Wetland Macroinvertebrate Monitoring
Metrics
Now that you have collected your sample, sorted and picked the macroinvertebrates, and have
identified them it is time to calculate some benthic metrics with your data. Metrics are any
characteristic of an organism that can be measured. In the case of benthic metrics, these characteristics
include such things as what order or family the organism belongs to, how the organism feeds, where the
organism lives, and how tolerant it is of pollution. The idea behind metrics is that they can inform you
about the water quality of a particular site. There are many different possible metrics, an important
component of using metrics is to pick ones that apply to the particular type of water body you are
studying. In other words, if you find a list of metrics that someone used for mountain streams in
Kentucky, they probably don’t work well for wetlands in North Dakota. Below is a list of four metrics for
you to calculate from your samples. These metrics were taken from the Minnesota Pollution Control
Agencies list of metrics for Depressional wetlands in the temperate Prairies ecoregion. Three of the
metrics are called “Richness measures”. These are simple to calculate, you look at your list of organisms
and count how many different types you have of each group. Your answer will be a whole number. The
simplest of the three is total taxa, a measure of how many different things you had in your sample. The
fourth metric is called a “Composition measure”. These metrics take a little more math because they
are usually the percent of the total sample that is a particular taxa or type of macroinvertebrate.
Total Taxa – number of total taxa in the sample
ETSD Taxa - A measurement of the number of Ephemeroptera (mayflies), Trichoptera (caddisflies),
Sphaeriidae (pill clams), and Anisoptera (damselflies)
Odonata Taxa – Taxa richness of Odonata (Dragonflies and Damselfilies)
% Chironomidae – Abundance of Chironomidae (midge larvae) divided by total abundance in sample
An important concept of benthic metrics is that you need to know that if the number changes from one
sampling to the next, what does it mean? This is called the disturbance response. For example, if you
go out one year and you have 30 total taxa, then the net year you go down to 18 total taxa that should
tell you that something happened to that wetland and you lost some types of organisms. For this metric
a decrease in the number means the wetland has had something negative occur, an increase would
indicate the wetland has improved. So in this case the disturbance response would be a decrease in the
metric. Here is the disturbance response for the metrics we will work with:
Total Taxa
decrease
ETSD Taxa
decrease
Odonata taxa
decrease
% Chironomidae
increase
On the next several pages you will find an example that shows how to calculate the different metrics for
a particular sample. On each page I have highlighted the information you will need to determine the
metric.
Example taxa list for a wetland:
Jar
#
1
2
Phylum/Order
Diptera
Diptera
Family/Subfamily
Chironominae
Tanypodinae
Genus species
Count
174
27
3
4
5
6
Oligochaeta
Crustacea
Gastropoda
Mullusca
Lymnaiedae
Sphaeriidae
Hyllela azteca
Sagnicola
Pisidium
7
8
9
10
11
Hemiptera
Odonata/Zygoptera
Crustacea
Trichoptera
Gastropoda
Corixidae
Gomphidae
Gammaridae
Phyraganeidae
Physidae
Sigara
Gomphus
Gammarus
Ptilostomus
Physa
1
5
4
6
5
12
13
14
15
16
17
Hemiptera
Coleoptera
Odonata/Zygoptera
Odonata/Anisoptera
Odonata/Zygoptera
Collembola
Corixidae
Dytiscidae
Libellulidae
Coenagrionidae
Aeshnidae
Hespercorixa
Coptotomus
Libelulla
Ischnura
Anax
4
1
2
2
1
1
18
19
20
21
22
23
Insecta/Diptera
Insecta/Trichoptera
Odonata/Anisoptera
Ephemeroptera
Ephemeroptera
Chaoboridae
Leptoceridae
Coenagrionidae
Baetidae
Caeinidae
Chaoborus
Nectopsyche
Enallagma
Callibaetis
Caenis
5
1
1
2
1
TOTAL
58
11
29
14
Life
stage
L
L
L
L
L
L
L
L
A
A
L
L
L
L
L
L
L
Common
Name
midge
midge
Aquatic
worms
scud
snail
Pill clam
Water
boatmen
dragonfly
scud
caddisfly
snail
Water
boatman
beetle
dragonfly
damselfly
dragonfly
springtail
Phantom
midge
caddisfly
Damselfly
mayfly
mayfly
355
Calculating Total Taxa
Once the data is in the form above this is relatively easy. You just look at the list and there are 22
different kinds of organisms so your total taxa metric = 22.
