Grete Sørnes

• Mahlangu, Sibusiso; Ewers, Isabelle; Carvalho, Cintia Oliveira; Schrøder-Nielsen, Audun; Dunthorn, Micah & Karlsen, Hans Erik [Show all 12 contributors for this article] (2025). Investigating the dynamics of the aquatic community in Oslofjord through time series analysis of eDNA. Journal of Fish Biology. ISSN 0022-1112. doi: 10.1111/jfb.70105. Full text in Research Archive Show summary

  Understanding the temporal dynamics of marine communities is critical for assessing ecosystem health and guiding conservation efforts. Here, we conducted a survey using environmental DNA (eDNA) metabarcoding with two primer sets, MiFish and Elas02, to investigate seasonal and interannual changes in the fish community of Oslofjord (Norway) over two consecutive years. Using the MitoFish reference database through the Global Biodiversity Information Facility querying tool, we identified 63 fish species and found significant changes in the dominant taxa between seasons and years. Clupea harengus (Atlantic herring) consistently peaked in early spring, while Scomber scombrus (Atlantic mackerel) dominated winter months in the second year. The MiFish primer set showed increased species richness in the second year, whereas the Elas02 primer set showed stable richness despite compositional turnover. Non-metric multidimensional scaling revealed distinct community separation between years in presence/absence of data, driven by species turnover rather than abundance read changes. Our findings support the use of eDNA metabarcoding to capture fine-scale (bi-monthly) temporal dynamics and emphasise the importance of multi-year datasets for distinguishing ecological trends from stochastic changes. This strategy improves monitoring practices for marine ecosystems under anthropogenic stressors.

• Carvalho, Cintia Oliveira; Gromstad, William Esbjug; Dunthorn, Micah; Karlsen, Hans Erik; Schrøder-Nielsen, Audun & Ready, Jonathan Stuart [Show all 10 contributors for this article] (2024). Harnessing eDNA metabarcoding to investigate fish community composition and its seasonal changes in the Oslo fjord. Scientific Reports. 14(1). doi: 10.1038/s41598-024-60762-8. Full text in Research Archive Show summary

  In the face of global ecosystem changes driven by anthropogenic activities, effective biomonitoring strategies are crucial for mitigating impacts on vulnerable aquatic habitats. Time series analysis underscores a great significance in understanding the dynamic nature of marine ecosystems, especially amidst climate change disrupting established seasonal patterns. Focusing on Norway's Oslo fjord, our research utilises eDNA-based monitoring for temporal analysis of aquatic biodiversity during a one year period, with bi-monthly sampling along a transect. To increase the robustness of the study, a taxonomic assignment comparing BLAST+ and SINTAX approaches was done. Utilising MiFish and Elas02 primer sets, our study detected 63 unique fish species, including several commercially important species. Our findings reveal a substantial increase in read abundance during specific migratory cycles, highlighting the efficacy of eDNA metabarcoding for fish composition characterization. Seasonal dynamics for certain species exhibit clear patterns, emphasising the method's utility in unravelling ecological complexities. eDNA metabarcoding emerges as a cost-effective tool with considerable potential for fish community monitoring for conservation purposes in dynamic marine environments like the Oslo fjord, contributing valuable insights for informed management strategies.

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• Mahlangu, Sibusiso; Ewers, Isabelle; Carvalho, Cintia Oliveira; Schrøder-Nielsen, Audun; Dunthorn, Micah & Karlsen, Hans Erik [Show all 12 contributors for this article] (2025). Investigating the dynamics of the aquatic community in Oslofjord through time series analysis of eDNA. BioRxiv. ISSN 0362-4331. doi: 10.1101/2025.02.05.636659. Full text in Research Archive
• Carvalho, Cintia Oliveira; Gromstad, William Esbjug; Dunthorn, Micah; Karlsen, Hans Erik; Schrøder-Nielsen, Audun & Ready, Jonathan Stuart [Show all 10 contributors for this article] (2024). Unveiling fish community dynamics in the Oslo fjord through eDNA metabarcoding. Full text in Research Archive

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