hyvarino

• Kline, Simon Hasselø; Hyvärinen, Olli Petteri; Valestrand, Louise; Andersen, Tom; Eikrem, Wenche & Titelman, Josefin [Show all 8 contributors for this article] (2026). 15-year shift in protist communities and a decline of heterotrophic dinoflagellates in the Oslofjord and Skagerrak. Frontiers in Marine Science. 13. doi: 10.3389/fmars.2026.1876109. Full text in Research Archive
• Hyvärinen, Olli Petteri; Beest, Mariska te; Roux, Elizabeth le; Kerley, Graham I H; Buitenwerf, Robert & Druce, Dave J [Show all 10 contributors for this article] (2025). Megagrazer loss drives complex landscape-scale biophysical cascades. Environmental Research Letters. 20(2). doi: 10.1088/1748-9326/ada16e. Full text in Research Archive Show summary

  Wild animals can modulate ecosystem-climate feedbacks, e.g. through impacts on vegetation and associated carbon dynamics. However, vegetation cover and composition also affect land surface albedo, which is an important component of the global energy budget. We currently know very little about the influence of wild animals on land surface albedo and the resulting climate forcing of these albedo changes. Leveraging a unique, ecosystem-scale, semi-experimental approach, we study how the local removals of the world’s largest, terrestrial grazer, white rhinoceros (Ceratotherium simum), affected the coupling between fire dynamics, woody encroachment and surface albedo in Hluhluwe–iMfolozi Park (HiP), South Africa. Our path analysis revealed that areas in the park where more rhinos had been removed showed a stronger increase in burnt area and woody encroachment compared to areas with fewer rhinos removed, which were both related to a decrease in surface albedo. Increasing burnt area was further associated with higher rates of woody encroachment, indirectly reinforcing the negative effect of rhino loss on albedo. Our study demonstrates that removals of megagrazers in HiP were related to complex ecosystem-wide cascades with measurable impacts on land cover and surface albedo and consequences on climate forcing. This highlights the importance of restoring functional ecosystems by reinstating trophic processes.

• Kvalheim, Lone; Stensrud, Eivind; Knutsen, Halvor; Hyvärinen, Olli Petteri & Eiler, Alexander (2024). Integration of citizen science and eDNA reveals novel ecological insights for marine fish conservation. Environmental DNA. 6(4). doi: 10.1002/edn3.584. Full text in Research Archive Show summary

  In the face of climate change, the accelerating nature crisis, and other anthropogenic impacts, conserving biodiversity demands effective monitoring. While innovative approaches have emerged to enhance biodiversity assessment, significant data gaps persist, particularly within marine ecosystems. In this study, we assess the utility of combining citizen (community) science with environmental DNA (eDNA) metabarcoding for characterizing and quantifying marine fish biodiversity. Over the summer of 2022, 32 volunteers conducted extensive water sampling in a large Norwegian fjord, yielding 96 samples. Contrasting eDNA findings with conventional observational surveys (such as a national species registration database and beach seine surveys) unveiled a substantial overlap in recorded species inventories. The eDNA citizen science initiative identified previously undocumented species and rediscovered others emphasizing an increase in warm-water species within the study area. Additionally, eDNA data unveiled reduced diversity within the inner fjord relative to the outer fjord. To conclude, our study demonstrates the successful integration of eDNA within a citizen science framework, facilitating comprehensive biodiversity tracking across coastal marine regions. These findings hold promise for advancing marine conservation efforts by providing valuable data to inform critical decision-making processes.

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• Stensrud, Eivind; Hyvärinen, Olli Petteri; Rostum, Tarjei; Angell, Thorvald; Knutsen, Halvor & Lundström, Karl [Show all 8 contributors for this article] (2026). PREDATORS AS SENTINELS: UNRAVELING TROPHIC SHIFTS IN A DARKENING FJORD USING dDNA AND STABLE ISOTOPES OVER THE LAST 20 YEARS. Full text in Research Archive Show summary

  The Greater Oslofjord, like many other coastal systems, is undergoing rapid ecological shifts driven by climate change, coastal freshening and darkening. To understand how these bottom-up stressors restructure food webs, we utilized a multi-trophic approach analyzing three sympatric predators (approx. 500 individuals): Harbour seals (Phoca vitulina), Great Cormorants (Phalacrocorax carbo), and Atlantic Cod (Gadus morhua). We combined dietary DNA (dDNA) metabarcoding with stable isotope analysis (δ13C, δ15N) to trace temporal and spatial dietary changes over 20 years. Traditional morphological methods often fail to capture soft-bodied prey and secondary consumption; thus, we used dDNA combined with novel reference databases to maximize taxonomic resolution. Our dDNA results revealed high-resolution predation data, including the detection of secondary consumption (zoo- and phytoplankton) alongside primary prey, effectively mapping the food web from top predators down to primary producers. Isotope data complemented this by delineating trophic niche widths and source of primary production (land vs. sea). We observed distinct dietary variations linking predator foraging behavior to environmental gradients. This included observable changes over the last 20 years, such as an increase in invasive species in their diet and a shift in zoo- and phytoplankton composition. These findings demonstrate that combining molecular and isotopic analysis of top predators provides a powerful tool for monitoring the cascading effects of anthropogenic changes on marine food webs.

