INCREASED OCEAN ACIDITY: EFFECT ON PHOTOSYNTHETIC PROCESS OF CHAETOMORPHA ALGAE

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1 CONTENTS 2 Acknowledgements ............................................................................................................................... 2

3 Abstract ................................................................................................................................................. 2

4 Literature Review .................................................................................................................................. 2

4.1 How CO2 Is Changing Globally .................................................................................................... 2

4.2 Increased CO2 in the ocean ........................................................................................................... 3

4.3 Photosynthesis ............................................................................................................................... 4

4.4 Leaf Anatomy ............................................................................................................................... 4

4.5 Chaeto ........................................................................................................................................... 7

5 Research Plan ........................................................................................................................................ 8

5.1 Rationale ....................................................................................................................................... 8

5.2 Researchable Question .................................................................................................................. 8

5.3 Hypothesis..................................................................................................................................... 8

5.4 Procedure ...................................................................................................................................... 8

5.5 Data Analysis ................................................................................................................................ 8

6 Methodology ......................................................................................................................................... 8

6.1 Materials ....................................................................................................................................... 8

6.2 Using the refractometer ................................................................................................................. 9

6.3 Using the Test Kits ...................................................................................................................... 10

6.4 pH sensor calibration .................................................................................................................. 10

6.5 Procedure .................................................................................................................................... 11

7 Results ................................................................................................................................................. 12

7.1 Qualitative ................................................................................................................................... 12

7.2 Quantitative ................................................................................................................................. 12

8 Analysis and Discussion ..................................................................................................................... 13

9 Conclusion .......................................................................................................................................... 14

10 References ....................................................................................................................................... 15

11 Appendix ......................................................................................................................................... 15

11.1 Limitations and Assumptions...................................................................................................... 15

11.2 Literature Review Procedure ...................................................... Error! Bookmark not defined.

11.3 Arduino Code .............................................................................................................................. 16

11.4 Poster Information ...................................................................... Error! Bookmark not defined.

11.5 Notes ........................................................................................... Error! Bookmark not defined.

11.6 Data ............................................................................................. Error! Bookmark not defined.

11.6.1 Tables .................................................................................. Error! Bookmark not defined.

11.6.2 Graphs ................................................................................. Error! Bookmark not defined.

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2 ACKNOWLEDGEMENTS I would like to express my appreciation to my parents for helping me with decision

making throughout my project, funding my project, and moral support. I would also like to thank

Mrs.Taricco and Mrs.Curran for their advice and help throughout the project. Lastly, I would like

to offer my thanks to Mr.Loven and Emma Beeler for their help regarding the sensors used in my

project.

3 ABSTRACT Atmospheric carbon dioxide levels are rising. The oceans absorb carbon dioxide, causing

the pH level of the ocean to decrease. When carbon dioxide reacts with water, it forms H+ ions,

lowering the pH level of the water. At the current rate, the global average pH level is projected to

drop by 0.4 within the next century. The effects that this decrease have on aquatic plants are not

well known. In land plants, increased atmospheric carbon dioxide levels cause the rate of

photosynthesis to increase. Eight buckets were set up with water at a pH level of 8.2, the global

pH level before the Industrial Revolution. Carbon dioxide was added to four of the buckets until

the pH levels reached 7.7. After three days, the Chaetomotropha algae was added to each bucket.

The dissolved oxygen and pH levels were measured every day. Throughout 14 days of testing,

the dissolved oxygen levels for the control group slowly increased, while the pH levels remained

constant. For the treatment groups, the dissolved oxygen concentration rose, then fell rapidly

after five days. The pH levels decreased, then began to stabilize. More testing is needed to

determine how future pH levels will affect aquatic plants.

4 INTRODUCTION

Atmospheric carbon dioxide (CO2) levels have been increasing in the last century. This has

caused the carbon dioxide concentrations of ocean water to increase dramatically. The pH level

of the ocean is directly proportional to the CO2 levels of the ocean, and as the carbon dioxide

concentration of the ocean, the pH level decreases. The pH level is expected to drop 0.4 units in

the next century. An acidification this rapid has not happened in millions of years, and it is

unknown how the rapid acidification will affect ocean life. The goal of the project was to test

how the photosynthetic process of aquatic plants was affected by this rapidly changing

environment.

