Abstract

Seagrasses are vital components of coastal ecosystems, and the intensity and quality of light significantly influence their growth and physiology. In this study, we investigated the responses of Enhalus acoroides seedlings to high light under different light qualities. The results indicated that high light had varying effects on seedling growth, depending on the quality of light. Root growth was promoted in high red light, while high blue light significantly suppressed shoot and root growth. Photoinhibition was not detected but rapid light response curves showed photoacclimation. High light exposure resulted in an increase in the maximum electron transport rates and the minimum saturating irradiance in white and red light, while blue light exposure reduced the initial slope of the light response curve. Furthermore, high light affected chlorophyll content, leading to a lower chlorophyll b/a ratio across all spectra, whereas carotenoid content was decreased under white and blue light. High light exposure also enhanced the non-photochemical quenching and de-epoxidation state of xanthophyll in white light but significantly reduced the xanthophyll pigment pool in blue light. Overall, our results suggest that the growth and photosynthetic characteristics of E. acoroides seedlings are influenced by the intensity and quality of light, highlighting the importance of light environments for seagrass health. These findings provide valuable insights into managing and conserving seagrass ecosystems, particularly in areas experiencing high light stress.