1. The main causes of pollution in rivers are:
River Pollution
Pollution is an addition to the environment with consequent adverse effects to that environment
The main causes of pollution in rivers are:
Agricultural Pollution - the effects of excess fertilisers and pesticides and farm slurry
Industrial Pollution - inorganic and organic waste that directly contaminates rivers
Dumps - spoil heaps and refuse tips release harmful chemicals that may leach into rivers
Domestic Pollution - treated effluent from sewage works is discharged into many of our rivers
Thermal Pollution - warm waste water from cooling towers and other industrial processes raises the temperature of the water and lowers oxygen solubility
Atmospheric Pollution - pollution of the atmosphere with nitrogen and sulphur oxides produces acid rain that modifies the pH of rivers which, in certain conditions, has lethal effects on the river organisms
Oil Pollution - can result from river traffic

2. a hillside from its source is crystal clear and unpolluted
Water tumbling down
a hillside from its source
is crystal clear and unpolluted
As rivers flow through towns, agricultural land and industrial areas, various pollutants enter the water body and influence the distribution and composition of aquatic life
As pollution loads increase, species diversity declines and the abundance of pollution-tolerant species increases

3. This river is becoming increasingly polluted as organic and inorganic
materials ‘run off’ from the surrounding agricultural land

4. Acid Rain
Industrial
Waste
Fertiliser
run off
Farmyard
Waste
Thermal Pollution
from cooling towers
Oil Pollution
Effluent from
sewage works

5. Methods for detecting and measuring river pollution include:
Sampling the populations of river invertebrates; river invertebrates are indicator organisms that serve as indicators of the state of the river by their presence or absence
Chemical testing to determine the amount of dissolved oxygen in the water
Chemical testing for determining levels of specific chemicals such as ammonia, nitrates and phosphates
Physical testing such as measurements of the turbidity of the water and the quantity of suspended solids
The amount of dissolved oxygen in the water is a major determinant for the presence and abundance of invertebrates in river ecosystems
The discharge of organic material into rivers lowers the oxygen availability and sensitive organisms are unable to survive

7. Plecoptera Stonefly nymphs Ephemeroptera Mayfly nymphs
These invertebrates are
intolerant of pollution
and low oxygen
concentrations; they feed
on detritus and other
invertebrates and have
flattened bodies and claws
for crawling over the
surface of stones
Mayfly and stonefly nymphs are clean water fauna and indicators of well-oxygenated unpolluted water
Plecoptera
Stonefly nymphs
Ephemeroptera
Mayfly nymphs

8. Trichoptera Caddis-fly larva Gammarus pulex Freshwater Shrimp
These invertebrates are tolerant of mild pollution and reappear in rivers polluted with organic material as oxygen levels return to normal

9. Asellus aquaticus water hog-louse Hirudinea Freshwater Leech Limnaea
Freshwater Snail
These invertebrates are tolerant of moderate pollution and reappear downstream from the polluting source

10. Bloodworm – midge larva
Annelida
Tubificid worms
in cases
Eristalis teneax
Larva of bee-fly
(rat-tailed maggot)
Chironomus thummi
Bloodworm – midge larva
These invertebrates are tolerant of high pollution and are adapted to survive the low oxygen levels in polluted water
Tubificid and Chironomus larvae possess a form of haemoglobin in their blood that exhibits a high affinity for oxygen
Rat-tailed maggots possess a breathing tube at their rear end which penetrates the river surface enabling these organisms to obtain oxygen from the atmosphere

11. intolerant of pollution
Clean water organisms
intolerant of pollution

12. Organisms tolerant of mild pollution that reappear as rivers recover from organic pollution

13. Organisms tolerant of mild pollution that reappear as rivers recover from organic pollution

14. The bright-red colour of Chironomus is due to the presence of haemoglobin, adapting this organism for survival in conditions of low oxygen concentration

