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Sampling the Ocean Bottom
Used to determine:
• sediment type and size
• organisms
• historical data
Sampling the Ocean Bottom- Must assume that a small
amount of material is representative of the larger area
- Therefore, must take as many samples as time and money allow
Grab or
Clamshell Grab
like a crane withjaws to grabsediment & organisms
Grab
Grab
• works differently indifferent seds
• soft seds – sinksdeeper
• hard seds – doesnot grab as much
Dredge
-Collects materials from oceanbottom
-Often used to clear channelsfor navigation
- Sometimes to collect organisms
Types of dredges:Dredge
clam shell dredge
scallopdredge
backhoedredge
Types of dredges:Dredge
Trawl
• net dragged behind boat• at various depths or
along bottom
Trawl
trawl tracks can damageocean bottom
Trawl
Epibenthic Sled • drag along bottom –
like dredge• can collect samples• can house equipment
Core or
Piston Core
drill to collect a long tube of sediment
Core good for analyzing historic changes over long periods of
time
Sediment Sieves
used to sort sediments into their different sizes and find
organisms living in the sediment
SCUBA
• self-contained underwater breathingapparatus
• allows person to see and sample• limited time on bottom• limited depth – about 100 feet
Submersible
Alvin
small researchsubmarine
Submersible
Johnson SeaLink
can go as deepas 4,000 meters
R.O.V. remotely operatedvehicle
• small robot operated from boat• cables to boat• safer and cheaper
A.U.V.
• autonomous underwater vehicle• small robot• no cables to surface
Satellites
• used for navigationand to map oceanbottom
Satellites
• Global map of ocean floor gravityfrom Geosat and ERS-1 satellite altimetry
Side scan sonar
• uses sound waves and computerimaging to get an image of theocean bottom
• towed behind ship• can determine benthic habitats
Side scan sonar
