|Difficulty: Advanced 9|
|Cost ($): 50|
Time required:2 hours to prepare, 10 hours for observation
Availability of materials:Guppies and tanks can be purchased at a nearby store
The mortality rate of fresh water guppies (Poecilia reticulata) increases as the acid level in the water increases.
With increased industrial pollution, gases such as nitrogen oxide and sulfur dioxide are released into the atmosphere and are subsequently absorbed by droplets of water which form in clouds. Acid is formed when these gases are dissolved in the water droplets. This acidic water then returns to us in the form of rain or snow. The acid rain that descends onto our towns, roads, farms and forests then flow into our rivers and lakes through existing drainage systems.
Water in the rivers and fresh water lakes normally have a pH level falling between 6 and 8. However as a result of acid rain, pH levels in rivers and lakes drop as the water becomes more acidic. These acidic waters are a danger to the survival of a myriad of aquatic plants and animals that live in our rivers and lakes.
pH is the measurement of acidity and alkalinity. It ranges from 1 to 14.
The materials required for this experiment are as follows:
The guppies in the more acidic water will die faster and the guppies in the least acidic water will live longer.
Use the below graph to plot the results of above observation.
The hypothesis that the mortality rate of fresh water guppiesincreases as the acid level in the water increases, is proven to be true. Acid is toxic to the guppies and as the level of acidity of the water increases, the guppies are poisoned and die.
The problem of acid rain and pollution is very serious.
Some aquatic animals may have higher tolerance for acidic water whereas others may die and become extinct. The increase in acidity can also affect the growth and development of the species. Some of the species may not be able to hatch the eggs in acidic water. All of these will have a serious impact on the food chain and biodiversity of the ecosystem.
The experiment can also be performed using aquatic plants to substitute the fish.
You might want to consider using different species of freshwater fish for the experiment, to ascertain if different species have a different level of tolerance for acidic water.
Vinegar can be replaced by soap detergent to see if it also has a toxic effect on fish.