There seems to be a distinct difference now between the bloom reported on nearly 2 weeks ago (see post from 7 April) and now, in that the level of nitrate is dropping away rapidly. Although the instrument (Satlantic SUNA) has not had a post field calibration applied, the values have dropped some 3 – 4 uM in the past two days, indicative of phytoplankton consumption of the nutrients. The levels of chlorophyll at 06:00 this morning were >4 mg/m3; the issues of high-light quenching of the fluorescence close to the surface is a known problem, especially on clear sunny days between mid-morning and early evening. For the latest from the L4 buoy data check out the figures below.
The CTD data is also clearly showing surface stratification with Tuesday’s profile (18 April) showing a top mixed layer extending down to 20m which is 0.5 degC warmer than the water beneath.