GLOBAL PATTERNS OF DIATOM DIVERSITY DERIVED FROM THE TARA OCEANS EXPEDITION

Diatoms are believed to be the most important group of photosynthetic eukaryotes in the oceans. Understanding patterns of diatom distribution is therefore important for understanding marine ecosystem functioning. From the Tara Oceans global sampling expedition a total of ca. 14.5 million V9-rRNA ribotypes assigned to diatoms derived from 47 sampling stations that span the global ocean euphotic zone are being analyzed to understand diatom community composition. The dataset contains 65,000 unique ribotypes, present in a wide range of abundances, and represents approximately 3,300 Operational Taxonomic Units. Some of these localize to specific areas such as the Southern Ocean or to sites of diatom blooms, or display interesting biogeographical patterns such as commonalities along the Agulhas current originating from the southwest Indian Ocean. The data also reveal an unexpectedly high level of diatom diversity in the open ocean. Clustering with environmental parameters further reveals correlations of some diatom groups with net primary production and carbon flux. Global comparisons of diatom co-occurrence and exclusion patterns with ribotypes from other organisms provide insights into the interactions of diatoms with other planktonic organisms.