5 LITERATURE REVIEW 5.1 HOW CO2 IS CHANGING GLOBALLY

Since the Industrial Revolution, carbon dioxide (CO2) levels have been rising. For the

past 650,000 years, the range of CO2 levels has been 180 ppm to 300 ppm. Preindustrial CO2

levels were about 280 parts per million (ppm), but as of 2013, the atmospheric CO2 levels have

risen to about 380 ppm. Since the 2000s, the atmospheric CO2 levels have been rising at a rate of

about 1.9 ppm per year (Brewer 2009).

This increased CO2 has many effects on the environment. For example, CO2 and methane

are two greenhouse gases partially responsible for global temperature increases. These

atmospheric gases trap heat, and while they become more abundant in the atmosphere, more heat

gets trapped. Globally, the atmospheric temperature has increased about 0.74⁰C in the past

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century alone. Not all CO2 emitted by humans ends up in the atmosphere. CO2 emissions are

partially absorbed by plants and the ocean. The amount of the CO2 emitted by humans that plants

absorb fluctuates from 30% to 80% based on weather conditions, vegetation, fires, and other

natural disasters (“Global Climate Change: Evidence and Causes”). Photosynthesis by plants,

algae, and bacteria converts about 10% of the total atmospheric carbon dioxide to carbohydrates

(Whitemarsh 2007). Meanwhile, the land absorbs about 25% of human CO2 emissions, whereas

the ocean absorbs 25% of humanity’s total CO2 emissions. The remaining 50% of human CO2

emissions could stay in the atmosphere for up to a century (“Global Climate Change: Evidence

and Causes”). The graph below shows how the atmospheric CO2 levels have been changing over

time.

Figure 1: This graph shows average atmospheric CO2 levels from 1960-2010.

5.2 INCREASED CO2 IN THE OCEAN

The increasing CO2 in the atmosphere has large effects on the ocean. Overall, the ocean

absorbs a total of about 85% of human’s total carbon dioxide emissions, and at this moment, the

oceans are absorbing about one million tons of carbon dioxide per hour (Brewer, 2009). One

major effect of increased carbon dioxide on the ocean is a decrease in the pH level. PH is the

measure of the amount of hydrogen ions found in a substance ranked on a logarithmic scale from

1-14, with 1 being acidic and 14 being basic (“The Chemistry of Ocean Acidification”). Since

the start of the Industrial Revolution, the pH level of the ocean has dropped from 8.2 units to 8.1

units, which represents a 30% increase in acidity. Over the next century, it is expected that the

pH of the ocean will drop another 0.4 units, representing a 150% increase in acidity (Brewer

2009). An acidity of this level has not occurred for over twenty million years. The CO2 also

affects the chemical composition of the ocean, particularly the concentration of carbonate ions

found in the ocean (NOAA). Carbonate ions (CO32-) are an essential molecule for many aquatic

organisms, particularly shellfish and snails. These organisms use carbonate ions to build their

skeletons. Carbonate ions also form the calcified plates of microscopic phytoplankton that make

up a large and essential part of the food chain (Brewer 2009). However, when carbon dioxide

reacts with ocean water, the carbonate ion reacts with the loose hydrogen ions to form

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bicarbonate, which is not used by organisms in the same way (HCO32-) (“The chemistry of

Ocean Acidifications). Scientists predict that over the next century, there will be a 50% decrease

in carbonate ion concentrations in the surface ocean layer (“What is Ocean Acidification?”).

5.3 PHOTOSYNTHESIS Photosynthesis occurs in plants, algae, and some bacteria. There are two types of

photosynthetic reactions: oxygenic and anoxygenic. Oxygenic reactions use H2O and release O2.

Anoxygenic reactions reduce other molecules, such as sulfur. Plants, algae, and some bacteria

use oxygenic, while some bacteria use anoxygenic. The equation for oxygenic photosynthesis is

6CO2 + 12H2O + Light Energy -> C6H12O6 + 6O2 + 6H2O. This means that 6 carbon dioxide

(CO2) molecules, 12 water (H2O) molecules, and light energy are used by the plant to create one

glucose compound (C6H12O6) and 6 molecules of water. Much of the process takes place in the

chloroplasts, and the plant provides the chloroplasts with carbon dioxide, nitrogen, water, and

other organic materials necessary for photosynthesis (“The Photosynthetic Process”).

