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Scientific Equipment – Water Quality Sampling

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The SeaBird contains a CTD (Conductivity-Temperature-Depth) sensor, which provides data on the physical properties of the marine environment. These properties include temperature, salinity, conductivity, and percent oxygen saturation at a given depth. The SeaBird is lowered through the water column and records and stores data at every half of a second. This instrument can be used to record data at greater depths than the YSI, but will cost an additional $500 per cruise.

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The YSI Handheld Electronic Sensor is a hand held instrument that displays temperature, depth, salinity, pH and dissolved oxygen. This can be used up to 25 meters depth at no additional cost.

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A Secchi Disk used to determine water clarity or turbidity. It is a black and white disk that is hand-lowered into the water until it is no longer visible. The rope that holds the disk is marked in meters, so students can determine the “extinction depth” (the depth at which the disk disappears). The disk is lowered one meter more than the extinction depth, then raised until it comes just into view. This depth is also noted, and the depth values are averaged.

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Forel Ule scales are used to determine water color. Lower the Secchi Disk one meter, and match the color on the scale to the color of the disk. The color depends on a variety of factors like the altitude, the amount of water vapor in the air, or the presence of clouds and dust. Suspended matter within the water can also change the color of the water.

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Refractometers measure the salinity of the water. Use a dropper to add a saltwater sample onto the prism of the device. The refractometer measures the change in light direction (AKA refraction) through the eyepiece for a salinity reading.

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