|Image1: Foam cup attached to ROV|
How much impact could a small Styrofoam cup have? For many people, when styrofoam and the ocean are associated with each other it is through images of plastic pollution littering beaches and the water. For Deep Sea researchers the styrofoam cup has become a tool to visualize the incredible conditions that are present in the dark depths they explore.1 Attached to the frame of a submersible, a normal 8 oz. foam cup will shrink to the size of a thimble after experiencing the weight of hundreds or even thousands of meters of ocean water.2 Explaining why this happens, its impact on the cup, on the equipment researchers use, and the animals they study has become a tool for involving and educating young scientists and the public in deep sea research. So why does the cup shrink?
Foam cups are made from polystyrene, a synthetic hydrocarbon polymer made from many small styrene units. These small “Lego” like styrene units allow polystyrene materials to take on many different forms.3 Starting off as small beads, they are typically heated with a pentane gas that allows the beads to expand to 40 to 50 times their original size. The beads will cool and then are reheated, compressed, and molded into large blocks.This Expanded Polystyrene (EPS) block is approximately 98% air making it an extremely light and durable product.4 Qualities that make EPS an excellent packing and building material also mean that it is not readily biodegradable, and it is often manufactured for single use. The amount of air is ultimately what is important to shrinking the foam cups our deep-sea researchers place on their abyssal vessels.
|Image 2: SEM photograph of normal (left) and compressed (right) EPS|
When submersibles, like a Remotely Operated Vehicles (ROV’s), descend into the deep sea they experience an increase of 10 atm for every 100 meters.1 When traveling to depths of > 1000 meters, the air bubbles in the foam cups are compressed and eventually collapse. The foam cup retains its shape because pressure is exerted evenly on all sides of the cup. ROV’s have many sensitive electronics and tools that are integrated into the vehicle and need to be engineered to withstand these intense pressures.2 Other materials such as steel, aluminum, glass, and even other plastics like PVC contain less air and therefore are less compressible when under deep ocean pressures. This allows researchers to send down ROV’s with sophisticated instruments such as flow cytometers, respirometry systems, and even laser spectroscopy tools.5 These tools have given us better insight into the oceanographic conditions that define the deep sea and the biological organisms that have adapted to this extreme environment.
|Image 3: A hadal snailfish, N. kermadecensis, photographed at 7,199m|
All respiring organisms have some air in them due to the requirement of oxygen for metabolic processes. Yet, how do deep feeding or deep dwelling organisms not become crushed by the intense pressures like the styrofoam cup? Mammals, which are osmoregulators, must go through a set of physiological changes called a dive reflex. These deep diving feeders, such as the Sperm Whales, Elephant Seals, and Cuvier’s Beaked Whales have an increase in hemoglobin content and blood volume which carries more oxygen and increases metabolic transport of oxygen. They dive with no air in their lungs allowing them to collapse, their heart rate slows, and their blood vessels constrict.6 The record of deepest living macro-organism goes to the Snailfish genus, though. Teleost’s, ray-finned fishes, are osmoconformers; and their lower depth limit may also be regulated by pressure. Biochemically, hydrostatic pressure can have detrimental effects on the proper function of proteins in metabolic pathways. A set of organic compounds called neutral amino acids, or TMAO, are not only essential to deep sea protein function, but as they accumulate and reach an osmotic disequilibrium, and the imbalance of intracellular solutes disrupt physiological function at depths greater than 8,400 meters.7 This shift in TMAO content may have larger implications for other deep dwelling taxa. This warrants further investigation which will be spearheaded by kids learning about the deep sea, drawing on styrofoam cups, and sending them to researchers.
The styrofoam cup is an easy and effective method of educating the world about one of the most dangerous and fascinating aspects of the deep ocean, pressure. Twitter images and blog sites from deep sea oceanographers show off their cup collections from previous expeditions, like little souvenirs from the deep. Hoards of small hand-drawn cups from elementary students are sent to institutions so they too can become a part of the science and have their own deep-sea treasure.1,8 Rarely, complex interdisciplinary fields such as oceanography and deep-sea biology have easily understandable tools and concepts, due to the alien world they work in. The Styrofoam cup lends a window into that hostile underwater world, but also acts as a symbol. Plastic doesn’t have to be a symbol of pollution. It is a durable material that if used properly can be an effective tool. It is our job as scientists to effectively communicate the sophisticated tools, the clever inventions, and even the common, every day, household, items that we use to accomplish our research goals. Sometimes it is the most common mundane instruments that have the greatest power to reach into the community and inspire curiosity, creativity, and conservation.
Image 1: Styrofoam cup mount: https://nautiluslive.org/blog/2014/08/21/shrinking-cups-deep
Image 2: Scanning electron microscope styrofoam structure:https://www.sciencefriday.com/educational-resources/high-pressure-in-the-deep-ocean/
Image 3: Hadal snailfish: Jamieson AJ, et al. (2011) Bait-attending fauna of the Kermadec Trench, SW Pacific Ocean: Evidence for an ecotone across the abyssal-hadal transition zone. Deep Sea Res Part I Oceanogr Res Pap 58(1):49–62.
1 Griffies, S. 2017. The styrofoam cup experiment & aspects of ocean mass, pressure, and heat. DynOPO Cruise 2017. https://dynopocruise2017.blogspot.com/2017/04/the-styrofoam-cup-experiment-aspects-of.html.
2Hinchey, E.K., Adams, J.M., Rose, C.M., Nestlerode, J.A., Patterson, M.R. 2013. The Incredible Shrinking Cup Lab: Connecting with Ocean and Great Lakes Scientists to Investigate the Effect of Depth and Water Pressure on Polystyrene. Science Activities, 50: 1-8. DOI: 10.1080/00368121.2012.727754.
3Wypych, G. (2012). Handbook of Polymers: PS polystyrene. pp. 541–7. doi:10.1016/B978-1-895198-47-8.50162-4. ISBN 978-1-895198-47-8.
4 Expanded Polystyrene Australia Inc. 2014. How is EPS made? http://epsa.org.au/about-eps/what-is-eps/how-is-eps-made/
5Zych, A, Rayner, R. 2016. High pressure in the deep Ocean. Science Friday. https://www.sciencefriday.com/educational-resources/high-pressure-in-the-deep-ocean/
6Panneton, W. M. (2013). The mammalian diving response: an enigmatic reflex to preserve life?. Physiology (Bethesda, Md.), 28(5), 284–297. doi:10.1152/physiol.00020.2013
7Yancey, P.H., Gerringer, M.E., Drazen, J.C., Rowden, A.A., Jamieson, A. 2014. Marine fish may be biochemically constrained from inhabiting the deepest ocean depths. PNAS. Proceedings of the National Academy of Sciences, 111 (12) 4461-4465. DOI: 10.1073/pnas.1322003111
8 Totten Expedition and Killara Primary School: Armand, L. 2014. Pressure. Totten Expedition. https://sites.google.com/site/tottenexpedition/home