Morphological and anatomical characteristics of eelgrass Zostera marina L. at two distinct environments of Shandong Peninsula, China: An implication of adaptation strategy of seagrasses

Abstract

Eelgrass Zostera marina L. is commonly found in protected areas. However, an eelgrass population was found in a wave exposed area in Mashanli in the Yellow Sea, China. To investigate its adaptation strategy, a comparative morphological and anatomical study was carried out on the population in Mashanli and on another one in Moon Lake, a lagoon nearly completely sheltered, during the period from November 2020 to September 2021. Results showed that eelgrass in Mashanli had smaller leaf length and width, shorter internode length, and increased root length. On the other hand, though there were no significant differences in the leaf thickness during most of the sampling events, significantly higher values of leaf epidermis thickness and vascular bundle area, and significantly lower values of air lacunae area in leaf transverse section were observed in Mashanli. While in the eelgrass rhizome transverse section, significantly higher values of epidermis area, exodermis area and cortex area were observed in the Moon Lake. The results indicated that in high-energy environment, eelgrass produced smaller leaves and shorter rhizome internodes, as well as longer roots to reduce the resistance of eelgrass shoots underwater and to anchor the plants to the substrate. At the same time, the eelgrass in Mashanli developed thicker leaf epidermis, higher vascular bundle area, and smaller air cavities in leaves, which are beneficial in resisting the high waves and currents. These results suggest that seagrasses will develop various morphological and anatomical adaptations to cope with environmental stress, especially in an era of global warming.