Our group has recently published two papers on a new global dataset of surface POM stoichiometry: (1) an analysis paper on the regulation of C:N:P variability and (2) a dataset paper documenting all the samples collected. 

The new dataset contains 2673 paired surface POC/N/P measurements from 70°S to 73°N across all major ocean basins at high spatial resolution from Bio-GO-SHIP and Arctic cruises. It also includes 965 measurements of oxygen demand for organic carbon respiration.

Altogether, our data suggest systematic regulation of elemental stoichiometry among ocean ecosystems via temperature and nutrients. This new dataset can help validate and calibrate the next generation of global ocean biogeochemical models with flexible elemental stoichiometry. We expect that incorporating variable C:N:P:-O2 into models will help improve our estimates of critical ocean biogeochemical fluxes such as carbon export, nitrogen fixation, and organic matter remineralization.

Variable elemental stoichiometry is essential for ocean biogeochemistry. Led by Alli Moreno (former Ph.D. student, now at UCLA), we showed that the carbon-to-oxygen ratio varies systematically between ocean biomes in the Atlantic Ocean. This spatial variability can cause a +20% higher oxygen demand for the same Carbon flux, which has important implications for future climate change and ocean deoxygenation.

This study shows a clear latitudinal gradient in the carbon-to-oxygen ratio, with higher ratios in the warm, low-nutrient biomes but lower beyond the subtropical fronts.

The study emphasizes the value of integrating ‘omics measurements with biogeochemistry. ‘omics can provide a wealth of information about plankton biodiversity and physiology. Here, ‘omics allowed us to determine if plankton were N vs. P stressed.

Beyond the latitudinal gradient, we observed a much higher carbon-to-oxygen ratio in N compared to P-limited regions. We speculate that phytoplankton somehow accumulates more lipids when N is stressed.

Allison Moreno, Alyse Larkin,  Jenna Lee, Skylar Gerace from UCI, and Glen Tarran did a fabulous job collecting the samples on AMT28, plus all the work analyzing the samples.

Here is the link to the artcie. 

I will be teaching a class (BIO E134) about ‘Microbiomes’ this fall. Most of the material will be related to human microbiomes but there will also be a lot of general microbiology and microbial ecology. Sign up if you are interested…

Adam

Figure: Fine-scale global variation of surface phosphate. Surface phosphate is here measured using high-sensitivity techniques revealed a previously unrecognized low latitude differences in phosphate drawdown.

Surface ocean phosphate is commonly below the analytical detection limit using the standard auto-analyzer technique. Thus, we know little about the geographic variation in phosphate across most low latitude regions. As the result of a global collaboration, a recent study in Science Advances combined phosphate measurements using high-sensitivity methods and produced a detailed map of surface phosphate (see figure). This revealed several previously unrecognized low phosphate areas. For example, we detect large regions of really low phosphate in the western North and to a lesser extent South Pacific Ocean. Atmospheric iron input and nitrogen fixation are commonly described as regulators of surface phosphate but we show that shifts in the elemental stoichiometry of the vertical nutrient supply play an additional role. Multiple past studies as well as climate models have suggested that the availability of phosphate is a first-order driver of ocean biogeochemical changes. However, we find that marine ecosystems are more resilient to phosphate stress than previously thought. Our study demonstrates the importance of accurately quantifying nutrients at low concentrations for understanding the regulation of ocean ecosystem processes and biogeochemistry now and under future climate conditions.