The R/V Planet is unlike any ship that I have ever seen. The ship is owned by FWG (WTD 71), a German naval research organization. While at first glance it appears to be a type of catamaran, it is actually a SWATH (Small Waterplane Area Twin Hull) vessel. The main difference between the two is in the volume of the ship that comes in contact with wave energy. Both ships are stabilized by twin hulls, but a catamaran has two conventional hulls, while a SWATH ship’s design is more like a platform built on top of two submarines. Because of this, only the parts of the ship that connect the platform to the submarines will be affected by wave energy. This makes the R/V Planet very stable in rough seas, which is beneficial for acoustic research work. Additional measures, such as suspending the ship’s diesel generators on springs, have been taken to minimize ship noise that may contaminate acoustic measurements.

This was the R/V Planet’s first trip across the Atlantic Ocean to collaborate with American scientists. The goal of our expedition was to better understand how mines bury in carbonate sediments and to classify the seafloor off the coast of Cape Canaveral, Florida, where carbonate sediments are known to be abundant. Additionally, we were able to collect information to expand dbSeabed, a database managed by Dr. Chris Jenkins (University of Colorado at Boulder) that provides geographic seafloor substrate data by compiling thousands of individual datasets.

We collected our data primarily using 3 instruments: 1. sidescan sonar, 2. a van Veen grab, and 3. a Burial Recording Mine produced by FWG. An underwater camera was also deployed as an additional means of ground truthing. The sidescan sonar provided images of the seafloor by transmitting a fan-shaped sound beam and interpreting the acoustic backscatter, or echoes, returned to the receiver. The sidescan data allowed us to categorize the seafloor by it’s acoustic profile. Grab samples were collected periodically along short transects to determine the relationship between actual seafloor properties and the acoustic backscatter data collected by the sidescan. For example, we observed higher backscatter in regions with courser grains and lower backscatter in regions with finer grains. We also deployed a Mine Burial Recorded (MBR), a tool developed by FWG to test seafloor mine burial. The MBR uses the case of an old mine that has three rings of light sensors attached. As the mine buries, the light sensors become covered and it is possible to tell how deeply the mine penetrated the seafloor.

What an experience!

Deploying the sidescan sonar from the R/V Planet.

The Mine Burial Recorder (MBR) developed by FWG – Kiel.

Just by looking at the cores and feeling the mud we can identify boundary and redox layers as well as differences in grain size. But to find out more, we take samples of these cores for future analysis.

If you like getting muddy, then you’ll love sediment work! To sub-sample these cores we remove a tube filled with sediment from the MUC and place it on a stand. Once the core is on the stand we can move it down centimeter-by-centimeter revealing 1 cm of sediment at a time and scraping it off. For the first few really wet centimeters we put the sub-samples in a glass jar. After that we fill syringes with sediment every few centimeters until we get to the end of the core. Since we’re dealing with mud, and not water, we have to cut the tip off the syringe and then push it into the sediment core to get our sub-sample. Once we’ve taken these sub-samples we can look at things like nitrogen isotopes, sediment grain size, and multiple other parameters. Ultimately, this information from the sediment helps us reveal a little bit more about what’s happening in the ocean above, both today and in the past.

An empty MUC on the ship before deployment

The MUC coming up!

Cores filled with sediment

Tip-less syringe to be filled with sediment

Putting the core on to the core stand

Sampling the first few muddy centimeters

Sampling with the tip-less syringe

The research work being conducted is, in general, geoscience. What does this mean to student scientists onboard? More often than not it means getting muddy. Inevitably on a geoscience cruise, some amount of mud will be brought up from the seafloor and processed. The fate of the mud varies and depends on who wants it and for what, which often determines how it was retrieved from seafloor. Processing onboard can involve splitting, cutting, sub-sampling mud/porewater, logging, and always labeling. You can see Liz sub-sampling a multi-corer tube in 1 cm slices and using a modified syringe in the pictures below.

Every now and then, crafty professors manage to escape the daily grind at the office and actually make it out on one of their cruises. Markus gets points for craftiness here: not only has he managed to make it out on a cruise, he’s selected a tropical location and is keeping his hands clean… or at least mud-free! You can see Markus sampling seawater from niskin bottles in a CTD rosette in the pictures below. He is hoping water column profiles of nutrient concentrations and the isotopic composition of nitrate will help explain water mass distributions in the study area, and aid in ground-truthing the interpretation of paleoceanographic proxy records.

This cruise (SO-228) combines three cruise proposals for research in the Western Pacific. Read more about the proposed research and cruise plans on the MARUM Bremen University website.