Calculating Odonata taxa metric
Go through the list and mark those taxa that are in the Order Odonata. See example below, Odonata
taxa are in gray:
Jar
#
1
2
Phylum/Order
Diptera
Diptera
Family/Subfamily
Chironominae
Tanypodinae
Genus species
Count
174
27
3
4
5
6
Oligochaeta
Crustacea
Gastropoda
Mullusca
Lymnaiedae
Sphaeriidae
Hyllela azteca
Sagnicola
Pisidium
7
8
9
10
11
Hemiptera
Odonata/Zygoptera
Crustacea
Trichoptera
Gastropoda
Corixidae
Gomphidae
Gammaridae
Phyraganeidae
Physidae
Sigara
Gomphus
Gammarus
Ptilostomus
Physa
1
5
4
6
5
12
13
14
15
16
17
Hemiptera
Coleoptera
Odonata/Zygoptera
Odonata/Anisoptera
Odonata/Zygoptera
Collembola
Corixidae
Dytiscidae
Libellulidae
Coenagrionidae
Aeshnidae
Hespercorixa
Coptotomus
Libelulla
Ischnura
Anax
4
1
2
2
1
1
18
19
20
21
22
23
Insecta/Diptera
Insecta/Trichoptera
Odonata/Anisoptera
Ephemeroptera
Ephemeroptera
Chaoboridae
Leptoceridae
Coenagrionidae
Baetidae
Caeinidae
Chaoborus
Nectopsyche
Enallagma
Callibaetis
Caenis
5
1
1
2
1
TOTAL
58
11
29
14
Life
stage
L
L
L
L
L
L
L
L
A
A
L
L
L
L
L
L
L
Common
Name
midge
midge
Aquatic
worms
scud
snail
Pill clam
Water
boatmen
dragonfly
scud
caddisfly
snail
Water
boatman
beetle
dragonfly
damselfly
dragonfly
springtail
Phantom
midge
caddisfly
Damselfly
mayfly
mayfly
355
In this example there are five taxa that are in the group Odonata (see taxa that are highlighted in gray)
so the value for this metric = 5. Five may not seem like a lot, but that is actually a pretty good number
for this metric.
Calculating ETSD taxa metric
Go back to the list and mark the taxa that are in the orders Ephemeroptera and Trichoptera, along with
taxa that have the family Sphaeriidae and the suborder Anisoptera. Anisoptera is the scientific name for
the damselflies.
Jar
#
1
2
Phylum/Order
Diptera
Diptera
Family/Subfamily
Chironominae
Tanypodinae
Genus species
Count
174
27
3
4
5
6
Oligochaeta
Crustacea
Gastropoda
Mullusca
Lymnaiedae
Sphaeriidae
Hyllela azteca
Sagnicola
Pisidium
7
8
9
10
11
Hemiptera
Odonata/Zygoptera
Crustacea
Trichoptera
Gastropoda
Corixidae
Gomphidae
Gammaridae
Phyraganeidae
Physidae
Sigara
Gomphus
Gammarus
Ptilostomus
Physa
1
5
4
6
5
12
13
14
15
16
17
Hemiptera
Coleoptera
Odonata/Zygoptera
Odonata/Anisoptera
Odonata/Zygoptera
Collembola
Corixidae
Dytiscidae
Libellulidae
Coenagrionidae
Aeshnidae
Hespercorixa
Coptotomus
Libelulla
Ischnura
Anax
4
1
2
2
1
1
18
19
20
21
22
23
Insecta/Diptera
Trichoptera
Odonata/Anisoptera
Ephemeroptera
Ephemeroptera
Chaoboridae
Leptoceridae
Coenagrionidae
Baetidae
Caeinidae
Chaoborus
Nectopsyche
Enallagma
Callibaetis
Caenis
5
1
1
2
1
TOTAL
58
11
29
14
Life
stage
L
L
L
L
L
L
L
L
A
A
L
L
L
L
L
L
L
Common
Name
midge
midge
Aquatic
worms
scud
snail
Pill clam
Water
boatmen
dragonfly
scud
caddisfly
snail
Water
boatman
beetle
dragonfly
damselfly
dragonfly
springtail
Phantom
midge
caddisfly
Damselfly
mayfly
mayfly
355
The value for this metric would be 7. This one is a little tricky cause you need to look for several
different taxa that are in different columns. Look at the example above for guidance.