5.4 LEAF ANATOMY Photosynthesis occurs in the chloroplasts, which are organelles found in the leaves of

plants. Chloroplasts have DNA, which makes them capable of replicating themselves, and are

believed to have once been a separate organism. The membranes of the chloroplasts are

semipermeable, meaning that they allow certain materials, such as water, CO2, and other small

molecules through while blocking others. The membrane system inside the chloroplasts contains

most of the proteins needed for the light reaction of photosynthesis. These membranes are made

up of proteins, lipids, and electron carriers. The membranes are surrounded by water, and an ion

or molecule must pass through the membrane to reach the other side. The aqueous section is

where the proteins necessary for the reduction of CO2 are located. The proteins are arranged

asymmetrically, which allows energy released during electron transport to create an

electrochemical gradient of proteins across the membrane (“The Photosynthetic Process”).

Plants use pigments to absorb light energy, which is used in photosynthesis. Visible light

(wavelengths 400-700 nm) is primarily used. These pigments are bound to light-harvesting

proteins located on the membrane. These proteins are effective, and under optimal

circumstances, over 90% of the energy is transferred to the reaction center within a few hundred

picoseconds (one trillionth of a second). The pigments used are mainly chlorophyll a,

chlorophyll b, and carotenoids. The figure below shows how much light is absorbed and how the

photosynthetic rate is affected based off the wavelength of light.

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Figure 2: These graphs demonstrate the percentage of light that is absorbed and how the photosynthetic rate changes based off

the wavelength of the light.

Chlorophyll a, chlorophyll b, and caratenoids are all optimal at different wavelength of

light, but none of them absrob light in the 550-625 nm range well. This is light in the green

range, and it is reflected, which is why plants appear to be green, and means that light that is

within this range is not capable of supplying the energy plants need to photosynthesize.

Photosynthesis is separated into two stages: light reactions and the dark reactions. The

light reactions include the electron and protein transfers, and takes place in a membrane system.

Photosynthesis consists of many electron transfers from one electron carrier to the other. Many

electron carriers are within protein complexes. The electron enters the protein at one site, is

transferred from one carrier to the other, and leaves the protein complex at a different site. The

protein controls the route the electron takes by placing metal ions and aromatic groups in specific

locations of the protein. This allows the protein to control electron transfer reactions. However,

not all electron carriers are within protein complexes. The reduced versions of

plastoquinone/ubiquinone and nicotinamide adenine dinucleotide phosphate (NaDPH), or NaDH,

act as mobile electron carriers. These carriers must bind to special parts of the protein known as

binding sites, which are very specific and control the rate and pathway of electron transfer (“The

Photosynthetic Process”).

Two reaction centers, photosystem II and photosystem one, are used in oxygenic

photosynthesis. Photosystem II uses light energy to oxidize water and drive the reduction of

plastoquinone. The complex in which photosystem II occurs is composed of over 15

polypeptides, and nine redox components (chlorophyll, plastoquinone, pheophytin, tyrosine,

manganese, iron, cytochrome b559, carotenoid and histidine) go through the process of light-

induced electron transfer. However, the function of all the redox components are not known. For

example, the presence of cytochrome b559 is necessary for photosystem II to occur, but the

function that this protein plays in the photosystem is unknown. The process is initiated by the

charge separation of P680 and pheophytin, creating P680+ and pheophytin-. Subsequent steps

prevent the charges from recombining by rapidly transferring the electron to a plastoquinone

molecule (QA), which is permanently bound to photosystem II. The electron is then transported

to another plastoquinone molecule: QB-. QB- becomes fully reduces when two hydrogen atoms

are added. QB- is located close to the membrane, and the hydrogen atoms are taken from outside

the membrane and brought in to reduce QB-. Photosystem II can oxidize water. It is one of the

only protein complexes that can do so, and the oxidation of H2O leads to the release of O2 into

the atmosphere. However, the steps that lead to the oxidation of water are still unknown (“The

Photosynthetic Process”). The figure below shows the steps the electron takes through

photosystem II.

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Figure 3: This figure shows the path the electron takes through photosystem II.

Photosystem I catalyzes the oxidation of plastocyanin, which is a small soluble Cu-

protein, and reduces ferredoxin, a small FeS protein. FeS proteins act as electron carriers. The

movement of electrons does not depend on protein translocation, unlike in photosystem II.

