Global surface ocean phytoplankton community structure determined from
co-variability in phytoplankton pigment concentrations
Abstract
High performance liquid chromatography (HPLC) remains one of the most
widely applied methods currently available for estimation of
phytoplankton taxonomy from ocean samples. This method measures the
concentrations of phytoplankton pigments, some of which are useful
chemotaxonomic markers that can be used to diagnose the relative
abundance of phytoplankton groups. Here, we use HPLC phytoplankton
pigment concentrations measured on surface water samples from 38 field
surveys for a total of over 3,000 distinct samples that cover every
major ocean basin and represent a wide range of ecological regimes. The
data compilation has been quality controlled to remove measurements
below pigment detection limits and outliers from the linear regression
of total chlorophyll-a concentration with total accessory pigment
concentrations and only samples from labs that have participated in
round-robin quality assurance experiments (e.g. NASA SeaHARRE) have been
included. We assess the environmental and spatial drivers controlling
the global distribution and co-variability of individual phytoplankton
pigments. Preliminary results of hierarchical clustering show strong
differentiation in phytoplankton pigments following known relationships
between phytoplankton size class and relative pigment concentration,
partitioning their contributions by micro-, nano-, and
pico-phytoplankton size classes. However, the exact clusters
relationships change when the data are divided by ocean basin or
latitude. We also use statistical techniques, including EOFs and
network-based exploration, to examine the associations between groups of
pigments over a range of environmental conditions on local to global
scales and diagnose the main controls on these associations.