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

9500601 Ducklow这是由dr。F Azam H. Ducklow将对细菌在调解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，作为美国联合基金阿拉伯海过程研究的一个组成部分。这些科学家将对细菌进行核心测量，以应对由于阿拉伯海季风逆转而经常发生的初级生产的巨大变化。JGOFS的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亮氨酸掺入方法），DOC， POC和PON。该研究旨在解决美国JGOFS确定的关于微生物异养过程的两个关键问题：1)在贫营养和富营养时期发生的群落结构如何对碳储量和出口通量产生差异影响？2)下沉颗粒在缺氧区分解是否减慢，是否导致通过该层的垂直通量增强？研究人员假设，高富营养化和低富营养化生产力制度的顺序发生，在贫营养化期间以牺牲富营养化期间积累的缓慢降解的DOM为代价，创造了一个独特的强大的微生物循环。他们预测，微生物环的强大优势使寡养期成为净异养期，这对碳氧化和交换的时空格局具有影响。“储存”的DOC也可能支持高细菌碳需求（高于颗粒通量所支持的）。他们希望验证的第二个假设是，地表水中的下沉颗粒被定植细菌的水解外酶迅速溶解，但酶的溶解作用在亚氧层中大大减少，导致POC的深度消散慢得多。

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.