Intro:

In the 1950s, a causeway was built across the Great Salt Lake. This effectively ended all water flow between the two sides. After awhile, it became apparent there were going to be differences between the two sides. One was cloudy and the other was clear(er). Halobacteria are bacteria that thrive in salt rich environments. They do this by regulating an internal salinity level and keeping water in the cell. Because saltwater flows into the north end, the halobacteria thrive there and “cloud up” the water. Does the presence of salt increase “cloudyness” of water?

Hypothesis:

I predict that the higher the salinity the more halobacteria will be present. This is because halobacteria thrive in salt rich environments.

Method:

Day one:

1.       Each group is assigned one salinity measurement.

2.       Four trials will be completed by each group, one a control.

3.       Place salinity solution in four falcon tubes.

4.       They will be incubated overnight.

Day Two:

1.       Retrieve four samples from incubator.

2.       Using a pipette, suck up 4 full pipettes (to the highest line) from each and put into a clean, empty cuvette.

3.       Set spectrophotometer to 600 nm.

4.       Put blank into spectrophotometer and center it.

5.       Put in each cuvette and record absorbance.

6.       In between cuvettes, center with blank again.

Manipulated:

Salinity

Responding:

Absorption level

Controlled variables:

Tube size, amount, centered spectrophotometer,

Results:

There is a vague curve to the results pointing towards higher salinity = more bacteria. Overall, the class results were pretty skewed.

Conclusion:

1.       My hypothesis was supported by the results, if you exclude the outliers.

2.       One thing that could have gone wrong was the different spectrophotometers. They could have read differently between the groups, or they could have been on the wrong frequency. I also think some groups simply didn’t care and didn’t produce quality work.

3.       The results show that salinity does affect the presence of bacteria, which effects the transparency of water. Therefore, according to our results, the higher the salinity the less transparent the water.

4.       Some organisms cannot survive in high salinity environments. Often single celled organisms “dry out” when put in high salt environments, so they cannot survive there. Also many fish are freshwater fish that cannot survive in high salt environments. These fish require a salinity of less than 0.05% to survive. 41% of all known fish species are freshwater, so if an environment becomes high salinity those fish cannot survive there. The reason these fish can survive is because their gills can diffuse water but also keep the fish’s internal salinity correct.