Phytoplankton was counted and identified from five sites over the 5-year period. Annual cycles in abundance are available (as cells mL-1), along with detailed species identification. Cell measurements and approximate geometric shape were also recorded for the calculation of biovolume (μL cell-1). Diatoms and dinoflagellates dominated the samples in terms of biomass, however, small cells were also very abundant throughout each year. The data are restricted to an integrated sample from the top 12 m of the water column. Fluorescence profiles elsewhere in this dataset can provide an indication of phytoplankton presence lower in the water column.
An integrated water column sample (12 m) using a weighted hose was collected for phytoplankton speciation and pigment analysis from February 2010. Prior to this, samples for phytoplankton speciation were collected from 1 m below the surface.
Phytoplankton samples were concentrated by sequential settling over ~ 1 week, reducing the sample down to approximately 15 mL. The final volume was recorded and the sample thoroughly mixed before a 1 mL aliquot was taken and examined by phase contrast light microscopy (Leica DMLB2) in a Sedgewick-Rafter chamber. The entire chamber was scanned at low power (x50) to count large or rare species, and then re-examined at x200 until 400 squares had been inspected, or at least 200 cells of the dominant species had been counted. Thecate dinoflagellates were occasionally examined using fluorescence microscopy and Calcalfluor to highlight plate structure. The identification of species was confirmed at higher magnification (x400), and a minimum of 20 squares was examined at x400 to count small flagellates (<5 μm), which were grouped into broad taxonomic categories based on shape and flagellae.