To reveal systematic differences in the taxonomic resolution of
phytoplankton counts between regions we calculated the proportion
of sample biomass that was identified to at least species or
genus levels, and presented the results as boxplots. Boxplots were
also used to compare sample based taxon richness (alpha diversity)
and wet weight biomass between regions. To visualize the relationship
between wet weight biomass and taxon richness we used
2D kernel density estimate (kde2d; library MASS in R software) on
the whole data set (n ¼ 44,871). Further, we used the nonparametric
generalized additive model fitting (gam; mgcv library
in R software) to show regional differences in the biomass e diversity
relationship.