ChAOS will quantify the effect of changing sea ice cover on organic matter quality, benthic biodiversity, biological transformations of carbon and nutrient pools, and resulting ecosystem function at the Arctic Ocean seafloor. We will achieve this by determining the amount, source, and bioavailability of organic matter (OM) and associated nutrients exported to the Arctic seafloor; its consumption, transformation, and cycling through the benthic food chain; and its eventual burial or recycling back into the water column. We will study these coupled biological and biogeochemical processes by combining (i) a detailed study of representative Arctic shelf sea habitats that intersect the ice edge, with (ii) broad-scale in situ validation studies and shipboard experiments, (iii) manipulative laboratory experiments that will identify causal relationships and mechanisms, (iv) analyses of highly spatially and temporally resolved data obtained by the Canadian, Norwegian and German Arctic programmes to establish generality, and (v) we will integrate new understanding of controls and effects on biodiversity, biogeochemical pathways and nutrient cycles into modelling approaches to explore how changes in Arctic sea ice alter ecosystems at regional scales. We will focus on parts of the Arctic Ocean where drastic changes in sea ice cover are the main environmental control, e.g., the Barents Sea. Common fieldwork campaigns will form the core of our research activity. Although our preferred focal region is a N-S transect along 30 degree East in the Barents Sea where ice expansion and retreat are well known and safely accessible, we will also use additional cruises to locations that share similar sediment and water conditions in Norway, retrieving key species for extended laboratory experiments that consider future environmental forcing. Importantly, the design of our campaign is not site specific, allowing our approach to be applied in other areas that share similar regional characteristics. This flexibility maximizes the scope for coordinated activities between all programme consortia (pelagic or benthic) should other areas of the Arctic shelf be preferable once all responses to the Announcement of Opportunity have been evaluated. In support of our field campaign, and informed by the analysis of field samples and data obtained by our international partners (in Norway, Canada, USA, Italy, Poland and Germany), we will conduct a range of well-constrained laboratory experiments, exposing incubated natural sediment to environmental conditions that are most likely to vary in response to the changing sea ice cover, and analysing the response of biology and biogeochemistry to these induced changes in present versus future environments (e.g., ocean acidification, warming). We will use existing complementary data sets provided by international project partners to achieve a wider spatial and temporal coverage of different parts of the Arctic Ocean. The unique combination of expertise (microbiologists, geochemists, ecologists, modellers) and facilities across eight leading UK research institutions will allow us to make new links between the quantity and quality of exported OM as a food source for benthic ecosystems, the response of the biodiversity and ecosystem functioning across the full spectrum of benthic organisms, and the effects on the partitioning of carbon and nutrients between recycled and buried pools. To link the benthic sub-system to the Arctic Ocean as a whole, we will establish close links with complementary projects studying biogeochemical processes in the water column, benthic environment (and their interactions) and across the land-ocean transition. This will provide the combined data sets and process understanding, as well as novel, numerically efficient upscaling tools, required to develop predictive models (e.g., MEDUSA) that allow for a quantitative inclusion seafloor into environmental predictions of the changing Arctic Ocean.

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The climate and ecological emergencies, Brexit and Covid-19 illustrate the enormity of change and disturbance currently impacting coastal communities in the UK, and the urgency of building resilience to accelerating, multi-faceted and new forms of risk. Our research aims to build the knowledge and know-how to enhance the resilience of marine resource-users to environmental, regulatory and socio-cultural change, while simultaneously improving their wellbeing and reducing adverse impacts on the marine environment. Marine investment, policy and management decisions are often understood as prioritisation decisions ("this or that"), but they can also involve system interactions and trade-offs, and so create winners and losers. Trade-off conflicts manifest in policy consultation, planning and licensing decisions, and in the everyday behaviours of resource-users choosing to support (or not) particular interventions. There is, therefore, increasing impetus to be explicit about trade-offs where they can explain the political acceptability, effectiveness and durability of marine plans, fisheries regulations, protected area designations or offshore wind farms. To date, research has focused on ecological trade-offs or social-ecological trade-offs related to tensions between environmental sustainability and human welfare and wellbeing, with little attention to resilience. Yet, emerging research shows trade-offs between resilience and wellbeing, and between resilience and sustainability with important implications for marine policy and practice. Our research will be the first to develop a nexus perspective on resilience, wellbeing and sustainability to acknowledge that any solution for one objective must equally consider the other two in the nexus. We apply the nexus perspective to on-the-ground and policy interventions to systematically evaluate synergies and trade-offs among resilience, wellbeing and sustainability