• Mørch, Mikkel Martinussen; Hyvärinen, Olli Petteri; Eiler, Alexander; Werner, Even; Gagnon, Karine & Thormar, Jonas (2026). Biodiversity patterns and blue carbon characteristics of Zostera marina meadows in the Oslofjord. Universitet i Oslo. Full text in Research Archive Show summary

  Seagrass meadows are coastal foundation habitats that support biodiversity and store organic carbon in sediments, a process often referred to as blue carbon storage. However, both biodiversity and sediment carbon storage can vary strongly among meadows, and it remains unclear how local meadow structure, hydrodynamic exposure, organic-matter sources, and associated fauna interact in temperate eelgrass systems. This thesis investigated biodiversity and blue carbon characteristics of Zostera marina meadows in the Oslofjord, Norway. The study combined two complementary approaches: citizen-science-based environmental DNA (eDNA) water sampling across eelgrass meadows and seasons, and researcher-led field sampling at three meadows along an inner-outer Oslofjord gradient. The field-sampled meadows represented contrasting coastal settings: an inner-fjord meadow at Fornebu, a sheltered meadow near Sætre/Sandspollen, and a more wave- exposed outer-fjord meadow at Holmestrand. The water eDNA dataset provided broad spatial and seasonal coverage, but ecological interpretation was limited by uneven sampling and read-depth loss after filtering. After taxonomic partitioning of the cytochrome c oxidase I (COI) metabarcoding dataset, only 20.5% of reads were retained as faunal reads, while 79.5% were classified as non-faunal reads. The retained faunal water eDNA dataset did not show clear winter-spring or Oslofjord-section structure. Instead, it contained a mixed coastal signal, including pelagic planktonic taxa and benthic or soft-sediment-associated taxa. In contrast, the non-faunal fraction showed clearer winter-spring structuring, largely associated with microalgal and protist groups. This indicates that broad COI water eDNA can capture useful biodiversity signals, but also that faunal and non-faunal datasets should be separated before ecological interpretation. The strongest ecological patterns were found in the field-measured meadows. The sheltered Sætre/Sandspollen meadow had continuous eelgrass cover, low sediment bulk density, high and consistent organic carbon stocks, and the highest apparent seagrass-like carbon contribution. The more wave- exposed Holmestrand meadow was patchier and had higher bulk density, lower organic carbon stocks, and the lowest apparent seagrass-like carbon contribution. The inner-fjord Fornebu meadow had intermediate sediment carbon stock, bulk density, and apparent seagrass-like carbon contribution, but showed greater within-meadow variability. Stable isotope composition supported these meadow-level differences and indicated variation in both carbon-source characteristics and assimilated nitrogen among meadows. Benthic eDNA showed clear separation between seagrass-blade epifaunal communities and sediment-core infaunal communities. Infaunal communities were most strongly associated with sedimentary gradients and were dominated by sediment-associated annelids, including lugworms and other ii taxa linked to deposit feeding, burrowing, sediment reworking, and bioirrigation. In contrast, the epifaunal signal was dominated more strongly by sessile or surface-associated taxa, including barnacles, bryozoans, and hydrozoans, rather than by mobile mesograzers. Overall, this thesis shows that eelgrass meadows in the Oslofjord can differ substantially in meadow structure, sediment carbon characteristics, stable isotope composition, and associated benthic fauna. The results support a descriptive interpretation in which blue-carbon characteristics and benthic biodiversity vary together at local meadow scale, particularly through the association between sediment conditions and infaunal community structure. Broader inference about Oslofjord-wide seasonal biodiversity patterns will require more balanced repeated sampling but the study demonstrates the value of combining citizen-science water eDNA with targeted field measurements when assessing biodiversity and blue carbon in eelgrass meadows.

• Negård, Jesper Nilsen; Hyvärinen, Olli Petteri & Eiler, Alexander (2025). Characterization of the Carbon Export Potential of Commercially Important Fish Species in the Oslofjord. Universitetet i Oslo. Full text in Research Archive

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