To understand the nutrients found in the middle layers of the southern seas, we need to be able to take samples of water at specific depths, and to bring this water to the surface without it being contaminated as it's hoisted up. This requires a device which remains open until the desired depth is reached, and then closes securely, retaining the sample.
Students will investigate how changes in salinity and temperature affect water density.
Students will design and evaluate the effectiveness of devices to sample specific water layers.
Demonstrate the making of a multi-layer system (see Procedure #1 on Activity 1.4.2 Student Worksheet). Challenge students to create a bottom sampling device. How can they get the sampling bottle down to the desired depth, and how will they keep it open? How can they close it quickly when it's where they want it to be?
Complete Activity 1.4.2 lab investigation. Allow time for design teams to demonstrate their "Bottom Sampling Devices" and share observations, successes and failures!
Ocean water is sampled for chemicals and organisms. The sampling device must have certain important characteristics:
It must gather enough water for conducting all the tests.
The depth at which the sample was gathered must be accurately known.
The temperature at time of collection must be known.
It must not allow contaminants to enter as it's being brought up on deck