Anaïs Sire de Vilar1, Maria Rakka2, Rachel Lacoste1, Antonio Godinho1, Gal-la Edery1, Beatriz Gouveia Arzeni1, Marina Carreiro-Silva1,
1University of the Azores, Portugal - 2Dalhousie University, Canada
Dentomuricea aff. meteor and Viminella flagellum are two important bioengineering cold-water octocorals (CWCs) in the Azores that often form mixed coral gardens at 200 to 500 m depth. D. meteor distribution is limited to seamounts close to the North Mid-Atlantic Ridge, while V. flagellum has a wider distribution, spanning the Mediterranean, Macaronesia, and the eastern North Atlantic. As the oceans are warming, it becomes essential to assess the effects of increasing seawater temperature on CWCs, particularly on the poorly studied early life stages that are critical for dispersal and population connectivity. Therefore, this study investigates how ocean warming affects the early life stages of D. meteor and V. flagellum, focusing on spawning time, embryonic development, larval swimming, settlement, polyp formation, and survival. For this purpose, parental colonies and early life stages were exposed to three temperature regimes: 14°C and 16°C, representing the species’ minimum and maximum natural temperature range, respectively, and 19°C, simulating the IPCC RCP8.5 scenario (+3°C above the maximum natural temperature). Developmental stages were monitored over 2–3 months, tracking progress from embryos to larvae and young polyps while assessing malformations and mortality rates. Horizontal and vertical swimming speeds, as well as larval trajectories (upward or downward), were evaluated using time-lapse photography on larvae aged of one, two, and three weeks old. Although data analysis is still ongoing, preliminary results suggest that higher temperature increases mortality and accelerates development, leading to earlier metamorphosis with potential malformations. This is likely due to the acceleration of metabolic processes, especially in D. meteor, which may be more sensitive to increased seawater temperature due to the observed fragility of the parent colonies. Larval swimming speed increased at higher temperatures but gradually decrease over time as larvae approach metamorphosis, with V. flagellum larvae swimming faster and longer, possibly related to the species’ broader geographic distribution. The findings of this study improve our understanding of how ocean warming affects the early life stages of CWCs. This knowledge will help predict impacts on recruitment, connectivity, and population persistence in a changing ocean, in order to guide conservation and restoration strategies for the deep-sea ecosystems of the Azores.
Biography
Anaïs Sire de Vilar is a PhD student at the University of the Azores. Her research focuses on the impacts of climate change and human activities on cold-water corals. She studies their effects both on adults during their reproductive season and on their early life stages, from embryos to larvae to the first polyp.