Benthos
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Your knowledge??
What? Define…
Give examples
Their function?
Classification
How to study them?
Objective(s) →Sampling design
Samples collection
Instruments/ equipment
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Benthos
A Greek word = “depths of the sea”
Can be used for freshwater habitats
Organisms at the bottom/ benthic zone
Live in/on/near the sedimentary environments
Important group for benthic foodweb
Dominated by scavengers & detrivores (why?)
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Benthic zone
Freshwater: Lake, river,
stream
Marine: from tidal pool,
mudflat, continental shelf…
abyssal
Dark & high pressure
10 m, 1 atm.
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classification
1. Size
2. Type
3. Location/habitat
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Classification (by size)
a) Macrobenthos
1 mm
E.g. polychaete worms, bivalves, echinoderms,
sea anemones, coral, sponges, sea squirts,
turbellarians, larger crustaceans (crabs, lobsters,
cumaceans)
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Classification (by size)
b) Meiobenthos
1 mm but 32m
E.g. nematodes, foraminiferans, water bears,
gastrotriches, smaller crustaceans (copepods,
ostracodes)
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Classification (by size)
c) Microbenthos
32 m
E.g. bacteria, diatoms, ciliates, amoeba,
flagellates
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Classification (by type)
a) Zoobenthos
Benthic animals
b) Phytobenthos
Benthic plants
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Classification (by location)
a) Epibenthos
Live on top of the sediment
b) Hyperbenthos
Live just above the sediment
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How to study them?
Objectives
Design your sampling
Choosing one study site or more
Quadrates along transect lines or belt transect?
Replication of samples
Type of instruments to use
How to use in a correct way
Taking care of them after usage
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How to study them?
Preserving samples
Sorting samples
Data analysis
Report writing
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Introduction to instruments
Quadrate
Line transect
Core sampler
for collecting a depth profile/ a cross-sectional slice of
sediments, thereby providing material for determination of
vertical distribution of variables
consist of a tube that enters the sediment by free falling
from a sufficient height (usually 3-5 m), a valve at the top
of the sampler closes by messenger, that prevents the
sediments from washing out
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Introduction to instruments (cont)
Core sampler
Note: Department has
• a Simple flow-through corer
• Modified Piston corer
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Introduction to instruments (cont)
Grab sampler
for collecting surface
sediments, thereby
providing material for
the determination of
horizontal distribution
of variables
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Introduction to instruments (cont)
Kick net
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Preservation of samples
Between 2.5 & 5% formalin for general
storage
Formalin becomes acidic with storage
For mollusc, need to used buffered formalin
(add borax or hexamine or sodium
bicarbonate)
Unbuffered formalin will erode shells
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Buffered Formalin (pH 7.5 – 8)
Weigh 5 g of sodium bicarbonate & add to a full
strength formalin (in small portion to avoid from
oversaturated – solution become whitish)
maximum of 2 L formalin, don’t prepare more than this
volume) →label this as 100% Buffered Formalin
Prepare under fume hood
Use magnetic stirrer to stir the salt
Use flask to mix the salt with formalin
From this solution, you can prepare the desired
concentration like 10%, 4% etc.
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Video on…
Deploy a gravity corer (Part 1)
http://www.youtube.com/watch?v=VaL9Fr3q2Oo&feature=related
Part 2
http://www.youtube.com/watch?v=RfZgLbkiE7Y&NR=1
Recovery
http://www.youtube.com/watch?v=hzBURksx6gQ&NR=1
The stream quality index: Biological index sampling
http://www.youtube.com/watch?v=wBX9LpZKV-
A&feature=PlayList&p=A5939E0C849C1BB4&playnext=1&playnext_from=PL
&index=4
Benthic invertebrates
http://www.youtube.com/watch?v=-ywcHb659X8&feature=related
Stream monitoring equipment
http://www.youtube.com/watch?v=59ftiITxpEc&feature=related
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Sieving a grab sample on ship -
https://www.youtube.com/watch?v=eMwaW5uCs24
Infauna sieving done in wet lab of a ship -
https://www.youtube.com/watch?v=YXmxRxZmphU
Benthic communities -
https://www.youtube.com/watch?v=VnBZDKbXg4U
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