Hypothesis
The more polluted the water is, the less diverse the fresh water habitat.
Materials
Phoxmeter, pH meter, Turbidity tube, shallow white tray, pond-dipping net (D-ring net), plastic spoon, Hydro-prop stream flow meter, photometer.
To measure the water quality in Site 1 and 2, two factors will be considered.
- Abiotic factors- Oxygen concentration (mg/l) and saturation (%), Temperature, pH etc
- Biotic factors- the biotic factors will be observed using indicator species.
Techniques
The Abiotic measurements is taken first, because taking the species out with the net and getting into the pond will affect the Abiotic factors and thus our result.
Oxygen saturation, Oxygen concentration and Temperature were measured by putting the Phoxmeter probe in the collected sample of water and the readings were recorded. A sample of water was placed in a beaker, the cap of the pH meter in the Phoxmeter was taken off and the beaker was placed in. The pH meter was swirled round and the pH reading recorded. Turbidity was measured by filling both halves of the turbidity tube with water. Then some of the water was tilted off until the black spot at the bottom of the tube was very clear and the reading was recorded in mg/l. We measured the velocity of the water by placing the hydro-prop stream flow meter at half the depth of the water and timed it. The chemicals, Nitrates, phosphates and ammonia were all measured using a direct reading photometer. A different solution was added for measuring the chemicals in the beakers of water along with an indicator to get a colour change. Then the readings were obtained by using a grid.
The Biotic sampling was done by a method known as Kick sampling. The shallow white tray was filled with water. The sediments were disturbed for 25seconds while the D-ring net with its mouth facing into the water flow was placed with the flat bottom down into the disturbed region of the water, the organisms were caught and put into the tray for counting and identification, using the species identification sheet.
Results
Calculating Simpson’s Diversity Index (D)
Site 1
D = N (N – 1)/ ∑ n (n – 1)
N = 500
D = 500(499) / 104664
= 249500 / 104664
= 2.38
Site 2
N = 183
D = 183 x 182 / 10750
= 3.10
Analysis
The diversity index at site 2 is higher than that in site 1. This is because the diversity index was not fully represented at site 1, due to having more niches less well sampled. From the Graph, the pH at site 2 is more acidic. This may be as a result of the trees which surrounds this region, because the conifers releases humic acids as they drop in making it more acidic. It may also have been caused by bacterial activities. When bacteria decompose, they release CO2, which dissolves in water forming carbonic acid.
From the graph, it can be seen that site 1 has more nitrate. This may be as a result of cowdungs or even from sewage. In sewage, NH4 is converted to NO3 by bacterial activities so they are not high. There is also an increase in phosphates. In site 2, turbidity is 100 while it is >5 in site 1. This is because Site 2 has a scrap yard beside it and the stream run through peoples garden. From the Biotic data, the freshwater shrimp was more dominant at site 1. This is because freshwater shrimp has a high metabolic rate i.e. they will detect pollution quickly and incorporate it into their system. Therefore anything detrimental will kill them. From the data, group1, 2,3 and 6 organisms are intolerant to pollution, while group 7,8 and 9 are tolerant to pollution. Organism like the leech and Tubifex worm have a low metabolic rate and so they are able to get rid of pollutants. The Tubifex worm was seen to be more dominant than other species in site 2. This is because they have more haemoglobin, seen by red body, and so can survive in low oxygen conditions. This makes them able to out compete other species. The conductivity at site 2 is higher than that of site 1 because in Site 2 there are lots of suspended
