Written by Clara Winguth, Master’s student at GEOMAR.
If you’ve caught a glimpse of the biological oceanography scientists on SO307, you may have noticed us rocking some fashionable polar jumpsuits, disappearing into the red-lit climate labs and thought to yourself, ‘what is going on here?’ Well, lucky for you, I’m here to give you the scoop.
The biological oceanography group, working under Prof. Dr. Anja Engel, currently has not one but two experiments running on board studying particulate organic matter (POM) degradation in the deep sea, analyzing the responsible bacterial communities, and comparing current conditions to a warmed +4 degrees scenario in the context of climate change.
The RV SONNE is equipped with two climate labs – one is set at the ambient deep-sea temperature of 2.5°C (a.k.a. very cold), while the other climate lab is set to 6.5°C (a.k.a. still cold but noticeably less cold). In addition to reproducing deep-sea conditions through temperature, we have all bulls-eye windows tightly shut and dimmed, red string lights hung up in the labs, since there is no light penetration at our sea depth of interest.
Now, let’s start at the beginning. As soon as we got to our first station, water was sampled from the deep sea using a CTD (conductivity, temperature, and depth) rosette, an instrument equipped with Niskin bottles filled with water samples at chosen depths.

Liters upon liters of water from 2000m was taken to the climate labs and filtered into a larger tank using a 3µm filter. We are using this filter size to keep in bacteria but filter out most other living things that may disturb the experiment — such as zooplankton. This filtration process filters out most preexisting POM, which is added back into the experiment as a treatment through ultrafiltered seawater mixed with alginic acid (a thickener) to create artificial marine gels.
The two experiments are distinguished by their container size – one POM experiment is in 1L bottles were as the other is in 20L containers. The second experiment has larger volume for analyzing the bacterial community through omics such as metagenomics and metatranscriptomics, which is spearheaded by our postdoc Benjamin Pontillier. Both experiments focus on parameters such as TEP and CSP, enzyme activity, and bacterial activity among others. TEP (Transparent Exopolymer Particles) and CSP (Coomassie Stainable Particles) are two types of transparent, organic-containing marine gel particles. TEP consists of carbohydrates and CSP of proteins (Cisternas-Novoa et al., 2015). The marine gels are dyed shades of gorgeous blue, ‘Alcian Blue’ for TEP and ‘Coomassie Brilliant Blue’ for CSP, and are filtered out of seawater. We conduct both microscopic and colorimetric filtrations of TEP and CSP, allowing for multiple measures of POM in this experiment.

After a few days we finally had a whopping 960L of seawater hauled from 2000m depth and filtered for the experiments. We then filled all containers with respective treatments and allowed them to adjust to proper conditions. Our first sampling timepoint was taken a couple days later. Since then, we have been sampling at least every two days in addition to gathering Indian Ocean water profiles.

Needless to say, these experiments would not be possible without an extremely dedicated team, in our case consisting of Ben, our technicians Ruth and Tania, PhD candidate Josi, and Masters’ students Nathalie, Denise, and myself. As we begin to wrap up the experiments, we are excited to see what happens to the artificial gels and gain more insight into the bacterial activity in both current and future conditions!
Cisternas-Novoa, C., Lee, C., & Engel, A. (2015). Transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP): Differences between their origin and vertical distributions in the ocean. Marine Chemistry, 175, 56-71. https://doi.org/10.1016/j.marchem.2015.03.009