Sampling methods are used to determine the diversity, biomass, and distribution of benthic life as well as collect historical data. A variety of methods are employed such as grabs, dredges, trawls, sleds, cores, and underwater vehicles to collect representative samples while accounting for limitations of time, money, depth, and habitat damage. The most advanced methods include remotely operated and autonomous underwater vehicles as well as satellite imaging and sonar mapping of ocean floors.

1. SAMPLING THE BENTHOS

2. Sampling the Benthos Used to determine: diversity biomass distribution of life historical data

3. 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

4. Grab Like a crane with jaws to grab sediment & organisms

5. Grab

6. Grab works differently in different seds soft seds – sinks deeper hard seds – does not grab as much

7. Dredge - Collects materials from benthic zone Often used to clear channels for navigation - Sometimes to collect organisms

8. Types of dredges: Dredge clam shell dredge

9. Types of dredges: Dredge suction dredge

10. scallop dredge backhoe dredge Types of dredges: Dredge

11. Trawl net dragged behind boat at various depths or along bottom

12. Trawl

13. trawl tracks can damage benthic habitat Trawl

14. Epibenthic Sled drag along bottom – like dredge can collect samples can house equipment

15. Core drill to collect a long tube of sediment

16. Core good for analyzing historic changes over long periods of time

17. SCUBA s elf- c ontained u nderwater b reathing a pparatus allows person to see and sample limited time on bottom limited depth – about 100 feet

18. Submersible Alvin small research submarine

19. Submersible Johnson Sea Link can go as deep as 4,000 meters

20. R.O.V. r emotely o perated v ehicle small robot operated from boat cables to boat safer and cheaper

21. A.U.V. autonomous underwater vehicle small robot no cables to surface

22. Satellites used for navigation and to map ocean bottom

23. Satellites Global map of ocean floor gravity from Geosat and ERS-1 satellite altimetry

24. Side scan sonar uses sound waves and computer imaging to get an image of the ocean bottom towed behind ship can determine benthic habitats

25. Side scan sonar