influence not only local ocean ecology, but also biogeochemical cycles on a greater scale. Methane seeps host specialized microbial communities that vary significantly based on geography, seep gross morphology, biogeochemistry, and a diversity of other ecological factors including cross-domain species interactions. In this study, we collected sediment cores from six seep and non-seep locations from Grays and Quinault Canyons (46–47°N) off Washington State, USA, as well as one non-seep site off the coast of Oregon, USA (45°N) to quantify the scale of seep influence on biodiversity within marine habitats. These samples were profiled using 16S rRNA gene sequencing. Predicted gene functions were generated using the program PICRUSt2, and the community composition and predicted functions were compared among samples. The microbial communities at seeps varied by seep morphology and habitat, whereas the microbial communities at non-seep sites varied by water depth. Microbial community composition and predicted gene function clearly transitioned from on-seep to off-seep in samples collected from transects moving away from seeps, with a clear ecotone and high diversity where methane-fueled habitats transition into the non-seep deep sea. Our work demonstrates the microbial and metabolic sphere of influence that extends outwards from methane seep habitats.

Cold seeps are areas characterised by specialized biological communities that rely on chemosynthesis for their nutrition. To date, research conducted on New Zealand’s Hikurangi Margin seep communities has focused on communities at 650-1200 m water depth. Here, we characterize the macrofaunal nematode communities of New Zealand cold seeps for the first time, and at deeper (> 1200 m) seep locations (Maungaroa, Glendhu and Urutī South). There were no significant difference in nematode abundance, species richness, diversity and evenness among the seep areas, which may reflect the lack of difference in most sediment variables. However, a consistent spatial pattern in nematode abundance was observed within all the seep areas on the Hikurangi Margin: abundance was highest at or near the seep centre, decreased steeply away from the centre and was low in the periphery. These spatially consistent patterns reflect the influence of methane seepage, which appears limited to the inner 150-200 m radius of each area, on nematode abundance via input of chemosynthetic food sources. We found significant differences in nematode community structure among all three areas, with most of the heterogeneity in community structure between the shallow Urutī South area and deeper Maungaroa and Glendhu areas, and differences among nematode communities of high, medium and low abundance associated with site-specific gradients in methane seepage. Within area variability in nematode community structure was mainly correlated with food availability and sediment grain size. Consistent with previous investigations of seep nematodes, we did not find evidence of seep endemics. Although deposit feeders were generally the most abundant feeding group, there were differences in the relative abundances of different feeding groups such as microvores and epigrowth feeders among the seep areas, and as a function of distance from the centre of the seep areas. Impact on seep communities from gas hydrate extraction processes may occur via reduction or potentially cessation of free-gas methane supply to the seafloor, ‘sand’ production at the seafloor due to the physical degradation of the substrate structure, or alteration of the structural integrity of the seafloor substrate. Any spatial management options considered for managing these impacts should reflect the differences in benthic community structure between depths and locations on the Hikurangi Margin.