Research published in Polar Biology and led by a former School of GeoSciences undergraduate has revealed how a key Antarctic phytoplankton species could respond to future ocean warming and changing light conditions – with important implications for climate regulation and Southern Ocean ecosystems. The Southern Ocean plays a critical role in regulating Earth's climate. As a major carbon sink, it absorbs a substantial proportion of the carbon dioxide released by human activities, helping to mitigate global climate change. It also supports rich marine biodiversity, sustaining fisheries and contributing to global food security. At the heart of this system are microscopic algae called diatoms. Diatoms are very important primary producers in the Southern Ocean and are key in regulating climate and supporting biodiversity in the region.These microscopic algae, characterised by their relatively large size and thick shells, form the foundation of marine food webs and drive the “biological carbon pump” – the process by which carbon is exported from the atmosphere to the deep ocean. Water sampling onboard the US research ship RV Laurence M. Gould in Ryder Bay on the West Antarctic Peninsula. Credits: Sian Henley Miscroscope image of Pseudo-nitzschia subcurvata taken during the lab work. Credits: Olivia le Gouvello How does temperature and light interaction affect climate change?As climate change alters the Southern Ocean, rising temperatures and changing light conditions may affect how these organisms grow and contribute to ocean productivity. However, how these environmental changes interact to influence diatom physiology and growth still remains poorly understood. The study focused on an ecologically important Antarctic diatom, Pseudo-nitzschia subcurvata (P. subcurvata) and set out to understand how warmer water and higher light intensities (conditions expected under climate change) interact to modify how P. subcurvata grows and photosynthesises.Understanding how diatoms are responding to climate change is crucial for predicting how Southern Ocean primary productivity, food webs and carbon uptake might change as the climate continues to warm.How the research was doneThe team used controlled laboratory experiments to investigate the individual and combined effects of temperature and light on P. subcurvata.They grew cultures of the diatom in incubators under conditions representative of present-day Southern Ocean temperatures and light levels and projected future conditions with warmer temperatures and higher light intensities. A diatom culture in the incubator. Although individual diatoms are too small to be seen by the naked eye, they become visible as brownish-green deposits when the population increases and the cells accumulate. Credits: Olivia le Gouvello. Olivia working in the lab during her dissertation. Credits: Olivia le Gouvello. Measuring key variables including growth rates, chlorophyll a content and particulate organic carbon content, they were able to assess how the diatoms responded to realistic climate-driven changes in their environment.Key findingsUnder future climate conditions in the Southern Ocean, characterised by warmer temperatures and higher light intensities, P. subcurvata diatoms showed higher productivity than under present-day conditions.The study found that the diatoms were able to increase their productivity by adjusting their photosynthetic physiology. They maintained a high capacity to absorb light, benefiting from the combined effects of warmer temperatures and higher light levels.By showing how temperature and light interact to influence diatom growth and photosynthesis, this work provides a better understanding of how Southern Ocean primary productivity may change as the climate warms. The findings can help improve future projections of ocean productivity, carbon cycling and climate feedbacks, while highlighting the potential for some phytoplankton species to benefit initially from changing conditions.Changes in phytoplankton productivity could have knock-on effects for marine food webs and carbon cycling, even as the wider ocean ecosystem faces increasing environmental pressures. The team suggests that future research should extend this approach to other diatom species and phytoplankton groups. This would help build a more complete picture of how Southern Ocean ecosystems, and the climate processes they support, may respond to ongoing environmental change.Further informationThe study began as a final-year project on the BSc Ecological and Environmental Sciences degree in the School of GeoSciences. Working closely with PhD researcher Ben Fisher and supervisor Dr Sian Henley, Olivia helped to design and carry out the experiments that underpin the paper. Over several months, Olivia and Ben conducted the Schools of GeoSciences and Biological Sciences. Olivia led the work, guiding it from undergraduate project to peer-reviewed article. Related links Read the full paper: Le Gouvello, O., Fisher, B.J. & Henley, S.F. Interactive effects of ocean warming and higher irradiances on the Southern Ocean diatom Pseudo-nitzschia subcurvata. Polar Biol 49, 116 (2026). https://doi.org/10.1007/s00300-026-03542-6 Study with us | Explore our degrees This article was published on Tuesday 27 October 2026
