Achieving global climate goals and securing future food supplies poses significant challenges, especially if efforts are limited to land-based solutions. Given that the ocean covers over 70% of the Earth’s surface and plays a critical role in CO2 sequestration, exploring ocean-based climate mitigation strategies will be essential. One promising approach is Ocean Alkalinity Enhancement (OAE), a form of marine geoengineering aimed at accelerating the ocean’s natural carbon sink, reducing atmospheric CO2 levels, and mitigating ocean acidification. However, the implications of OAE for global fisheries, which are vital for food security and livelihoods worldwide, remain underexplored. This study develops and analyzes future scenarios for global fisheries under different socioeconomic and climate trajectories, utilizing the Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs) framework. Specifically, we focus on three combined pathways: SSP1-2.6, SSP3-7.0, and SSP5-8.5, to explore the potential impacts of OAE implementation. Through an integrated narrative approach, we (semi-)quantify changes in key bio-economic parameters such as technological progress, fishing costs, fisheries management, marine aquaculture, and carrying capacity, providing an explorative assessment of how OAE could influence these under varying global conditions. With this approach, we contribute to the development of sector-specific and long-term interdisciplinary models that are crucial for future policy and management strategies aimed at climate change mitigation and the sustainable use of marine ecosystems. Our framework aligns with global scenarios that are being applied internationally.

Now published: Spilling K, Heinemann M, Vanharanta M, et al. (2023) Respiration rate scales inversely with sinking speed of settling marine aggregates. PLoS ONE 18(3): e0282294. https://doi.org/10.1371/journal.pone.0282294 Sinking marine particles have been studied for a long time to understand its role in carbon sequestration. Traditionally, sinking speed and respiration rates have been treated as independent variables, but two recent papers suggest a connection albeit in contrasting directions. Alcolombri et al. [2021] demonstrated that slow moving particles are respired faster than motionless particles, whereas García‐Martín et al. [2021] found that respiration rate was higher for suspended particles compared with slow- and fast-sinking particles. Here we collected settling aggregates and determined respiration rates of particles sinking at different velocities. The average respiration rate of fast sinking particles (>100 m d-1) was 0.12 d-1. Slower sinking particles (<50 m d-1) had on average higher and more variable respiration rates. These findings provide insights into the efficiency of the biological carbon pump and help resolve the apparent discrepancy in the recent studies of the correlation between respiration and sinking speed. Alcolombri, U., F. J. Peaudecerf, V. I. Fernandez, L. Behrendt, K. S. Lee, and R. Stocker (2021), Sinking enhances the degradation of organic particles by marine bacteria, Nat Geosci, 1-6. García‐Martín, E. E., K. Davidson, C. Davis, C. Mahaffey, S. Mcneill, D. Purdie, and C. Robinson (2021), Low contribution of the fast‐sinking particle fraction to total plankton metabolism in a temperate shelf sea, Glob Biogeochem Cycles, 35(9), e2021GB007015.