Global patterns and predictors of C:N:P in marine ecosystems

Abstract

Oceanic nutrient cycles are coupled, yet carbon-nitrogen-phosphorus (C:N:P) stoichiometry in marine ecosystems is variable through space and time, with no clear consensus on the controls on variability. Here, we analyze hydrographic, plankton genomic diversity, and particulate organic matter data from 1970 stations sampled during a global ocean observation program (Bio-GO-SHIP) to investigate the biogeography of surface ocean particulate organic matter stoichiometry. We find latitudinal variability in C:N:P stoichiometry, with surface temperature and macronutrient availability as strong predictors of stoichiometry at high latitudes. Genomic observations indicated community nutrient stress and suggested that nutrient supply rate and nitrogen-versus-phosphorus stress are predictive of hemispheric and regional variations in stoichiometry. Our data-derived statistical model suggests that C:P and N:P ratios will increase at high latitudes in the future, however, changes at low latitudes are uncertain. Our findings suggest systematic regulation of elemental stoichiometry among ocean ecosystems, but that future changes remain highly uncertain.

Nutrient uptake plasticity in phytoplankton sustains future ocean net primary production

“…A previous study ( 46 ) also argued that some phytoplankton, especially N 2 -fixing microbes, can acquire P by vertically migrating to P-replete subsurface waters. These physiological processes, as well as the interactive temperature and nutrient-supply control of phytoplankton C:P, may evolve in ways that are not necessarily consistent with the assumed contemporary relationship between surface PO 4 concentrations and phytoplankton C:P uptake, likely generating additional uncertainty ( 10 , 12 , 16 ) beyond those discussed here. Additional sources of uncertainty include an assumption of the C:P responses that are equally applied to all phytoplankton functional types and an assumption of a fixed phytoplankton C:N, all of which could lead to an uncertainty in relative contributions of each phytoplankton function type to the simulated NPP responses.…”

“…This plasticity of elemental allocations from molecules to communities is one of the key features that allows phytoplankton assemblages to acclimate and adapt to a wide range of environmental conditions ( 13 – 15 ). This stoichiometric plasticity adds considerable uncertainty to projections of marine net primary production (NPP) and the global carbon cycle, which depend, in part, on how phytoplankton C:N:P composition may respond to climate change ( 16 ) and how the stoichiometric modulation of NPP may feed back on rising atmospheric carbon dioxide (CO 2 ) ( 17 , 18 ).…”

Biodiversity and Stoichiometric Plasticity Increase Pico‐Phytoplankton Contributions to Marine Net Primary Productivity and the Biological Pump

“…These cellular nutrient quotas are invariant for fixed stoichiometry models (i.e., at Redfield proportions; Aumont et al., 2015; Dunne et al., 2010; Ilyina et al., 2013; Moore et al., 2004) or can be variable, dependent on in situ environmental parameters such as nutrient concentration (Galbraith & Martiny, 2015) or optimal resource allocation theory describing phytoplankton cellular functions (Dunne, 2013; Klausmeier et al., 2004; Kwiatkowski et al., 2018). Many culture and field observations have documented variability in cellular nutrient quotas that vary both with ambient nutrient concentrations (Karl et al., 2001; Rhee, 1978; Tanioka et al., 2022) and/or across PFTs (Baer et al., 2017; Geider & La Roche, 2002; Martiny et al., 2013a; Quigg et al., 2003). Additionally, with the emergence of flow cytometry for the study of marine microbes (Lomas et al., 2011), a large literature of field and culture‐based studies have accumulated in recent decades describing the physiology, biogeography, and phylogeny of marine pico‐phytoplankton, more specifically the cyanobacterial lineages Prochlorococcus and Synechococcus and pico‐eukaryotic phytoplankton, which now allows for their representation in numerical marine ecosystem models (e.g., Baer et al., 2017; Buitenhuis et al., 2012; DuRand et al., 2001; Flombaum et al., 2013, 2020; Martiny et al., 2009; Moore et al., 1998; Partensky et al., 1999; Pasulka et al., 2013; Sohm et al., 2016).…”

Intraspecific trait variation modulates the temperature effect on elemental quotas and stoichiometry in marineSynechococcus

“…The Redfield ratio describes the ocean C:N:P stoichiometry and is used in models to assess export and productivity [5,6]. However, elemental ratios are variable in surface ecosystem [7,8], and ratios in the interior ocean may change over long-time scales, thereby influencing the ability of the oceans to sequester carbon relative to other nutrient elements [9]. Small cyanobacteria are currently estimated to account for approximately 25% of marine net primary production [10].…”