Functional Biodiversity

Figure 3: Functional Biodiversity 

Figure 3 Legend: 

The following figures describe the functional biodiversity using different measures. To gather this data, an EcoPlate was used and the values gathered by the EcoPlate were used to calculate the richness, evenness, and Shannon index. The graphs describe the averages for the each for both pesticide and no pesticide, as well as the standard deviations for each. Figures 3A, 3B, 3C, all had a sample size of 8. An unpaired t-test assuming equal variance was conducted on each of the richness, evenness, and Shannon index to determine all were statistically insignificant. The last graph included describes the Relative Utilization Efficiency percentage of Carboxylic Acids, Amino Acids, Carbohydrates, Polymers, and Amines. No t-test was conducted for these figures, as the sample size was 1. 

Figure 3 Method: 

To measure the biodiversity, a 0.5 grams of each soil sample were diluted using deionized water. The diluted solution was then distributed across an EcoPlate. The EcoPlate was left to process, and using a spectrophotometer measured the absorbance of each well using a 595nm wavelength. These values were then processed using Excel to calculate the Richness (S), Evenness (E) and Shannon Diversity Index (H). 

Figure 3 Evidence:

Regarding evenness, the average for the pesticide condition was 0.99, whereas the average for the no pesticide was 0.99. There was essentially no difference in this data. The standard deviation for the evenness for the pesticide condition was 0.01, whereas for the no pesticide it was .005. In regard to richness, the average for the pesticide condition was 28.13, whereas for the no pesticide condition the average was 29.38. There was only a very slight difference in data between the two. The standard deviation for the evenness for the pesticide condition was 2.10, whereas for the no pesticide condition it was 1.30. In regard to the Shannon index, the average for the pesticide condition was 3.28, whereas for the no pesticide condition it was 3.34. There was essentially no difference in the data. The standard deviation in regard to the Shannon Index was 0.10 for the pesticide condition, and 0.05 for the no pesticide condition. The T-tests for the richness, evenness, and Shannon Index were all over the threshold of 0.05, and therefore they are all statistically insignificant. The DNA in our soil samples looked for bacteria more in the pesticide groups than the no pesticides groups, which is why the richness and Shannon index are higher in pesticide than in no pesticide.

Figure 3 Conclusion: 

The data collected could not be used to support the claim that pesticides have a significant impact on moisture content. Despite there being a slight difference in average between all the values (no pesticide having a slightly higher average values for each) there is no statistically significant difference in evenness, richness, or Shannon between the two treatments. This can be shown by the overlapping error bars in each graph and the calculated p values being greater than 0.05. The lack of statistically significant differences is shown by the “nd” marking at the top of each graph.  The final figure of relative utilization efficiency shows the composition of both samples is similar due to the evidence pointing to a lack of statistical difference between the two. 

Figure 3 Explanation:  

Since there is no statistical significance between the Richness, Evenness, and Shannon Diversity Index between soil with or without pesticide, it reveals that the pesticide does not have a significant impact on all of these values. Evenness characterizes how similar soil microbes utilize different carbon sources. Possible reasons why pesticide does not change the Evenness values is that soil microbes often have a high resilience, meaning that they can maintain similar utilization patterns of carbon sources even when impacted by pesticides (Muturi et al). Richness represents the total number of substrates able to be effectively metabolized by the microbial community. Some microbes have the ability to rapidly adapt to pesticide stress through genetic mechanisms, allowing them to survive and maintain population levels, which would account for the no change between soil without pesticide (Tan et al.) The Shannon Diversity Index is a composite measure of biodiversity of carbon source utilization. Two possible reasons there was not a significant difference could be due to low pesticide concentration and/or community composition, which means that if the soil had a high diversity of microbes, the impact of pesticide on a single group might be compensated by the presence of others (Romero et al). Also, there was no difference in uses of carbon groups shown by the last graph, revealing the bacteria utilized the different carbon groups the same and that pesticide did not affect that. Since there was no statistical significance between the Richness, Evenness, and Shannon Diversity Index between soil with or without pesticide, we know to run more tests in order to see how or even if pesticide will change the microbe diversity in soil and how we can help the plants reach their healthiest lives.