Killer Seaweeds: Allelopathy against Fijian Corals

珊瑚礁在全球范围内急剧减少，珊瑚礁通常从以珊瑚为主的物种丰富和地形复杂的群落转变为以海藻为主的物种贫乏和地形简化的群落。这些相移导致了生态系统功能的基本丧失。尽管关于珊瑚到藻类的转变是否通常是珊瑚死亡的主要原因或仅仅是后果的争论，但对海藻-珊瑚竞争的严格实地调查受到的关注有限。关于海藻-珊瑚竞争的结果在不同物种之间如何变化或不同竞争机制在促进海藻优势方面的相对重要性的信息有限。为了解决这一问题，PI将在热带南太平洋（斐济）进行实地实验，以确定海藻直接接触时对珊瑚的影响，哪种海藻对珊瑚的破坏性最大，通过接触转移的化感脂在产生这些影响中的作用，这些代谢物的特性和表面浓度，以及海藻代谢物产生和珊瑚反应的动态性质。将确定对控制化感海藻最有责任的草食性鱼类，研究海藻代谢物在化感作用与食草动物威慑中的作用，并研究更好地管理和保护关键珊瑚礁食草动物的潜力，从而减缓或逆转珊瑚礁向海藻草甸的转变。初步结果表明，海藻通常通过脂溶性化感物质破坏珊瑚。这种化学介导的相互作用可能会杀死或损害成年珊瑚，并产生先前调查人员注意到的珊瑚繁殖力和招募的抑制，并可能促成正反馈机制，使珊瑚礁随着海藻丰富度的增加而越来越不可能恢复。化学介导的海藻-珊瑚竞争可能在当今珊瑚礁的退化中起关键作用。增加关于哪些海藻对珊瑚最具侵略性以及哪些食草动物对这些海藻的限制最好的信息，可能有助于更好地管理珊瑚礁，以促进恢复能力和可能的恢复，尽管面临全球范围的压力威胁。斐济已经建立了260个海洋保护区，斐济村民已经认识到海洋保护区的价值，斐济当地管理的海洋区域（FLMMA）网络组织良好，可以以文化敏感和有用的方式向村民提供信息，因此，斐济完全有能力迅速利用该项目的研究结果来更好地管理珊瑚礁资源。这个项目的广泛影响是深远的。本项目每年培养2-2.5名海洋生态学、海洋保护、海洋化学生态学交叉领域的博士生和1名本科生。该项目的研究结果将立即纳入Ga Tech的课程，并通过一个基金会和网站在斐济全国范围内提供，该基金会和网站已经建立，以支持斐济的海洋保护工作以及斐济国内外的海洋教育工作。来自亚特兰大的商业和社区领袖（通过扶轮国际服务的努力）已被招募来帮助组织和资助斐济的社区服务和外展项目——其中一些可能涉及海洋保护和教育，部分基于这些努力。媒体（国家地理、美国国家公共电台、动物星球、奥杜邦杂志等）和当地扶轮社将被用来更好地向公众传播这些发现。

Coral reefs are in dramatic global decline, with reefs commonly converting from species-rich and topographically-complex communities dominated by corals to species- poor and topographically-simplified communities dominated by seaweeds. These phase-shifts result in fundamental loss of ecosystem function. Despite debate about whether coral-to-algal transitions are commonly a primary cause, or simply a consequence, of coral mortality, rigorous field investigation of seaweed-coral competition has received limited attention. There is limited information on how the outcome of seaweed-coral competition varies among species or the relative importance of different competitive mechanisms in facilitating seaweed dominance. In an effort to address this topic, the PI will conduct field experiments in the tropical South Pacific (Fiji) to determine the effects of seaweeds on corals when in direct contact, which seaweeds are most damaging to corals, the role allelopathic lipids that are transferred via contact in producing these effects, the identity and surface concentrations of these metabolites, and the dynamic nature of seaweed metabolite production and coral response following contact. The herbivorous fishes most responsible for controlling allelopathic seaweeds will be identified, the roles of seaweed metabolites in allelopathy vs herbivore deterrence will be studied, and the potential for better managing and conserving critical reef herbivores so as to slow or reverse conversion of coral reef to seaweed meadows will be examined. Preliminary results indicate that seaweeds may commonly damage corals via lipid- soluble allelochemicals. Such chemically-mediated interactions could kill or damage adult corals and produce the suppression of coral fecundity and recruitment noted by previous investigators and could precipitate positive feedback mechanisms making reef recovery increasingly unlikely as seaweed abundance increases. Chemically-mediated seaweed-coral competition may play a critical role in the degradation of present-day coral reefs. Increasing information on which seaweeds are most aggressive to corals and which herbivores best limit these seaweeds may prove useful in better managing reefs to facilitate resilience and possible recovery despite threats of global-scale stresses. Fiji is well positioned to rapidly use findings from this project for better management of reef resources because it has already erected 260 MPAs, Fijian villagers have already bought-in to the value of MPAs, and the Fiji Locally-Managed Marine Area (FLMMA) Network is well organized to get information to villagers in a culturally sensitive and useful manner. The broader impacts of this project are far reaching. The project provides training opportunities for 2-2.5 Ph.D students and 1 undergraduate student each year in the interdisciplinary areas of marine ecology, marine conservation, and marine chemical ecology. Findings from this project will be immediately integrated into classes at Ga Tech and made available throughout Fiji via a foundation and web site that have already set-up to support marine conservation efforts in Fiji and marine education efforts both within Fiji and internationally. Business and community leaders from Atlanta (via Rotary International Service efforts) have been recruited to help organize and fund community service and outreach projects in Fiji -- several of which are likely to involve marine conservation and education based in part on these efforts there. Media outlets (National Geographic, NPR, Animal Planet, Audubon Magazine, etc.) and local Rotary clubs will be used to better disseminate these discoveries to the public.