Calculating % Chironomid metric
In this one you not only need to find the taxa, but also the number of individuals, listed under the count
column. See example below.
Jar
#
1
2
Phylum/Order
Diptera
Diptera
Family
Chironomidae
Chironomdae
Subfamily/
Genus species
Chironominae
Tanypodinae
Count
174
27
58
11
29
14
3
4
5
6
Oligochaeta
Crustacea
Gastropoda
Mullusca
Lymnaiedae
Sphaeriidae
Hyllela azteca
Sagnicola
Pisidium
7
8
9
10
11
Hemiptera
Odonata/Zygoptera
Crustacea
Trichoptera
Gastropoda
Corixidae
Gomphidae
Gammaridae
Phyraganeidae
Physidae
Sigara
Gomphus
Gammarus
Ptilostomus
Physa
1
5
4
6
5
12
13
14
15
16
17
Hemiptera
Coleoptera
Odonata/Zygoptera
Odonata/Anisoptera
Odonata/Zygoptera
Collembola
Corixidae
Dytiscidae
Libellulidae
Coenagrionidae
Aeshnidae
Hespercorixa
Coptotomus
Libelulla
Ischnura
Anax
4
1
2
2
1
1
18
19
20
21
22
23
Insecta/Diptera
Insecta/Trichoptera
Odonata/Anisoptera
Ephemeroptera
Ephemeroptera
Chaoboridae
Leptoceridae
Coenagrionidae
Baetidae
Caeinidae
Chaoborus
Nectopsyche
Enallagma
Callibaetis
Caenis
5
1
1
2
1
TOTAL
Life
stage
L
L
L
L
L
L
L
L
A
A
L
L
L
L
L
L
L
Common
Name
midge
midge
Aquatic
worms
scud
snail
Pill clam
Water
boatmen
dragonfly
scud
caddisfly
snail
Water
boatman
beetle
dragonfly
damselfly
dragonfly
springtail
Phantom
midge
caddisfly
Damselfly
mayfly
mayfly
355
We had two taxa that are in the family Chironomidae. One had 174 individuals the other 27 for a total
of 195. The total for the entire sample was 355 individuals so
%Chironomid = 174/335 = 52%
So for the sample in the example your metrics would come out like this:
Total Taxa = 22
Odonata Taxa = 5
ETSD Taxa = 7
%Chironomid = 52%
You may have figured out by now that just doing one site and having only one set of data does not tell
you a whole lot. Theoretically you would want to repeat your sampling each year or you would want to
sample more than one wetland and compare them using these metrics. Lets compare metrics for two
different wetlands;
Metric
Wetland #1
Wetland #2
Total Taxa
22
17
Odonata Taxa
5
2
ETSD Taxa
7
4
%Chironomid
52
76
In this example all four metrics point to wetland #1 being healthier. The first three metrics all have a
disturbance response that is indicated by a decrease or lower number. Since wetland #2 has lower
values it is considered “more disturbed”. The fourth metric, % Chironomid, has a disturbance response
that is indicated by an increased or higher number. Since wetland #2 has a higher value for this metric it
is considered more disturbed.