An important tool for taking oceanographic measurement is an electronic instrument known as the CTD (Conductivity-Temperature-Depth sensor).   The CTD records salinity by measuring the electrical conductivity of the seawater, and temperature and depth with other sensors.  This information is sent by electronic signal up an insulated cable that suspends the CTD in the water.   This information is fed directly into computers and forms part of the BATS data base you will be working with today.  Most CTDs are mounted on what is called a “rosette”, a frame with a number of water bottle samplers attached.  These bottles can be triggered by electronic signal to open and close at depth, so water from various depths can be collected and analyzed.  Many properties of the water can be analyzed, including oxygen, chlorophyll (plant pigments), and nutrient content — to name a few.