Fatty acid dynamics during the spring bloom in a High Arctic fjord: importance of abiotic factors versus community changes

Abstract

We followed the fatty acid composition of particulate organic matter (POM) in a High Arctic fjord (79°N; Svalbard, Norway) during and after the spring bloom. The content of essential polyunsaturated fatty acids (PUFAs) was highest (45% of total fatty acids) at the beginning of the bloom, well before the biomass maximum, and decreased linearly towards the end (30%). During the postbloom period, the concentrations of PUFAs remained stable, between 25% and 30%. Redundancy analysis was used to identify the environmental factors that explained the observed variability in the fatty acid composition of phytoplankton. A particular emphasis was put on the potential influence of high irradiances. During the spring bloom, nutrient availability (Si and N), as well as shifts in phytoplankton community composition and chlorophyll a, were shown to account for much of the pattern in fatty acid composition. During the postbloom period, particularly during periods of stratification, light had a pronounced effect on the fatty acid composition. In general, we found a decrease in the relative amount of PUFAs under high light intensities and nutrient limitation.