中国温带海域新发现较大面积(大于50ha)海草床:Ⅲ渤海兴城-觉华岛海域大面积海草床鳗草种群动力学及补充机制

NEW DISCOVERY OF LARGER SEAGRASS BEDS WITH AREAS >50ha IN TEMPERATE WATERS OF CHINA: Ⅲ POPULATION DYNAMICS AND RECRUITMENT MECHANISM OF ZOSTERA MARINA IN THE XINGCHENG-JUEHUADAO COASTAL WATERS OF BOHAI SEA

鳗草(ZosteramarinaL.)广布于北半球温带浅海海域,其形成的鳗草床具有重要的生态价值。近些年来,我国黄渤海海域鳗草退化严重,较大面积、连续分布的海草床已经非常少见。在渤海兴城-觉华岛海域发现较大面积的海草床,可以作为渤海沿海海草床的典型代表。基于此,2018年5月、9月、11月和2019年3月对该海草床进行了初步调查,探究了渤海兴城-觉华岛海草床鳗草种群补充等生态特征,分析了海草床生境的主要威胁,并提出了对海草床进行有效保护和科学管理的相关建议。结果表明:渤海兴城-觉华岛海草床总面积为791.61ha,海草种类为鳗草和日本鳗草(Z.japonica),以鳗草为优势种,日本鳗草极少且呈斑块状分布;鳗草生物量在2018年5月达到最大值(1241.22-1632.64g/m2);鳗草叶片碳、氮、磷元素含量分别为35.35%-36.57%、1.89%-3.35%、0.14%-0.48%;鳗草海草床以无性繁殖为主要补充方式,有性繁殖补充比例平均仅为1.92%,明显低于国内其他鳗草草床,具有鲜明的独特性;该海草床主要受围填海、捕蛤、围网捕鱼等人类活动的严重影响,并致使海草床边缘区域呈现斑块化趋势。建议对这片珍贵的海草床加以保护和修复。

The eelgrass Zostera marina L. is a dominant seagrass species circumglobally distributed in temperate coastal environments in the North Hemisphere, and eelgrass beds have an important ecological value. In recent years, it has been found that eelgrass beds in China have declined rapidly, and large and continuous seagrass beds became very rare. A large area of seagrass was recently found in the Xingcheng-Juehuadao coastal waters of Bohai Sea, and thus was used as a representative seagrass bed in Bohai Sea. Surveys were conducted on the seagrass bed in May, September, November, and March 2019, and the ecological characteristics, including population recruitment of Z. marina population, were explored. The threats to the seagrass bed were analyzed and recommendations for effective protection and scientific management were proposed. The results show that the total area of the seagrass bed was 791.61 ha, in which eelgrass was the dominant species and Z. japonica distributed rare and patchy. The eelgrass biomass reached its maximum in May 2018(1241.22-1632.64 g/m2);the contents of carbon, nitrogen, and phosphorus for eelgrass leaves were 35.35%-36.57%, 1.89%-3.35%, and 0.14%-0.48%, respectively;the recruitment of eelgrass bed was mainly by asexual reproduction. The average contribution of sexual reproduction recruitment was only 1.92%, which is significantly lower than those of other domestic eelgrass beds. The impact of human activities, including local reclamation, fishing, and clam harvesting, have disrupted the seagrass bed into patchy distribution. Therefore, protection and restoration of this precious seagrass bed habitat is strongly recommended.