Seasonal biochemical plasticity of the green tide seaweed Ulva stenophylloides and its implications for biomass valorization
摘要
Green tides dominated by Ulva species generate large amounts of underutilized biomass that represent both an environmental challenge and an opportunity for sustainable valorization. In central Chile, Ulva stenophylloides accounts for major proportions of green-tide biomass (~ 53% dominance), nevertheless, its seasonal biochemical variability remains poorly characterized. This study evaluated the influence of seasonality on environmental drivers (light and temperature), biochemical composition, and total antioxidant capacity in U. stenophylloides over an annual cycle in Algarrobo Bay. Light intensity varied seasonally, ranging from 680–2240 µmol photons m−2 s−1, whereas temperature showed a significant interaction between season and intertidal zone, with higher values in the upper intertidal during spring and summer (22.38–26.9 °C). Phenolic compounds (2.20–2.97%) and total antioxidant capacity (6.53–13.31%) peaked in spring, suggesting enhanced photoprotective and antioxidant responses during this period. In contrast, soluble proteins, total lipids, chlorophyll a and carotenoids remained relatively stable throughout the year, while chlorophyll b reached its highest levels during winter (~ 46%) relative to summer, consistent with a compensatory response to reduced irradiance. Multivariate analysis revealed clear seasonal clustering, linking winter to photosynthetic pigments and spring–autumn to antioxidant-related compounds. Overall, these results demonstrate that seasonal environmental stress modulates the biochemical performance of U. stenophylloides, providing a functional basis for defining optimal harvesting windows and supporting the valorization of green-tide biomass within a sustainable biorefinery framework.