16. Fresh water fauna return
The Effect
of Organic
Pollution on
River Fauna
Clean water fauna
Fauna tolerant
of high
pollution
Fauna tolerant
of moderate
pollution
Fauna tolerant of
slight pollution
Fresh water fauna return

17.
(song)

18. The Effect of Raw Sewage on the Chemical Composition
of a River Ecosystem
Ammonium ions
(NH4+)
Dissolved
oxygen
Biological
Oxygen
Demand
(BOD)
Nitrates
(NO3)
Suspended solids
Explain the graph

19. the river increases the quantity of suspended solids, and light
Entry of sewage into
the river increases the
quantity of suspended
solids, and light
availability to oxygen-
producing aquatic
plants is reduced
Ammonium ions
(NH4+)
Dissolved
oxygen
Biochemical
Oxygen
Demand
(BOD)
Nitrates
(NO3)
Nitrates stimulate
the growth of algae
Suspended solids
Organic material in the discharge provides an abundant source of food for bacteria and other decomposers resulting in a rapid growth of their populations
The oxygen level falls dramatically as it is utilised
by decomposers for respiration and the BOD is high
Organic material is gradually broken down and the river recovers from the polluting effects as it flows downstream
The Biochemical Oxygen Demand reflects the demand for oxygen by the decomposers; it is a measure of the dissolved oxygen taken up by microorganisms in decaying the available organic matter
Ammonium ions are released as decomposers oxidise the organic matter and these are rapidly oxidised to nitrates by nitrifying bacteria

20. Species diversity decreases with high pollution and gradually
The increased nitrate levels, resulting from microbial decomposition of organic material, stimulates the growth of algae
River invertebrates are indicators of the degree of pollution in the river
Species diversity decreases with high pollution and gradually
increases again as the river recovers

21. Pollution from Nitrogen Fertilisers
Nitrogen based fertilisers have many benefits such as increased productivity in plants/crops but they have had detrimental effects:
Reduced species diversity – grass/nettles prefer nitrogen rich soil, so they out compete other species e.g. silage fields
Leaching – Rain water removes nitrates from soil and then into streams/rivers. This can be harmful if water is a source of drinking water. High nitrate levels can lead to inefficient oxygen transport in babies and stomach cancer.
Eutrophication – Fertilisers leaching into watercourses.

22. Eutrophication
Eutrophication is a natural process but can be made worse by over use of fertilisers (usually inorganic).
In most lakes and rivers, nitrates exist in low amounts and are limiting factor for plant and algal growth
Over use of fertiliser on agricultural land near watercourses can lead to leaching of nitrates into lakes and rivers, leading to nitrate levels increasing.
Algal and plant growth increases exponentially. Algal growth is mainly on surface and upper layers – leads to ‘algal bloom’
This dense layer absorbs most sunlight and prevents it from penetrating lower layers. Light is now limiting factor for lower plant life – starts to die.
Dead plants and algae provide food for saprobiotic bacteria, so their population number grows exponentially.
These decomposers require more oxygen for respiration, so the concentration of oxygen decreases but nitrates increase due to decomposition.
Oxygen levels are now limiting factor for population of aerobic organisms (fish, invertebrates) and these die off.
Less competition for anaerobic organisms. These continue to grow in numbers.
Dead material is further broken down releasing more nitrates and toxic waste such as Hydrogen Sulphide – Water becomes putrid.

23. Complete troubled waters activity

24. Biotic Data
Biotic data was used to calculate the Simpson’s Diversity Index and the Trent Biotic Index for each site
The Biotic Index is given as a Roman Numeral which describes the quality of the stream, from 0 for
very polluted, to X for very clean
The index is dependent upon the presence or absence of certain indicator species, as well as the composition of the community
Instructions for determining the index are provided in the workbook

25. (After F. Woodiwiss, Trent River Authority
Trent Biotic index
(After F. Woodiwiss, Trent River Authority