Collaborative Research: JGOFS: Bacterial Cycling of Dissolved and Particulate Carbon in the Oligotrophic and Eutrophic Production Regimes of the Arabian Sea

小行星9500601 这是一个由F Azam H博士联合开展的研究项目。 Ducklow对细菌在介导和调节阿拉伯海碳和氮的生物地球化学通量方面的重要性进行定量研究，作为USJGOFS阿拉伯海过程研究的一个组成部分。 这些科学家将进行细菌使用的核心测量，以应对由于阿拉伯海季风逆转而定期发生的初级生产的巨大变化。JGOFS核心测量将包括细菌丰度和生物量、细菌产量（通过3H胸苷和3H亮氨酸掺入法）、DOC、POC和PON。 该研究旨在解决美国JGOFS确定的微生物异养过程的两个关键问题：1）在贫营养和富营养时期发生的群落结构如何差异影响碳储存和输出通量？下沉颗粒的分解是否在低氧层减慢并导致通过该层的垂直通量增加？ 研究人员假设，高度富营养和贫营养生产力制度的连续发生在贫营养期以缓慢降解的DOM为代价，在富营养期积累了一个独特的强大的微生物循环。 他们预测，微生物循环的强大优势使贫营养期成为净异养，这对碳氧化和交换的空间和时间模式有影响。 “存储”DOC也可能支持高细菌的碳需求（高于粒子通量支持）以下的混合层变浅的密度跃层。 他们希望检验的第二个假设是，表层沃茨中的下沉颗粒被定殖细菌的水解胞外酶迅速溶解，但在低氧层中酶促溶解作用大大降低，导致POC的深度增加慢得多。

9500601 Ducklow This is a joint research project by Drs. F Azam H. Ducklow to perform quantitative studies on the significance of bacteria in mediating and regulating biogeochemical fluxes of carbon and nitrogen in the Arabian Sea, as a component of the USJGOFS Arabian Sea Process Study. These scientists will make core measurements used by bacteria to respond to dramatic changes in primary production that occurs regularly due to monsoonal reversals in the Arabian Sea. The JGOFS core measurement s will include bacterial abundance and biomass, bacteria production (by both 3H thymidine and 3H leucine incorporation methods), DOC, POC and PON. The research is designed to address two key questions concerning microbial heterotrophic processes identified by US JGOFS: 1) How do the community structures which occur during the oligotrophic vs. eutrophic periods differentially impact carbon storage and export fluxes? and 2) Does the decomposition of sinking particles slow down in the suboxic zone and result in enhanced vertical flux through this layer? The investigators hypothesize that sequential occurrence of highly eutrophic and oligotrophic productivity regimes creates a uniquely robust microbial loop during the oligotrophic period at the expense of slow- to-degrade DOM which accumulates during the eutrophic period. They predict that the strong dominance of the microbial loop renders the oligotrophic period net- heterotrophic and this has implications for spatial and temporal patterns of carbon oxidation and exchange. The 'stored' DOC may also support high bacterial carbon demand (higher than would be supported by particle flux) below the mixed layer following shoaling of the pycnocline. A second hypothesis they wish to test is that sinking particles in the surface waters are rapidly solubilized by hydrolytic exoenzymes of colonizing bacteria but the enzymatic solubilization is greatly reduced in the suboxic layer resulting in much slower depth dissipat ion of POC.