Oceanography, or marine science, is the study of the ocean. Oceanographers use many different types of equipment for their research. Some common oceanographic instruments are a CTD, sediment trap, and incubator. These are the three pieces of equipment that evert oceanographic vessel should have on board.
CTD
A standard piece of equipment for any oceanographic vessel at sea is a CTD, which stands for conductivity, temperature, and depth. CTDs measure more than those three factors, but those are the main three oceanographers are often concerned with. A CTD can also look at other physical factors like pH levels, dissolved oxygen, chlorophyll, sunlight, and transmissivity. They are made of small probes and sensors that send data directly back to the ship in real-time on larger CTDs. The real-time results allow for selective collection of water samples and deploying of other instruments as needed. Smaller CTDs have autonomous functions and are programmed to collect by themselves at certain depths or times. A standard CTD deployment is between two and five hours depending upon the depth reached.
CTDs are typically deployed with a rosette of Niskin bottles. They are cylindrical and arranged vertically, surrounded by a metal cage for protection. They are controlled by a mechanism on the ship and allow the collection of many different water samples without risking contamination by other water samples collected when the CTD returns to the surface. CTDs are lightweight by themselves, very accurate, and can reach depths of several thousand meters. One of the disadvantages of using a CTD is that each sensor must be calibrated, particularly on the smaller autonomous devices.
Sediment traps
Sediment traps come in three designs. One is a mesh funnel used to collect falling sediments in ocean water, known as marine snow. Sediment traps closer to the surface do not require the large funnels because surface water contains a great deal of sediment. There are also neutrally buoyant traps that catch sediments in currents. Each is moored to a desired location and their purpose is the same. They are important to scientists studying the carbon cycle.
The funnel traps are most often used and deployed in water columns. They catch any marine snow and have baffles at the top to keep out larger objects that may clog the funnel. They are typically on a programmed schedule that closes the funnel every five days to a month. The vial at the bottom of the funnel where the sediments have accumulated seals and then a new vial is put in its place. When hauled back up the funnel closes to prevent contamination. Among the sediment collected are things like dead plankton and algae and other organic as well as inorganic compounds.
Incubator
An incubator is a combination of a CTD and a sediment trap. Incubators have two incubation chambers with small CTDs secured at their bottoms. A sediment trap is secured to the top of one chamber and the other is open. When at a desired depth is reached, the chambers close to form isolated systems and the two can be compared to study exchange rates in the sediment. The CTDs measure the characteristics of the water in the chambers and controlled environments can be created.
