It’s not always serious science around here. Sometimes we have fun with facts! Lately we’ve been shrinking spheres and creating cute cups.
Before leaving land, we had students from schools in the U.S. and Germany decorate polystyrene cups – you know, the type you might use for hot chocolate. People on the ship also had fun decorating cups and I decorated a sphere (see photo below). We put crumpled paper into the cups to keep them from nesting together and help them stay open. All the cups went into a net bag and were strapped securely to the tow line above the dredge. They were submerged in the ocean about 1000 meters deep for several hours. When we got our artwork back it was much smaller!
The cups are made of beads of a type of plastic called polystyrene that are puffed up with air and stuck together to make well-insulated and light-weight containers. Water is heavy, about 8 1/3 pounds per gallon, and placing objects under water increases the pressure on them. The pressure of air at sea level is 14.7 pounds per square inch (1 atmosphere), but we don’t notice it because it matches the pressure inside our bodies. As you go under water, pressure increases by 1 atmosphere for every 10 meters of water depth. Scuba divers rarely go more than 30 meters deep because any more pressure than that can damage their bodies. When we lower the cups 1000 meters below sea level, we add 100 atmospheres of pressure, about 1470 pounds per square inch, and the air is squeezed out of each little polystyrene bead shrinking the cups and spheres.
Surprisingly, pressure pushes the same amount in all directions and is dependent on depth, not volume. If you dive 3 meters deep in a swimming pool, you’re under more pressure than if you dive 2 meters deep in the ocean! Even though the pressure is the same on all sides of the beads in the cup, sometimes the cups come back misshapen. That’s because the beads are not uniform – they’re slightly different sizes, so shrink at different rates. It’s fun to see a bag bulging with full-size cups disappear into the ocean and return with miniatures. The cups are so cute with their tiny decorations!
Wait a minute! What about the animals living down there? According to Kim Martini at Deep Sea News, Whales and seals have collapsible lungs, along with other adaptations, to deal with the extreme pressure. Penguins basically shut down all organs except their heart and brain during deep dives. Fish have air bladders that can expand or compress with depth. But even fish can’t survive deeper than 8200 meters because the pressure literally crushes the proteins they need to function. Other creatures like amphipods, jellyfish and sea cucumbers can survive where fish can’t, we just don’t understand how.
The mesopelagic is deep enough for me. I live between 500 and 1000 meters deep and that’s just right for my body.