SAMPLING THEBENTHOS
Sampling the Benthos
Used to determine:
• diversity
• biomass
• distribution of life
• historical data
Sampling the Benthos- 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
Like a crane withjaws to grabsediment & organisms
Grab
• works differently indifferent seds
• soft seds – sinksdeeper
• hard seds – doesnot grab as much
Dredge
- Collects materials from benthic zone
-Often used to clear channelsfor navigation
- Sometimes to collect organisms
Types of dredges:Dre
dge
clam shell dredge
Types of dredges:Dre
dge
suction dredge
scallopdredge
backhoedredge
Types of dredges:Dredge
Trawl
• net dragged behind boat• at various depths or
along bottom
trawl tracks can damagebenthic habitat
Trawl
Epibenthic Sled • drag along bottom –
like dredge• can collect samples• can house equipment
Coredrill to collect a long tube of
sediment
Core good for analyzing historic changes over long periods of
time
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 operated
vehicle
• 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