Arctic PRIZE will address the core objective of the Changing Arctic Ocean Program by seeking to understand and predict how change in sea ice and ocean properties will affect the large-scale ecosystem structure of the Arctic Ocean. We will investigate the seasonally and spatially varying relationship between sea ice, water column structure, light, nutrients and productivity and the roles they play in structuring energy transfer to pelagic zooplankton and benthic megafauna. We focus on the seasonal ice zone (SIZ) of the Barents Sea - a highly productive region that is undergoing considerable change in its sea ice distribution - and target the critically important but under-sampled seasonal transition from winter into the post-bloom summer period. Of critical importance is the need to develop the predictive tools necessary to assess how the Arctic ecosystems will respond to a reducing sea ice cover. This will be achieved through a combined experimental/modelling programme. The project is embedded within international Arctic networks based in Norway and Canada and coordinated with ongoing US projects in the Pacific Arctic. Through these international research networks our proposal will have a legacy of cooperation far beyond the lifetime of the funding. The project comprises five integrated work packages. WP1 Physical Parameters: We will measure properties of the water column (temperature, salinity, turbulent fluxes, light, fluorometry) in both open water and under sea ice by deploying animal-borne tags on seals which preferentially inhabit the marginal ice zone (MIZ). We will use ocean gliders to patrol the water around the MIZ and track it as the ice retreats northwards in summer. Measurements of underwater light fields will support development of improved regional remote sensing algorithms to extend the spatial and temporal context of the proposal beyond the immediate deployment period. WP2 Nutrient Dynamics: We will undertake an extensive program of measuring inorganic and organic nutrients, their concentrations, isotopic signatures and vertical fluxes to understand the role of vertical mixing and advection (WP1) in regulating nutrient supply to PP in the surface ocean. WP3 Phytoplankton Production: We will investigate nutrient supply (WP2) and light availability (WP1) linked to sea ice affect the magnitude, timing, and composition of phytoplankton production, and the role of seasonal physiological plasticity. Through new numerical parameterisations - cross-tuned and validated using a rich array of observations - we will develop predictive skill related to biological production and its fate; resolve longstanding questions about the competing effects of increased light and wind mixing associated with sea ice loss; and therefore contribute to the international effort to project the functioning of Pan-Arctic ecosystems. WP4 Zooplankton: Zooplankton undergo vertical migrations to graze on PP at the surface. We will use acoustic instruments on moorings and AUVs, with nets and video profiles to measure the composition and behaviours of pelagic organisms in relation in light and mixing (WP1) and phytoplankton production (WP3) over the seasonal cycle of sea ice cover. The behaviours identified will be used to improve models that capture the life-history and behavioural traits of Arctic zooplankton. These models can then be used to investigate how feeding strategies of key Arctic zooplankton species may be modified during an era of reducing sea ice cover. WP5 Benthic Community: We will use an AUV equipped with camera system to acquire imagery of the large seabed-dwelling organisms to investigate how changes in sea ice duration (WP1), timing of PP (WP3) and bentho-pelagic coupling (WP4) can modify the spatial variation in benthic community composition. We will also conduct time series-studies in an Arctic fjord using a photolander system to record the seasonally varying community response to pulses of organic matter.

Ecosystems are communities of organisms that interact with each other and their environment. They are often considered in terms of food webs or chains, which describe the interactions between different organisms and their relative hierarchies, known as trophic position. Ocean ecosystems provide key services, such as nutrition, control of climate, support of nutrient cycling and have cultural significance for certain communities. It is thus important that we understand how changes to the environment reshape ecosystems in order to manage climate change impacts. The Arctic Ocean is already being heavily impacted by climate change. It is warming faster than any other ocean region and as it absorbs fossil fuel emissions, it is gradually acidifying. Arctic sea ice is declining by 10% per decade. This affects the availability of sea ice habitats for organisms from plankton to mammals and modifies the ocean environment. Finally, the Arctic is affected by changes in the magnitude of water movement to and from the Pacific and Atlantic Oceans and composition of these waters. Thus Arctic ecosystems are being impacted by multiple concurrent stressors and must adapt. To understand how Arctic ecosystems will evolve in response to multiple stressors, it is crucial to evaluate the effects of on going change. Often these questions are tackled by studies that focus on a specific ecosystem in one location and document the various components of the food chain. However the Arctic is diverse, with a wide range of environments that are responding to unique stressors differently. We require a new approach that can provide information on Arctic ecosystems from a pan-Arctic perspective over decadal timescales. To effectively monitor changes to pan-Arctic ecosystems requires tracers that focus on key ecosystem components and provide quantitative information on ecosystem structure, providing information for management and conservation of ecosystem services. Our goal is to respond to this challenge. We will focus simultaneously on the base of the food chain, controlled by the activity of marine phytoplankton, and key Arctic predators, harp and ringed seals. Seals are excellent candidates to monitor the food web due to their pan-Arctic distribution and foraging behaviour, which means they are exposed to the changing environment. Nitrogen and carbon stable isotopes are often used to examine ecosystems as they are modified during trophic transfer up the food chain. Hence, they can quantify seal trophic position and food chain length, key determinants of ecosystem structure. Crucial in this context however is the isotope value of the base of the food web, known as the isoscape, which is itself affected by a range of environmental characteristics and fluctuates in space and time. Equally, by virtue of changing migration patterns, seals themselves may feed on similar prey in different isoscapes, which would affect the interpretation of ecosystem structure from stable isotopes. These are the major challenges in using stable isotopes. We will link stable isotopes to novel tracers of the food web, known as biomarkers. When these tracers are compared against observations of the shifting isoscape and data on seal foraging, they permit seals to be used to monitor the Arctic ecosystem by quantifying their trophic position and overall food chain length. Via a range of observational platforms, our new food web tracers will be mechanistically linked to the spatial and seasonal trends in the Arctic isoscape and seal behaviour. By then combining historical observations from around the Arctic basin with state of the art ocean and seal population modelling, we can quantify past and future changes in Arctic ecosystems. This will provide information on past changes to Arctic ecosystems, but also put in place an approach that can be used to monitor future changes and aid in the management and conservation of ecosystem services.