The aim of the experiment is to determine whether the depth within a pond that water samples are taken from affects net and gross primary productivity of the water samples.
It is hypothesized that oxygen levels will be lower deeper in the pond, therefore leading to lower net and gross primary productivity, and oxygen levels will be higher shallower in the pond, leading to higher net and gross primary productivity.
This is because the algae found in the pond water use photosynthesis like all producers in order to produce a source of energy. A main product of photosynthesis is water, and this is one of the main sources of dissolved oxygen in an aquatic environment. An essential part of photosynthesis is sunlight, used by a plant through its chloroplast. Therefore, in order to photosynthesize, the producer must have access to sunlight. As light has a limited penetration through water, as you get deeper, the light becomes less available. This means algae deeper down in the pond will have less access to light, meaning there is less photosynthesis and therefore less oxygen being produced.
Independent variable: Net and gross primary productivity
Measured using the Winkler method to measure dissolved oxygen levels, then using this to determine primary productivity. Given in mg (of oxygen)/L.
Dependant variable: Depth that water samples are taken from within the pond.
Water samples will be taken from:
* Surface – 20cm deep
* 21cm – 30cm deep
* 31cm – 40cm deep
* 41cm – 50cm deep
* 51cm – 60cm deep
Size of water samples -
* Each water sample will be 300ml (full BOD bottle), and tested in a 300ml Biological Oxygen Demand (BOD) bottle with a stopper.
Where pond water samples are taken from -
* All taken from the largest pond located at Monte Sant’ Angelo Mercy College, North Sydney.
* All taken from the same location within the pond, only changing the depth at which they...