Study On Physiology, Ecology, Conservation And Restoration Of Eelgrass In Sango Bay

Seagrass is a kind of higher flowering plants that are completely adapted to marine environment. This paper focused on physiology, ecology, and restoration of common temperate eelgrass Zostera marina Linnaeusin Sango Bay, Shandong Peninsula, China. Field study on morphological and ecological changes of eelgrass in cofferdam pool has been carried on to analyze impact of environmental factors on eelgrass growth and reproduction. In situ photosynthetic activities of three common seagrass species Z. marina, Zostera caespitosa Miki and Phyllospadix iwatensis Makino were identified through chlorophyll fluorescence characteristics, measured by underwater pulse modulated fluorescence (DIVTNG-PAM). In order to find ways to restore eelgrass habitat, iron frame method was used at different seasons for eelgrass transplantation in the bay. Main findings are:The results of study on production dynamics of eelgrass in cofferdam pool of Sango Bay showed that eelgrass shoot density, biomass, and leaf productivities exhibited clear seasonal variations, which were strongly correlated with water temperature. Optimal water temperature for eelgrass growth in the present study site was14～18℃in spring, and growth was inhibited when water temperature was higher than18℃during summer. Densities of terminal, lateral and reproductive shoots showed their unique seasonal peak. Seasonal trends of shoot densities suggest that new eelgrass shoots were created through formation of lateral shoots during spring and a part of vegetative shoots were transformed into flowering shoots from April. Senescent reproductive shoots were detached around June, and contributed to reductions of shoot density and biomass during summer period. Ambient nutrient level appeared to provide an adequate reserve of nutrient for eelgrass growth throughout the experimental period.The photosynthetic activity of three commonly distributed Zosteraceae seagrasses Z marina, Z. caespitosa and P. iwatensis from populations of eastern water of Chudao island showed that photosynthetic activity of Z. marina, Z. caespitosa and P. iwatensis was strongly influenced by leaf age, chlorophyll content and AF values increased with leaf age within the plant of seagrass. Young leaves had higher electron transport rates than old ones (Zm:Leaf1=26.56, Leaf2=16.3, Leaf3=19.98; Pi:Leaf1=22.31, Leaf2=19.23, Leaf3=17.06; and Zc:Leaf1=20.16, Leaf2=16.10, Leaf3=13.10). Among the three species, Z. marina had the highest photosynthetic activity (ETRmax=22.67), in accordance with the highest production in field in comparison with the other two species.During October2010, April2011, June2011and August2011, eelgrass was transplanted by TERFS (Transplanting Eelgrass Remotely with Frame Systems) method in Chu Island waters in Sango Bay. Survival rates and morphological characteristics of transplanting eelgrass were monthly measured during three months. Environmental factors that influenced eelgrass survival were also analyzed. After one month of transplant, the highest and lowest survival rates were81%and70%respectively. While after three months of transplant the rates were70%and45%, respectively. It could be obtained that the best time for seagrass transplantation in Sango Bay is April.