Andreas Altenburger

HHUMTBT26 (Helmer Hanssen, University Museum, Tromsø–Bergen–Tromsø, 2026) was a research cruise conducted aboard the R/V Helmer Hanssen, a multipurpose research vessel owned by UiT The Arctic University of Norway (Fig. 1). The cruise was organised and carried out by The Arctic University Museum of Norway, in cooperation with the UArctic Thematic Network on Arctic Marine Biodiversity and Artsdatabanken, and with participation from several research projects aimed at advancing our understanding of marine biodiversity, taxonomy, and ecosystem history in northern and central Norway.

Secondary endosymbiosis drives eukaryotic diversification by integrating genetic compartments from disparate lineages, yet how the host and endosymbiont genomes co‐evolve over deep time remains poorly understood. Cryptophytes provide a compelling model to dissect this integration, as they uniquely retain four distinct genomes within a single cell: the host nucleus and mitochondrion, alongside a red algal‐derived plastid and its relict nucleus (nucleomorph). Here, we investigate the evolutionary and regulatory dynamics of these four coexisting genomes in two ecologically important cryptophytes, Teleaulax amphioxeia and Teleaulax acuta . We reveal a striking decoupling of evolutionary tempos across these genomic compartments. Plastid genomes exhibit structural and functional stasis, while mitochondrial genomes, despite also maintaining high synteny, show faster sequence evolution and mobile element invasion. Nucleomorph genomes evolves even more rapidly, but their gene expression is rigid, with regulatory flexibility limited to a small, conserved set of plastid‐supporting genes. Intriguingly, Teleaulax host nuclear genomes have undergone massive expansion, likely driven by ancient whole‐genome duplication that might explain their greatest divergence among the four genomic compartments. This divergence is further characterised by differential expansion of gene families (e.g., PHYB ‐like photoreceptors and motor‐related proteins) potentially linked to ecological adaptation. Diel transcriptomic analyses highlight conserved core metabolic responses across both species, but also unveil lineage‐specific adaptations, such as enhanced circadian regulation in T. acuta associated with PHYB ‐like gene expansion. Overall, our findings uncover a constraint gradient from plastid stasis to high evolutionary flexibility toward nucleus, highlighting how secondary plastid‐bearing cells achieve a balance between long‐term stability and adaptive innovation.

This is a report of the cruise that was part of the course Arctic Future Pathfinders, implemented by UiT The Arctic University of Norway (UiT) in the autumn semester of 2025. The description of the course can be found here: https://uit.no/arctic-future-pathfinders. The course was designed to provide a space to study the future of the Arctic. In an interdisciplinary setting, participants were guided to analyse environmental changes and socio-economic impacts of the past, identify driving trends, and imagine possible, probable, and preferable alternative futures of the Arctic.A cruise through the Northwest Passage on board the sailing vessel Statsraad Lehmkuhl was planned as part of the course, from Nuuk in Kalaallit Nunaat/Greenland, starting on 5th of August, to Iqaluktuuttiaq1/Cambridge Bay, Nunavut, Canada until the 8th of August (Leg 1 of the cruise), and then to Whittier, Alaska, US until the 4th of October (Leg 2 of the cruise). However, after a few days of sailing north, the vessel had to change course, as, due to ice conditions in the Passage, Transport Canada denied her access to Canadian waters. Consequently, the cruise itinerary was changed: the first leg ended on the 20th of August in St. John’s, Canada, while the second leg took place on land, starting in Edmonton, Canada, on the 28th of August and ending in Alaska, US, on the 15th of September.

R/V Helmer Hanssen is a multipurpose research vessel owned by UiT The Arctic University of Norway. The cruise ‘HHUMTKT25’ was organized and executed by The Arctic University Museum of Norway (units ‘UM’ and ‘UMAK’ at UiT). The six participating projects in this cruise were (1) Scalidophora of Norway, (2) Microfauna and macrofauna in Northern Norway, (3) Reconstruction of past ecosystems using sedimentary ancient DNA, (4) ArKoBi studying the population connectivity of Arctica islandica in Northern Norway, (5) DragonNest studying population genetics and distribution patterns of Kinorhyncha in the Arctic region and (6) NUDIST studying biogeography and taxonomy of nudibranchs in northern Norway and the Arctic. Projects (1) ‘Scalidophora of Norway’ and (5) DragonNest aimed at sampling scalidophoran fauna in Northern Norway, primarily the phylum Kinorhyncha, using a box corer. Projects (2), (4) and (6) relied on a triangular dredge to obtain specimens, and project (3) utilized a gravity corer to capture a 5-m long sediment core. The cruise leader was Andreas Altenburger (UiT).

