Can we detect changes in Arctic ecosystems?

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.

The main beneficiaries of this project will be policy makers concerned with conservation of Arctic marine mammals, Inuit communities, school pupils, teachers and the wider general public.

Throughout much of their range, seals and other mammals are important cultural and nutritional resources for indigenous and non-indigenous communities. However, seals are being measurably impacted by climate change. Our project will provide observational and modelling evidence regarding the drivers of alterations to seals' trophic position, food web structure or foraging behaviour over decadal time scales. Using multiple tools, we will delineate if changes in seal trophic position, food chain length or foraging behaviour are due to environmental factors (e.g. sea ice changes), variations in the base of the food web (e.g. from reduced nutrient supply) or the addition of new trophic levels (e.g. migration of boreal species). Our work directly benefits ongoing programmes that monitor the Arctic, such as the Five-year Science Research Agenda from the Department of Fisheries and Oceans (Canada). Our work will benefit work by DFO and aid Inuit communities develop adaptation strategies (Letter of Support from Ferguson, DFO). We will disseminate results from our project to key international organisations, such as the International Council for Exploration of the Seas (ICES) and North Atlantic Marine Mammal Commission (NAMMCO), facilitated by NAMMCO General Secretary and project partner, Desportes. Other project partners (Stenson, Hammill, Ferguson and Hop) are also involved in ICES and NAMMCO, as well as the Circumpolar Biodiversity Monitoring Programme (CBMP), making them able to disseminate our results in the context of management and policy. A one year PDRA will collate, analyse and model historical data on harp and ringed seal body condition and fecundity alongside environmental variables and determine the factors driving long term change in seal populations, disseminating their findings to ICES and NAMMCO at international meetings. This will allow the practical and applied project outputs to inform management and policy for marine mammals in the Arctic, with the potential to affect future decision making for seal populations. Thus, we directly address NERC strategy by providing tools for the 'Management of Environmental Change'.

It is essential that our research outcomes are disseminated to the UK community. This is challenging but vital to recruit students into sciences, convince the public that it is worthwhile funding this type of research and increase awareness of the sensitivity of the Arctic to a changing climate. Our project will provide teachers with tools to demonstrate key concepts in our research programme. To this end, we will produce three posters to convey for example, 'Arctic food webs', 'Stable isotopes in Arctic ecology' and 'Impact of climate change on the Arctic' to school pupils in order to demonstrate how food webs operate in the Arctic. Posters will be hand-drawn by a visual artist with experience of communicating complex ideas concisely and digitized by co-PI Heath.

The general public tends to engage with popular wild life television programmes that illustrate the fauna of the Arctic and the pressures imposed by climate change. We will explain the vital role of microscopic phytoplankton and nutrients within the environment by creating one short accessible scored video, with combinations of film, hand and digital animations with commentaries aimed at the general public. The video will be distributed via a project YouTube channel and via our own website.

At the programme level we suggest (a) creating a dedicated programme website and social media outlets, (b) soliciting the BBC or Discovery Channel to produce a short documentary about the programme and (c) hiring an expert in science communication and impact to represent the programme and/or train members of the research programme in science communication.