Assessing the impact of CO 2 -equilibrated ocean alkalinity enhancement on microbial metabolic rates in an oligotrophic system

作者：Laura Marín-Samper, Javier Arı́stegui, Nauzet Hernández‐Hernández, Joaquín Ortiz, Stephen D. Archer, Andrea Ludwig, Ulf Riebesell · 发表于：Biogeosciences · 年份：2024 · DOI：10.5194/bg-21-2859-2024 · 被引用次数：20 · 研究领域：Ocean Acidification Effects and Responses、Marine and coastal ecosystems、Marine Biology and Ecology Research

Abstract. Ocean alkalinity enhancement (OAE) is a negative emissions technology (NET) that shows significant potential for climate change mitigation. By increasing the bicarbonate ion concentration in ocean water, OAE could enhance long-term carbon storage and mitigate ocean acidification. However, the side effects and/or potential co-benefits of OAE on natural planktonic communities remain poorly understood. To address this knowledge gap, a mesocosm experiment was conducted in the oligotrophic waters of Gran Canaria. A CO2-equilibrated total alkalinity (TA) gradient was employed in increments of 300 µmol L−1, ranging from ∼ 2400 to ∼ 4800 µmol L−1. This study represents the first attempt to evaluate the potential impacts of OAE on planktonic communities under natural conditions. The results show that net community production (NCP), gross production (GP), community respiration (CR) rates, and the metabolic balance (GP:CR) did not exhibit a linear response to the whole alkalinity gradient. Instead, significant polynomial and linear regression models were observed for all rates up to ΔTA 1800 µmol L−1, in relation to the dissolved inorganic carbon (DIC) concentrations. Notably, the ΔTA 1500 and 1800 µmol L−1 treatments showed peaks in NCP shifting from a heterotrophic to an autotrophic state, with NCP values of 4 and 8 µmol O2 kg−1 d−1, respectively. These peaks and the optimum curve were also reflected in the nanoplankton abundance, size-fractionated chlorophyll a, and 14C upt...