# lab 1 interreach variability

**Topics:**Biotic component, Abiotic component, Statistical hypothesis testing

**Pages:**5 (2190 words)

**Published:**October 21, 2014

Interreach variability and correlation analyses between biotic and abiotic factors of the Old Chelsea stream BIO2129 Section

Demonstrators:

October 1, 2014

Department of Biology

Hypotheses

Water quality parameters such as pH, dissolved oxygen, seston, water temperature etc. are important variables in the abundance and diversity of benthic macroinvertebrates of the Old Chelsea stream. Therefore, it can be hypothesized that pH and dissolved oxygen have a direct correlation on biotic factors within the stream. Furthermore, due to the surface water velocity variations of the stream, it is hypothesized that water pH and dissolved oxygen interreach variability is statistically significant. Results

Note that for figures 1 and 2, the black bars and white bars represent site 1 and site 2 respectively. Furthermore, the horizontal axes represent the reach in this order: reach 5vs reach 7, reach 5 vs reach 1, reach 7 vs reach 1.

Figure 1. Bar graph showing the mean (+ standard error) of pH vs reach for both site 1 and site 2.

Figure 2. Bar graph showing the mean (+ standard error) of dissolved oxygen vs reach for both site 1 and site 2. Table 1. t-tests comparing reaches 1+5, 5 +7, and 7+1 for pH and dissolved oxygen within site 2. The means of 6 samples are demonstrated. The interreach variability is demonstrated by the calculated t column and is followed by a statistical conclusion. Site 2

Abiotic factors Reach # Mean Standard deviation Reach comparison Calculated t Statistical conclusion pH 1 8.206666667 0.015275252 1 v. 5 -2.218800785 Fail to reject 5 8.19 0.017320508 5 v. 7 -1.25 Fail to reject

7 8.216666667 0.011547005 7 v. 1 0.904534034 Fail to reject Dissolved oxygen 1 9.863333333 9.863333333 1 v. 5 -5.350053918 Reject 5 9.656666667 0.065064071 5 v. 7 -2.514432028 Fail to reject 7 9.86 0.01 7 v. 1 -0.045454545 Fail to reject

a_ α = 0.05

b_ Critical t = 2.776

c_ Degrees of freedom = 4

Figure 3. Significant correlation between an abiotic factor, pH, and a biotic factor, Simpson’s Diversity Index. This graph represents 20 data entries representing the 10 reaches from both site 1 and site 2.

Figure 4. Unsupported correlation between an abiotic factor, pH, and a biotic factor, total taxa. This graph represents 20 data entries representing the 10 reaches from both site 1 and site 2.

Figure 5. Unsupported correlation between an abiotic factor, dissolved oxygen, and a biotic factor, Simpson’s Diversity Index. This graph represents 20 data entries representing the 10 reaches from both site 1 and site 2.

Figure 6. Unsupported correlation between an abiotic factor, dissolved oxygen, and a biotic factor, total taxa. This graph represents 20 data entries representing the 10 reaches from both site 1 and site 2. Table 2. Results of the two correlation analyses of pH and dissolved oxygen in relation to biotic factors. The correlation is demonstrated by the r coefficient column and is followed by a statistical conclusion. Abiotic parameters Biotic variables r coefficient Statistical conclusion Mean Dissolved oxygen Total taxa/Nombre total de taxa 0.191611821 Fail to reject the null Total organisms/Nombre total d'organismes -0.311781239 Fail to reject the null Simpson's Diversity Index/Index de diversité0.381087476 Fail to reject the null E(1/D) 0.326179708 Fail to reject the null

Margalef's Taxa Richness index 0.306694027 Fail to reject the null Mean pH Total taxa/Nombre total de taxa 0.267408721 Fail to reject the null Total organisms/Nombre total d'organismes -0.373211203 Fail to reject the null Simpson's Diversity Index/Index de diversité0.605919154 Reject the null E(1/D) 0.498467217 Reject the null

Margalef's Taxa Richness index 0.440097839 Fail to reject the null a_ α = 0.05

b_ Critical r = 0.444

c_ Degrees of freedom = 18

Figure 7. Bar graph showing the mean % relative abundance with standard error of the 5 most abundant taxa in site 1 and site 2. In figure 1, we...

References: ngelier, E. 2003. Ecology of streams and rivers. pp. 27-99. Science Publishers, EnfeildGiller, P.S., Malmqvist,B. 1998. The biology of streams and rivers. pp. 30-98. Oxford University Press, New York

Michaud, J

ts = (8.19 - 8.206667) / [(0.0173212 + 0.0152752) / 3]½

ts = 0.904534

r = [1116.87 – (160.58 x 139) / 20]

[(1289.869– 25785.94 / 20) x (987 – 19321 / 20)]½r = 0.267408721

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