Once that biomass was rinsed off, the real work was just beginning! Thanks to an army of volunteers and a core team of committed lab members, that biomass was sorted into living rhizomes, living roots, and dead biomass, which we then dried, weighed, and ground up to analyze its C and N content.

Then we took those sediment samples, held in PVC half-pipes and plastic wrap, and saw them down the middle. One half of the sample we dried and ground up to analyze the sediment itself, but the other half we rinsed the sediment away on a sieve, leaving just the belowground biomass.

Watch Stephanie Tsui (Ph.D. candidate in the Bowen Lab @bowenlab.bsky.social ) and me carefully remove the sediment from the surface down to 30 cm from a marsh organ pipe in South Carolina. The different pipe elevations represent different marsh elevation/sea-level rise scenarios. It's muddy work!

These are our experimental plots in summer 2024, in SC and MA respectively. Some have been given ammonium, some nitrate, and others are controls. Can you see the plants' response to treatment?

Then every 45 minutes we pump back up ("pull") a sample of porewater into an airtight tube to be analyzed back at the lab to find out how much of that 15N-nitrate, as well as the nitrate already present, has been converted into N2 gas. Lots of work (with intervals of waiting) in a beautiful place!

and the water and added nitrate is mixed using this fun magnet trick, all without mixing the porewater with the atmosphere, which would affect its dissolved gas content. Then that mixture is then pumped ("pushed") back underground to incubate over the course of high tide.

We insert one of these metal tubes below the marsh surface and use them to pump porewater (the water down among the roots and sediment beneath the marsh surface) up into one of these graduated cylinders. 15N-isotopically-labelled nitrate is added to the porewater in the cylinder,