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Water en land

  • Dut: Schuimalg
  • Lat: Phaeocystis globosa, Ph. pouchetii
  • Eng: Phaeocystis (foam algae)
  • Ger: Phaeocystis (Schaumalge, Gallertalge)
  • Dan: Phaeocystis (skumalger)
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Phaeocystis, foto fitis, sytske dijksen

Phaeocystis ('foam algae')

You may have never heard of Phaeocystis, but if you ever take a walk along the beach in late spring or summer and see lots of foam along the waterline, you are looking at these one-celled algae. No wonder it's nicknamed foam algae. Phaeocystis is brown and slimy. Lots of people mistake the brownish foam as pollution. However, it is a natural phenomenon. After the algae have died (blossomed), the wind and waves whip it up into foam. The foam is eventually degraded by bacteria. Large colonies of Phaeocystis can sink to the bottom in shallower waters, suffocating the animals living underneath, such as mussels. In 2001 in the Oosterschelde, 10 million kilograms of mussels died due to such a bloom.

  • The secret to success
    Phaocystis foam, foto fitis, sytske dijksen

    Phaeocystis is a colony-forming one-celled algae. Unlike the colonies, the separate cells cannot be detected with the naked eye. The individual cells in the colonies of Phaeocystis are embedded in a kind of gelatin layer. The colonies use this slimy layer to temporarily store organic material formed by photosynthesis during the day. This provides the cells with an energy supply at night, allowing them to grow both night and day. The slimy layer also protects the algae from being eaten. Many plankton are unable to grow at night so these advantages have made Phaeocystis a successful phytoplankton.

    Since the 1970s, the amount of Phaeocystis in the Atlantic Ocean and the North Sea increased due to the discharge of too many nutrients. Despite the use of phosphate-free detergents, which has decreased the concentration of phosphate in the water, there has been little decrease in nitrogen. Runoff from fertilized agricultural lands is still a large source of nitrate and ammonia in water.

    Studies predicting the situation in the year 2100, when climate change is expected to increase the average summer water temperature in the North Sea to 22 degrees Centigrade, expect Phaeocystis to decline considerably. This alga can't withstand such high temperatures.

  • Viruses and bacteria
    Phaeocystis at sunset, foto fitis, sytske dijksen

    Phaeocystis begins to die when there are too few nutrients in the water. Viruses are also responsible for the death of algae cells. Viruses multiply in the cell, making the cell explode. Bacteria take advantage of the exploded cell and eat its contents.