Sampling Marine Environments

Question 1

What is necessary when conducting research in a marine environment?

Answer 1

Sampling and an un-biased estimate of “what is there”

Question 2

What sampling methods are used to sample the shallow-waterter benthos (< 30m)?

advantages/disadvantages

Answer 2

SCUBA

epibenthic organisms

• video and cameras
• transects
• very useful for rocky shore habitats

Hydroplanes

• covers a large area
• problem with position
• qualitative data

cores/quadrats

• size and shape of sampling unit
• sometimes too small
• sometimes too large -> difficult to sample, reduces number of replicates

suction samplers
good in less then 30 m depth

Question 3

What sampling methods are used to sample the deep water benthos?

advantages/disadvantages

Answer 3

• ROVs
• AUVs
• Manned submersibles

only a few facilities that can go that deep

grab samplers (box corers)

• to take a piece of seabed
• only small samples possible

benthic dredges

• unprecise (overfill, bounce around, samples escape)
• limited penetration depth
• semi-quantitative rather than qualitative
• take a long time (1/h)
• expensive due to running costs of research vessels

create a lot of material that needs processing

Question 4

What sampling methods are used to sample the pelagic environment?

advantages/disadvantages

Answer 4

MOCNESS

• multiple opening-closing nets
• net minders

Longhurst-Hardy plankton recorder

Trawls and seines

• stock assessments
• quantification
• difficult
• consistent methods (depth, speed, time) -> overlap of two years when new vessels are introduced to match methods
• the patchy distribution of species makes stock assessment difficult

Sediment Traps

• measure vertical fluxes
• swimmers
• high concentration of phytoplankton might attract predators that influence the sample

Question 5

What are some values and limitations of remote sensing?

Answer 5

Acoustics

• sound waves and frequency
• non-destructive sampling
• requires calibration and data processing
• common in fish stock assessment

Towed sensors

• optical
• chemical

Satellites

• synoptic view (shows chlorophyll a distribution -> to find base of food chain)
• address large-scale variability
• only surface sampling possible, no deep penetration