海草场生态系统及其修复研究进展

海草场能够提供重要的生态系统服务。自20世纪末以来,由于人类活动和自然灾害的影响,全球范围内的海草场出现了急剧衰退,由此也促进了海草场生态系统的研究以及海草场人工修复技术的发展。近年来,针对海草场生境流失的现状,中国也开始开展海草场修复工作。从以下方面进行论述:(1)海草的种类、分布,海草场生态系统功能及其生态系统服务:与陆地系统相比,全球海草物种多样性较低,了解海草的分布特征有助于通过了解海草如何适应当地环境压力,以揭示海草适应环境的能力;海草场提供重要而广泛的自然生态系统服务,特别是在维护近岸生态系统健康和满足人类需求过程中起到重要的作用;(2)海草场的衰退及其原因:认识并缓解人类压力对海草场的危害是促进海草场生态系统可持续发展的重要一环;(3)国内外海草场修复现状:以此阐明海草场修复原理,为海草场修复提供科学的方法;(4)总结与讨论:基于科学研究背景,为中国海草场生态系统保护和修复提出建议。海草场的修复和保护应当相辅相成,并与我国海岸长远规划相结合,以此推动我国海草场生态系统服务的可持续发展。

Seagrass meadow ecosystem and its restoration: a review

Seagrass meadows have long been recognized for the important ecosystem services they provide. Seagrass meadows not only play critical roles in near shore primary production and nutrient cycling, but also provide feeding, refuge and nursery habitat for a diverse array of marine organisms, and increase the stability of the seafloor. However, seagrass meadows have suffered great declines in the last century from anthropogenic effects, which in turn stimulated studies of seagrass ecosystems as well as development of restoration techniques. More recently, China has initiated restoration work on seagrass ecosystems in direct response to observed and anticipated loss of seagrass habitat. Here, four topics are reviewed that form the basis of the Chinese restoration effort:(1) Seagrass meadow ecosystem analysis, (2) Declines of seagrass meadows and its reasons, (3) Progress of seagrass restoration techniques abroad and in China, and (4) Actionable guidance. Under (1), seagrass species and their distribution, functions and ecosystem services will be inventoried. Although seagrasses globally have comparatively (to terrestrial systems) low taxonomic diversity they still have discernible niches whose ecological limits must be understood in order to forecast their response and resiliency when faced with local stressors. Because seagrasses have successfully colonized all but the most polar seas and thus have occupied wider latitudinal ranges as compared with the other major coastal marine habitats (mangroves and coral reefs in tropical regions, salt marshes in temperate regions), defining their ecological limits is a significant challenge. Moreover, although seagrasses indisputably provide important and extensive natural resource services, specifically identifying those services in the context of the near shore ecology and human needs are fundamental to establishing effective protection. Under (2), identification and mitigation of human stressors that impair or eliminate seagrasses in coastal waters is a fundamental step to creating a sustainable resource base. The impact of local, anthropogenic stressors (eutrophication, dredging and near shore engineering) needs also to be separated from far-field effects such as global warming, sea level change, natural diseases, and disturbance events such as typhoons in order to understand that which is manageable and that which is natural or beyond local boundaries and thus not practicable for intervention. Under (3), seagrass restoration has been practiced for decades, with the first documented attempt at seagrass restoration being carried out in the USA in 1947. However, it was not until the mid-1970s that development of seagrass restoration techniques began to move beyond the experimental stage. In the past 40 years there has been considerable development of restoration methodologies and techniques, and a significant increase in the number of locations and species involved. Nonetheless, because seagrass restoration typically takes place in open (uncontrolled or non-engineered) settings, the restoration process is widely recognized as being complex and expensive. The most common method has involved the transplantation of adult plants, because they result in an immediate presence of the seagrass community. Some of these methods have involved transplantation of seagrass and associated sediments, whilst with other methods only the seagrass plant is utilized. But in recent years, new seeding techniques for a few species have been developed and successfully employed. Regardless of the method, the general success of previous restoration attempts have been variable and unfortunately in many cases, have resulted in limited survival and coverage (average success has been 50%). In most cases the transplantation of seagrasses relies on harvest from otherwise healthy meadows, which for some species (but not many in China) have extremely slow recovery rates, making donor bed impacts a concern for those species. Nonetheless, there remains an urgent need for better understanding of the limiting factors for seagrass in a restoration context and to employ new advances in applied research and methodology to conduct seagrass restoration in a cost-effective manner over large spatial extents. Finally, under (4) we propose to provide actionable guidance for seagrass conservation and restoration efforts in China. China covers two geographic bioregions and has a vast (but poorly inventoried) expanse of seagrass meadows along its coast. But China has not yet developed a comprehensive study of seagrass meadow ecosystems and applied practices in restoration. As a consequence of limited studies and popular understanding of the importance of seagrass resources, seagrass meadows in China are widely vulnerable and threatened. Consequently, seagrass meadows in China have, like many other under-managed seagrass ecosystems worldwide, suffered great declines from excessive emission of nutrients and pollution of coastal waters. Although there have been some limited studies that have been highly focused on seagrass restoration, China's ability to incorporate restoration into a management strategy has been severely limited by knowledge gaps identified in the four topic areas defined here. Without a balance of studies involving inventories, functions and services, population ecology and disturbance responses in which to place seagrass restoration in context, it is likely that (as occurred in the U.S. during the 1960's and 1970's) seagrass restoration could be perceived as an inappropriate solution to many coastal development problems, resulting in failed projects and continued seagrass losses. We conclude that conservation and restoration of seagrass meadows should be integrated with coastal planning in China for sustainable seagrass ecosystem services.