期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：1
DOI：10.1073/pnas.2114602118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
As they grow, die, and sink into the ocean’s interior, oceanic phytoplankton drive the so-called biological carbon pump, one of the main biological processes regulating atmospheric carbon concentrations. The biological carbon pump is, therefore, key to climate regulation. Its efficiency is largely determined by the coupling of marine biology to ocean geochemistry through the C:N:P:Fe stoichiometry of phytoplankton biomass, yet what determines this stoichiometry remains poorly understood. Based on a model of plankton biology, we characterize control mechanisms of the C:N ratio of phytoplankton biomass in the North Atlantic, which explain extensive sets of apparently conflicting observations. These findings could improve the predictive ability of global ocean models regarding climate change and the role of marine biology in its mitigation/aggravation.
The stoichiometric coupling of carbon to limiting nutrients in marine phytoplankton regulates the magnitude of biological carbon sequestration in the ocean. While clear links between plankton C:N ratios and environmental drivers have been identified, the nature and direction of these links, as well as their underlying physiological and ecological controls, remain uncertain. We show, with a well-constrained mechanistic model of plankton ecophysiology, that while nitrogen availability and temperature emerge as the main drivers of phytoplankton C:N stoichiometry in the North Atlantic, the biological mechanisms involved vary depending on the spatiotemporal scale and region considered. We find that phytoplankton C:N stoichiometry is overall controlled by nitrogen availability below 40° N, predominantly driven by ecoevolutionary shifts in the functional composition of the phytoplankton communities, while phytoplankton stoichiometric plasticity in response to dropping temperatures and increased grazing pressure dominates at higher latitudes. Our findings highlight the potential of “organisms-to-ecosystems” modeling approaches based on mechanistic models of plankton biology accounting for physiology, ecology, and trait evolution to explore and explain complex observational data and ultimately improve the predictions of global ocean models.