We applied FlowCam analysis cross‐validated by 18S rDNA sequences and taxonomic literature to study seasonal and short‐term population dynamics and species turnover in ciliate plankton during 15 months with high‐frequency samplings in a shallow temperate estuary in Denmark. FlowCam imagery identified 27 phenotypic ciliate entities, and 8 genotypes were identified. The analyses showed strong seasonality in biomass, abundance, diversity, trophy, and species turnover. The abundance of mixotrophic ciliates increased 30‐fold from winter to summer, whereas that of heterotrophic ciliates increased only five times. The two trophic groups also displayed contrasting seasonal diversity patterns. Heterotrophic ciliates increased in richness from 5.5 species in winter to 10.5 species in summer in 10 mL, whereas species richness of the mixotrophic community, dominated by Mesodinium rubrum, remained relatively constant with three species per 10 mL sample. Daily species turnover calculated from the decay of similarity was highest for heterotrophic ciliates, and community change rates of 3.1, 15.8, and 30.6% day⁻¹ were significantly related to ambient temperatures of 4.8, 8.4, and 16°C, respectively. Oscillating species‐specific growth rates due to prey–predator interactions can explain faster species turnover rates in heterotrophic ciliates. By contrast, the mixotrophic ciliate community harvests a common supplementary energy source, which may dampen their species‐specific population oscillations.

Flatworms in the family Otoplanidae Hallez, 1892, are ubiquitous inhabitants of the swash zone of marine sandy beaches worldwide. We present new insights into the morphology and phylogenetic position of the otoplanid Itaspiella helgolandica (Meixner, 1938) based on specimens sampled in northern Norway. While the species was originally described from the German coast, it has since been reported in the High Arctic as well as in Greenland, Canada and Alaska, indicating that it has a circumpolar distribution. Apart from these reports, I. helgolandica has received marginal scientific attention beyond the original species description, and apart from drawings, there is not much detailed data available of its morphology. We employ antibody staining and confocal laser microscopy to provide detailed morphological information on the ciliation, myoanatomy and genital organs of specimens of I. helgolandica and compare their morphology with other accounts of the species from across the Arctic. We investigate the phylogenetic relationships of Itaspiella Ax, 1955 through a Bayesian/RAxML analysis of 28S sequences and confirm the morphologically underpinned notion that this genus sits within the subfamily Otoplaninae Hallez, 1910, as the sister taxon to Xenotoplana Ax, Weidemann & Ehlers, 1978. In light of our findings, we explore the question of the apparent circumpolar distribution of Itaspiella in the context of the larger “meiofauna paradox” and touch upon various evolutionary phenomena that may have contributed to phenotypic stability despite its limited dispersal capabilities and the vicariance imposed by the complex recent geological history of the Arctic.

Marine invertebrate habitats are experiencing warming, and oceanic carbon dioxide levels are on the rise. These changes result in shifts in species distributions. Monitoring and understanding these shifts provides vital information because each species plays a unique ecological role, and the human utilization of marine species is intrinsically linked to their geographic locations. Here, we examine distribution shifts of marine invertebrates in the Barents Sea since pre-1900. Using data from the Global Biodiversity Information Facility, we analyzed species occurrences across warm, cold and mixed temperature zones, distinguishing between benthic and pelagic taxa. Our findings indicate community shifts in each of five separated time periods, with the most pronounced shifts occurring after 1980 in the cold and mixed zones, and earlier in the warm zone. The significant biogeographical changes at the community scale occurred both in benthic and pelagic realms, yet with differing trajectories in the period past 2000, and largely coincided with increased Atlantic Water inflow and reduced ice cover. Several invertebrate taxa exhibited a northward movement, falling into two categories: species migrating into the Barents Sea from the Norwegian mainland shelf, and those relocating from the southern Barents Sea to areas with mixed and colder temperatures. Some of these species may serve as indicator species for monitoring ecosystem and community change. The study highlights the importance of long-term datasets in quantifying community distribution shifts and understanding their ecological impacts.

BioStudies – one package for all the data supporting a study

R/V Helmer Hanssen is an ice class research vessel owned by UiT The Arctic University of Norway. The HHUMLT24 cruise onboard R/V Helmer Hanssen was an initiative by The Arctic University Museum of Norway (UMAK, UiT). Sampling was conducted for the following four projects: 1. The Scalidophora of Norway, 2. The role of microRNAs in animal evolution, 3. The diversity of benthic fauna around Svalbard and the Barents Sea, 4. Reconstruction of past ecosystems using sedimentary ancient DNA. For the first project, which aimed to sample scalidophoran fauna, primarily kinorhynchs, for the Scalidophora of Norway project funded by Artsdatabanken, box cores were taken. The second project employed plankton nets, box cores, and a triangular dredge. The third project used samples from box cores, plankton nets, and a triangular dredge to collect marine macrofauna for the museum collections. All macrofauna present in plankton nets, box cores, and triangular dredge samples were photographed, and records were uploaded to GBIF. The fourth project took gravity cores. The cruise leader was Andreas Altenburger (UiT).