GROUP
Plymouth Field Course 2019
4
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OFF-SHORE
Chlorophyll
This figure displays the change in chlorophyll with depth at each station where the CTD was deployed, with station C25 being located at L4 and C28 being located at E1. The chlorophyll data displays a distinct increase in the 5m to 30m range below the sea surface. This was likely the mixed layer depth where the supply of nutrients was at its greatest, whilst light penetration was sufficient for photosynthesis to occur due to the clear conditions of the water. This resulted in a higher amount of chlorophyll fluorescence, due to the abundance of photosynthesising organisms such as phytoplankton in the mixed layer.
Chlorophyll concentration decreased with distance from the coast, as shown from the general decrease in concentration from C25 to C28, along with the decrease at depth beyond the thermocline. However, at station C27 a deep chlorophyll maximum (DCM) was observed, as the chlorophyll concentration increased from 0.769µg/L at 14.2m to 1.783µg/L at 22.9m. The seabed measurement at C27 is missing as the niskin bottle failed to close when fired resulting in the loss of this sample.
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Figure 1: A graph showing the variation of chlorophyll concentration with depth