Photosystem I is composed of many proteins that act as ligands, or molecules that bond to

another. Similarly to photosystem II, chlorophyll molecules provide energy for the system.

However, unlike photosystem II, the chlorophyll is directly bonded to the reaction centers.

Charge separation in photosystem I is between P700 and a chlorophyll monomer. The figure

below shows the subsequent electron transfer steps (“The Photosynthetic Process”).

Figure 4: This figure shows the steps the electron takes through photosystem I.

Electrons are transported from photosystem II to photosystem I by intermediate carriers.

The electron is transported from water to NaDP+, forming NaDPH. NaDPH stores much of the

initial light energy that the plant receives. This light energy is stored as redox free energy, which

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is a type of chemical free energy. In addition, this transfer of electrons creates a proton

imbalance, which creates an electric field (“The Photosynthetic Process”). Through this process,

the redox free energy stored in NaDPH is converted to an electrochemical potential of proteins

(“The Photosynthetic Process”). An electrochemical potential is the sum of chemical and

electrical potentials of the component (“Lecture 9”), while potential is the maximal capacity for

work (“Energy, Work, and Heat”).

The electrochemical potential stored is used by ATP-Synthase, a protein bound complex,

to attach phosphate to adenosine diphosphate (ADP) to form adenosine triphosphate (ATP). This

process changes the energy from electrochemical potential energy to phosphate-group transfer

potential. The energy stored can be transferred from ATP to another molecule by transferring the

phosphate group to another molecule. The net result of this reaction is the conversion of radiant

energy to energy in the form of redox free energy found in NaDPH and phosphate-group transfer

potential in the form of ATP (“The Photosynthetic Process”).

The dark reaction, also known as the Calvin Cycle, consist of the synthesis of

carbohydrates from CO2, and uses the energy from ATP and NaDPH produced in the light cycle.

The reduction of CO2 takes place in the aqueous section of the chloroplast, and involves a series

of enzyme reactions. The first step of the process is catalyzed by Rubisco, a protein that attaches

the CO2 to a five-carbon compound. This reaction produces two molecules of a three-carbon

compound. Subsequent reactions use several enzymes to reduce the carbon compounds and

rearrange them to form carbohydrates (“The Photosynthetic Process”). The figure below shows

the steps of the dark reaction.

Figure 5: This image demonstrates the steps of the Calvin Cycle.

5.5 CHAETO Chaetomorpha algae, or chaeto for short, is a free floating saltwater plant. Chaeto is sold

as a clump of the live plant, and is simply added to the water. When growing chaeto, a large

amount of lighting and a moderate amount of water flow is necessary for the plant to flourish

(Chaetomorpha algae, aquacultured). Power heads are a device that commonly used in aquariums

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to create water flow. This water flow is used to spread out the warm water, ensuring that there

are no hot or cold spots in the water (What Is an Aquarium Powerhead? Do I Need One?).

Chaeto requires water that is 22-25⁰C to grow, as well as a pH level of 8.1-8.4. The dKH

(carbonate hardness) of the water should be 8-12. The specific gravity (salinity) of the water

should also be at 1.025. Chaeto absorbs phosphates and nitrites in the water, which makes it a

popular choice for people who are keeping aquariums and wish to keep the phosphate and nitrite

of the water in the aquarium low (“Chaetomorpha algae, aquacultured”).

6 RESEARCH PLAN

6.1 RATIONALE The increased levels of CO2 in the atmosphere are causing the pH of the ocean to rapidly

decrease. The effect of this decrease in pH on plant life has not been well studied, but it has been

shown to affect animal life in various ways. Carbon dioxide is a necessary resource for

photosynthesis, but it is uncertain whether increasing the concentration of carbon dioxide will

help an aquatic plant photosynthesize.

6.2 RESEARCHABLE QUESTION How will increasing the acidity of ocean water by adding condensed carbon dioxide affect

the photosynthetic process of Chaetomotropha algae as seen through the dissolved oxygen

concentration of the water?

6.3 HYPOTHESIS The increased carbon dioxide in the water will cause the rate of change of the dissolved

oxygen concentration to increase.

