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Ocean acidification state in Kongsfjorden

Kongsfjorden must be one of the most breathtaking places on earth. With its icy water, spectacular mountains, and mighty glaciers, it epitomises the pristine Arctic. But something in the crystal clear air is affecting the water in a way that may spell trouble for the organisms in the fjord. 

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Sampling for calanus and pteropods. Front photo: A typical catc from the sampler: Photo: Ella Guscelli, Institute of Marine Research.

By Agneta Fransson, Peter Thor and Allison Bailey // Norwegian Polar Institute Melissa Chierici // Institute of Marine Research

In recent years, Kongsfjorden has been through major changes due to a warming climate, such as thinning of sea ice and decreased sea ice extent. Its glaciers are retreating and more warm Atlantic water enters the fjord than previously. This affects water temperature, melting processes and surface stratification, all of which have important consequences for biogeochemical processes and the marine ecosystem. But our focus is on pH and carbonate ions in the fjord’s water and how they are changing.

When the amount of carbon dioxide in the atmosphere increases, the ocean becomes less basic (see fact box). There is reason to believe that the process differs in Atlantic and Arctic conditions. That is where Kongsfjorden comes in. This 20-kilometre-long fjord in western Spitsbergen has a shallow inner part of less than 100 metres depth and a sill of about 20 metres. Further out, the fjord seabed plunges to 300 metres and there is no sill. Two tide-water glaciers (Kronebreen and Kongsbreen) and some rivers supply inner Kongsfjorden with glacial meltwater and create cold and fresh surface water, which make it comparable to Arctic conditions. The outer parts of Kongsfjorden are affected by warm, salty Atlantic water. These two contrasting conditions result in large differences I in physical and chemical characteristics and make the fjord a natural laboratory to investigate impacts of climate change (effects of warming, freshening), ocean acidification (OA), and the processes driving the evolution and adaptation of the marine ecosystem.

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Sea ice sampling using an ice corer. Photo: Melissa Chierici, Institute of Marine Research.

Since 2012, we have performed field studies in Kongsfjorden in winter and summer, collecting seawater from several depths in the water column and at several locations from the glacier front to the outer fjord. We have also collected sea ice and glacial ice. Seawater samples are analysed for pH, carbon dioxide and carbonate ion content to investigate how the acidification state varies from season to season and year to year. Our results show that freshwater supply from glaciers, sea-ice melt and river runoff accelerates OA. In other words, acidification appears to be faster in Arctic water. Atlantic water is generally warmer than the freshwater in the fjord and contains more carbonate ions.

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Calanus glacialis. Photo: Allison Bailey, Norwegian Polar Institute.

To assess the effects of OA on the Kongsfjorden ecosystem, we are conducting a series of experiments on key species in the ecosystem. Copepods of the Calanus genus play a pivotal role in the pelagic ecosystem as the main prey for most larval and juvenile fish, but also for baleen whales and some seabirds. Thus, they are the main conveyor of organic matter from primary production to the upper trophic levels. So far, our efforts have focused on C. glacialis, the most abundant Calanus species in the fjord. We capture copepods in the fjord and incubate them at a pH range covering global predictions from the present to 2300. In the laboratory, we measure changes in energy intake, energy expenditure, expression of specific genes involved in stress responses and the resulting changes in a variety of metabolites. This enables us to establish what we call pH reaction norms, which describe how a specific trait changes with changing pH. Reaction norms are very useful as input into models predicting the flow of energy through food webs and development of populations in an acidified future ocean. Within the Fram Centre Ocean Acidification Flagship we are presently refining computer models to help us predict the effects of OA.

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Water sampling under the ice. Photo: Agneta Fransson, Norwegian Polar Institute.

Carbonate ions are essential for the formation of the calcium carbonate shells of some organisms. While copepods do not use calcium carbonate in their shells, pteropods do. Therefore we also collect pteropods (butterfly snails) for analysis. The thin calcareous shell of these beautiful organisms is especially vulnerable to warming and ocean acidification because they have a limited ability to control changes in pH, and suffer under low carbonate ion content: both factors reduce their ability to form their shells. In this project, we focus on the pteropod Limacina helicina and measure shell condition in terms of thickness, porosity and chemical composition.

The results from Kongsfjorden will be compared with results from other fjords and coastal systems in the Arctic and northern Norway with different characteristics. In this way, we will explore the connection between environments and the effects on marine organisms.

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The pteropod Limacina helicina. Photo: Hopcroft UAF/CoML

 

What is ocean acidification?

Ocean acidification is an indirect consequence of increased CO2 levels. Of the CO2 humanity has released to the atmosphere, the ocean has taken up about a third. The resulting changes the marine CO2 system include decreased ocean pH and carbonate ion content. This phenomenon, called ocean acidification (OA), has raised a number of questions about the effects on organisms and the marine ecosystem. The cold, relatively fresh waters of the polar oceans are particularly sensitive to changes, since they already have low carbonate ion concentrations and cold water can take up more atmospheric CO2 than warm water. This is why polar seas are the first to show a decrease in pH. Acidification is detrimental to organisms such as shellfish and corals because it dissolves the calcium carbonate in their shells or skeletons. It also threatens other marine organisms by increasing the amount of energy they must spend to maintain acid-base balance in their cells.

Project information

The research project described here is part of the Ocean Acidification Flagship programme at the Fram Centre and was initiated in 2012. The project is interdisciplinary: chemical and physical oceanographers and marine biologists from the Norwegian Polar Institute and the Institute of Marine Research collaborate to resolve trends and effects of ocean acidification in the arctic marine ecosystem. In summer, samples are taken in collaboration with the MOSJ project (Environmental Monitoring of Svalbard and Jan Mayen), usually from the RV Lance, and experiments to assess the biological effects of OA are conducted at the Kings Bay Marine Laboratory. In winter, sampling is done from small boats stationed in Ny-Ålesund and the seawater samples are transported to the Institute of Marine Research in Tromsø for analyses of ocean acidification state.

Further reading

Fransson A, Chierici M, Nomura D, Granskog MA, Kristiansen S, Martma T, Nehrke G. (2015) Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater-glacier fjord during two contrasting years. Journal of Geophysical Research-Oceans, 120, doi:10.1002/2014JC010320. Thor P, Halsband C, Browman H. (2014)

Ocean acidification - CO2 effects in Northern waters. Fram Forum 2014, pp 40-44. Read online at http://issuu.com/ framcentre/docs/framforum-2014-web Fransson A, Chierici M, Granskog M. (2013)

Understanding ocean acidification - Is the Arctic turning acid? Fram Forum 2013, pp 10-13. Download from https://issuu.com/framcentre.

Published in Fram Forum 2016

Fram Forum is published once a year on behalf of FRAM - High North Research Centre for Climate and the Environment. Its aim is to imform the general public about the wide activities that take place within the Fram Centre. The magazine is available online free of charge  to any and all who are interested in topics related to climate, environment and people in the high north. Do you want a printed copy, please send an email to post@framsenteret.no