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

9500601 Ducklow这是F Azam H.Ducklow博士的一个联合研究项目，目的是作为USJGOFS阿拉伯海过程研究的一个组成部分，对细菌在调节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。这些科学家将进行细菌使用的岩心测量，以应对由于阿拉伯海季风逆转而定期发生的初级生产力的戏剧性变化。JGOFS核心测量S将包括细菌丰度和生物量、细菌产量(通过~3H胸腺嘧啶核苷和~3H亮氨酸掺入法)、DOC、POC和PON。这项研究旨在解决美国JGOFS确定的关于微生物异养过程的两个关键问题：1)在低营养期和富营养期发生的群落结构如何不同地影响碳储存和输出通量？2)下沉粒子在亚氧区的分解是否减慢，并导致通过这一层的垂直通量增加？研究人员假设，高营养和低营养生产力制度的连续出现在低营养时期创造了一个独特的强大的微生物循环，代价是在富营养时期积累的缓慢降解的DOM。他们预测，微生物环的强大优势使寡养期呈现净异养，这对碳氧化和交换的空间和时间模式有影响。“储存的”DOC也可能支持混合层以下的高细菌碳需求(高于颗粒通量所能支持的水平)。他们希望检验的第二个假设是，表层水中的下沉颗粒会被定植细菌的水解胞外酶迅速溶解，但亚氧层的酶促溶解作用大大减少，导致POC的深度消散速度要慢得多。

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.