Strathclyde mathematician joins Arctic climate change venture

Expedition explores the activity of some of the smallest links in the food chain

14 August 2019

A mathematics researcher at the University of Strathclyde has joined a scientific venture to the Arctic Ocean which is to understand the behaviour of tiny organisms that are key to the food chain.

Dr Aidan Hunter is part of the crew seeking to understand the impacts of climate change on marine life in the Arctic.

The scientists are conducting sampling and a number of experiments for four projects that are part of the £20 million Changing Arctic Ocean scientific research programme. Dr Hunter is a member of the DIAPOD team, which is studying zooplankton – small crustaceans the size of a rice grain – that are the main source of food for fish and other species.

It has a particular focus on Calanus, a family which makes up around 80% of the zooplankton biomass in the Arctic region.

Dr Hunter said:

Life at sea in the Arctic is very enjoyable, I find it a rare treat to be somewhere so isolated and beautiful – especially when the ship ventures into sea ice. There have been several whale sightings, orcas, fin whales, and apparently a humpback was spotted along the ice edge – but no polar bears yet.

The daily 12-hour shifts are quite gruelling. There’s plenty of team spirit, however, and the excitement of it all keeps everyone going strong. Overall, being up close to the data sampling and experimental work is fascinating, and as a non-biologist I’m learning a tremendous amount about the realities and difficulties of collecting data.

Calanus zooplankton are being collected from a range of depths, down as far as 1 km, using a trawling net called a MOCNESS. As it is late summer, we are finding some of these animals feeding in surface waters while others have already accrued enough lipid to fatten them up, are in a sleepy state, known as diapause, in deep water.

The ship-board experiments on Calanus include measuring their ammonia excretion and respiration to provide information on metabolic rates and processes; lipid analyses to determine what they are eating and which food sources provide them the nutrients important to various biological functions; and behavioural studies – followed by clock-gene analyses when back on land – to figure out how the animals ‘decide’ when to enter diapause.

All of this data will help us to forecast the fate of Calanus populations as they respond to the rapidly heating Arctic Ocean, which is crucial to predicting ecosystem-wide consequences of the ever diminishing sea-ice cover. It will be useful to our mathematical modelling research at Strathclyde because it will inform us about how various arctic Calanus species burn through their lipid stores as they overwinter in diapause, and will provide data on nutrient feedback to the phytoplankton on which they graze.

Calanus organisms live in the surface layers of the Arctic Ocean during the summer months, where they are the major food of fish and seabirds. During the autumn and winter, they migrate to enormous depths where they enter a state of hibernation called diapause.

The researchers will determine their biochemical composition to help work out how they fuel their mass migration and manage to survive without eating for up to six months, before they return to the surface to breed.

Dr Hunter took part in a previous Changing Arctic Ocean expedition in which DIAPOD researchers gathered plankton, with a view to creating a realistic mathematical model to predict the impact of climate change on the species.

Three other Changing Arctic Ocean projects – CHASE, Micro-ARC and PETRA – are represented on the voyage. The programme has a total of 16 projects and Strathclyde participates in a further three:

• Arctic PRIZE (Arctic productivity in the seasonal ice zone) – aimed at understanding how seasonality, ice cover and ocean properties determine the large-scale ecosystem structure of the Arctic Ocean.
• MiMeMo (Microbes to Megafauna Modelling of Arctic Seas) – using mathematics and computer science to predict flows of nutrient through the marine food web, as the physical environment in the Atlantic Arctic changes. Led by Professor Michael Heath, of Strathclyde’s Department of Mathematics & Statistics.
• PEANUTS (Primary Productivity Driven by Escalating Arctic Nutrient Fluxes) – investigating whether increases in Arctic net primary productivity – the overall amount of chemical energy produced by plants – have been accelerated by changes in the way nutrients are transported towards the ocean surface.

Funded by NERC and the German Federal Ministry for Education and Research, the Changing Arctic Ocean programme aims to generate a better understanding of how the Arctic Ocean is responding to climate change. This will help to predict more accurately future change to the environment and ecosystems.