Planktonic microbial communities from Monterey Bay, CA. Monterey Bay is a well-studied coastal environment characterized by strong seasonal upwelling, with active local fisheries and adjacent to one of the most productive agriculture areas in the country, and within the Monterey Bay National Marine Sanctuary. The microbial communities in the Bay have been studied for over a decade and have produced important insights into coastal marine microbial community composition (e.g. Beja et al., 2002a, 2002b, Suzuki et al., 2000, 2001, 2004), community dynamics (e.g. Suzuki et al., 2004), potential to mediate biogeochemistry (e.g. Ward, 2005, O'Mullan and Ward, 2005, Mincer et al., 2007), and novel biochemistry (e.g. Beja et al., 2000, de la Torre et al., 2003). The Monterey Bay Aquarium Research Institute.s Biological Oceanography Group has conducted monthly monitoring cruises transecting the Bay (Figure 1) over the last 19 years, and microbial fraction samples were synoptically collected over seven of those years (1997-2004). As part of ongoing research using these time-series samples (Rich et al. in prep.), three surface water samples from mid-bay station M1 (36.747d N, 122.022d W) were pyrosequenced. These samples were selected based on environmental parameters and on DNA yield, and span October 2000 to May 2001 (Figure 2). They represent non-bloom conditions (10/15/00) and two post-bloom response points (4/25/01 and 5/15/01). The surface water picoplankton DNA samples that were pyrosequenced are being analyzed for taxon and functional gene content, as well as for use in validating and intercalibrating .genome proxy. microarray experiments (Rich et al., 2008; Rich et al. in prep.), conducted with the same samples.