- Changes in weather
- Water speed
- Water temperature
Apparatus:
- Universal Indicator Paper
- Biotic Index Chart
- Large net
- Water basin
- Magnifying glass
- pH chart
Method:
- Select three different sites to collect data from
- Using the net, create a whirlpool in the stream so that organisms come up above the sand
- Sweep the net around in one direction, upstream to collect organisms
- Keeping the net still in the water but the top of it out of the water so that organisms are unable to escape, look at each organism with a magnifying glass and identify the organism using a biotic index chart.
- Record down the name of the organisms identified and calculate its biotic index value between 1 and 10, 1 being the most polluted water and 10 being the cleanest water.
- Using Universal Indicator paper, place the strip of paper into the water for 10 seconds and then take it out. There may have been a colour change.
- Compare the Universal Indicator paper to a pH chart to see which colour it is closest to, and record down the pH value of that water
Results:
A table to show the organisms present at the three sites and their Biotic Index Values
A table to show the Water Quality comparison with the Biotic Index
A table to show the pH level
A table to show the pH level, Biotic Index and Water Quality
Conclusion:
To conclude, the table above shows us that a relationship exists between the pH level and the Biotic Index. It can be seen that the acidity of the stream affects the organisms living in the water. These results show that between Site 1 and Site 3, there is pollution entering the water. This is shown by the water quality decreasing and also the water becoming acidic. The water quality reduces downstream as the Biotic Index increases, and the pH level decreases. This shows that the more polluted the water is, the more acidic the water is. I predicted ‘that the stream will be most polluted at the third site’ and ‘the pH level of the water high up in the stream will be less acidic.’ This shows that my hypothesis for this experiment was correct, due to the increase amounts of pollution entering the stream as we travel downstream.
Evaluation:
In future experiments, I can hopefully achieve better results by not committing the results I committed during this experiment. One of the problems I encountered was identifying organisms. Because they were small in size, it was not easy to identify them, and this may have caused some wrong identification which may have led to calculating an incorrect Biotic Index. For future experiments, to reduce the chance of this happening again, I may use a more detailed key with a brief description of the organism, and I will also have to be more careful in identifying organisms.
Another problem I came about was with the pH level. As there was a lack of a pH probe, I had to take the measurement manually, and this may have caused an incorrect reading. Not only that, I find that I may have kept the Universal Indicator in the water for not long enough, or possibly too long, which would have caused an incorrect reading of the pH level in the water. To reduce this error, next time, if I use a Universal Indicator again, I will keep the indicator in the water for an exact amount of time, but to make the results more precise, I will use a pH probe.
The final problem I came across during this experiment was when I was collecting the various organisms from the stream. I found that I may have not collected enough organisms. To collect more organisms, I should have used various different sizes of nets that way there was a higher chance of collecting smaller organisms which is blind to our eyes and can be seen only under a magnifying glass. If I had collected more organisms, there would have been a possibility of finding a wider spread of variety in organisms, which may have affected the Biotic Index.