Fig. 3
Variation in biogeochemistry and phytoplankton communities across space and time during HaDS. (a) Chlorophyll a and silicate concentrations and Synechococcus cellular abundances are higher at coastal station HP1 compared to offshore station STO1, while Prochlorococcus cells are more abundant at offshore station STO1. (b) At station HP1, chlorophyll a concentrations and Synechococcus cellular abundances follow diel oscillations, with early morning (~03:00 HST) minimums and late afternoon (~15:00–21:00 HST) maximums. (c) Chlorophyll a concentrations at station HP1 rise during daylight hours and decline after sunset. Samples are plotted by time of day over a 24 h cycle. (d) At station STO1, Prochlorococcus cellular abundances show a clear trend that emerges on the order of days while chlorophyll a concentrations decline briefly at the beginning of the sampling period. (e) Chlorophyll a concentrations at station STO1 reach a minimum in the late evening. Like panel c, this plot shows samples by time of day over a 24-hour cycle. The shaded areas in panels c and e depict the standard error around a local polynomial regression fit line for chlorophyll a concentrations per hour of the day. Gray bars in panels b-e indicate nighttime.
