Chlorophyll-
At all stations the fluorescence and chlorophyll concentrations start low and increase to a sharp peak at a certain depth, before rapidly declining and maintaining a constant concentration. Peak chlorophyll and fluorescence indicate the location of the Deep Chlorophyll Maximum (DCM); this peak point fluctuated between 19m and 24m. At station 34 the peak fluorescence was found at 19m but the peak chlorophyll was found at 24m, 5m below the thermocline.
The thermocline was located from the temperature recordings in the CTD data as the
point at which there is a rapid decrease in temperature in a very small change in
depth. For each of the stations except station 34, the thermocline can be found at
the point at which the fluorescence and chlorophyll concentrations peak. This implies
that at each of these stations, the deep chlorophyll maximum sits on the thermocline.
There are a number of reasons as to why station 34 may be showing differing results-
Nutrients-
All nutrient concentrations increase with depth to around 25-
The theory behind this is that nutrients accumulated in the winter are used up by phytoplankton in the upper layers during the spring, when light levels begin to increase. During the summer, phytoplankton have to move deeper into the water column where there is still enough light but there is also access to the deeper, mixed layers of nutrient rich water (peak seen just below the DCM). This causes there to be low nutrient levels above the DCM, but peak nutrient levels just below the DCM as this is the phytoplankton’s lower limit (Huisman et al., 2006).
Figure 2. Profiles of multiple different nutrient concentrations against depth for each of 6 stations sampled at E1 observatory buoy.
Oxygen-
The oxygen saturation data from the E1 time series shows that most measurements from
all stations were taken between 15 -
Chemistry
Huisman, J., Pham Thi, N.N., Karl, D.M., Sommeijer, B., 2006. “Reduced Mixing Generates Oscillations and Chaos in the Oceanic Deep Chlorophyll Maximum”, Nature, 439(7074) pp.332.
Muacho, S. et al, 2013, ‘Effect of internal waves on near-
Figure 3. O2 % saturation vs Depth for all sample stations at E1 observatory buoy.
All opinions expressed are of our own, and not of the University of Southampton
Niskin bottles from
CTD deployments were
sampled to calculate nutrient
concentrations at different depths.
Figure 1. Chlorophyll concentrations against depth for all E1 observatory buoy stations on Monday 8th July 2019