An upright life-form of an epipelic motile diatom: on the behaviour of Gyrosigma balticum

Abstract

Previously undescribed behaviour of the large (≈ 400 μm) motile diatom Gyrosigma balticum was observed in intact sediment cores from a non-tidal mudflat. Instead of lying flat against the sediment surface, the individual cells were found orientated with their long axes perpendicular to the sediment surface. Staining with toluidine blue indicated that the mechanism behind the erect position was a short (100–200 μm) mucilage tube produced at the lower end of the cell. It is suggested that the upright life-form may be common among epipelic diatoms. A diurnal/vertical rhythm into and out of the sediment was also observed. The peak of the oxygen profile in the Gyrosigma mat occurred 250–300 μm above the sediment surface, i.e. within the layer of upright cells.

Keywords :

• Diatoms
• Epipelic
• Motility
• Oxygen profile
• sediment
• vertical migration