The Arctic environment is currently changing at an unprecedented rate, leading to complex and hitherto poorly understood consequences for the marine ecosystems. Small microalgae represent the basis of the marine food web, and are affected by these changes in multiple ways:
(1) altered light conditions owing to a decrease of sea ice extent and thickness,
(2) ocean acidification (OA), resulting from an uptake of anthropogenic CO2 into the water,
(3) invasion of more temperate species from the south through increased transport of water masses from lower latitudes and higher temperatures in Arctic waters.
Together, these three processes are expected to change the timing, species composition, productivity, and food quality of Arctic algal blooms, with far-reaching implications for the entire ecosystem.
This project aims at studying the combined effect of these three processes on Arctic algal blooms in sea ice and water, with a special focus on the control of the onset and development of a bloom. This will be done by combining (i) extensive field studies in two Arctic fjord systems with contrasting environmental characteristics, (ii) experiments to study the combined effect of increased light and CO2 on natural algae communities and single species, and (iii) developing models that allow us to study the relative importance (and joint effects) of different stress factors.
The experimental studies will indicate which algal groups (or species) might be best adapted to tolerate the environmental conditions in the future Arctic ocean, in particular with respect to ocean acidification. These results can be used to identify potential indicator species for OA that can be used in the indicator system for the Barents Sea (developed by Miljødirektoratet).
Furthermore, results from this project will also be used to improve and validate a global model projecting future Arctic sea ice and ocean development with respect to the crucial role of algal blooms.
Seasonal succession of algae blooms in sea-ice covered Arctic marine systems, and their importance for different groups of grazers (from Leu et al. 2015, Prog Oceanogr)
Relevant publications from the project group:
· Hegseth, E.N., Assmy, P., Wiktor, J.M., Wiktor, J.M.Jr, Kristiansen, S., Leu, E., Tverberg, V., Gabrielsen, T.M., Cottier, F. (subm.) Phytoplankton seasonal dynamics in Kongsfjorden, Svalbard and the adjacent shelf. Pol Biol
· Leu, E., Mundy, C.J., Campbell, K., Gabrielsen, T., Gosselin, M., Juul-Pedersen, T., Gradinger, R. (2015) Arctic spring awakening – steering principles behind the winter-spring transition in marine ecosystems. Prog Oceanogr 139: 151-170.
· Berge, J., Cottier, F. Darnis, G., Falk-Petersen, S., Gabrielsen, T., Johnsen, G., Last, K. Leu, E., Lønne, O.J., Moline, M., Nahrgang, J., Renaud, P.E., Seuthe, L., Søreide, J., Varpe, Ø., Weslawski, J.M. (2015) In the dark: paradigms of Arctic ecosystems during Polar night challenged by new understanding. Prog Oceanogr 139: 258-271. doi:10.1016/j.pocean.2015.08.005
· Berge, J., Daase, M., Renaud, P.E., Ambrose, W.G jr., Darnis, G., Last, K.S., Leu, E., et al. (2015). Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic. Current Biology 25(19): 2555-2561. http://dx.doi.org/10.1016/j.cub.2015.08.024
· Leu, E., Søreide, J.E., Hessen, D.O., Falk-Petersen, S., Berge, J. (2011) Consequences of changing sea ice cover for primary and secondary producers in European Arctic shelf seas: timing, quantity and quality. Prog Oceanogr 90: 18-32.
· Søreide, J.E, Leu, E., Berge, J., Graeve M., Falk-Petersen, S. (2010) Timing of blooms, algal food quality and Calanus glacialis reproduction and growth in a changing Arctic.Global Change Biol 16(11): 3154-3163.
· Leu, E., Wiktor, J., Søreide, J.E., Berge, J., Falk-Petersen, S. (2010) Increased irradiance reduces food quality of sea ice algae.Mar Ecol Prog Ser411: 49-60
· Leu, E., Falk-Petersen S., Kwasniewski S., Wulff A., Edvardsen K., Hessen D.O. (2006) Fatty acid dynamics during the spring bloom in a high Arctic fjord: importance of abiotic factors vs. community changes. Can J Fish Aquat Sci. 63: 2660-2779.