Download Biotic indices and indicator species

Conservation of biodiversity
Use of biotic indices and indicator species
in monitoring environmental change
What are biotic indices?
• Biotic indices are numerical values based on
the presence of indicator species which are
species sensitive to different environmental
conditions
• Biotic indices use pollution tolerances of
endemic organisms and are regionally specific.
Human activities and the effect on
major biomes
• The effect of human activities is not always
known
• Important to have early detection of
environmental change
• Environmental impact assessment (EIA)
• It is important to have baseline data when
measuring the environmental impact of a
human activity
Biotic indices and indicator species of
environmental change
• Some organisms are particularly sensitive to
change in their environment
• Numbers and the condition of these species in
threatened habitats can be monitored.
• Their health can therefore function as
biological indicators, or biotic indices, of
impending environmental change.
Direct and indirect methods of
measuring environmental status,
e.g. water quality
Direct methods
• These record the abiotic
aspects of the
environment
• Such as turbidity, flow,
temperature, pH, light
intensity etc
• And include chemical
tests to measure disovled
oxygen, salinity, turbidity,
nitrates, phosphates etc.
• But, these methods can
only give an indication of
the water quality at one
point in time
Indirect methods
• The biotic part of the ecosystems
• Biodiversity within an ecosystem
e.g the Simpsons Index
• BOD (Biological oxygen demand)
• The biotic index, using the
presence of species sensitive to
different environmental
pressures within the ecosystem,
i.e. indicator species
• These values give a better
understanding of the effects of
environmental changes as they
show health of the whole
community over extended time
periods
Types of indicator species
• Macroinvertebrates, for detecting changes in
aquatic ecosystems
• Lichens for early detection of atmospheric
pollution (SO2)
• Large trees, for long term changes in terrestrial
biomes and ecosystems
Macroinvertebrate indicator species
• Easy to see and identify e.g. mayflies,
caddisflies, true flies, snails (see keys)
• Have a life cycle of at least a year
• Relatively sedentary, confined to the area
being sampled
• They have a range of responses to different
pressures.
• Individual species have specific tolerance
ranges and habitat requirements
Macroinvertebrate biotic indices
• Individual species, genera or families in a
sample are scored according to their
sensitivity or tolerance to the pressure
Aquatic Invertebrate Data Recording
Sheet
Using the biotic index
• These scores are then combined to produce a
single value which can be used to interpret
the current state of the environment.
• Examples of biotic indices
• Trent Biotic Index, the Chandler Score and the
Biological Monitoring Working Party (BMWP)
score
Examples of aquatic indicator
species
Pollution Tolerance Indices For
Aquatic Invertebrates
The damselfly larva Calopteryx
splendens
The damselfly larva Calopteryx
splendens
• The presence of this larva
indicates clean water
• Slow flowing water and a silted
river bed.
• It is also intolerant of
acidification and increased
salinity
• Species like C. Splendens are
used to formulate biotic
indices based on acidification,
flow velocity and siltation
Pollution Tolerant Species:
• Presence of these species
indicate water of low
quality, however they
may be present in all
types of water.
• blackfly larvae
• Flatworms
• Leeches
• Roundworms
• Blood worms/midge
larvae
Moderately Tolerant Species:
• Presence of these
species in great
numbers may be a
• sign of fair water
quality.
• caddisfly larvae
• dragonfly nymphs
• damselfly nymphs
Pollution Intolerant species
• Presence of these
species in great
numbers may indicate
good water quality.
• mayfly nymphs
• stonefly nymphs
Aquatic Invertebrate Data Recording
Sheet
Example of Biotic Index Calculation
Using Macroinvertebrate Information
You may find in an aquatic ecosystem:
•
•
•
•
•
25 Mayfly larvae
15 Caddisfly larvae
20 Stonefly larvae
20 leeches
20 Midge larvae
Multiply each by the Biotic Value:
BIOTIC
VALUE
25 Mayflies
5.5
15 Caddisflies
5.5
20 Stoneflies
1.5
20 leeches
8.0
20 Midge larva
4.0
Total number of organisms =
No of
organisms X
biotic value
Biotic value
TOTAL biotic value =
Divide total biotic value by the total number of
organisms to get the biotic index value
• The biotic index
value is …………….
• Use chart to
determine water
quality based on
Biotic Index Value
• Based on the Biotic
Index Value, the
water quality is
…………………………….
Water Quality Biotic Index
Very poor
> 9.0
poor
7.6-8.9
Fair
6.1-7.5
good
< 6.0
Worked example:
BIOTIC
VALUE
25 Mayflies
5.5
25 x 5.5
137.5
15 Caddisflies
5.5
15 x 5.5
82.5
20 Stoneflies
1.5
20 x 1.5
30
20 leeches
8.0
20 x 8
160
20 Midge larva
4.0
20 x 4
80
Total number of organisms = 100
TOTAL biotic value = 490
Divide total biotic value by the total number of
organisms to get the biotic index value
Water Quality Biotic Index
• 490/100 = 4.9
Very poor
> 9.0
• Use chart to determine
water quality based on
Biotic Index Value
poor
7.6-8.9
Fair
6.1-7.5
good
< 6.0
• Based on the Biotic Index
Value, the water quality is
good.
Lichens
Indicator species of air pollution
Lichens: mutualistic organisms
Lichens are mutualistic organisms.
• Their bodies consist of a
leaf like thallus made of
the fungal part and algae
(or cyanobacteria,
photosynthetic bacteria)
• Several thousand
different species of
lichens
• The fungal part absorbs
and retains water and
ions
• the algal part carries out
photosynthesis
Lichens are highly susceptible to air
borne pollutants
• They have no waxy cuticle and the lichen thallus
absorbs and accumulates pollutant
• Lichens rapidly accumulate sulphur when exposed
sulphur dioxide pollution
• The algal part is most affected by the sulphur dioxide;
chlorophyll is destroyed and photosynthesis is
inhibited.
• Some species are more vulnerable than others
• bushy lichens need really clean air
• leafy lichens can survive a small amount of air pollution
• crusty lichens can survive in more polluted air
Lichens as indicators of SO2 levels
• Since industrialisation,
many lichen species
have become extinct in
Britain
• For example the beard
moss Usnea articulata.
Trees as indicator species
• The sweet chestnut
tree grows on acidic
soils not on soil rich in
lime.
• This species is an
indicator of soil
conditions
Other indicator species
River otters have been used as indicators of healthy,
clean river systems.
The spotted owl is an indicator of old
growth habitat.
Coral bleaching is an indication of
rising ocean temperatures.
The Northern Cricket Frog is an
indicator species for water quality.