6.4 PROCEDURE 8 four gallon containers with a salinity of 1.025 was set up. The temperature was

maintained at 26⁰C. The nitrate, nitrite, and ammonia levels were measured to ensure that they

are at 0 ppm. In the first one, no dry ice was added. 1 teaspoon of alkaline buffer and ¼ teaspoon

of acid buffer were added every day to each bucket for 2 days to set the pH level to 8.2. Then,

900 grams of dry ice were added until the pH is 7.7. After 3 days, ¼ lb of chaeto was added to

each bucket. Every day, the pH and dissolved oxygen concentration of the water inside the tank

were measured. Every week, the salinity, nitrate, nitrite, and ammonia levels were measured. The

testing period lasted for two weeks.

6.5 DATA ANALYSIS During photosynthesis, plants take in CO2, light, and water, and expel O2. As algae

photosynthesizes, it uses the CO2 in the water, and expels O2, causing the concentrations of these

two compounds in the water to change. If there is less CO2 in the water, the plant is taking in

more CO2 for photosynthesis. If the O2 concentrations are higher, the plant is producing more O2,

due to its increased rate of photosynthesis. Both the CO2 and O2 concentrations will be graphed

on a scatter plot, and a line of best fit will be found to see how the rate that CO2 and O2 change

are different. T-tests will be used to see if there is a statistical difference between their

concentrations.

7 METHODOLOGY 7.1 MATERIALS

Table 1: This table lists out all the materials used in the project, as well as the brand, quantity, and location of purchase.

Quantity Material Brand Store

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8 plants Chaetomorpha algae Live Aquaria LiveAquaria

0.75 gallons Reef Salt Instant Ocean Krystal Clear Aquatics

24 gallons Water Tap

1 Refractometer Aqua Craft Amaon

60 mL Refractometer Calibration Solution Aqua Craft Amazon

1 kit Ammonia Test Kit API Krystal Clear Aquatics

1 kit Nitrate Test Kit API Krystal Clear Aquatics

1 kit Nitrite Test Kit API Krystal Clear Aquatics

1 Aquarium Thermometer Zoo Med Krystal Clear Aquatics

8 Four Gallon Buckets Market Basket Market Basket

1 4100K Florescent Light Philips Home Depot

1 pH sensor DFRobot Robot Shop

1 pH Circuit Board DFRobot Robot Shop

1 Dissolved Oxygen Meter Milwaukee Test Equipment Depot

1 Arduino Uno Arduino Mass Academy

2 Florescent Lights Lithona Home Depot

1 Acidity Buffer Seachem Krystal Clear Aquatics

1 Alkalinity Buffer Seachem Krystal Clear Aquatics

720 grams Dry Ice Penguin Brand Lake Boone Ice Company

7.2 USING THE REFRACTOMETER

Figure 6: These are the various parts of a refractometer.

The refractometers was used to measure the salinity and specific gravity of a water. The

refractometer (Figure 6) was calibrated to 35 ppm. Three drops of refractometer calibration

solution were placed on the daylight plate. The setup was left for 30 seconds. The refractometer

was held up to the light and a small flathead screwdriver was used to screw in the calibration

screw until the measurement level was at 35 ppm. Then, the saltwater sample was added to the

daylight plate and the refractometer was held up to the light. The salinity of the water was read

by looking through the eyepiece of the device and noting where measurement level was located.

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After the necessary measurements were taken, the daylight plate was cleaned and the

refractometer was stored in its container.

7.3 USING THE TEST KITS

These test kits were used to measure the nitrate, nitrite, and ammonia levels of the water.

For each test kit, 5 mL of the water was taken and placed in a covered cylinder. The number of

drops specified by the instruction manual were added to the water, and the water is covered with

a cap and shaken for the required number of seconds. To see the number of drops needed and the

amount of time the solution needed to be shaken, refer to table 2. The solution was left for the

required time. To measure the ammonia and nitrate, the process was repeated with the second

solution. After the required time had passed, the color of the water was compared to the color

charts given with the kits to determine the level of these gases in the water. Table 2: This table shows the solution needed, number of drops needed, time the water was shaken, and the time waited before

the color was measured.

Solution Drops Added Time Shaken Time Waited

Nitrate Nitrate #1 10 drops 5 seconds 30 seconds

Nitrate #2 10 drops 1 minute 5 minutes

Nitrite Nitrite #1 5 drops 5 seconds 5 minutes

Ammonia Ammonia #1 8 drops 0 seconds 0 minutes

Ammonia #2 8 drops 5 seconds 5 minutes

7.4 PH SENSOR CALIBRATION

Figure 7: This is the diagram of the circuit for the pH meter.

