Abstract. Polar oceans are particularly susceptible to ocean acidification and warming. Diatoms play a significant role in sea ice biogeochemistry and provide an important food source to grazers in ice-covered oceans, especially during early spring. However, the ecophysiology of ice-living organisms has received little attention in terms of ocean acidification. In this study, the synergism between temperature and partial pressure of CO 2 (pCO 2 ) was investigated in relationship to the optimal growth temperature of the Antarctic sea ice diatom Nitzschia lecointei. Diatoms were kept in cultures at controlled levels of pCO 2 (∼ 390 and ∼ 960 µatm) and temperature (−1.8 and 2.5 • C) for 14 days. Synergism between temperature and pCO 2 was detected in growth rate and acyl lipid fatty acid (FA) content. Optimal growth rate was observed around 5 • C in a separate experiment. Carbon enrichment only promoted (6 %) growth rate closer to the optimal growth, but not at the control temperature (−1.8 • C). At −1.8 • C and at ∼ 960 µatm pCO 2 , the total FA content was reduced relative to the ∼ 390 µatm treatment, although no difference between pCO 2 treatments was observed at 2.5 • C. A large proportion (97 %) of the total FAs comprised on average of polyunsaturated fatty acids (PUFA) at −1.8 • C. Cellular PUFA content was reduced at ∼ 960 relative to ∼ 390 µatm pCO 2 . Effects of carbon enrichment may be different depending on ocean warming scenario or season, e.g. reduced cellular FA content in response to elevated CO 2 at low temperatures only, reflected as reduced food quality for higher trophic levels. Synergy between warming and acidification may be particularly important in polar areas since a narrow thermal window generally limits cold-water organisms.

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Polar oceans are particularly susceptible to ocean acidification and warming. Diatoms play a significant role in sea ice biogeochemistry and provide an important food source to grazers in ice-covered oceans, especially during early spring. However, the ecophysiology of ice living organisms has received little attention in terms of ocean acidification. In this study, the synergism between temperature and partial pressure of CO₂ (pCO₂) was investigated in relationship to the optimal growth temperature of the Antarctic sea ice diatom Nitzschia lecointei. Diatoms were kept in cultures at controlled levels of pCO₂ (∼390 and ∼960 μatm}) and temperature (−1.8 and 2.5 °C) for 14 days. Synergism between temperature and pCO₂ was detected in growth rate and acyl lipid fatty acid content. Carbon enrichment only promoted (3%) growth rate closer to the optimal growth, but not at the control temperature (−1.8 °C). Optimal growth rate was observed around 5 °C in a separate experiment. Polyunsaturated fatty acids (PUFA) comprised up to 98% of the total acyl lipid fatty acid pool at −1.8 °C. However, the total content of fatty acids was reduced by 39% at elevated pCO₂, but only at the control temperature. PUFAs were reduced by 30% at high pCO₂. Effects of carbon enrichment may be different depending on ocean warming scenario or season, e.g. reduced food quality for higher trophic levels during spring. Synergy between temperature and pCO₂ may be particularly important in polar areas since a narrow thermal window generally limits cold-water organisms

BACKGROUND Previous studies have shown that rapid treatment for stroke, especially ischemic stroke, reduces mortality and disability. The focus has mainly been on reducing time from arrival at hospital to start of treatment. However, the main reason for delay is often time from symptom onset to arrival at hospital. This study therefore aimed to explore decision‐making processes after the onset of stroke symptoms in patients experiencing a first‐time stroke. METHODS We included 36 patients aged 18 and older, all of whom were hospitalized with a first‐time stroke between October 2018 and April 2020. All patients were interviewed once within 4 weeks of symptom onset and before hospital discharge. Eligible patients were identified retrospectively through a targeted review of medical records. The data were collected and analyzed according to the grounded theory methodology. RESULTS In total, 43 potential patients were identified and asked to participate. Overall, 36 patients were included in the study: 17 women (median age 77.0 years, interquartile range 17.5) and 19 men (median age 65.7 years, interquartile range 17.2). All interviewees felt fear, and this affected their decision to seek emergency care. The decision‐making processes were described by the core category of “Acting on fear.” The reason for feeling frightened determined the actions taken. The reasons were sorted into 3 main categories: (1) “seeking care”–recognized stroke symptoms and acted immediately; (2) “pending and reluctance”–suspected stroke but awaited to seek care; and (3) “seeking an explanation”–confused by symptoms. CONCLUSION We found that decision‐making when experiencing stroke symptoms was complex. All patients felt fear, which determined their actions. Some patients knew about stroke symptoms and acted immediately. Others suspected stroke but still chose to wait, whereas others were confused and tried to find answers. These results could contribute to form future awareness campaigns.