mathielu

• Lutier, Mathieu; Skari, Andrea Emilie Thorstensen; Thomsen, Nele; Reinardy, Helena Christine & Dinh, van Khuong (2025). The Arctic copepod Calanus hyperboreus is more tolerant to marine heatwaves than temperate copepods in the Oslofjord. Royal Society Open Science. 12(10), p. 1–10. doi: 10.1098/rsos.250365. Full text in Research Archive Show summary

  Calanus hyperboreus plays a key role in the functioning of Arctic ecosystems. It is considered highly vulnerable to ocean warming and marine heatwaves, which would reduce its range, expected to shift northward. Yet, C. hyperboreus is reported as far south as the Skagerrak, where it is considered non-native and transported by ocean currents. We argue that this may be an isolated population adapted to warmer temperatures. To test this hypothesis, we exposed C. hyperboreus from the Oslofjord to temperatures from 0°C to 24°C, for 5 days. We recorded survival to identify the upper threshold of thermal tolerance and DNA damage to detect sublethal effects. The thermal response of C. hyperboreus was compared with that of the dominant copepod species in the Oslofjord, Calanus finmarchicus and Metridia longa . We found that the survival of C. hyperboreus did not decrease before reaching 16°C–20°C which was much higher than 13°C–16°C and 4°C–8°C for C. finmarchicus and M. longa , respectively. Calanus hyperboreus showed the least DNA damage, highlighting the adaptation of its physiology to the Oslofjord. Our results suggest the existence of local adaptations to warming in C. hyperboreus that could determine its fate under climate change.

• Caillon, Coline; Pernet, Fabrice; Lutier, Mathieu & Poi, Carole Di (2023). Differential reaction norms to ocean acidification in two oyster species from contrasting habitats. Journal of Experimental Biology. ISSN 0022-0949. 226(23), p. 1–11. doi: 10.1242/jeb.246432. Full text in Research Archive

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• Dijkstra, Jildou; Schott, Schott; Thomsen, Nele; Lutier, Mathieu; Dinh, van Khuong & Reinardy, Helena Christine [Show all 7 contributors for this article] (2023). Influence of ocean warming and acidification on Arctic zooplankton during the polar night. Full text in Research Archive
• Heimböck, Martin Paul; Lutier, Mathieu; Albini, Dania; Borgå, Katrine & Dinh, van Khuong (2023). Egg production as a stress-response in arctic copepod C. glacialis. Full text in Research Archive
• Skari, Andrea Emilie Thorstensen; Dinh, van Khuong; Lutier, Mathieu; Konestabo, Heidi Sjursen & Borgå, Katrine (2024). Effect of global changes on marine copepods: Influence of pyrene or salinity on thermal tipping points. Universitetet i Oslo. Full text in Research Archive Show summary

  The ocean is warming at a rate unprecedented over the past twenty thousand years, and extreme warming events are increasing in frequency, duration, and intensity. This could surpass the thermal tolerance thresholds of marine species, tipping points that, when exceeded, can lead to abrupt and irreversible consequences. At the same time, the intensification of extreme weather events and anthropogenic activities increase the exposure of marine organisms to contaminants such as polycyclic aromatic hydrocarbons (PAHs) and to decreasing salinities. As organisms are simultaneously exposed to multiple stressors in their natural environment, it is therefore crucial to identify the effects these stressors have when combined to project their future in a changing world. The present study investigated how the PAH pyrene or decreasing salinity affect thermal tipping points of coastal marine copepods. Copepods are key planktonic organisms in marine ecosystems due to their essential role in energy transfer in the food web. The first experiment aimed to determine how oil contamination alters thermal tipping points of Aetideopsis sp. copepods. As a proxy for oil, the copepods were exposed to the PAH pyrene, at five concentrations and seven temperatures for ten days. The second experiment aimed to determine how decreasing salinities alters thermal tipping points of Calanus sp. copepods. The copepods were exposed to five decreasing salinities at five temperatures for eight days. Copepods for both experiments were collected in the Oslofjord, Norway, and survival was checked every day during the experiments. Both Aetideopsis sp. and Calanus sp. had thermal tipping points within environmentally relevant temperatures, between 13 °C and 16 °C for Aetideopsis sp. and between 14 °C and 18 °C for Calanus sp. Although pyrene did not affect thermal tipping points of Aetideopsis sp., it significantly decreased survival at the highest concentration of 200 nM. Decreasing salinity decreased the thermal tipping points of Calanus sp. at 23 PSU and 29 PSU, both environmentally relevant salinities. These findings suggest that the thermal niche of coastal marine copepods, already sensitive to pollutants such as pyrene, can be narrowed by decreasing salinities. This could ultimately have severe consequences on the ecological niches and distributions of copepod species and highlights the importance of determining tipping points in a multiple stressor context.

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