Chemical ecology of sponges on Caribbean coral reefs

海绵现在是大多数加勒比珊瑚礁的主要栖息地形成动物。与珊瑚和一些大型藻类不同，海绵具有未钙化的骨骼，并且不太容易受到海洋酸化的影响。最近发表的一项关于佛罗里达礁群巨型桶形海绵的人口统计研究显示，2000年至2006年期间，其数量增加了约40%。这一更新项目将调查加勒比珊瑚礁海绵的化学生态学，这一群体的分类和次级代谢物已得到很好的描述。一些珊瑚礁海绵产生化学防御，而另一些则受到鱼类捕食者的放牧。集体社区被发现在一个大的地理区域，可变的人为影响允许测试的基本假设生态系统功能，间接影响和资源分配。知识价值：以前NSF资助的研究已经改变了对加勒比珊瑚礁生态系统的理解。一项调查的化学，结构和营养的反掠夺性防御超过70种的加勒比海海绵，随后使用珊瑚礁鱼类的自然种群的实地实验，导致隔离和识别威慑化合物超过15个物种。一系列的操纵实验清楚地表明，吃海绵的鱼类限制海绵分布，鹦鹉鱼是主要的海绵动物，从而推翻了传统的想法吃海绵的鱼类对珊瑚礁群落的影响。新的凝胶为基础的分析显示差异化感作用的海绵代谢物对其他海绵和珊瑚物种。因此，加勒比珊瑚礁的生态系统模型涉及营养和竞争相互作用，预测其他生态系统已知的级联和间接影响。测试生态系统模型的三个主要目标是：（1）扩展海绵群落自上而下控制的研究。在世界资源研究所“有风险的珊瑚礁”数据库的指导下，将对加勒比各次区域过度捕捞珊瑚礁和保护良好珊瑚礁上的海绵及其捕食者的群落结构进行预测和比较。鹦嘴鱼捕食海绵将在不同影响的珊瑚礁的食物选择实验期间进行视频记录。将继续使用改良的凝胶实地测定法和潜水PAM荧光测定法，研究海绵和珊瑚之间的化感竞争相互作用（海绵代谢物对珊瑚光合作用和漂白的影响）;（2）更好地检验另一种假设，即自下而上的过程-微型浮游生物作为食物的可获得性-控制着珊瑚礁群落。捕食者排斥实验将脱钩的捕食作用，从海绵生长在picoadenton丰富和贫穷，深和浅的珊瑚礁网站;（3）扩大海绵生活史的化学防御，生长和繁殖之间的资源分配权衡的研究。在人工鱼礁表面上，将研究已知年龄的海绵群落在补充和演替方面的差异。这一组成部分建立在最近发现的海绵群落演替的甲板上的斯皮格尔格罗夫沉船关闭基拉戈，佛罗里达州，这强烈表明化学防御和繁殖或生长之间的资源权衡。更广泛的影响：更新这一研究计划将提供（1）支持和培训本科生和研究生在教学密集型，主要是硕士水平的大学（68%的直接费用用于学生支持），（2）来自美国和国外的科学家和学生之间的合作，为期两周的研究巡航，（3）基于网络的推广，包括人口统计学，漂白，和加勒比海海绵的化学防御和进一步完善的一个易于使用的摄影关键加勒比海海绵。该项目的结果将有助于判断从陆地生态系统研究中得出的化学防御理论的普遍适用性，同时促进对珊瑚礁环境中底栖无脊椎动物、其捕食者及其竞争者之间复杂关系的理解，在珊瑚礁环境中，全球气候变化和海洋酸化的影响可能使竞争平衡向海绵等非钙化生物倾斜。

Sponges are now the dominant habitat-forming animals on most Caribbean coral reefs. Unlike corals and some macroalgae, sponges have uncalcified skeletons, and are less prone to effects of ocean acidification. A recently published demographic study of the giant barrel sponge on the Florida Keys reefs showed population increases by ~40% between 2000 and 2006. This renewal project would investigate the chemical ecology of Caribbean reef sponges, a group whose taxonomy and secondary metabolites are well described. Some reef sponges produce chemical defenses, while others are subject to grazing by fish predators. The collective community is found over a large biogeographic area where variable anthropogenic impacts permit the testing of fundamental hypotheses about ecosystem function, indirect effects, and resource allocation. Intellectual merits: Previous NSF-funded research has transformed understanding of Caribbean coral reef ecosystems. A survey of chemical, structural and nutritional anti-predatory defenses of over 70 species of Caribbean sponges, followed by field experiments using natural populations of reef fishes, resulted in the isolation and identification of deterrent compounds from over 15 species. A series of manipulative experiments clearly demonstrated that sponge-eating fishes limit sponge distributions, and that parrotfishes are major spongivores, thereby overturning conventional ideas about effects of sponge-eating fishes on reef communities. Novel gel-based assays revealed differential allelopathic effects of sponge metabolites against other sponge and coral species. The ecosystem model for Caribbean reefs thus involves trophic and competitive interactions, predicting cascades and indirect effects known for other ecosystems. Three primary objectives for testing the ecosystem model are to: (1) extend studies of top-down control of the sponge community. Guided by the World Resources Institute "Reefs at Risk" database, predictions and comparisons will be made of the community structure of sponges and their predators on overfished vs. well-protected reefs across sub-regions of the Caribbean. Parrotfish predation on sponges will be video recorded during food choice experiments on differently impacted reefs. Studies of allelopathic competitive interactions between sponges and corals (sponge metabolites on coral photosynthesis and bleaching) will continue using a modified gel-based field assay and diving-PAM fluorometry; (2) improve testing of the alternative hypothesis that bottom-up processes -- availability of picoplankton as food -- control reef communities. Predator-exclusion experiments will decouple effects of predation from sponge growth at picoplankton-rich and -poor, deep- and shallow-reef sites; (3) expand studies of sponge life history trade-offs in resource allocation between chemical defense, growth and reproduction. Differences in recruitment and succession will be examined among sponge communities of known age on artificial reef surfaces. This component builds on the recent discovery of sponge community succession on the deck of the Spiegel Grove shipwreck off Key Largo, FL, which strongly suggests a resource trade-off between chemical defenses and reproduction or growth. Broader impacts: Renewal of this research program will provide (1) support and training for undergraduate and graduate students at a teaching-intensive, predominantly MS-level university (68% of direct costs for student support), (2) collaboration between scientists and students from the US and abroad on three 2-week research cruises, (3) web-based outreach, including updated links on the demographics, bleaching, and chemical defenses of Caribbean sponges and further refinement of an easy-to-use photographic key to sponges of the Caribbean. Results of this project will be useful in judging the general applicability of chemical defense theories derived from studies of terrestrial ecosystems, while advancing understanding of the complex relationships between benthic invertebrates, their predators and their competitors in coral reef environments where the effects of global climate change and ocean acidification may be tipping the competitive balance toward non-calcifying organisms, such as sponges.