2. Ecosystems   (6/6)

In this module you have learned that algae and humans are part of the same ecosystem and food chain. You have also learned that coastal zones are rich in nutrients and fixation of Carbon by algae (primary production) is very abundant in these zones. We finish this tutorial with a view by ocean colour remote sensing of one of the most productive coastal seas in the world: the North Sea.

Noctiluca Scintillans

Although most algae are green, there are also species with a very distinct red-coloured. One of these is Noctiluca scintillans. This is relatively large (0.5 mm in diameter) dinoflagellate which get its food not by photosynthesis but by phagocytosis (engulfing other algae, bacteria and fish eggs).  

Noctiluca scintillans
Noctiluca scintillans
Source: NOAA

N. scintillans is best known for its bioluminescence. When it perceives danger it gives over a phosphorescent pulse to frighten off its enemies. We can see this as sparkles in the water, the common name for this algae is also sea sparkle. 

With satellites we can measure the concentration of these algae and other species. High concentrations of Noctiluca scintillans were perceived off the Belgian coast in 2003 (Van Mol et al., 2007).

Spring
Algal concentrations in March and April 2003 off the Belgian Coast.
Source: REVAMP


interpretation of the images

Before we have a better look at these images, it is first important to have a better look at the colour code (the legend) of the maps. The legend is provided here:

Legend to the Chlorophyll-a maps
Legend to the Chlorophyll-a maps
Source: REVAMP

Question: What is the highest concentration that is shown in this map?

Answer ↓

Question: Near the coast values of 5 to 20 mg m-3 are considered to be too high for a healthy ecosystem and indicate the influence of high nutient concentrations. What is their colour?

Answer ↓

More maps of the Southern North Sea

With satellites we can observe the coastal zones many times in one year. With the MERIS instrument we could observe the Belgian and Dutch coast almost 80 times in 2003. When we combine these images for every month, we get the following maps for May and June:

summer end
Algal concentrations in May and June 2003
Source: REVAMP

Do you know now when it happened ?

Question: Compare the maps from March to June 2003. When was the highest Chlorophyll-a concentration near the coast off Belgium and in the Voordelta near the Dutch province Zeeland?

Answer ↓