Abstract:Surfgrass Phyllospadix iwatensis belongs to the family Zosteraceae. Similar to most seagrass species, surfgrass beds has declined in the past decades. Unlike most of the seagrasses that colonize soft substrates (e.g., sand or mud), surfgrass grows predominantly on rocky substrates and can survive in high-energy environments. Therefore, the widely used transplanting methods for seagrasses growing in sandy or muddy sediments cannot be used in surfgrass transplantation. To explore the feasibility of restoring degraded surfgrass beds through transplantation, a transplanting unit was designed specifically for surfgrass, and a transplanting experiment was carried out from April 2019 to August 2020 at three sites with different hydrodynamic regimes (high, middle, and low levels) in the coastal area of Mashanli in Rongcheng, Shandong Province. After transplantation, transplant survival and morphological and physiological characteristics were examined bimonthly. The results showed that at 16 months after transplantation, the survival rates of the surfgrass transplants were 63.7%, 61.0%, and 60.0% under the high, middle, and low hydrodynamic regimes, respectively, but these differences were not significant. The plant size (shoot height, leaf width, rhizome diameter, etc.), photosynthetic pigment content (chlorophyll a, total chlorophyll and carotenoids), and soluble sugar and starch content were all highest under high hydrodynamic regimes, and significant temporal variations were observed in these measurements. The results suggest that a higher survival rate can be achieved in all the three hydrodynamic regimes by using the transplanting method, and the area of the high hydrodynamic regime is more suitable for the growth of surfgrass transplants. The results of this experiment confirmed the feasibility of restoring degraded surfgrass beds at any of the three hydrodynamic regimes in the Mashanli area using the transplanting system and methods applied in this study.
