PUPCYCLE II Day 6 – The Nitrogen Team

Friday, June 02, 2023 – North Pacific Ocean (Latitude: 42.50.802 N, Longitude: 124.40.196W)

You Are What You Eat –
Figure 18 – Double and triple filtering stages are used to assist Raquel Flynn (UCT) and the Nitrogen Team in capturing 3 different sizes of plankton.

Raquel Flynn (University of Cape Town, South Africa), Yeongsun Ryu (Princeton), and Julie Granger (University of Connecticut) are researching one of the key components of the biogeochemical cycle (Figure 12, Day 4): Nitrogen. Their research will also measure how the phytoplankton are using Nitrogen during an upwelling cycle. (Figure 4, Day 2) The Nitrogen Team is investigating the nitrogen uptake of various sizes of phytoplankton: 0.4 – 5um (Cyanobacteria and other <5um microbes), 5 – 10um (Single-celled Diatoms), and larger than 10um (Chains of Diatoms such as Chaetoceros, Figure 19). “The filtration system we are using is designed to separate the three sizes before we prepare them for further analysis in the lab,” explained Julie Granger. “A Flow cytometer will sort and count the different microbes and a Mass Spectrometer will identify which form of nitrogen the different microbes are using: Nitrates (NO3–) or Ammonia (NH4+).”

Figure 19 – Larger Diatoms, such as Chaetoceros, form long chains. Image Source: Kudela Lab: Ocean Data Center. Phytoplankton Identification: Diatoms and Dinoflagellates. CeNCOOS and HABMAP. University of California – Santa Cruz. http://oceandatacenter.ucsc.edu/PhytoGallery/dinos vs diatoms.html.
Figure 20 – Nitrogen (N2) comprises over 70% of the air we breathe but marine microbes need the nitrogen to be converted (or fixed) into a different form of nitrogen to be taken up by organisms living in the ocean.
Figure 21 – The Nitrogen Team is comprised of: (Left-Right: Yeongjun Ryu (Princeton), Raquel Flynn (UCT), and Julie Granger (UCONN)