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ABSTRACT The chapter provides a brief introduction to the underlying causes of climate change in the deep ocean, and the mechanisms by which these affect deep-ocean ecosystems (Figure 2). Climate change is interpreted in the broad sense here and incorporates the many changes in ocean environments linked to atmospheric and ocean warming and/ or ocean acidification, including oxygen loss, changes in POC flux to depth, altered hydrodynamics and circulation, as well as bentho-pelagic coupling.

ABSTRACT Despite considerable technological advances in recent decades that have enabled the ecosystems of the deeper parts of the oceans to be discovered and explored, large knowledge gaps still exist on the biology and ecology of such ecosystems. This is largely due to challenges related to observation and experimentation in situ, and to maintaining deepwater species under ex situ experimental conditions. Deep-sea organisms have evolved life strategies and physiological adaptations (e.g. slow metabolism and growth rates, high longevity, and late maturity) that allow them to succeed in the cold and generally food-limited deep-sea environment but that may partially impair their ability to physiologically compensate for and adapt to changes in climate. Therefore, a deeper understanding of species' biological and ecological traits, as well as their tolerance thresholds to single and cumulative climatic stressors (e.g. temperature and nutrition, pH and O2) is much needed. Most experiments to date have been conducted under short-term (i.e. acute) conditions, thereby hindering the mechanisms potentially involved in species resilience and acclimation. Studies addressing the impact of climate change on species gametogenesis, reproductive output, or larval development and physiology are also largely lacking. While efforts continue to build a knowledge base on the impacts over the physiological and ecological processes affecting individual species, it is also necessary to start to address the impacts that climate change will have on wider ecosystem functioning.

International audience ; The ocean plays a central role in climate change mitigation and adaptation. However, climate and ocean policies have been historically siloed. After decades of slow convergence, the Ocean and Climate Change Dialogue, decided at COP25 and launched online in December 2020, was the first forum for Parties and non-Party stakeholders to the UNFCCC to give their perspectives on how the climate regime should address ocean-related mitigation and adaptation. The Ocean Dialogue was informed by 47 prior open submissions provided by a broad swath of actors from across the UN system and from civil society, including traditional and youth voices. Our analysis of the submissions demonstrates a political evolution towards the nexus among climate, ocean, and biodiversity regimes. The submissions uniformly acknowledge that ocean and climate systems are inextricably linked, and that consideration of ocean-based action will strengthen climate action and vice versa. Salient themes of the submissions include changing ocean impacts, carbon sinks and blue carbon opportunities, and the need for ecosystem resilience, biodiversity management and improved understanding of normative and institutional frameworks. There is a strong call to recognize the interconnectedness of the biophysical world. Similar themes emerged during the actual Ocean Dialogue and the subsequent informal meeting on next steps. The main message conveyed is the dire necessity to implement strong stewardship and good governance of the blue planet in a disrupted climate using cooperative and concrete actions. This analysis highlights the need for a continued transdisciplinary international dialogue on the ocean and climate change which elevates the ocean-climate-biodiversity nexus via collaborative science, finance, and policy. Key policy insights:. Ocean and marine ecosystem impacts of climate change were widely acknowledged, and referenced by ninety-one percent of submissions. After decades of slow integration of ocean into climate policy, the ...

International audience ; The ocean plays a central role in climate change mitigation and adaptation. However, climate and ocean policies have been historically siloed. After decades of slow convergence, the Ocean and Climate Change Dialogue, decided at COP25 and launched online in December 2020, was the first forum for Parties and non-Party stakeholders to the UNFCCC to give their perspectives on how the climate regime should address ocean-related mitigation and adaptation. The Ocean Dialogue was informed by 47 prior open submissions provided by a broad swath of actors from across the UN system and from civil society, including traditional and youth voices. Our analysis of the submissions demonstrates a political evolution towards the nexus among climate, ocean, and biodiversity regimes. The submissions uniformly acknowledge that ocean and climate systems are inextricably linked, and that consideration of ocean-based action will strengthen climate action and vice versa. Salient themes of the submissions include changing ocean impacts, carbon sinks and blue carbon opportunities, and the need for ecosystem resilience, biodiversity management and improved understanding of normative and institutional frameworks. There is a strong call to recognize the interconnectedness of the biophysical world. Similar themes emerged during the actual Ocean Dialogue and the subsequent informal meeting on next steps. The main message conveyed is the dire necessity to implement strong stewardship and good governance of the blue planet in a disrupted climate using cooperative and concrete actions. This analysis highlights the need for a continued transdisciplinary international dialogue on the ocean and climate change which elevates the ocean-climate-biodiversity nexus via collaborative science, finance, and policy. Key policy insights:. Ocean and marine ecosystem impacts of climate change were widely acknowledged, and referenced by ninety-one percent of submissions. After decades of slow integration of ocean into climate policy, the ...

