A meta-analysis on environmental drivers of marine phytoplankton C : N : P

Abstract

Abstract. The elemental stoichiometry of marine phytoplankton plays a critical role in the global carbon cycle through carbon export. Although extensive laboratory experiments have been carried out over the years to assess the influence of different environmental drivers on the elemental composition of phytoplankton, a comprehensive quantitative assessment of the processes is still lacking. Here, we synthesized the responses of P : C and N : C ratios of marine phytoplankton to five major drivers (phosphate and nitrate, irradiance, temperature, and iron) by meta-analysis of laboratory experimental data available in the literature. Our results show that the response of the ratios to changes in macronutrients is consistent across all the studies, where the nutrient availability is positively related to changes in P : C and N : C ratios. We found that diatoms are more sensitive to the changes in macronutrients compared to other eukaryotes and cyanobacteria, possibly due to their larger cell size and their abilities to quickly regulate their gene expression patterns required for nutrient uptake. The effect of irradiance on P : C was mixed and not significant, but the same effect on N : C was significant and constant across all studies where an increase in irradiance decreased N : C. The response to temperature changes was mixed by species, except warming consistently decreased P : C ratio in cyanobacteria. This may explain why P : C is consistently low in the cyanobacteria-dominated subtropical oceans. The effect of iron on P : C and N : C for cyanobacteria were statistically significant but the small sample size precludes drawing firm conclusions. Overall, our findings highlight the high stoichiometric plasticity of diatoms and the importance of macronutrients in determining P : C and N : C ratios, which both provide us insights on how to understand and model plankton diversity and productivity.

Carbon Export Buffering and CO2 Drawdown by Flexible Phytoplankton C:N:P Under Glacial Conditions

“…The sensitivity factors express the dependence of P:C and N:C on environmental drivers according to Equations 1 and 2 in the main text. They were determined by a recent metaanalysis (Tanioka & Matsumoto, 2019a). The reference values for drivers [PO4], [NO3], and temperature are global annual mean from the top 100 m in the World Ocean Atlas (H. E. Garcia et al, 2013;Locarnini et al, 2013).…”

“…They also studied different strains of algae often under dissimilar conditions. In order to overcome this challenge and in a separate study, we conducted an exhaustive meta-analysis of laboratory studies of marine phytoplankton stoichiometry in order to quantify the sensitivity factors (Tanioka & Matsumoto, 2019a). Meta-analysis is a powerful statistical framework for synthesizing multiple, independent studies and uncovering trends, and it follows rigorous formal protocols to ensure reproducibility and reduce bias (Gurevitch et al, 2018).…”

“…Our meta-analysis analyzed 81 experimental units of P:C and 165 experimental units of N:C encompassing 7 taxonomic phyla (Tanioka & Matsumoto, 2019a), which we translated to the three PFTs represented in our biogeochemistry model for this study (Table 1). In our meta-analysis, we also examined Fe as a possible driver, but there was an insufficient number of experimental units to determine the sensitivity factor for Fe.…”

“…There are a number of reasons why phytoplankton become more C rich under warmer conditions, including increased metabolic stimulation of C fixation. The interested reader is referred to the meta-analysis (Tanioka & Matsumoto, 2019a) for a discussion of the underlying biochemical reasons for the sense and magnitude of .…”

Geologic controls on phytoplankton elemental composition

“…Phanerozoic Global Average Temperature and Surface-Ocean Phosphate Concentration Phytoplankton C:N:Porg ratios are thought to depend mostly on the temperature and/or phosphate concentration of the phytoplankton's growth environment (24,26,27). Below we review the Phanerozoic trajectories of these variables in response to tectonic and evolutionary forcings, as predicted by a model for the long-term cycles of phosphate, carbon, O2, and calcium, which is fully described and discussed elsewhere (29).…”