For gut pigment samples, total gut pigment concentration in units of µg pigment/copepod (combining chl a and pheophytin) was calculated according to EPA Method 445.0 as:

Gut Pigment Concentration = K (r/r-1) (r Ra - Ra) E / n

where K is the response factor from the fluorometer calibration, r is the before-to-after acidification ratio of a pure chlorophyll a solution, Ra is the fluorescence reading after acidification, E is the volume of acetone in L, and n is the number of copepods per sample (2 in our case).

To account for differences in fluorescence between growth phases and between phytoplankton and aggregates (since the aggregates were formed in the dark for 3 days), the fluorescence in the tank water in units of µg pigment/L (combined chlorophyll-a and pheophytin) was calculated from the fluorometer measurements of the tank water samples based on EPA method 445.0. These values were averaged for every treatment (separately for each experiment and growth phase), after removing any outliers (defined as any values greater than 3 interquartile ranges above the third quartile or any values less than 3 interquartile ranges below the first quartile). The average fluorescence per cell (F, in units of µg pigment/cell) was then calculated for each treatment of every growth phase and experiment according to the equation:

Fluorescence per Cell = Fl_tw / C / (1-p)

where Fl_tw is the average fluorescence in the tank water as described above, C is the initial phytoplankton concentration in the tank in cells/L (5,000,000 cells/L for T. weissflogii experiments and 9,750,000 cells/L for S. marinoi experiments), and p is the proportion of initial fluorescence that was consumed by copepods, calculated as:

p=(n_t)(G_ave)/((n_t)(G_ave)+(Vt)(Fl_tw))

where n_t is the number of copepods in each tank, G_ave is the average gut pigment content per copepod, and Vt is the volume of the experimental tank (2.2 L).

In this data set, the average gut pigment content (G_ave), the average fluorescence in the tank water (Fl_tw), the proportion of fluorescence consumed by copepods (p), and the fluorescence per cell data is provided. For the associated gut pigment concentration measurements used to calculate copepod ingestion, see related dataset https://www.bco-dmo.org/dataset/824364

Dataset Version History:
2021-10-04 (v2) - dataset updated; includes corrections to data values
2021-02-16 (v1) - dataset updated
2020-09-15 (v0) - preliminary data