MEPS 411:49-60 (2010)  -  doi:10.3354/meps08647

Increased irradiance reduces food quality of sea ice algae

E. Leu1,*, J. Wiktor2, J. E. Søreide3, J. Berge3,4, S. Falk-Petersen1,5

1Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromsø, Norway
2Institute of Oceanology, Polish Academy of Sciences, Powstanców Warszawy 55, 81-712 Sopot, Poland
3The University Centre in Svalbard, PO Box 156, 9171 Longyearbyen, Norway
4Akvaplan-niva, Polar Environmental Centre, 9296 Tromsø, Norway
5Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, University of Tromsø,
9037 Tromsø, Norway

ABSTRACT: The accelerating decrease of Arctic sea ice substantially changes the growth conditions for primary producers, particularly with respect to light. This affects the biochemical composition of sea ice algae, which are an essential high-quality food source for herbivores early in the season. Their high nutritional value is related to their content of polyunsaturated fatty acids (PUFAs), which play an important role for successful maturation, egg production, hatching and nauplii development in grazers. We followed the fatty acid composition of an assemblage of sea ice algae in a high Arctic fjord during spring from the early bloom stage to post bloom. Light conditions proved to be decisive in determining the nutritional quality of sea ice algae, and irradiance was negatively correlated with the relative amount of PUFAs. Algal PUFA content decreased on average by 40% from April to June, while algal biomass (measured as particulate carbon, C) did not differ. This decrease was even more pronounced when algae were exposed to higher irradiances due to reduced snow cover. The ratio of chlorophyll a (chl a) to C, as well as the level of photoprotective pigments, confirmed a physiological adaptation to higher light levels in algae of poorer nutritional quality. We conclude that high irradiances are detrimental to sea ice algal food quality, and that the biochemical composition of sea ice algae is strongly dependent on growth conditions.

KEY WORDS: Fatty acid composition · PUFA · Ice algae · Irradiance · Arctic · Diatom · Stable isotopes

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Cite this article as: Leu E, Wiktor J, Søreide JE, Berge J, Falk-Petersen S (2010) Increased irradiance reduces food quality of sea ice algae. Mar Ecol Prog Ser 411:49-60

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