Chlamydomonas nivalis

red-coloured green algae in white

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The green algae Chlamydomonas nivalis is mostly known by its occurrence in snowy mountains. With its red pigments it forms so called watermelon snow. There are two mating types in this species, analogous to sexes. Instead of males and females the mating types are called + and −.

The green algae Chlamydomonas nivalis is mostly known by its occurrence in snowy mountains. With its red pigments it forms so called watermelon snow. There are two mating types in this species, analogous to sexes. Instead of males and females the mating types are called + and −.

The genus Chlamydomonas includes a few hundred species of single-celled green algae that all have two flagella to propel the cell. The oval to round cells of C. nivalis are usually 5–15 µm in diameter, but can grow up to 40 µm in their immobile, red stage. 

Reflect on algae 

How can micro algae influence a macroscopic process such as climate? This can be explained by the pigments of Chlamydomonas nivalis, the melting of snow, and the albedo of snow. The pigments protect the algae against UV radiation. The radiation is transformed into heat within the cells, which causes snow around the cells to melt. Albedo is the reflectivity of an object or surface. For example, a forest reflects little solar radiation; the albedo of forest is low. Snow on the other hand reflects most of the radiation that falls on it and has a high albedo. Large snow plains hardly absorb any heat. If a lot of overwintering C. nivalis are present, they absorb a lot of radiant heat, and the albedo of the snow plain becomes lower. The result is that the entire area retains much more heat, and also warms up the air layers above it. In such a way, many microbes together can have a major effect on the climate.

Algae like a traffic light

De levenscyclus van Chlamydomonas nivalis kent drie fases: groen, oranje en rood. In de lente en vroege zomer ontstaan in smeltwater groene, bewegende cellen door rijpingsdeling. Deze cellen hebben de karakteristieke twee flagella en zwemmen rond om optimale lichtcondities te vinden. De groene cellen bevatten gedurende deze fase vooral chlorofyl, het pigment dat in alle fotosynthetiserende organismen hebben. Later in de zomer beginnen de nutriënten schaarser te worden en de zonne-instraling steeds heftiger. De cellen beginnen in de oranje fase met suikers en vetten opslaan en ze verliezen hun flagella. Gedurende de oranje fase wordt ook de celwand dikker om de naderende vrieskou te overleven. Als de winter arriveert verandert de oranje cel in een rode spore. In de rode fase bevatten de cellen veel van de stof astaxanthine, een rood pigment dat de cel beschermt tegen UV-straling. Als rode cellen wachten ze tot de lente weer begint en de groene nakomelingen weer op pad kunnen gaan.

Advanced freezing

An extremophile is an organism that can live well under extreme conditions. Circumstances in which a human would not survive even a microsecond. Most extremophiles are microorganisms such as fungi, algae, bacteria and especially archaea. Extremophiles living at extremely low temperatures are called psychrophiles. There are microbes that can survive in the coldest areas on earth. The nematode Panagrolaimus davidi mainly occurs along the coast of Antarctica and can withstand temperatures of -80°C. It is one of the few organisms that can survive internal freezing. More than 80% of the moisture in its cells can freeze without dying. It prevents cracks in the cell membranes with the sugar molecule trehalose. To protect themselves, many psychrophiles produce anti-freeze proteins. These bind with the microscopic ice crystals and prevent them from clumping into larger crystals and puncturing the cell. At the exhibit "Extremophiles" you discover in which other extreme places of the world microbes can survive.