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Before the pH sensor could be used, it needed to be calibrated. The code for the Arduino

was found on DFRobots website. The code was downloaded and the probe was washed in

distilled water. To calibrate the sensor, the sensor was placed in a standard acid solution with a

pH of 4. After a few seconds, once the readings stabilized, acid:4.00 was typed into the program

and the program finished Acid Calibration. The probe was washed again and placed into the

alkali buffer with a pH of 10. Once the readings stabilized, alkali:10.00 was typed in and the

program finished alkali calibration. After both alkali and acid calibration were complete, exit

was typed in, and the calibration was complete.

7.5 PROCEDURE Eight 4-gallon buckets were placed into a four by two grid (Figure 8). One florescent

light was placed 1 meter above the buckets. The florescent light was turned on and remained on

for 24 hours every day. 24 gallons of freshwater were obtained. 12 cups of reef salt were added

to create water with a salinity of 1.025 ppm. The solution was thoroughly mixed and the solution

was left for 10 minutes. After 10 minutes, 3 gallons of the solution were poured into each bucket.

The salinity of the solution in each bucket was tested with a refractometer to ensure that it was at

1.025 ppm. The nitrate, nitrite, and ammonia test kits were used to test the nitrate, nitrite, and

ammonia levels and make sure they were 0 ppm. The pH level of the water in each of the buckets

was tested and set it to 8.2 with the necessary amount of acid and alkaline buffers. Every day for

three days, ¼ teaspoon of acid buffer and 1 teaspoon alkaline buffer were added to each of the

buckets. In the treatment groups, 900 g of dry ice was added. Gloves and long sleeves were worn

when handling the dry ice. Dry ice was stored in a cooler. The cooler was not airtight to avoid

having pressure build up inside of the container, leading to possible explosions. The water was

left alone for two days, to allow the specific gravity and pH levels to stabilize.

Orange – Treatment Bucket

Blue – Control Bucket

Yellow - Lights

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Figure 8: This figure shows the setup of the lights and buckets for the experiment.

After the environment was set up, 0.5 kg of chaeto was added to each bucket. Every day

at 10:00 pm, the pH level and dissolved oxygen level of the water were measured. The plant was

grown for two weeks. At the end of each week, the ammonia, nitrate, nitrite, and salinity levels

of the water in each of the buckets was measured. The averages of the oxygen levels was found

for each day, and a scatterplot for each group was created. The line of best fit for both groups

was found. This line showed the rate of change of the O2 levels.

8 RESULTS 8.1 QUALITATIVE

Throughout the experiment, the plants in the control groups grew and remained green. The

plants in the treatment groups started out green, but throughout the experiment, got darker. By

the twelfth day, the plant was mostly green. However, portions of the plants were brown or clear.

After the fourteenth day, the plants were removed. The plants in the control group were stronger

and much more difficult to pull apart than the plants in the treatment group. The plants in the

treatment group fell apart much more easily and were much more limp than the ones in the

control group.

8.2 QUANTITATIVE

Figure 9: The graph above shows the average pH level of the different groups each day.

Table 3: The table below shows the equation of the line, R squared value, and derivative of the graph for the average pH levels

of each group.

Group\Day Equation of the Line R2 value Derivative

C Average y = 8E-05x2 - 0.001x + 8.2121 R² = 0.1303 0.00016x+0.0001

T Average y = 0.0003x2 - 0.0098x + 7.7298 R² = 0.937 0.0006x-0.0098

7.6

7.7

7.8

7.9

8

8.1

8.2

8.3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

pH

leve

l

Day

pH Level Over Time (Averages)

Control

Treatment Group

Poly. (Control)

Poly. (Treatment Group)

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A parabolic line of best fit was found for each individual plant. The derivative of each

line was found to represent the rate of change. The averages were found for the control and

treatment groups, and the line of best fit was found. The derivative of each line was found as

well. The R-squared value was 0.1303 for the control group and 0.937 for the treatment group.

Figure 10: The graph above shows the dissolved oxygen concentration of the different groups each day.

Table 4: The table below shows the equation of the line, R squared value, and derivative of the graph for the average dissolved

oxygen concentration of each group.