Deep-sea tailing disposal (DSTD) and its shallow water counterpart, submarine tailings disposal (STD), are practiced in many areas of the world, whereby mining industries discharge processed mud- and rock waste slurries (tailings) directly into the marine environment. Pipeline discharges and other land-based sources of marine pollution fall beyond the regulatory scope of the London Convention and the London Protocols (LC/LP). However, guidelines have been developed (Papua New Guinea) to improve tailing waste management frameworks in which mining companies can operate. DSTD can impact ocean ecosystems in addition to other sources of stress, such as from fishing, pollution, energy extraction, tourism, eutrophication, climate change and, potentially in the future, from deep-seabed mining. Environmental management of DSTD may be most effective when placed in a broader context, drawing expertise, data and lessons from multiple sectors (academia, government, society, industry and regulators) and engaging with international deep-ocean observing programs, databases and stewardship consortia. Here, the challenges associated with DSTD are identified, along with possible solutions, based on the results of a number of robust scientific studies. Also highlighted are the key issues, trends of improved practice and techniques that could be used if considering DSTD and research needed to address current knowledge gaps are documented.

Deep-sea tailings disposal (DSTD) and its shallow water counterpart, submarine tailings disposal (STD), are practiced in many areas of the world, whereby mining industries discharge processed mud- and rock-waste slurries (tailings) directly into the marine environment. Pipeline discharges and other land-based sources of marine pollution fall beyond the regulatory scope of the London Convention and the London Protocols (LC/LP). However, guidelines have been developed in Papua New Guinea (PNG) to improve tailings waste management frameworks in which mining companies can operate. DSTD can impact ocean ecosystems in addition to other sources of stress, such as from fishing, pollution, energy extraction, tourism, eutrophication, climate change and, potentially in the future, from deep-seabed mining. Environmental management of DSTD may be most effective when placed in a broader context, drawing expertise, data and lessons from multiple sectors (academia, government, society, industry, and regulators) and engaging with international deep-ocean observing programs, databases and stewardship consortia. Here, the challenges associated with DSTD are identified, along with possible solutions, based on the results of a number of robust scientific studies. Also highlighted are the key issues, trends of improved practice and techniques that could be used if considering DSTD (such as increased precaution if considering submarine canyon locations), likely cumulative impacts, and research needed to address current knowledge gaps. ; publishedVersion

Deep-sea tailings disposal (DSTD) and its shallow water counterpart, submarine tailings disposal (STD), are practiced in many areas of the world, whereby mining industries discharge processed mud- and rock-waste slurries (tailings) directly into the marine environment. Pipeline discharges and other land-based sources of marine pollution fall beyond the regulatory scope of the London Convention and the London Protocols (LC/LP). However, guidelines have been developed in Papua New Guinea (PNG) to improve tailings waste management frameworks in which mining companies can operate. DSTD can impact ocean ecosystems in addition to other sources of stress, such as from fishing, pollution, energy extraction, tourism, eutrophication, climate change and, potentially in the future, from deep-seabed mining. Environmental management of DSTD may be most effective when placed in a broader context, drawing expertise, data and lessons from multiple sectors (academia, government, society, industry, and regulators) and engaging with international deep-ocean observing programs, databases and stewardship consortia. Here, the challenges associated with DSTD are identified, along with possible solutions, based on the results of a number of robust scientific studies. Also highlighted are the key issues, trends of improved practice and techniques that could be used if considering DSTD (such as increased precaution if considering submarine canyon locations), likely cumulative impacts, and research needed to address current knowledge gaps.

International audience ; Of all the interconnected threats facing the planet the top two are the climate and biodiversity crises. Neither will be be solved if we ignore the ocean. To turn the tide in favour of humanity and a habitable planet we need to recognise and better value the fundamental role that the ocean plays in the earth system, and prioritize urgent action needed to heal and protect it at the 'Earthscape' level-the planetary scale at which processes to support life operate. The countries gathering at COP26 have unparalleled political capacity and leadership to make this happen. COP26 could be the turning point, where we not only see commitments to united action for the ocean but also plans to meet those commitments based on science-led solutions that address the interconnectivity between the ocean, climate, and biodiversity. Here we first summarise some of the key ways in which the ocean contributes to and has acted as the major buffer of climate change focussing on temperature although not forgetting its role in storing CO2. Noting in particular with 'high confidence' that the ocean has stored 91% of the excess heat from global warming with land, melting ice and the atmosphere only taking up approximately 5%, 3% and 1% respectively (IPCC, 2021). We also highlight the impact of the recent large release of heat from the ocean to the atmosphere during the 2015/16 El Niño. We then present six science-based policy actions that form a recovery-stimulus package for people, climate, nature, and the planet. Our proposals highlight what is needed to view, value, and treat the planet, including the ocean, for the benefit and future of all life.