1. Environmental Chemistry Lab:
Biological Assessment of
River Water Quality Using
Aquatic Benthic Macroinvertebrates
Prof. Rita Yam
Dept. Bioenvironmental Systems Engineering
National Taiwan University
2. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Biodiversity & water pollution
• High biodiversity in streams and rivers
• Different species different sensitivity to environmental factors
• Tolerance of aquatic species to pollution biological assesssment
for stream and river quality
• When a clean river is polluted, several events can occur including
– in the number of species of organisms
– a change in the type of species present
– a change in the number of individuals of each species present
• These changes resulted from
– Death or the moving away of organisms intolerate (sensitive) to
the pollution
– in number of tolerant organisms which thrive on pollution
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3. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Biological assessment
• Biological assessment = integrated assessment of water quality in streams
and rivers based on biodiversity
• Major advantages of bio-indicators over chemical methods of assessing
water quality:
– Long-term biological response to pollution events vs. snapshot
analysis for water chemistry analysis
– Biological community responds to the entire river environmental
condition including all water chemistry parameters and pollutants
• Major groups of organisms used as bio-indicators of environmental pollution:
bacteria, algae, higher plants, benthic macroinvertebrates and fish
(USEPA, European Union, Australia and New Zealand)
• Benthic macroinvertebrates = good ecological indicators:
– Diverse habitat preference
– Relatively low mobility
– Relatively large easyto sample and identify
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5. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Bio-assessment of river water quality
• BMWP = The Biological Monitoring Working Party (BMWP) score
based on the presence/absence of different benthic macroinvertebrate
groups used as a measure of the pollution at a particular site
• The more sensitive organisms (e.g. stonefly larvae) have high scores
while the more tolerant species (e.g. midge larvae) have low scores.
The total score gives an indication of the degree of pollution at that
site.
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Pollution tolerance Low High
Pollution tolerance
score
1 2 3 4
Benthic
macroinvertebrate
taxa group
Stonefly
Mayfly
Caddisfly
Dobsonfly
Riffle beetle
Water penny
Right-
handed snail
Damselfly
Dragonfly
Cranefly
Beetle
(others)
Mussel
Water mite
Midge
Planaria
Blackfly
Water bug
Leech
Aquatic worm
Blood worm
Left-handed
snail
Most sensitive species Tolerant species
6. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Field survey and sampling
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量測水中物理化學因子
採集水樣
底棲生物調查作業-採集生物
Water chemistry Biological assessment
7. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
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Score group Taxa Calculation formula
Group 1 1 Taxon 1 x 1 = 1
Group 2 4 different Taxa 2 x 4 = 8
Group 3 2 different Taxa 3 x 2 = 6
Group 4 0 Taxon 4 x 0 = 0
Total number of taxa = 7 Total sum of score = 15
Pollution
index
Water quality rating Description
1.0-2.0 Excellent water quality All measurements are within objectives
virtually all of the time
2.1-2.5 Good water quality Conditions rarely depart from natural or
desirable levels
2.6-3.5 Marginal water quality Conditions often depart from natural or
desirable levels
>3.5 Poor water quality Conditions usually depart from natural or
desirable levels
Pollution index = 15/7 = 2.14 (Check water quality index)
Step 1:
Step 2:
Step 3:
Calculation of pollution index
8. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Lab work
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Examine the sample
under microscope
9. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Example
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Sample
No.
Taxa Score
group
Total number
of taxa
Total sum of
score
Pollution
index
Water quality
status
Example Mayfly 1 7 2+2+6+8=18 2.6 Marginal water
quality
Caddisfly 1
Dragonfly 2
Midge larva 3
Planaria 3
Blood worm 4
Aquatic worm 4
13. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Question
• Based on the pollution index and water quality
status of the three samples, determine the
corresponding site that each sample was
collected from? Give reason(s) to support your
answer.
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14. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
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Feitsui Reservoir
Danshuei River
Xindian River
Keelung River
Site 1
Jingmei River
Site 2
Site 3
16. Bio-Assessment of River Quality Using Macroinvertebrates Rita Yam
Lab report
• Individual-based, each student must submit one report to NTU
COOL
• Lab report must be submitted to designated link of
<Assignment> on NTU COOL
• Submission deadline: 17:00 on 5/13 (Monday group),
17:00 on 5/16 (Wednesday group)
• If direct copying of answers between students is found, all
students involved will receive ZERO mark
• You can use either English or Chinese to complete your lab
report
• Any delayed submission will result in zero mark!
• Any file of reports cannot be opened OR cannot be seen from
NTUCOOL website will be given zero mark.
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