We are finding that the WET Labs C-Star beam transmissometers on the floats are much more sensitive to the initial bloom dynamics than backscattering at 700 nm. We are seeing about 50 counts descrease in transmissivity vs. 5-10 counts increase in b
bp. So, acknowledging this, let's examine one diagnostic we'll be using during the course of the bloom: beam attenuation vs. chlorophyll fluorescence.
The ratio of attenuation due to particles (c
p) to chlorophyll can be used as a diagnostic of the progress of the bloom. Currently we see a corresponding increase in chlorophyll
and beam attenuation
(data from daily averages on Biofloat48).
 |
When we plot the full resolution data against each other, we see the current trajectory where chlorophyll (as one proxy for biomass) and beam attenuation (a proxy for particulate organic carbon) move to the upper right. (What is actually plotted is c(662) vs. chl fluorescence, not cp vs. chl.) |
 | As the bloom moves past its peak in a month or so, we expect a decrease in chlorophyll, but less of a reduction in beam attenuation as phytoplankton detritus and decay products remain in the water column. FYI, the zoomed out axis limits in this figure compared to the one above are derived from an excellent paper on bio-optical variability that came out of the Marine Light Mixed Layers (MLML) experiment, performed in same area of the N. Atlantic. (Stramska et al. 1995, Bio-optical variability associated with phytoplankton dynamics in the N. Atlantic Ocean during spring and summer 1991, JGR 100-C4) |
