1.3.2

Tools of the Oceanographer: Measuring Equipment

TOOLS OF THE OCEANOGRAPHER: Equipment: Measuring tools

B. Taking Measurements of the Marine Environment
1. Temperature • Standard Thermometer • Bucket Thermometer • Reversing Thermometer (for Nansen Bottle) • Bathythermograph (BT)	2. Salinity • Hydrometer (quick test type for aquariums) • Hydrometer Set • Chemical Test Kit (Knudsen) • Salinometer
3. Oxygen • Chemical Test Kit (Winkler Titration) • Dissolved Oxygen Probe	4. pH • pH test strips • Chemical Test Kit • pH meter
5. Visibility & Color • Secchi Disk (used by itself) • Forel/Ule Scale (used with the Secchi disk)	6. Other • There are chemical tests for numerous dissolved substances including Carbon Dioxide, Nitrogen, Phosphates, Ammonia, Lead, Copper and Manganese
7. Depth & Profile • Sounder (lead line) • Fathometer •Surveying Equipment	8. Currents • Current Meter • Dye • Drogues • Drift Bottles • Drift Cards

1. Temperature

Standard Thermometer

Measures:	Temperature in degrees
Operates:	At any depth by cable or line or by hand
Notes:	Mercury has been replaced in many standard thermometers by less toxic materials (SW image)

Bucket Thermometer

Measures:	Temperature in degrees
Operates:	At the surface by hand or line
Notes:	An easy way to get a quick surface sea temperature from a big vessel when you are unable to reach the water (SW image)

Reversing Thermometer (for Nansen Bottle)

Measures:	Temperature in degrees
Operates:	Only when turned 180 degrees (the mercury breaks in the special loop and will not get back together until reset thus, temperature at depth can be recorded with a 180 degree flip (as is done with the Nansen Bottle) and there will be no change on the way up.
Notes:	Each thermometer is about $400 now however, instant read out temperature sensors are most often used to determine temperature at depth (SW image)

Bathythermograph (BT)

Measures:	Water
Operates:	Over any depth with a cable or line by hand or with a hydraulic winch
Notes:	This model records the information inside and is retrieved however there are expendable models (XBTs) that free fall on a copper line and transmit the temperature and depth information through the copper wire before dropping to the bottom (SW image)

2. Salinity

Hydrometer (quick test type for aquariums)

Measures:	Salinity in parts per thousand (o/oo)
Operates:	By reading the density (specific gravity) of the water that corresponds to salinity. Increasing dissolved salts increase the density.
Notes:	Very easy to use this but it does not correct for density changes due to temperature. (SW image)

Hydrometer Set (cylinder, hydrometer, thermometer, TSD graph)

Measures:	Salinity in parts per thousand (^o/oo)
Operates:	With a water sample by using a hydrometer to measure the density of the water (water with more salt is more dense and will float the hydrometer higher in the cylinder) which can then be used along with the temperature in a standard TSD graph (temperature, salinity, density) to find the salinity since these three variables have a known relationship
Notes:	Very hard to do on a rocking boat but easy on solid land (SW image)

Chemical Test Kit (Knudsen Titration modification) for Salinity

Measures:	Salinity in parts per thousand (o/oo)
Operates:	By a chemical titration with a water sample to determine just one of the salts (chloride ion) and extrapolate the rest of the salinity
Notes:	Not very accurate because of interaction of other salts (SW image)

Salinometer

Measures:	Salinity in parts per thousand (o/oo)
Operates:	By measuring the electrical conductivity and extrapolating (saltier water is a better conductor)
Notes:	Very accurate (SW image)

3. Oxygen

Chemical Test Kit (Winkler Titration) for Oxygen

Measures:	Oxygen in parts per million (ppm)
Operates:	By chemical titration with a water sample to determine the amount of dissolved oxygen (DO), not the bubbles
Notes:	Very accurate (SW image)

Dissolved Oxygen Probe

Measures:	Oxygen in parts per million (ppm)
Operates:	Electronically
Notes:	Very accurate (SW images)

4. pH

pH test strips

Measures:	pH (in numbers)
Operates:	By a color comparator
Notes:	This set is specific for the 7.5 to 8.5 range of seawater. (SW image)

Chemical Test Kit for Saltwater pH

Measures:	pH (in numbers)
Operates:	By a color indicator
Notes:	Sometimes hard to make a color choice (SW image)

pH meter

Measures:	pH
Operates:	Electronically
Notes:	Fast and easy way to record pH (SW images)

5. Visibility & Color

Secchi Disk

Measures:	Visibility (vertical)
Operates:	By hand on a line to the depth where it becomes invisible
Notes:	May be hard for the viewer to be exact but a good approximation (SW image)

Forel/Ule Scale

Measures:	Color of the water (in roman numerals associated with colors from brown to green to blue)
Operates:	As a color comparator with the use of the secchi disk lowered to one meter for background so the color of the bottom won't interfere
Notes:	Can be hard for the viewer to choose the exact color (SW image)

6. Other Test Kits

Other Test Kits

Measures:	Almost anything (carbon dioxide, nitrogen, nitrates, phosphates, ammonia, lead, copper, manganese)
Operates:	Chemically
Notes:	Test kits are available for almost anything found dissolved in seawater

7. Depth & Profile

Sounder (lead line)

Measures:	Depth (in meters or feet)
Operates:	At any depth on a cable or line generally by hand
Notes:	Until 1993 most of the hydrographic (ocean bottom) maps from Santa Barbara Harbor north for many miles were done with a hand held sounder (SW image)

Fathometer

strip chart from fathometer

Measures:	Depth (in meters or feet)
Operates:	Electronically by sending a sound from the boat and receiving the sound waves that bounce back from the bottom, the depth is read from a paper chart moving through the fathometer calibrated to record the depth
Notes:	A chart strip is used not only to determine the depth but also the profile of the bottom - important for times when a net is being dragged on the bottom to avoid getting it caught on a big rock or outcrop. (SW image)

Surveying Equipment (Sighting level, Tripod, Stadia Rod)

Measures:	Profile of the beach and shallow (to a few feet) wave wash area
Operates:	By sighting through the sighting level (stabilized and leveled on the tripod) to stadia rods (marked in feet) held on the beach
Notes:	This tool is used to survey mountains and in construction as well (SW image)

8. Currents

Current Meters

Measures:	Relative speed of water flow (current)
Operates:	At any depth by cable or line
Notes:	Other current meters are much larger and some have directional recorders as well (SW image)

Dye for Currents

Measures:	To stain the water so that its movement (current) can be traced
Operates:	By pouring
Notes:	Nontoxic and biodegradable (is gone in about 20 minutes) (SW image)

Drogues (bottom with weight, and surface with float)

Above picture: surface drogue (with float)

Above picture: bottom drogue (with weight)

Measures:	Currents over long distances
Operates:	By releasing many and hoping for recapture (only a few percent are ever recaptured)
Notes:	Like the note in a bottle, this can be a form of pollution and is not often used anymore. There are expensive buoys deployed for this purpose with the ability to send signals to satellites which can be recorded several times a day (SW images)

Drift Bottles

Measures:	Currents
Operates:	By releasing a few
Notes:	May be affected by the wind but a quick and easy way to measure a current. May be considered pollution if not retrieved. (SW image)

Drift Cards

Measures:	Currents
Operates:	By releasing
Notes:	Weighted to stay just below the surface of the water. May be considered pollution if not retrieved. (SW image)

(Revised 27 Sept. 2007)