Benthic Sampling

Question 1

What is quantitative sampling

Answer 1

Produces datât that can be measured numerically & transformed into usable statistics.
Grabs are used to take quantitative samples of infauna from the top 15cm of the sediment.

Question 2

Explain a grab used for sampling benthic macrofauna

Answer 2

Peterson grab.
Sampling area 0.1 - 0.2m2
Lowering rope slacks when gear hits substrate, release hook opérâtes & buckets close together before grab leaves bottom.
Gauze covered window. To allow water to escape when grab closes.

Question 3

Disadvantages of Peterson grab

Answer 3

Grab may close prematurely if ripe slacks as ship rolls.
Grab may not penetrate into sediment sufficiently.
May not close completely - lose sediment

Question 4

Explain box corer

Answer 4

Deploys corer into sample.
Sample area 20x30 cm to 45cm depth.
Cutting arm released to close bottom of tube.
Modified designs can take multiple cores.
Provide deep & undisturbed sediment sample.

Expensive
Requires good conditions & large vessel to deploy.

Question 5

How are macrobenthos samples processed

Answer 5

Sample is placed into metal sieving table or hopper
*diagram
Hopper design
Efficient processing of sample
Potentially damaging to fauna if water pressure too high.