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Ekman Dredge

Overview:

 The Ekman Dredge (or Ekman Grab) is used to sample the bottom sediments and macro-invertebrates in aqueous environments. It is ideal for soft, unconsolidated substrates such as sand, silt, or soft clay (not packed clay). The Ekman Dredge has hinged doors on top that open as the dredge is lowered to allow water to flow through the apparatus such that bottom disturbance is minimized. The spring-loaded jaws on the bottom of the dredge snap shut to prevent a wash-out sample.

Requirements: The Ekman Dredge is used to sample the bottom sediments and fauna of rivers, lakes, estuaries, and coastal areas. It can be deployed from a boat or dock using the 100 feet of line included.

Manufacturer:
Suggested Grade Levels
: 8th and above
Suggested Courses: Environmental Science, Earth Science
Video Demonstration:

AMS Ekman Dredge with Messenger


Directions:

  1. CAREFULLY open the spring-loaded jaws by pulling the black button on the metal wire upward and attach each loop of the metal wire to the spring-loaded pins at the top of the dredge. You will notice that the open jaws are under a tremendous amount of pressure. Caution should be used not to push the pins down that would release the jaws prematurely.

  2. Swiftly lower the dredge down through the water until it lodges into the substrate. Keep the messenger above the water with you. 

  3. Release the metal messenger weight down the rope to close the jaws.

  4. Pull the dredge up to the surface.

  5. Empty the contents into a large tub or bucket. Remember to keep the water that is with the sample if you are sampling for organisms. If the sediments are released from the dredge carefully, it will look approximately as it did on the bottom.

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SAGE Bristol,
Feb 7, 2012, 8:13 AM
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