Ocean alkalinity enhancement (OAE) does not cause cellular stress in a phytoplankton community of the subtropical Atlantic Ocean

作者：Librada Ramírez, Leonardo J. Pozzo-Pirotta, Aja Trebec, Víctor Manzanares-Vázquez, José-Luis Díez, Javier Arı́stegui, Ulf Riebesell, Stephen D. Archer, Marı́a Segovia · 发表于：Biogeosciences · 年份：2025 · DOI：10.5194/bg-22-1865-2025 · 被引用次数：11 · 研究领域：Ocean Acidification Effects and Responses、Marine and coastal ecosystems、Marine Biology and Ecology Research

Abstract. A natural plankton community from oligotrophic subtropical waters of the Atlantic near Gran Canaria, Spain, was subjected to varying degrees of ocean alkalinity enhancement (OAE) to assess the potential physiological effects in the context of the application of ocean carbon dioxide removal (CDR) techniques. We employed nine mesocosms with sediment traps attached to the bottom, each enclosing a volume of 8.3 m3, to create a gradient in total alkalinity (TA). OAE was based on the addition of carbonates (NaHCO3 and Na2CO3). The lowest point on this gradient was 2400 µmol L−1, which corresponded to the natural alkalinity of the environment, and the highest point was 4800 µmol L−1. Over the course of the 33 d experiment, the plankton community exhibited two distinct phases. In phase I (days 5–20), a notable decline in the photosynthetic efficiency (Fv/Fm) was observed. This change was accompanied by substantial reductions in the abundances of picoeukaryotes, small-size nanoeukaryotes (nanoeukaryotes-1), and microplankton. The cell viability of picoeukaryotes, as indicated by fluorescein diacetate hydrolysis by cellular esterases (FDA green fluorescence), slightly increased by the end of phase I, whilst the viability of nanoeukaryotes-1 and Synechococcus spp. did not change. Reactive oxygen species levels (ROS green fluorescence) showed no significant changes for any of the functional groups. In contrast, in phase II (days 21–33), a pronounced community response was obser...