"Microorganisms drive the biogeochemical cycles on Earth. Traditionally, biogeochemical studies have relied on the analysis of microorganisms isolated from the environment, but they only represent a minor percentage of the existing diversity (<1%). New approaches such as metagenomics or functional genomics have revolutionized our ability to link microbial ecology to biogeochemical processes, expanding our knowledge about the genes involved in key biogechemical processes, the microorganisms imediating them, and the distribution and redundancy of functions in the environment. A central but seldom addressed question is whether different bacterial taxa are unique or redundant in their functions in the environment. This has important implications for the modeling of biogeochemical cycles. The objective of this project is to identify functional groups of bacteria and analyse their levels of redundancy in a marine long-term ecological station which has been monthly sampled for physical, chemical, and biological variables since 2001. We will incorporate molecular analyses during 3 years and make use of cutting-edge tools such as metagenomics and pyrosequencing to analyze the structure of functional bacterial groups. We will test whether the diversity of functional groups of bacteria change at a seasonal scale, whether these changes are related to environmental or biological parameters, and in turn, whether they affect the biogeochemical cycling. As a result, we expect to verify whether some ecosystem processes are a common metabolic strategy among different bacterial phylotypes and identify key bacterial populations involved in biogeochemical cycling in this coastal marine site. Identifying functional groups of microbes and their ecological characteristics will allow recognizing “microbial boxes” of different biogeochemical significance, improve the predictions of the models, and, overall, transform our understanding of globally important biogeochemical processes."