Synechococcus microscopy counts collected from CTD casts aboard the R/V ATLANTIS, from the euphotic zone of the Eastern Tropical South Pacific during February, 2010 (NODC Accession 0069125)

This cruise provides the opportunity to expand the database we are amassing on Synechococcus diversity and distribution for our NSF project "The role of iron (Fe) in controlling in situ distributions and activities of marine Synechococcus" into an area that has not been well studied, and also provides the opportunity to test out hypotheses with controlled experimental manipulations of Fe, light, and temperature in the field.

The Eastern Tropical South Pacific (ETSP) is a highly productive area where the small size (0.6-2 micron) fraction generally dominates biomass and accounts for ~40% of primary productivity (Duhamel & Moutin 2009). Synechococcus, a cosmopolitan picocyanobacterium, is a component of this fraction, and can be greater than 104 ml-1 in parts of the upwelling (Masquelier & Vaulot 2008). Despite this recent knowledge, the area is chronically under sampled and our understanding of the dynamics of picocyanobacteria in this region are lacking.