Science in the deep sea

developed by school children and executed by scientists during a cruise

The purpose of a scientific experiment is to find answers for specific questions. Often an experiment lasts long, is very complicated and expensive. We present you in detail some of the experiments we conducted during previous expeditions and new experiments conducted during this SOI cruise in 2023.

Yeast Sees the Deep Sea (from a previous cruise)
Background: We know yeast because we use it to bake bread, to brew beer and to make wine and all this for already a few thousand years. However, that yeasts are living organisms was firstly described by Louis Pasteur (1822-1895) in his book “Études sur la bière“ (Studies about the beer). Yeasts are unicellular fungi, which grow to a size of 10 micrometer (a tenth part of a millimeter). Yeasts are heterotrophic that means they eat organic material (sugar, protein, fat) which is produced by other creatures. They use oxygen to break down sugar into water and carbon dioxide and they utilize the released energy for their metabolism. If there is no oxygen around, yeasts can live at least for some time and with less cell division. Then, the yeasts turn the sugar into the less energy rich ethyl alcohol (instead of water) and carbon dioxide. This is called fermentation. We utilize the carbon dioxide for example to let bread dough rise or to aerate beverage. The yeast itself provides us with vitamin B. Yeast extracts are used as flavor enhancer in food. In biotechnology sterile yeast extracts are used as culture media for other types of fungi or bacteria. Yeasts either reproduces by budding and cell division (asexual) or they produce spores (sexual).

Hypothesis: We hypothesized that yeast will survive in the deep sea, at least for some hours.

Material and Methods: We put bread dough containing living yeast into a container and mounted it outside of the submersible. The dive lasted 8 hours, the yeast was in a depth of 2500 meters for 5 hours. After the dive the ship’s cook made bread out the dough to see whether bread can be made of this dough indicating the yeast was surviving the pressure and cold conditions in the deep sea.

Yeast dough in open white container put into a blue plastic net and mounted to the outside of Alvin. After the dive we saw that the dough has increased in size a lot. Photographs: Bright lab.

Results: The cook took the dough that we recovered and immediately added flour to make bread. All of us tasted it and we found that it is not as airy and fluffily and as normal bread but it tasted like bread.

The ship’s cook made bread out the dough. Photographs: Bright lab

Conclusion: Yeast does not die because of the high pressure or darkness or low temperatures. At least not within 5 hours. Furthermore, the salty seawater does not harm the yeast.

We learned that plastic bags are not suitable as wrapping in the deep-sea, because they break. Moreover, the dough rose during the journey to the deep. Probably even several times and this is always bad for dough as the cook told us. The dough was relatively small when we took it out of the fridge. The outside temperature was already 25°C in the early morning. The water temperature at the surface was 28°C. This temperature continually decreases with increasing depth, but the yeast had enough time to become active when the bag was fixed to Alvin, during the descent and ascent of the submersible and during the recovery at the end of the dive.

The Styrofoam Experiment (from a previous cruise)

Background: Styrofoam is a synthetic material, brought onto the market by the German company BASF as early as 1951. The base materials are small pearls of Polystyrol, which is obtained from crude oil in a very complicated procedure. The pearls gets foamed with the aid of foaming agent and heat and gets turned into small pellets. These pellets can be forced out into almost any shape with heat and pressure. The complete Styrofoam comprises 98% air. It is very suitable as packing and insulation material. many items of daily life are made out of Styrofoam. For example, decorations and party cups.

Hypothesis: We hypothesized that Styrofoam cups change under pressure.

Material and Methods: To find out what happens with Styrofoam cups under pressure we took some of these cups with us into the depth. To keep their shapes, we stuff them tightly with paper towels. The submersible pilot fixed one of the cups on Alvin’s basket and aimed one camera at it, before the dive.

Results and Conclusion: The Styrofoam cups got considerably smaller under high pressure. This happened because the air got compressed when under pressure during the descent of the submersible. Note that liquids and solids do not get compressed with pressure, while gases react differently.

1. Cups after the after dive. 2. Comparison after and before dive. Photographs: Bright lab.