The aim of this study was a comparative analysis of phytoplankton
data sets from seven geographic regions of the world
coastal ocean, incorporating over 40 thousand quantitative samples,
two thousand taxa and 1.2 million records. After careful
taxonomic harmonization we analyzed if the regional taxon richness,
compositional and phylogenetic turnover of communities
reveals any large-scale geographic pattern. Resource competition of
phytoplankton may lead to chaotic fluctuations in species abundances,
allowing stochastic coexistence of many species (Huisman
and Weissing, 1999). We thus expected high compositional and
phylogenetic diversity within each coastal region, and asked if this
within region variation is equal or comparable to the overall variation
of coastal phytoplankton communities. Alternatively, the
geographic regions could show idiosyncratic phylogenetic and
community composition patterns, which could be driven by differences
in environmental conditions (environmental filtering), or
dispersal limitation due to large distance