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Introduction

Higher Level Biology Ecology Open Investigation Does the geographic location affect the biotic and abiotic factors in Brown Lake and 18 Mile Swamp located at North Stradbroke Island. I. Background Information North Stradbroke Island (NSI) is a sand island that is sitting on top of a layer of bedrock. This sand island is located in 20 kilometres off Brisbane City in south-east Queensland, Australia. [4] In this investigation, two specific sites in NSI will be looked at - Brown Lake and 18 Mile Swamp. The first experiment site that was tested was called Brown Lake. Brown Lake is classified as a perched lake. Perched Lakes are the most common of the sand island lakes. These types of lakes are found at elevations of 100 metres of more above sea level. As perched lakes are directly reliant on rainfall for their water source, they can rise and fall by several meters or more from year to year, depending on the climatic conditions at the time. Brown Lake is frequently visited by people, with thousands of families swimming and canoeing in its clam water each year. Until in 2005, even motorized water sports were allowed on the lake. Brown Lake possesses a clear "tea" colour. This is due to the surrounding trees and reeds and also from the layer of organic matter, which forms the bed of the lake. [3] The natural bushland surrounding the lake is home to many delicate wildflowers, including small ground orchids. Eighteen Mile Swamp was the second experiment site of this investigation. Eighteen Mile Swamp also known as 18 Mile Swamp is located behind the sand dunes of Main Beach and stretches from The Keyholes to the southern end of the island to Jumpinpin. [4] 18 Mile Swamp plays is ecologically important to North Stradbroke Island for over 260 species of birds are found in the swamp - much of the Island's wildlife can be observed at this location. ...read more.

Middle

Turbidity is a term to describe how clear the water is. The clearness of the water depends on the amount of total suspended solids, also known as TTS. The greater the amount of TTS, the murkier the water is thus causing the level of turbidity to be high. [1] Graph 1.0 shows that 18MS's turbidity level is much higher than BL. More specifically the mean turbidity level of BL is 5.50 NTU (Table 3.0) whereas 18MS is a significant, 14.5 NTU (Table 3.1). The spread of data (standard deviation) of BL shown in Graph 1.0 is less than 18MS. BL turbidity values ranged from 2.00-8.00 (Table 1.2) and 18MS values ranged from 3.00-30.00 (Table 1.3). 18 Mile Swamp turbidity level is much higher than that of Brown Lake for the 18MS has more organic detritus. More organic detritus was also recorded in Table 1.4 - "a lot of moss". Another reason for the high level of turbidity in 18MS is the lack of activity carried out at this site therefore there is an increase in erosion and nutrient are able to be suspended in the water. With increase number of organic matter and nutrients in the swamp this will affect algae growth. All of these types of vegetation may be the cause of 18MS colour being dark brown and the presence of moss (Table 1.4). Though the data values of Brown Lake and 18 Mile Swamp is clearly different when graphed, statistically there is no difference the turbidity level of BL and 18MS thus accepting the Null Hypothesis. Graph 1.1 compares the average level of oxygen of Brown Lake and 18 Mile Swamp. Oxygen levels are at a low concentration at lakes and swamps - low enough to still sustain aquatic life. Oxygen levels are also known as dissolved oxygen. [1] Graph 1.1 shows that the oxygen level of Brown Lake is higher than 18 Mile Swamp - BL oxygen level being 7.13 mg/l (Table 3.0) ...read more.

Conclusion

The human impacts may have affected the number of macroinvertebrates collected and the temperature and oxygen levels of the lake. 18 Mile Swamp is located beside the causeway built for vehicles. When collecting the data at 18 Mile Swamp, several vehicles drove pass. Because the swamp is below land level, this may have affect turbidity level for as the car droves pass the sand dirt were swirled up. Temperature and oxygen level may also be affected to due to the vehicle generating heat on the surface. Ensure that Brown Lake is undisturbed before carrying out the experiment. Also when carrying out the experiment at 18 Mile Swamp, divide the causeway and have a lane in the middle. Appoint the cars to drive on the other side of the causeway, furthest from the Swamp. This was decrease the impact of vehicles on the swamp. Random errors Random errors are changes in conditions and material used for the investigation. Random errors may have slightly tampered with results. Because they are random errors, they is no definite solution for this but it can be kept at a minimal level by carrying out several tests and keeping controllable other factors controlled. Appendix History data on the sensitivity score of Brown Lake and 18 Mile Swamp Date Brown Lake 18 Mile Swamp 04/08/2004 4.4 3.8 09/09/2004 4.8 3.9 01/08/2005 4.0 4.5 01/09/2005 4.7 3.5 Brown Lake Physical Parameters History Data Date Turbidity (NTU) Oxygen Level (mg/l) pH Level Salinity (0/00) Nitrites (mg/l) Nitrates (mg/l) 04/08/04 10 9 7.16 0 <0.3 0 09/08/04 10 8.30 7.11 0 0.1-0.3 <0.3 01/08/05 4.6 9 5.4 0 <0.3 0 01/09/05 10 8.5 7.2 0 <0.3 0 18 Mile Swamp Physical Parameters History Data Date Turbidity (NTU) Oxygen Level (mg/l) pH Level Salinity (0/00) Nitrites (mg/l) Nitrates (mg/l) 04/08/04 10 6 8.5 0 <0.3 0 09/08/04 10 7.37 6.18 0 0.3 <0.3 01/08/05 36 7.5 5.44 0 <0.3 0 01/09/05 10 7 6.8 0 <0.3 0 Table for Critical Values for T ?? ?? ?? ?? ...read more.

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