Stress due to low nitrate availability reduces the biochemical acclimation potential of the giant kelp Macrocystis pyrifera to high temperature

The performance and survival of macroalgae is largely determined by their ability to adjust to varying environmental conditions. In this study, we investigated the short-term response of the giant kelp Macrocystis pyrifera to varying temperatures (6, 17 and 24 °C) and low and high nitrate conditions (5 μM and 80 μM nitrate) on lipid and fatty acid levels. Results revealed that M. pyrifera was able to rapidly adjust to varying temperatures by changing the saturation level of the fatty acid composition at low and high nitrate conditions. On a lipid level, we observed interactive effects of temperature and nutrient conditions. Under high nitrate conditions, M. pyrifera maintained the same lipid profile. However, under low nitrate and high temperature conditions, an increase in free fatty acids (FFA) was observed, indicative of lipid degeneration at high temperatures. Results show that low nitrogen concentrations can magnify the negative effects of short term temperature stress in the giant kelp M. pyrifera. Our findings indicate that under rapid warming events, local nitrate availability might be a decisive factor for the acclimation potential of M. pyrifera.