The role of sponges in altering seawater DOM on Caribbean reefs

经过几十年造礁珊瑚数量的减少，海绵现在主宰着加勒比海的珊瑚礁。与大多数底栖珊瑚礁生物不同，海绵是生态系统工程师，他们抽出和过滤大量海水，翻转水柱，改变海水化学。海绵改变溶解有机质(DOM)的能力最近引起了越来越多的科学兴趣，同时海藻大量产生DOM的新证据也促使人们对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提出了新的假设。加勒比海珊瑚礁上最常见的紧急(大型、非神秘)海绵物种从组织中微生物共生体丰度高的海绵(HMA)到微生物丰度低的海绵(LMA)不等。对紧急海绵的大多数研究表明，HMA物种是DOM的净消费者，而LMA物种是净生产者。虽然海水中DOM的数量很容易测量，但人们对海绵处理的DOM的组成知之甚少。该项目正在使用免费的分析方法，包括新的化学衍生技术，以确定海水中环境和海藻衍生的DOM成分的特征，以及在实验室条件下和在珊瑚礁环境中，HMA和LMA海绵加工对这些成分的影响。这些研究提供了迄今为止热带珊瑚礁上海绵的DOM和营养循环的最完整的特征。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员提供研究支持；通过联合国妇女发展中心的MarineQuest计划将女性榜样从STEM推广到当地一所专门为代表不足的群体提供服务的女子特许小学；通过YouTube教育视频向世界范围内的公众推广。在海绵加工对海水中DOM池影响的最新发现的基础上，这一跨学科和协作研究项目正在改变我们对珊瑚礁生物地球化学循环的知识，并启发对热带珊瑚礁韧性差异的新解释，包括加勒比海珊瑚礁珊瑚的持续减少。该项目的目标是4个HMA和2个LMA圆柱形海绵物种，并使用一套免费的分析方法来表征海绵处理前后海水中自然存在的DOM化合物，使用现场和实验室实验。采用LC-MS/MS、GC/MS和UPLC-QToF等定向和非定向方法对海水中DOM进行了测定，包括衍生化前后的体积定量、碳水化合物和氨基酸定量以及固相萃取。非靶向UPLC-QToF MS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着变化。实验室孵化实验表征了3种常见海藻分类群生产DOM的特征，以及6种目标海绵物种的后续加工。考虑到DOM是地球上最大的有机碳库之一，这项研究项目正在改变我们对热带珊瑚礁生态系统中海绵海水DOM的组成和循环的理解。该项目由生物和化学海洋学项目资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.