The role of sponges in altering seawater DOM on Caribbean reefs

经过几十年造礁珊瑚的减少，海绵现在主宰了加勒比海的珊瑚礁。与大多数底栖珊瑚礁生物不同，海绵是生态系统的工程师，它们泵送和过滤大量海水，翻转水柱，改变海水的化学成分。海绵改变溶解有机物（DOM）的能力最近引起了越来越多的科学兴趣，随着新的证据表明海藻大量产生DOM，提出了关于海绵在碳和营养生物地球化学循环和生态系统功能中的作用的新假设。加勒比珊瑚礁上最常见的涌现海绵（大型、非隐生）种类从组织中微生物共生体丰度高（HMA）到微生物丰度低（LMA）不等。大多数关于涌现海绵的研究表明，HMA物种是DOM的净消费者，而LMA物种是DOM的净生产者。虽然海水中DOM的含量很容易测量，但海绵处理的DOM的成分却鲜为人知。该项目使用互补的分析方法，包括新的化学衍生技术，来表征海水中环境和海藻衍生的DOM成分，以及在实验室条件下和珊瑚礁环境下，HMA和LMA海绵处理对这些成分的影响。这些研究提供了迄今为止热带珊瑚礁上海绵DOM和养分循环最完整的特征。该项目的更广泛影响包括为化学和生物化学系的两名新女教师提供研究支持，通过UNCW的MarineQuest项目向当地一所专门为弱势群体服务的女子特许小学提供女性榜样的STEM推广，以及通过YouTube教育视频向全球公众推广。基于海绵加工对海水中DOM池影响的最新发现，这一跨学科合作研究项目正在改变我们对珊瑚礁生物地球化学循环的认识，并激发对热带地区珊瑚礁恢复力差异的新解释，包括加勒比珊瑚礁珊瑚的持续衰退。该项目针对4个HMA和2个LMA圆柱形海绵物种，并使用一套互补的分析方法，通过现场和实验室实验来表征海绵加工前后海水中天然存在的DOM化合物。海水中DOM的测量包括大宗定量、碳水化合物和氨基酸定量以及衍生化前后的固相萃取，采用了LC-MS/MS、GC/MS和UPLC-QToF等靶向和非靶向方法。非靶向UPLC-QToF质谱代谢组学技术揭示了当海水穿过珊瑚礁上的海绵体时，哪些化合物发生了显著变化。实验室孵化实验表征了3种常见海藻分类产生DOM以及6种目标海绵物种中的每一种随后的加工过程。考虑到DOM是地球上最大的有机碳储存库之一，该研究项目正在改变我们对热带珊瑚礁生态系统海绵海水DOM组成和循环的理解。本项目由生物和化学海洋学计划资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Sponges now dominate Caribbean reefs after decades of declines of reef-building corals. Unlike most benthic reef organisms, sponges are ecosystem engineers that pump and filter huge volumes of seawater, turning-over the water-column and transforming seawater chemistry. The ability of sponges to alter dissolved organic matter (DOM) is recently the subject of increased scientific interest, along with new evidence of ample production of DOM by seaweeds, prompting novel hypotheses about the role of sponges in carbon and nutrient biogeochemical cycling and ecosystem function. The most common species of emergent (large, non-cryptic) sponges on Caribbean reefs range from those having a high abundance of microbial symbionts in their tissues (HMA) to those with low microbial abundance (LMA). Most studies of emergent sponges have shown that HMA species are net consumers of DOM, while LMA species are net producers. While the quantity of DOM in seawater is easily measured, little is known about the composition of the DOM that is processed by sponges. This project is using complimentary analytical approaches, including new chemical derivatization techniques, to characterize ambient and seaweed-derived DOM components in seawater and the effects of processing by HMA and LMA sponges on these components under laboratory conditions and in the coral reef environment. These studies are providing the most complete characterization of DOM and nutrient cycling by sponges on tropical reefs to date. Broader impacts of this project include research support for two new female faculty in a Department of Chemistry and Biochemistry, STEM outreach from female role-models through UNCW’s MarineQuest program to a local charter grade school for girls that specializes in serving under-represented groups, and world-wide public outreach through educational YouTube videos. Building on recent discoveries of the effects of sponge processing on the DOM pool in seawater, this interdisciplinary and collaborative research project is transforming our knowledge of biogeochemical cycling on coral reefs and inspiring novel explanations for differences in reef resilience across the tropics, including the continued decline of Caribbean reef corals. This project is targeting 4 HMA and 2 LMA sponge species with cylindrical shapes and uses a suite of complimentary analytical methods to characterize the naturally occurring DOM compounds in seawater before and after sponge processing using both field and laboratory experiments. Measurements of DOM in seawater include bulk quantification, carbohydrate and amino acid quantification, and solid phase extraction before and after derivatization using targeted and untargeted approaches that employ LC-MS/MS, GC/MS and UPLC-QToF. Untargeted UPLC-QToF MS metabolomics techniques reveal which compounds are significantly altered as seawater moves through the sponge body on the reef. Laboratory incubation experiments characterize the production of DOM by 3 common seaweed taxa and subsequent processing by each of the 6 target sponge species. Considering that DOM is one of the largest reservoirs of organic carbon on the planet, this research project is transforming our understanding of the composition and cycling of seawater DOM by sponges for a tropical reef ecosystem.This project is funded by the Biological and Chemical Oceanography Programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.