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

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

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

Side scan sonar