Zostera Marina (Eelgrass) Ecosystem Restoration In Miaodao Islands

According to field investigations and distribution of seagrass in nearshore of Shandong Peninsula, Zostera marina is used as the key species for ecosystem restoration on Miaodao Islands. The main content includes suitable sites selection for Z. marina transplantation based on PTSI model and habitat suitable index; the foundation of seeds collection, storage and germination principles based on seeds collection from natural populations and storage and germination experiments in controlled laboratory conditions; the foundation of a Z. marina restored population based on seeds application with two different methods in Xiaoheishan Island; the monitoring of restored and natural populations dynamics based on field investigations. The main conclusions are as follows:(I) The results of field investigations of distribution status shows that the natural Z. marina populations around Xiaoheishan Island have been declined seriously. The result of PTSI model shows only S9 and S10 on the west side of Xiaoheishan island are potential suitable transplantation sites for Z. marina, and the result of Habitat Suitable Index based on ArcGIS shows that the core habitat is mainly distributed in the southwest corner and a small shallow water area on the east side of Xiaoheishan island, the moderate habitat is distributed from southeast to the north, while the marginal habitat is distributed in northwest and southwest.(Ⅱ) In field investigations, reproductive stage occurs from late March to late August, the reproductive properties show obvious seasonal variation and had significant impacts on accumulative seed production. Seeds begin to release in early June and the cumulative seed production was 10450.69 seeds·m-2, while the maximum production in a single week was 2907.49 seeds·m-2(Ⅲ) The result of germination experiments shows that seed germination rates decrease with salinity increasing. Temperature, salinity and the interaction of both factors has significant effects on germination rate (p<0.01).5 ppt and 14 ℃ are suitable germination conditions for Z. marina seeds with germination rate reaching beyond 80% after 8 weeks. The optimal germination conditions for Z. marina seeds based on orthogonal experimental are 12 ppt, pH 6.2,10℃ and 960/60 μmol·L-1 (N/P concentration).Seed germination experiment shows significant effects of seed burial depth as well as the interaction between sediment type and burial depth on both seed germination rate and seedling establishment rate (p<0.001), while the effects of sediment type are not significant (p=0.910, p=0.885). When on the sediment surface or buried in 1 cm, seeds could maintain germination rates (75.73 ± 11.50)% and (89.73 ± 1.50)%, respectively despite of sediment type. With burial depth increasing, germination rates decrease gradually and are less than 40% in all sediment types. Only in group sand:silt = 2:1 could seeds germinate when burial depth increasing to 5 cm. The earliest germination appears in the fifth week and the cumulative germination rate is lower than 3%. Seedling establishment rate shows similar trends that seeds buried in shallow depth show higher seedling establishment rate, The maximum seedling establishment is recorded in seeds which buried in 1 cm in group sand:silt= 2:1 (30.67%).(IV) A restored Z. marina population is founded based on the collection of seeds baring reproductive shoots with two different methods:Reproductive Method and Mature Seeds Method.(V) The results of a consecutive field monitoring after restoration showing the similar levels (p> 0.05) in parameters such as shoot height, density, biomass, root:shoot ratio and N/P in leaves between restored populations and natural populations indicate the primarily successful foundation of a restored population.