Influence of Temperature on Physiological Responses of Nannochloropsis gaditana Isolated from Southeastern Coastal Waters of India
摘要
Rising ocean temperatures disrupt marine ecosystems and impact the survival of marine organisms. In this study, the effect of temperature on the cell density, photosynthetic activity, biochemical composition, and fatty acid profile of N. gaditana isolated from the Gulf of Mannar region at different growth phases was evaluated. The results were subjected to dimensionality reduction using Principal Component Analysis (PCA). A maximum cell density of 79.9 ± 2.40 × 106 cells mL− 1 was obtained at 26 °C accompanied with high concentration of chlorophyll a, b, and carotenoid (5.95 ± 0.23, 2.97 ± 0.08, and 2.01 ± 0.06 µg mL− 1) at stationary phase compared to exponential phase (3.70 ± 0.11, 1.80 ± 0.05, 0.58 ± 0.04 µg mL− 1). This study confirms that N. gaditana exhibits optimal growth at 26 °C, followed by 28 and 30 °C, as the growth sharply declines at 32 °C. Particularly, a 65% reduction in area under the growth curve and a two-fold decrease in chlorophyll-a content was observed at 32 °C. Such heat stress caused a one to two-fold decrease in the metabolic pool irrespective of its growth phases. The increase in temperature from 26 to 32 °C has increased the percentage of saturated fatty acids to 56.17 ± 1.68 by decreasing the monounsaturated and polyunsaturated fatty acids, which were recorded as 18.79 ± 0.56% and 9.34 ± 0.28%, respectively. The findings elicit a thermal threshold between 32 and 34 °C for the wild-type N. gaditana. This study may help to understand the metabolic adaptation of microalgae under changing environmental conditions.