Team Libbie

A Seasonal Correlation Analysis Between Sunlight and Carbon Dioxide.

Libbie Randolph, Nicholas Przybyl, Sam Stark-Rankins, Ju-Hwan Lim

Introduction- This lesson will introduce and explain the the mechanics and relationship between Sunlight and Carbon Dioxide measurements at the Christchurch School waterfront. We will discuss the biological effects that could change this relationship. It is proven that the absorption of energy from sunlight causes photoautotrophs, to begin the process of photosynthesis. Carbon dioxide is used in this reaction, and oxygen is a resulting byproduct. In contrast to this process, the lack of sunlight at night induces the process of respiration. During respiration, heterotrophs produce carbon dioxide, and the oxygen level decreases. With this general knowledge, it is predicted that sunlight and carbon dioxide level should negatively correlate.

Waterfront Monitoring System

Below is a video explanation of our Christchurch School Waterfront Monitoring System and an explanation of our web page.

Because of the dependency on sunlight, photosynthesis occurs during the day time. Carbon dioxide is used in this reaction and oxygen is produced, therefore oxygen levels increase during the daytime compared to carbon dioxide levels which decrease. As the amount of sunlight decreases, so does the plant's supply of energy, resulting in the process of respiration. During the process of respiration, a heterotroph relies on itself to produce the energy it needs. A simple representation of the reaction is shown below.

During respiration, a heterotroph uses stored oxygen and glucose to produce carbon dioxide, water, and ATP (energy.) This results in the decrease of oxygen levels, and an increase in CO2 production. Based on this knowledge, we can determine that as sunlight increases, O2 levels increase as well, while CO2 levels decrease; and as sunlight is limited, O2 levels decrease, while CO2 levels increase.

(Photosynthesis and Respiration Powerpoint)

Relationship between pH and Carbon Dioxide

The data we collect from the Christchurch Waterfront Monitoring system does not include carbon dioxide measurements, so we resort to using pH measurements. When CO2 dissolves in the water carbonic acid is a result, which in turn lowers pH. So in conclusion, when carbon dioxide measurements are high, pH measurements will be low and vice-versa. The graphs later in this presentation show pH measurements instead of CO2 measurements, so please take their relationship into account when analyzing the graphs.

Correlation Analysis

A correlation analysis shows to what extent one variable is affected by the other. The closer the value of the correlation is to 1 or -1, the closer the correlation is to perfect. (Further explanation of correlation analysis)

Summer Correlation between Sunlight and Carbon Dioxide

In this graph CO2 is measured by pH, the higher the pH, the lower the amounts of CO2; and the lower the pH the higher the amounts of CO2. During the summer, you can see that there is a correlation between sunlight and CO2. However, although there is a correlation between sunlight and CO2 levels, there is no correlation between the amount of sunlight effecting how much CO2 there is. For example, although the 22nd has a higher amount of sunlight, the 21st and 26th have higher levels of CO2. CO2 consistently peaks just after the highest amount of sunlight each day, about 4 p.m. You can also see that the CO2 levels are much more erratic than those of during the winter. This could be because more biology is involved during the summer, and depending on how many photosynthesizing plants and bacteria are in the water, you could have either super high, super low, or average levels of CO2. You can also see that for all but one measurement, CO2 levels are lower than measurements taken in the Winter. This could be as a result of warmer water, which less CO2 to be dissolved into the water. Also, because of the warmer water, more plants and bacteria are able to survive, which use up more CO2 and produce O2. It is because of this increase in biology that during the night respiration is able to produce enough CO2 that the water holds on to it and levels spike to highs averaging about what the highs do in the Winter, and during the day, photosynthesis is able to use up enough CO2 to where CO2 levels are lower than in the Winter.

Winter Correlation Between Sunlight and pH

During the winter, the same correlation can be seen as in the Summer. However, you can see that the pH has a more steady and consistent up and down pattern than the Summer, which could be caused by a decreased activity of biology. A possibility is that in the winter months, the pH levels are more dependent on temperature than biology, which accounts for the more consistent levels. Also, sunlight levels are considerably lower in the Winter than in the Summer, which results in lower water temperatures, and higher dissolved gas levels. As you can see, CO2 levels are about .15 higher in the winter than in the summer. A few things can account for this; 1. more CO2 is able to be dissolved in the lower water temperatures. 2. With less sunlight, less plants are able to survive, and photosynthesize, which takes up CO2 producing O2. You can also see that there is less of a variation from day to night levels than in the summer, which can also be explained by the decreased activity in biology.

Below are two graphs demonstrating the daily relationship between pH and sunlight on August 21, 2008 and December 25, 2008.

Both of these graphs show that as long as there is sunlight, the pH level will continue to increase; but as soon as sunlight reaches 0, there is a noticeable decrease in the production of CO2. In the summer these trends seem to be more obvious simply because the days are longer and the changes in pH are more noticeable. However, the relationship between pH and sunlight is not a 1 to 1 correlation because even when the measurements of sunlight begin to decrease, the pH level continues to increase until the sunlight has completely disappeared. These two variables are not in correlation. Although the trend may seem similar, and pH levels are affected by sunlight, the resulting correlation would not turn out to be worth measuring.

The graph above shows a comparison between the sunlight measurements in the winter and summer and the pH levels in the summer and winter. Clearly visible is the yearly cycle of how the days shorten during the winter, and the amount of sunlight decreases in the winter. Also noticeable is the pH relationship and how both summer and winter measurements start out the same, but while the pH levels in the winter time have a less visible increase, the pH levels spike in the summer time while the sunlight is at its highest measurement.

Conclusion

Before researching for information and data, we predicted through basic knowledge that the carbon dioxide and sunlight measurements at the Christchurch School Waterfront would negatively correlate. With the knowledge that sunlight induces photoautotrophs to begin the photosynthesis process which absorbes CO2 and produces O2 as a byproduct of the reaction, we determined that as sunlight and photsynthesis increased during the day, carbon dioxide levels would decrease. Likewise at night, when there was no sunlight and heterotrophs began the process of respiration that absorbed oxygen and produced carbon dioxide as a byproduct, we predicted that the carbon dioxide levels would increase as sunlight decreased. We relayed our collection of data, using pH as a substitute for CO2 , into graphs and correlation plots. We found that instead of the perfect, predicted correlation, our data proved to not correlate at all.

We concluded that carbon dioxide did not form a 1-to-1 correlation with sunlight because it did not depend on the specific measurement of sunlight, but whether there was any sunlight or not any at all. With the smallest amount of sunlight, photosynthesis still produces O2 and absorbes carbon dioxide. This is what causes the pH graph to continue to increase even though the sunlight is decreasing. Although the relationship between sunlight and carbon dioxide is not a perfect 1-to-1 correlation, there is still a distinct relationship between these two variables. The production of carbon dioxide still depends heavily on sunlight and the processes of photosynthesis and respiration.

To further test your knowledge on what we presented and review on this webpage, click on the review links below.