Ecological Preliminary Study On Eelgrass Of Inshore Areas In Shandong

Understanding of the importance of seagrass ecosystems ought to be enhanced, in order to restore injured seagrass beds in the northern inshore areas of China. Eelgrass was the research object in this paper. Morphological and experiment ecological methods were adopted. The author mainly investigate the seagrass species in inshore areas of Shandong and ecological environment of eelgrass beds, and carry out some basic research in anniversary growth changes of eelgrass, in addition, preliminary study the restoration methods of eelgrass in representative sea area. The most results are summarized as follows:Preliminary survey for seagrass was performed in inshore areas of Qingdao in March 2009. Seagrass distribution areas mainly contain Qingdao Bay, Huiquan Bay and Fushan Bay. According to the description of morphological characteristics of seagrasses distributing in inshore areas of Qingdao on the basis of documentary record, three species of seagrasses including Zostera marina L., Phyllospadix iwatensis Makino and Zostera japonica Ascherson & Graebner were found during the present investigation.Research showed that sea surface average temperature was 15.3℃in Qingdao Bay from March to July in 2009. Eelgrass show a patch-shape distribution, the area reach 3000m2. The average spacing density and average biomass of eelgrass are 400ind/m2 and 0.69g/ind, respectively. The annual average biomass of eelgrass bed is 276g/m2. The biomass and height changes of eelgrass are related to sea surface temperature and distribution depth. The content of organic carbon, total nitrogen and total phosphorus of eelgrass are seasonally varied. Content of organic carbon begin to increase in spring, reach to summer peak, drop dramatically in fall and have a small increase in winter, but seasonal changes for total nitrogen and total phosphorus are reversed. The variation in content of organic carbon, organic nitrogen and organic phosphorus in the surface sediment associated with organic matter due to degradation and detachment of eelgrass. The sediment under the eelgrass bed mainly consists of sand and sandy silt. Concentration of nitrites, Phosphates, ammonia nitrogen and nitrates are conformed to the standard of class seawater.To find effective method of transplant and restoration, eelgrass was transplanted using methods of direct planting and tied cotton thread planting in inshore areas of Huiquan Bay from July to November in 2009. Growth, survival and proliferation of transplanting eelgrass were monitored after one year. The key factors to ensure the survival of transplanting eelgrass were analyzed. Results showed that the rate of increase of tied cotton thread planting was higher, three transplant sites reached to 60%, 67.56% and 117.78% respectively until May in 2009. There was a remarkable correlation between growth and survival of transplanting eelgrass and primary environmental factors containing water flow and sediment. The findings will provide data for developing feasible restoration technology of injured Z. marina biome. Only the immature and mature seeds preserved by 4℃seawater could geminate, and the rate of germination and survival were about 80% and 9.7%. Therefore, eelgrass restoration by seed breeding is different and needs further research.Typical bays in Weihai inshore areas contain Swan Lake, Ailian Bay and Sanggou Bay which were investigated from June 2008 to June 2009. Two species of seagrasses including Zostera marina L. and Zostera japonica Ascherson & Graebner were found in Swan Lake. The former show a patch-shape distribution, the area reach 1500m2, the latter area is 600m2. Research showed that sea surface average temperature was 12.4℃in Swan Lake. The average spacing density and average biomass of eelgrass are 576 ind/m2 and 1.03g/ind, respectively. The annual average biomass of eelgrass bed is 593g/m2. Two species of seagrasses including Zostera marina L. and Phyllospadix iwatensis Makino were found in Ailian Bay which distribute deeper. Research showed that sea surface average temperature was 10.4℃in Ailian Bay. The average biomass of eelgrass is 1.55g/ind. Two species of seagrasses including Zostera marina L. and Zostera caespitosa Miki were found in Sangou Bay. The former show a patch-shape distribution, the distribution area could reach 6000m2 and the eelgrass bed has a higher biodiversity. The latter distribute deeper and grow in the reefs or rocks. Research showed that sea surface average temperature was 10.9℃in Sanggou Bay. The average spacing density and average biomass of eelgrass are 388 ind/m2 and 0.66g/ind, respectively. The annual average biomass of eelgrass bed is 256g/m2. The biomass and height changes of eelgrass are related to sea surface temperature and distribution depth in the three typical bays. The seasonal variation in content of organic carbon, total nitrogen and total phosphorus of eelgrass are similar to Qingdao Bay. The sediment under the eelgrass bed mainly consists of sandy silt, but contents of gravel sand and shell in Sanggou Bay are higher. Concentration of nitrites, Phosphates, ammonia nitrogen and nitrates are conformed to the standard of class seawater. Because of latitude, eelgrass breeding season in Weihai will delay almost one month compared with Qingdao inshore areas.In this study, simulating lab experiment was adopted to understand the nutrient relations between Z. marina and A. japonicus. Mixture of Z. marina debris and seafloor surface sediments was used as food to feed A. japonicus, then specific growth rate and feces production rate were measured. According to Z. marina debris proportion, we designed five experiment treatments, i.e., ES0(0%), ES10(10%), ES20(20%), ES40(40%)and ES100(100%). Results showed that the food had a great influence on growth of A. japonicus. The organic content of mixture of Z. marina debris and seafloor surface sediments was 17～20% and the most suitable water temperature was 13～17℃, which lead to higher SGR (1.54%·d^-1) and FPR (1.31g·ind.^-1 d^-1). Seagrass bed can not only provide habitat for A. japonicus, but also provide food source for the latter, which is of significance to A. japonicus resource restoration and nutritional ecology research.