Restoration effect and influencing factors of seagrass bed in Gaolong Bay, Hainan
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Graphical Abstract
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Abstract
In order to alleviate the degradation of seagrass bed on the east coast of Hainan Island,Thalassia hemprichii and Enhalus acoroides were transplanted by single plant with fixed distance to a 1 000 m2 bare beach in Gaolong Bay. When using iron frames and nets to fix the transplanted seagrass, the average survival rate of T. hemprichii was 56.39% one year after the transplantation. The survival rate decreased sharply after seven months of transplantation as the plants were buried easily. In contrast, a taller E. acoroides was less affected by the waves and its one-year survaival rate was 88.75%. However,T. hemprichii took roots and spouted easily and had higher branching rate than E. acoroides. One year after transplantation, the average branching rate of T. hemprichii was 22.64%,which was much higher than that of E. acoroides (3.13%) though the tougher E. acoroides had a higher coverage rate (21.90%) than T. Hemprichii. When using coconut shell, bamboo basket, or mud frame to fix the seagrass, the survival rate, branching rate, and coverage rate were much lower than the previous method. The performance of the restoration was affected by the hydrodynamics, suspended sediments, seagrass species, aritificial island, and anthropogenic activities. To mantain a good effect of restoration, this study proposed that T. hemprichii andE. acoroides be suitable for the transplantation in open waters where the sediments of coral reef detritus has stronger tidal currents. Besides, warning signs should be set up and the transplanted seagrass guarded. Regular monitoring and maintenances of community structure and functions are also discussed. This study can provide basic data and theory for future seagrass restoration in open waters.
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