Sea background

Phytoplankton is mostly single celled and microscopic algae and therefore cannot been seen in the naked eye. However, phytoplankton is everywhere in the ocean, and is despite its size the basis of the food chain of the ocean. Therefore the phytoplankton has the same role as plants on land.

Like plants on land, phytoplankton only needs sunshine and a few nutrients (such as nitrates and phosphates) to photosynthesise.   When photosynthesising they in fact make their own food, that is convert inorganic molecules to organic. Animals cannot do that and therefore have to eat plants, algae or other animals. The organic molecules that the algae in the ocean make is therefore the basis for the entire food chain in the ocean. There is only enough sunlight in the upper 10 – 50 m for photosynthesis, algae therefore cannot grow below that.

Benthic algae looks more like plants on land as they are multicellular. They can only be found on a narrow belt along the coast where sunlight can reach the bottom, usually not below 20 depth. The total production by the benthic algae is therefore much smaller than for phytoplankton that does cover much greater area.

The most common phytoplankton groups in Icelandic waters are dinoflagellates and diatoms. The main difference between these groups is that dinoflagellates have a skeleton made from chitin, while in diatoms it is made of silicates. Diatoms cannot move and are therefore entirely dependent on oceanic currents, the do also often form chains. However dinoflagellates have flagella so they can move, they also rarely form chains.

A few other groups can be found in Eyjafjörður but they are very small in inconspicuous. Some, like coccolithophores (Haptophyceae) can under favourable conditions multiply enormously and colour the ocean milky white seen from satellites. Coccolithophore bloom has been observed north of Iceland.


Chaetoceros_gracilis The diatom Chaetoceros gracilis (photo Friðbjörn Möller) The diatom Chaetoceros gracilis (photo Friðbjörn Möller)

Rhizosolenia_setigera The dinoflagellate Rhizosolenia setigera (photo Friðbjörn Möller) The dinoflagellate Rhizosolenia setigera (photo Friðbjörn Möller)



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