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Chara baltica (Hartm.) Bruz. was found in the bays of the northern part of the Black Sea as a result of our joint efforts for clarification of some charophyte species from the region. The species was reported new to Ukraine. This is the first reliable record of this species in the Black Sea Region and Russia. In the studied populations, C. baltica had a variable arrangement of stipulodes because of the presence of extrastipulodes as a common trait. The morphology of the specimens studied may suggest a possible explanation of old uncheckable regional records of C. horrida Wahlst., species known from the Baltic Sea only. The worldwide range of C. baltica was summarised with a map according to the published records, GBIF data and some checked specimens. It highlighted the records, which need to be confirmed. The presence of extrastipulodes in the specimen studied, as well as the indication and illustration of some species of charophytes, allowed to suggest several additions to the terminology of charophyte morphology useful for further studies. Their application was demonstrated with the specimens studied and the illustrations published elsewhere.

Combined genetic, morphological and ontogenetic observations show that the circumarctic boreal green algal macrophyte Kornmannia leptoderma has expanded its distribution range into the Baltic Sea, on a German coastal section of 220 km length. The species is also again (or still) established at its former extreme southern distribution limit in the North Sea, the German island of Helgoland, where it has not been detected during the last four decades. Macroscopic visible sporophytes of K. leptoderma are nowadays present in the Baltic Sea and at Helgoland from February to September, while they were in the past only detected from February to May at Helgoland. This capacity for formation of sporophytes in summer correlates with the circumstance that K. leptoderma from the Baltic Sea can complete its life cycle at 15°C while several studies conducted decades ago with material from Helgoland and from Pacific coasts consistently reported an inhibition of the algal gametogenesis at temperatures that exceed 12°C. Possibly K. leptoderma has undergone adaptations that facilitate its spread into warmer environments, unless the Kornmannia present in the Baltic Sea and on Helgoland today represents a newly introduced cryptic species.

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