HIPPODONTA SUBCOSTULATA (HUSTEDT) LANGE-BERTALOT, METZELTIN ET WITKOWSKI AND SOME FRAGILARIOID DIATOM TAXA FROM THE HOLOCENE LACUSTRINE SEDIMENTS OF THE FAEROE ISLANDS

Abstract

The present paper deals with several freshwater diatom taxa from the Faeroe Islands that were either recently described using only light microscope observations or that were known for a longer period but without SEM documentation. They belong to two genera, StaurosiraEhrenberg and Hippodonta Lange-Bertalot, Metzeltin et Witkowski. The material studied was derived from early Holocene lacustrine deposits documented in sediment cores from the Skalafjord, Faeroe Islands. The diatom flora of these sediments represents a rather unique assemblage inhabiting oligotrophic to dystrophic, acidic to circumneutral habitats that have nearly disappeared from most of the continental part of Europe. They only persist in northern Scandinavia, Iceland and in some intact peat bogs (e.g. in Pomerania). The taxa studied include Hippodonta subcostulata (Hustedt) Lange-Bertalot, Metzeltin et Witkowski, Fragilaria opacolineata Lange-Bertalot and Fragilaria construens var. binodis f. borealis Foged. SEM studies revealed that the two fragilarioid taxa possess features typical of the genus Staurosira sensu lato. Therefore a formal transfer is made to Staurosira borealis (Foged) nom. nov. et comb. nov. and S. opacolineata (Lange-Bertalot) comb. nov. H. subcostulata and S. borealis seem to be very rare species, so far known only from the type locality and a few sites elsewhere in Europe. The distribution of S. opacolineata is less known.

Key words:

• Freshwater diatoms
• taxonomy
• ecology
• distribution
• Holocene