Project: RAPID: Synechococcus diversity and Fe stress and the relationship to dissolved metals in the Eastern Tropical South Pacific

The unicellular cyanobacterium Synechococcus is one of the most widespread and abundant photosynthetic organisms in the ocean, contributing substantially to marine primary production. It is also extremely diverse, with 16 clades identified so far. This diversity, however, has yet to be correlated with specific, well-defined ecological niches. It is important to define what these ecological niches are in order to determine the significance of Synechococcus diversity, i.e., does the clade present in a certain regime have a large impact on biogeochemical cycling in that area? In parallel, the distribution of the clades must also be defined, to able to understand more clearly the role of Synechococcus in the ocean, and how it might change in the future. In the funded project, "The role of iron (Fe) in controlling in situ distributions and activities of marine Synechococcus OCE-0825922" investigators Jill A Sohm (J.A.S.) and Eric Webb have been mapping the distribution of Synechococcus clades in the western Pacific, the North and South Atlantic, and off the coast of Los Angeles, in order to better define the ecological niches of the many clades of Synechococcus. In this project, Webb and Sohm will participate in a research cruise occurring in February 2010 in the Eastern Tropical South Pacific (ETSP), a data poor region with little known about the ecology of its picocyanobacteria. While it has been shown the Synechococcus from clade four dominate the upwelling region farther south of the proposed cruise, the diversity of the population farther offshore is much less well defined. This cruise would allow expansion of the current database of Synechococcus clade distribution to an area where there is little to no data, and add experimental field work to an existing project, testing the specific affects of Fe, light, temperature and nutrients on the diversity of field populations. These data combined with concurrent lab research will provide insight into the potential of oceanic change to affect the distribution and the activity of Synechococcus.

In addition to defining the role and impact of Fe limitation on marine Synechococcus activity and diversity in the field, this project will develop field incubation-tested, quantitative PCR-based Fe stress diagnostics that will be available to the community. Furthermore, the investigators will attempt to isolate and make available Synechococcus strains from the region; as such representatives are not in existence. The upkeep and addition to the culture collection in the Webb lab is an important service for the oceanographic community, as these strains are sent to any researcher that requests them without charge. Metadata obtained on this cruise will be shared with the oceanographic community by depositing them in a national database. Lastly this project will provide valuable research cruise experience and career development for one post-doctoral fellow, J.A.S., and one graduate student.