Biotic Index.docx

Biotic Index Biodiversity can also be used an indicator of environmental quality. In aquatic ecosystems, for example, you can use the type and amount of macro-invertegrates to determine the quality of the water and the amount of organic pollution (usually from waste and excess nutrients) in the water. Macro-invertebrates are invertebrates larger than 1mm including arthropods, mollusks, annelids, nematodes, and platyhelminthes. You will be looking at two different “streams” and identifying the macro-invertebrates that were found there. Using the data table below, and the calculation for biotic index, determine the health of each stream. Stream A

A X Pollution Tolerance Value 3.6

B Number Found 3

= C Total Tolerance Value 10.8

Plecoptera (stoneflies)

1.0

0

0.0

Trichoptera (caddosflies) Most Caddisflies

2.8

0

0.0

Odonata Anisoptera (dragonflies)

4.0

0

0.0

Zygoptera (damselflies)

7.0

2

14.0

2.0

0

0.0

4.6

0

0.0

0

0.0

Taxon Ephemeroptera (mayflies)

Megaloptera (dobsonflies & alderflies) Cloeoptera (beetles) Hemiptera (true bugs) Diptera (True Flies) Chironomidae (midges)

6.0

0

0.0

Simuliidae (black flies)

6.0

2

12.0

Tipulidae (crane flies)

3.0

0

0.0

Amphipoda (scuds)

6.0

0

0.0

Isopoda (sowbugs)

8.0

3

24.0

Oligochaeta (earthworms)

8.0

0

0.0

Hirudinea (leeches)

10

0

0.0

Turbellaria (planarians)

4.0

2

8.0

Gastropoda (snails)

7.0

0

0.0

Total:

12

68.8

Stream B

A X Pollution Tolerance Value 3.6

B Number Found 3

= C Total Tolerance Value 10.8

Plecoptera (stoneflies)

1.0

5

5.0

Trichoptera (caddosflies) Most Caddisflies

2.8

0

0.0

Odonata Anisoptera (dragonflies)

4.0

0

0.0

Zygoptera (damselflies)

7.0

0

0.0

2.0

2

4.0

4.6

2

9.2

0

0.0

Taxon Ephemeroptera (mayflies)

Megaloptera (dobsonflies & alderflies) Cloeoptera (beetles) Hemiptera (true bugs) Diptera (True Flies) Chironomidae (midges)

6.0

0

0.0

Simuliidae (black flies)

6.0

0

0.0

Tipulidae (crane flies)

3.0

0

0.0

Amphipoda (scuds)

6.0

0

0.0

Isopoda (sowbugs)

8.0

0

0.0

Oligochaeta (earthworms)

8.0

0

0.0

Hirudinea (leeches)

10

0

0.0

Turbellaria (planarians)

4.0

0

0.0

Gastropoda (snails)

7.0

0

0.0

Total:

12

29.0

Calculation:

𝑆𝑆𝑆 𝑆𝑆 𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆𝑆 = 𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆 𝑆𝑆 𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆𝑆 𝑆𝑆𝑆𝑆𝑆 Stream A

Stream B

68.8/12 = 5.733

29.0/12 = 2.417

Reference:

Biotic Index

Water Quality

<3.75

Excellent

Degree of Organic Pollution Organic pollution unlikely

3.76-5.0

Good

Some Organic Pollution

5.1-6.5

Fair

6.6-10.0

Poor

Substantial Pollution likely Severe organic pollution likely

Conclusion: Write in FULL sentences to answer the questions below in paragraph form. ● What is the Biotic Index of your streams? ● What does that tell you about the water quality of your stream? ● What does that tell you about the amount of organic pollution? ● (Use your data/calculations to support your conclusions) The biotic index is a measure of water quality and organic pollution. The higher the biotic index, the lower the water quality and the higher the organic pollution. If an animal has a higher pollution tolerance value, it will increase the biotic index, and thus decrease water quality and increase organic pollution. Stream A had a biotic index of 5.733. According to the table above, this causes fair water quality and substantial organic pollution. Stream A, on the other hand, had a biotic index of 2.417. According to the same table, this creates excellent water quality as well as unlikelihood of organic pollution.

Stream A:

Stream B: