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I will be working in a freshwater environment measuring certain variables in order to investigate my hypothesis, which is as follows - My hypothesis is that there will be wider species diversity with increasing oxygen saturation.

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Introduction

Middle

At site one a 'kick sample' was used due to a solid surface, with little mud. Sites 2,3 and 4 required a 'sweep netting' technique due to a highly sedimented surface and unsuitable for 'kick sampling'. Each technique involved either poking or kicking the surface in order to move the sediment about, and increase the chance of finding a higher species diversity. At each site a net would be used, and kicking or poking, whilst collecting, would only be going for one minute. This is to make sure it's a fair test. This is an example of net sweeping : 1. A net will be moved in a clockwise/anticlockwise direction in order to obtain species. A figure of 8 movement, with the net, would best suit this sampling technique, as it increase the chances of obtaining species. 2. A long stick would be ideal to poke the surface of the site, as it will disturb the sediment and allow more species to be obtained. This is an example of a kick sampling method: 1. A net will be moved in a clockwise/anticlockwise direction in order to obtain species. A figure of 8 movement, with the net, would best suit this sampling technique, as it increase the chances of obtaining species. 2. Moving feet forward and backwards, kicking the sediment, will allow the sediment to be broken up and allow species to enter the net. Collected species were placed into a white tray, so that the species were easier to identify. But before all of this white tray was washed, to make identification easier. The trays were then filled with stream water, so that the species collected were able to move about, this is important because species movement is a key factor of identification. From the tray, the species were put into petri dishes, so that the species can be identified individually. This would be done using pipettes and a species key. ...read more.

Conclusion

The velocity of the water decreases rapidly, allowing a calmer flow of water. This calmness is more appealing to species as they aren't' constantly being moved about by the flowing water. The decrease in flow also reduces the amount of sediment the water can carry as it's loosing energy. This then reduces the amount of dissolved solid flowing in the water. Once again the area is more open than secluded, allowing light to enter the site allowing any plants in the water to photosynthesise and thus replacing lost oxygen due to the slow flowing water. How the experiment could be improved The time allocated wasn't long enough, as the investigation seemed rushed. Over a longer period of time, samples and species counts would have been repeated in order to get an accurate average overall. With more accurate results a better conclusion can be made. Justification of Jacards Similarity Index This test is very beneficial as it allows us to compare any two sites in terms of species composition. With this test we can see how dramitcally, for example, the species diversity changes between sites 1 and 4, 2 and 3 etc. Justification of Simpson-Yule This stats test is used to determine the species diversity at each site. This can be done by calculating the number of species observed at each site. If high species diversity is to appear then the species must be present is approximately equal numbers. This stats test was seen to be useful as the species diversity can be related to the oxygen saturation and the presence or absence of species itself. Justification of stats tests The reason these two stats were used is that they give a good indication of species composition and how it changes as you go from site 1 to site 4. Both stats test help justify the original hypothesis, as the species diversity and similarity between sites can be directly related to oxygen saturation. ...read more.

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