The water bodies along a continuum from estuaries to open ocean display significant changes in their physical, chemical and biological characteristics. In the current study, we report the influence of such changes on the abundance and community structure of bacteria and archaea in a continuum from Cochin Estuary, in the southwest coast of India, to the open ocean of Arabian Sea. The bacterial and archaeal abundances were in the range of 10${}^4$ to 10⁶ and 10${}^3$ to 10⁵ cells ml⁻¹ respectively in all the stations and showed a clear dependence on nutrients. The bacterial abundance decreased with depth in the open ocean, whereas the archaea showed a similar reduction at both shelf and open ocean stations. The $\alpha$- Proteobacteria (35 %) and Cyanobacteria (23 %) were dominant in the estuary. More than 70 % of the community of bacteria on the shelf and in the open ocean were similar. The $\alpha$- and $\gamma$-Proteobacteria contributed 37 & 27 % of the OTUs in the clone library of shelf and 20 & 29 % in the open ocean. The archaeal community structure in the open ocean and shelf were similar (90 %) composed mostly of Nitrosopumilaceae (70%–75%), while they were highly diverse in the estuary. In short, our study shows that the archaea are more diverse in the estuary compared to shelf and open ocean, while bacteria are equally diverse in all ecosystems.

从河口到大洋的连续水域的水体在其物理，化学和生物特征方面表现出重大变化。在当前的研究中，我们报告了这种变化对从印度西南海岸的科钦河口到阿拉伯海的公海的连续统中细菌和古细菌的丰度和群落结构的影响。细菌和古细菌的丰度范围为10${}^4$到10 ⁶和10${}^3$在所有站中分别达到10 ⁵细胞ml ^-1，并显示出对养分的明显依赖性。在远洋中细菌的丰度随着深度的增加而降低，而古细菌在陆架和远洋站都显示出类似的减少。的$\alpha$-河口以细菌杆菌（35％）和蓝细菌（23％）为主。架子上和远洋中超过70％的细菌群落是相似的。的$\alpha$-和 $\gamma$-细菌在架子的克隆文库中贡献了37％和27％的OTU，而在公海中贡献了20％和29％。在公海和陆架上的古细菌群落结构相似（占90％），主要由亚硝基眼科（70％–75％）组成，而在河口则高度多样。简而言之，我们的研究表明，与大陆架和远洋相比，河口古细菌的种类更多，而在所有生态系统中细菌的种类也一样。