Equipment and Instruments

There are many instruments and pieces of equipment an oceanographer uses to collect data. Below is a list of instruments used on a typical Yellowfin Cruise.

The YSI Hydrometer is used to measure water chemistry, including temperature, pH, Dissolved Oxygen, and salinity levels. This instrument will only extend down to a depth of 35 meters, which limits it to shallower waters.



XBT (expendable bathythermograph) is used to measure temperature. This instrument is not used very often.


The Sea-bird (SBE 19plus V2 SeaCAT Profiler CTD) is similar to the YSI hydrolab in that it measures water chemistry, including temperature, pH, Dissolved Oxygen, and salinity levels. However, this instrument can reach depths of greater than 600 m, which makes it ideal for deeper waters.



The Forel Ule Color Scale measures water color. Why do we need to do this? Everyone perceives color slightly differently, so what is blue to one person may be blue-green to another. Next to each vial of color is a window; one looks through the window and tries to match the color of the seawater with that in the vial. Each color is given a Roman numeral designation from I to XXI. Healthy values for the color of the sea water is between II and VIII. A value of XXI indicates red tide conditions.



The Secchi Disk is a beautifully simple devise that is used to measure water clarity. Basically, it is a metal disk welded to a metal rod, upon which the lid of a white 5-gallon paint drum is laid on top. Attached to the rod is a rope knotted off in 1/2 meter increments. The disk is slowly lowered into the water until you can't see it anymore. That is called the extinction depth, which is a simple estimation of where the photic/aphotic zone boundary is.



The Van Veen Mud Grab is, like the name implies, used to collect sediment samples from the seafloor.



The BioDredge is a large metal box that is open on one end. The dredge is lowered and dragged along the seafloor for a short distance before being brought back up to the surface. Benthic (bottom dwelling) flora and fauna are collected in the box to be examined on the boat. Afterwards, they are returned to the ocean.

Since this can be a very damaging procedure, it is important to carefully select your site prior to dredging so that the area can recover.



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What is an Otter Trawl and what does it have to do with Otters? Well, it really doesn't have anything to do with otters - it's just a mispronunciation of the word "outer". The boards attached to the top of the net are called "outer" boards which are used to stabilize and hold open the net. The net is lowered into the water to the desired depth and dragged along behind the boat for various lengths of time. Then, it is brought to the surface where we can see the neritic (swimming) organisms collected in the net. After viewing, the organisms are returned to the ocean.

Note: Click on image to enlarge