Benthic Sampling

Question 1

Benthos is

Answer 1

The community of organisms that live on or near the seabed or in the bottom of freshwater bodies

Question 2

What are benthic organisms classed as according to size

Answer 2

Macrobenthos >1mm polychaetes
Meiobenthos 0.1-1mm copepods
Microbenthos <0.1mm diatoms

Question 3

What are the classes of benthic organisms from their position in the habitat

Answer 3

Hyperbenthos: live just above sediment
Epibenthos/Epifauna: live on substrate
Endobenthos/Infauna: live in subsrtate

Question 4

What are the benthos sampling methods

Answer 4

Ex-situ sampling methods
In-situ sampling methods

Question 5

What’s in-situ sampling

Answer 5

Benthos directly observed
Onshore observation, imaging, scuba diving, submersibles, ROV

Question 6

What’s ex-situ sampling

Answer 6

A portion of sediment and fauna are removed for later processing and examination
Trawls, dredges, cores, grabs, remotely operated ROV’s

Question 7

How are Benthos sampled quantitatively

Answer 7

Sampling producing data that can be measured numerically and transformed into useable stats
Quadrats, core provide density estimates

Question 8

How are benthos sampled qualitatively

Answer 8

Descriptive sampling, data can be observed but not measured explicitly
Some trawls/dredges

Question 9

How are benthos sampled semi-quantitatively

Answer 9

CPUE
Some measure of numerical data

Question 10

What’s a Riley push net (Qualitative)

Answer 10

Designed to sample benthic macro fauna (shrimp juvenile fish) in shallow intertidal water
Light metal frame seated I’d two metal skis
Net 5-10mm mesh with finer mesh cod end
Weighted foot rope
Tickler chains in front of mouth disturb organisms and drive into net

Question 11

Trawl

Answer 11

Qualitative/ semi-quantitative. Suitable for epifauna on mud/sand substrates.
Can be used from small vessel

Question 12

Dredges

Answer 12

General use in all bottom types.
Qualitative
Anchor dredge design semi-quantitative

Question 13

Grab

Answer 13

Peterson, Van Veen
Suitable for mud/sands
Quantitative
For shallow infauna
Suitable for small vessels

Question 14

Box corer

Answer 14

Heavy needs large vessel
Good depth penetration
Quantitative
For mud/sand

Question 15

Remote suction sampler

Answer 15

Aka Knudsen
Heavy, needs calm conditions
Collect relatively deep
Quantitative samples

Question 16

Driver operated suction sampler

Answer 16

Can collect known area by great depth within core
Large amount to sort
Very good to find what other methods miss and to calibrate other techniques

Question 17

Cameras: remote and in-situ

Answer 17

See only surface species or marks
Need to be able to identify from film

Question 18

Sediment profile imagery

Answer 18

See cross section of bottom, can get much data
But not many species

Question 19

What’s artificial substrates

Answer 19

Synthetic structures used to collect settling organisms

Question 20

Advantages of artificial substrates

Answer 20

Allow sample collection in locations that are difficult to sample
Confounding effects of habitat differences are minimized by providing a standardized micro habitat

Question 21

Disadvantages of artificial substrates

Answer 21

Must be deployed & recovered (2 sampling trips)
Prone to loss natural damage vandalism
Substrate material will influence the composition and structure of the community