Ultrastructural studies of the flagellate and cyst stages of Pseudopedinella tricostata (Pedinellales, Chrysophyceae)

Abstract

During the winter of 1985 the uppermost part of the water column of the ice-covered Danish fjord, Isefjorden, was coloured yellowish brown by a growth of the small flagellate Pseudopedinella tricostata (ca. 75 × 10⁶ cells 1^-1). The species differs from others of the genus by having three chloroplasts only, each with an embedded pyrenoid. In March a distinct yellowish band was found in the lower part of the ice which electron microscopical examination showed to be due to the presence of millions of cysts of P. tricostata. The P. tricostata cyst has a continuous three-layered wall, thus differing markedly from the typical bipartite chrysophycean cyst. The outermost wall-layer contains a significant amount of iron.