Here is your essay on Ecological Indicators !

Since, specific factors often determine rather precisely what kinds of organisms will be present in a particular habitat; we can turn the situation around and judge the kind of physical environ­ment from the organism present. It is found that certain species of micro-organisms, plants and animals have one or more specific requirements and they become very much limited in their distribu­tion.

Thus, the occurrence of such species in a particular area indicates special habitat conditions, and such species are called bio­logical or ecological indicators, since they indicate some very speci­fic condition of the environment. Some of the Indian plant species which serve as ecological indicators have been tabulated in (Table: 171):

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Table: 17-1. Certain ecological indicators of plant species:

Name of species

Indicator (s) of

1. Utricularia, Chara. Wolffia, Oltelia alismoides

Water pollution

2. Peiridium sp.

Burnt and highly disturbed conifer­ous forest

3. Argemone maxicana

Recently disturbed or flooded soil

4. Rumex acetcsella

Acid grassland soil

5. Carissa spinarum and Capp ris spinosa

Intense soil erosion

6. Enicostema liuorale

Well drained soil

7. Saccharum spontaneum

Poorly drained soil

8. Ziryphus rotundifola

Soil deposition

9. Andropogon sccparium

Sandy loam type soil

10. Lippia nodiflora and Rumex sp.

Nitrate rich soil

11. Woodfordio foribunda and Chlorii virgata

High lime content of soil

12. Airiplen, Salsola, and Saueda

Saline water condition

13. Hydrilla veriic llcta and Cerato- phyllum demersum

Hard water

14. Watheria indica ste cutiasceae

Copper, lead and zinc rich soil

15. Equisetum plebejum and E. arvense

Gold rich soil

16. Silene cobahicola and Crotalaria eobaliicola

Cobalt rich soil

17. Spermacoce stricta

Iron rich soil

18. Pines and junipers

Uranium rich soil

In fact, Central Arid Zone Research Institute, Jodhpur has made the use of certain plant communities of Indian deserts to indicate the salinity and depth of groundwater (Table 17 2).

Table 172. Certain ecological indicators for groundwater of Indian deserts (Chatterjii arid Bharkar, 1977):

Plant Community

Indicated depth to water in meters (m)

Indicated total soluble salt contents in pph) in ground­water

1. Euphorbia caducifolia

12 to 18 m

1500 to 7000

2. Acacia Senegal—Anogeissus pendula

12 to 18 m

500 to 1500

3. Salvadora persica—Tainarix sp.

6 m

1500 to 3200

4. Salvadora oleoides—Prosopis cine­raria

10 to 20 m

500 to 2000

5. Prosopis cineraria—Ziz vphus nummularia, Capparis decidua

6 to 18 m

5000 to 10,000

6. Salvadora oleoides. Capparis deci­dua

6 to 12 m

-do-

7. Salvadora oleoides—Zizyphus nummularia

IS to 28 m

-4C-

8. Panicum lurgidum—CaHigonium polygonoides

6 to 18 m

1500 to 3200

9. Panicum lurgidum—Zizyplius com­plex

6 to 18 m

5000 to 10,000

10. Crotahria burhia—Lepladenia pyrotechnica

6 to TO m

5000 to 3200

11. Suaeda fruiicosa—Aebtropkms lagopiJes

6 m

11.000 »o 12.000

12. Capparis decidua

12 to 20 m

180 to 15000

13. Acacia indica—Nilothica sp.— Prosnp; s cineraria—Salvado ru oleoides

P. to 20 m

400 to 1500

Besides plants, certain micro-organisms serve as ecological indicators. For example, Escherichia coli, a bacterium, is an index organism for aquatic pollution. Some species of diatoms (Arphidinae) indicate the degree of sewage pollution of lakes. The pre­sence of Fusilinids (protozoans) in the soil indicated the petroleum deposits.

Similarly, certain animal species serve as ecological indicators. Chironomid larvae and maggots increase in number as the pollution increases. Burrowing may fly Hexagenia serves as indicator for well oxygenated aquatic environments.

Emigration and consequent dis­appearance of certain Indian fish species as Catla catla I abeo gonius, Labeo bata, Labeo rohita, Notopterus notopterus, etc., from Kalinadi river near Mansurpur Sugar Factory, indicate industrial pollution of water, as these fishes are found to be very sensitive to aquatic pollution (Verma, 1971).