Gert Hansen

A dinoflagellate isolated from a small rainwater rockpool in Finland was found to be a new species of Baldinia, here described as B. droopii sp. nov. This is only the third formally described Baldinia species and the second described by modern methods. The new species had a complement of generic characters that clearly affiliated it to Baldinia: presence of an internal honeycomb structure, termed a lamellar body, a ventral fibre associated with the longitudinal basal body and a pentagonal resting cyst; and the absence of an apical structure, thecal plates and trichocysts. The most distinctive species-specific characters were the presence of a resting cyst with tubiform processes, a paratabulation matching the pattern of the motile cell, and a life cycle exhibiting a diel rhythm, alternating between motile and non-motile coccoid cells. Motile cells occurred during the light period, peaking after 3–4 h of light period, while practically no motile cells occurred during the dark period. LSU rDNA sequences confirmed B. droopii as a new species, showing c. 14% sequence difference compared to B. anauniensis. Asexual reproduction occurred primarily by binary fission or via a so-called division cyst. Sexual reproduction occurred in the culture indicating that D. droopii is homothallic. The zygote may form a resistant cyst with tubiform processes, but there were indications that this stage may be by-passed. Different stages of the asexual and putative sexual reproduction were observed and documented by video recordings.

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrometry. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved.

Phytoplankton are present in a large variety of aquatic environments, ranging from small freshwater ponds to the oceans. Typically, freshwater and marine species are not closely related, indicating an ancient divergence and that salinity poses a strong dispersal barrier. Here we reveal a common recent origin of two dinoflagellates that are well adapted to different habitats. Gymnodinium baicalense inhabits the geologically old freshwater Lake Baikal, which is located in the middle of the Eurasian continent. Gymnodinium corollarium, on the other hand, is a brackish water species from the Baltic Sea. Both species form blooms under ice during the spring. We generated 10 DNA sequences from these species. The partial 28S rRNA gene from G. baicalense and the partial 18S rRNA gene and internal transcribed spacer-2 (ITS2) from G. corollarium were sequenced for the first time. A more detailed description of G. baicalense, which was previously known only from light microscopy observations, is also provided. In the laboratory we demonstrated that G. baicalense is strictly adapted to fresh water, while G. corollarium had a wide salinity tolerance. However, the two species have almost identical morphology, identical SSU rRNA gene sequences, and only small differences in the LSU rRNA gene and ITS2. We infer a common ancestor, which was a species from the Arctic region with a tolerance to a range of salinities. Our data support the scenario that the under-ice phytoplankton community in Lake Baikal has been formed recently, even though the lake is the oldest in the world.

Desmids are unicellular green algae dominating habitats that are vulnerable and highly threatened, like raised bogs, mires and fens. Here, we studied the desmid diversity in four different localities on the Danish island Bornholm. A total of 186 species, 58 of which not previously recorded from Denmark, were observed. The species composition of the locality ‘Kohullet’ was compared to more than 130 year‐old records. In the 1880s this locality contained 65 species vs 70 in in the present study. The species composition has changed towards more oligo‐mesotrophic and more acidophilic species. The reasons for these changes may be the 1960‒1970s’ increase in atmospheric deposition of nitrous‐ and sulphurous oxides leading to a pH‐decrease, and the possible use of Kohullet in the 1880s for cattle drinking leading to more mesotrophic conditions than present days conditions. We used an empirical system developed by Coesel for classifying the trophic state or ‘conservation value’ of freshwater habitats using desmids as indicator organisms. All localities studied had maximum scores, i.e. represented highly structured and well‐balanced ecosystems. Thirty of the recorded species were potential Red List species, using the Dutch Red List criteria for desmids. We suggest that Kohullet should be considered an Important Plant Area (IPA), as it has a high diversity of desmids, a long history of algal records including desmids and may be considered a threatened habitat of major significance to desmids. Furthermore, it is suggested that several desmids are considered Red List species.

Northern peatlands hold large amounts of organic carbon (C) in their soils and are as such important in a climate change context. Blanket bogs, i.e. nutrient-poor peatlands restricted to maritime climates, may be extra vulnerable to global warming since they require a positive water balance to sustain their moss dominated vegetation andCsink functioning. This study presents a 4.5 year record of land– atmosphere carbon dioxide (CO2) exchange from the Andøya blanket bog in northern Norway. Compared with other peatlands, the Andøya peatland exhibited low flux rates, related to the low productivity of the dominating moss and lichen communities and the maritime settings that attenuated seasonal temperature variations. It was observed that under periods of high vapour pressure deficit, net ecosystem exchange was reduced, which was mainly caused by a decrease in gross primary production. However, no persistent effects of dry conditions on theCO2 exchange dynamics were observed, indicating that under present conditions and within the range of observed meteorological conditions the Andøya blanket bog retained its Cuptake function. Continued monitoring of these ecosystem types is essential in order to detect possible effects of a changing climate. peatland, carbon, blanket bog, eddy covariance, climate change, net ecosystem exchang

In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.