Thursday, March 20, 2014

Ocean Zones

In February we started our Ocean Zone Installation at school. Our display depicts each of the five ocean layers (sunlight zone, twilight zone, midnight zone, abyssal zone, and hadal zone/trenches). Students began by investigating the ways that certain species are physically and behaviorally adapted to survive in their particular zone (from sun-drenched plankton near the surface to the tube worms found in the darkest trenches below). Students studied the food chain and learned about microscopic plant-like and animal-like plankton. They found that phytoplankton are adapted to remain in the sunlight zone, making their own food thanks to the sun and serving as food for zooplankton. We were surprised to see, in photos of crab larva and reef fish larva, that some zooplankton spend only part of their life cycle as plankton and then turn into the adult crabs and beautiful reef fish that we more readily recognize. 

Students researched the exact depths that differentiate each layer (based on how much sunlight passes through) and they spent time at the library collecting photography books of sea life. After reading about the different types of creatures that are found in each zone, the class created some beautiful observational drawings and placed them on our mural in the correct zones.

Our students were especially interested in researching the coldest and darkest zone. Much of our research was focused on this lowest layer of the ocean, the Trenches or Hadal Zone. We spent time discussing the Challenger Deep (a.k.a. Mariana Trench), where some of the most primitive species on earth are found. Down there, instead of a food chain based on energy from the sun, we learned about a food chain based on the process of chemosynthesis. Students wondered how the trenches were made, which led us into a discussion of tectonic plate movements and subduction - a process leading to the formation of the deepest trench. Children were introduced (through video) to the scientists, past and present, who have ventured there and we marveled about the risks these explorers took in traveling to such amazing depths. Students were fascinated by the immense pressure and the types of vessels that are constructed for traveling to the Challenger Deep. While learning about bathymetry, and the tools that scientists use to make measurements of underwater depths, some of the students pointed out that the ocean floor maps looked similar to the topographical maps that they created last year! This astute observation is gratifying as they are making connections and beginning to understand and articulate the physical characteristics of the surface of our planet.