Ice diatoms are principally characterised by pennate species that sometimes form colonies (such as Fragilariopsis oceanica, in the photo). They develop well in advance of diatoms in the water column, which can be either pennate or centric.

Ice diatoms are principally characterised by pennate species that sometimes form colonies (such as Fragilariopsis oceanica, in the photo). They develop well in advance of diatoms in the water column, which can be either pennate or centric.