across scales and sectors, and to identify opportunities to improve these outcomes together. We address the three call themes by: THEME 1: Investigating how diverse marine resource-users respond to varied disturbance events, how their resilience intersects with their wellbeing and engagement with sustainability, and what they VALUE as important for maintaining and improving nexus outcomes. THEME 2: Applying the nexus perspective to the policy context to understand how diverse values and nexus dynamics are traded off in decision-making currently. Working closely with policy and industry stakeholders we will develop a DECISION-SUPPORT FRAMEWORK to interrogate the acceptability of trade-off decisions within and across marine sectors. THEME 3: Applying the nexus perspective to on-the-ground INTERVENTIONS to assess how initiatives intend to improve resilience, wellbeing and/or sustainability, and currently deal with trade-offs across the nexus. Working closely with practitioners, we will identify opportunities to improve future iterations of these interventions so they can better deliver triple benefits across the nexus. Project deliverables include: a new nexus perspective; a low-tech trade-off decision-support framework for use by policy-makers and implementers, and; evidence that applying a nexus perspective can improve both policy and on-the-ground interventions in marine social-ecological systems in the UK across the domains of marine heritage, sustainable development of communities, and marine environmental regulation. This research will be world leading and of international importance. The resilience of people, communities and ecosystems underpins global action to sustainably manage aquatic ecosystems (SDG14), respond to climate change (SDG13), and deliver enduring improvements in wellbeing (SDG1+2). Our research addresses a significant gap in knowledge of how nexus dynamics play out across scales that will be fundamental to successful delivery of these Sustainable Development Goals.

Copepod species of the genus Calanus (Calanus hereafter) are rice grain-sized crustaceans, distant relatives of crabs and lobsters, that occur throughout the Arctic Ocean consuming enormous quantities of microscopic algae (phytoplankton). These tiny animals represent the primary food source for many Arctic fish, seabirds and whales. During early spring they gorge on extensive seasonal blooms of diatoms, fat-rich phytoplankton that proliferate both beneath the sea ice and in the open ocean. This allows Calanus to rapidly obtain sufficient fat to survive during the many months of food scarcity during the Arctic winter. Diatoms also produce one of the main marine omega-3 polyunsaturated fatty acids that Calanus require to successfully survive and reproduce in the frozen Arctic waters. Calanus seasonally migrate into deeper waters to save energy and reduce their losses to predation in an overwintering process called diapause that is fuelled entirely by carbon-rich fat (lipids). This vertical 'lipid pump' transfers vast quantities of carbon into the ocean's interior and ultimately represents the draw-down of atmospheric carbon dioxide (CO2), an important process within the global carbon cycle. Continued global warming throughout the 21st century is expected to exert a strong influence on the timing, magnitude and spatial distribution of diatom productivity in the Arctic Ocean. Little is known about how Calanus will respond to these changes, making it difficult to understand how the wider Arctic ecosystem and its biogeochemistry will be affected by climate change. The overarching goal of this proposal is to develop a predictive understanding of how Calanus in the Arctic will be affected by future climate change. We will achieve this goal through five main areas of research: We will synthesise past datasets of Calanus in the Arctic alongside satellite-derived data on primary production. This undertaking will examine whether smaller, more temperate species have been increasingly colonising of Arctic. Furthermore, it will consider how the timing of life-cycle events may have changed over past decades and between different Arctic regions. The resulting data will be used to validate modelling efforts. We will conduct field based experiments to examine how climate-driven changes in the quantity and omega-3 content of phytoplankton will affect crucial features of the Calanus life-cycle, including reproduction and lipid storage for diapause. Cutting-edge techniques will investigate how and why Calanus use stored fats to reproduce in the absence of food. The new understanding gained will be used to produce numerical models of Calanus' life cycle for future forecasting. The research programme will develop life-cycle models of Calanus and simulate present day distribution patterns, the timing of life-cycle events, and the quantities of stored lipid (body condition), over large areas of the Arctic. These projections will be compared to historical data. We will investigate how the omega-3 fatty acid content of Calanus is affected by the food environment and in turn dictates patterns of their diapause- and reproductive success. Reproductive strategies differ between the different species of Calanus and this approach provides a powerful means by which to predict how each species will be impacted, allowing us to identify the winners and losers under various scenarios of future environmental changes. The project synthesis will draw upon previous all elements of the proposal to generate new numerical models of Calanus and how the food environment influences their reproductive strategy and hence capacity for survival in a changing Arctic Ocean. This will allow us to explore how the productivity and biogeochemistry of the Arctic Ocean will change in the future. These models will be interfaced with the UK's Earth System Model that directly feeds into international efforts to understand global feedbacks to climate change.