Light microscope footage of a diatom algal bloom in a small brook, showing the diatom movement in timelapse. The original capturing time was about 2 min. In the middle of the captured field a huge Gyrosigma cell in valve view moves to the right and back again. At the bottom of the captured field a Nitzschia moves slowly to the right, showing the valve view and the nucleus. In this habitat the benthic forms of diatoms predominate, such as Navicula, Nitzschia and Gyrosigma. Mostly Navicula, which has a boat shaped valve, can be seen here. Some Nitzschia forms are visible, about double in length of Navicula forms seen here. Diatom cells are enclosed within a rigged lidded box, called frustule or theca, which is composed of amorphous opaline silica with organic coatings. Diatoms seen from the top or bottom are in valve view, whereas diatoms seen from their sides when in girdle view. The same diatom frustule often has a different appearance when viewed from the valve side compared to the girdle view. Nearly all of the Navicula cells here are in valve view, some Nitzschia forms in girdle view. In early spring the diatom reproduction reaches a first annual maximum, easily visible by the fawn brown layers on the bottom of ponds, brooks or other freshwater habitats. Diatoms are very abundant and are important primary producers, responsible for about 20% of carbon fixation. Microscopic contrast method used : Differential interference contrast. Captured field width : 0, 23mm |