A parabolic line of best fit was found for each individual plant The derivative of each line

was found to represent the rate of change. The averages were found for the control and treatment

groups, and the line of best fit was found. The derivative of each line was found as well. The

derivative was higher for the treatment group than the control group. The R-squared value was

0.6612 for the control group and 0.7754 for the treatment group.

9 ANALYSIS AND DISCUSSION For the pH levels, after finding the averages, the derivative of the line for the treatment

group was higher than the derivative for the control group. However the equation of the line for

the control group did not fit the data well. The R-squared value was 0.1303, signifying that the

data are not closely fitted to the line that was obtained. The y-intercepts of both equations

referred to the initial pH levels. Both values, 8.2121 and 7.7298 were very close to the wanted

values.

For the dissolved oxygen, the derivative of the line for the average of the treatment group

was higher than the derivative for the average of the control group. The R-squared values were

on the lower side. However, at 0.6612 for the control group and 0.7754 for the treatment group,

they represented the data much better than the control group of the pH levels. The initial rapid

increase showed that initially, the plant was photosynthesizing quite rapidly. However, after a

few days, the plant began to photosynthesize less rapidly.

More data is needed to determine the significance of these results. The hypothesis cannot

be proven or disproven. In the future, there are many ways this project could be improved. More

data could be collected, which would give a better representation of how the decrease in pH

4

4.5

5

5.5

6

6.5

7

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Dis

solv

ed O

xyge

n (

mg/

L)

Day

Dissolved Oxygen Concentration Over Time (Average)

Average Control

Average Treatment

Poly. (Average Control)

Poly. (Average Treatment)

Group\Day Equation of the Line R2 value Derivative

C Average y = -0.0019x2 + 0.0445x + 5.4387 R² = 0.6612 -0.0038x+0.0445

T Average y = -0.0096x2 + 0.0959x + 5.514 R² = 0.7754 -0.0192x+0.0959

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would affect aquatic plants. Various species of aquatic plants could be used as well to give a

better representation of how the ecosystem as a whole would be affected.

10 CONCLUSION How a plant’s rate of photosynthesis is affected when grown in water with a lower pH is

inconclusive. However, it was observed that the plants grown in water with a lower pH did not

grow as well, and by the end of the testing period, were beginning to die out. At the rate the pH

of the ocean is decreasing right now, the pH will reach a value of 7.7 in the next century. This

rapid acidification will likely have large effects on aquatic life. It was seen in plants that plants

grown at the lower pH began to die out. Algae is responsible for absorbing a large part of the

atmospheres carbon dioxide. Without algae, the carbon dioxide levels in the atmosphere and

oceans would likely increase, leading to other unwanted effects, such as global temperature

increases.

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2016, from http://intmstat.com/blog/2008/02/co2-data-noaab.gif

Brewer, P. (2009). Acidity and rising carbon-dioxide levels in the oceans. Scientific American,

Retrieved October 13, 2016 from

http://search.credoreference.com/content/entry/abcgwst/acidity_and_rising_carbon_dioxi

de_levels_in_the_oceans/0" \t "_blank

Chaetomorpha algae, aquacultured. Ithaca, NY: LiveAquaria. Retrieved

from http://www.liveaquaria.com/product/prod_display.cfm?c=3468+2190+2401&pcatid

=2401

DFRobot. (n.d.). [Arduino Diagram]. Retrieved January 31, 2017, from

https://www.dfrobot.com/wiki/images/thumb/e/e7/PH_meter_connection1_(1).png/450px

-PH_meter_connection1_(1).png

Energy, Work and Heat. (n.d.). Retrieved December 04, 2016, from

http://www.life.illinois.edu/crofts/bioph354/thermo_summary.html

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https://globalclimate.ucr.edu/resources.html

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amazon.com/images/I/41Ow9PwPjoL._SX425_.jpg

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Set, 24, 592-604. Retrieved from https://www.life.illinois.edu/govindjee/paper/gov.html

12 APPENDIX 12.1 LIMITATIONS AND ASSUMPTIONS

Throughout this project, many factors that limited the scope and potential of the project.

One of these factors was cost. Along with space, cost and time limited the number of plants used

per trial as well as the number of trials that were run. The location of the experiment cannot fit a

very large number of buckets, leading to a decreased control and treatment group size. Cost

played a role in limiting the experiment as well. Cost limited the quantity of materials able to be

purchased for the experiment, as well as the types of materials. Some of the materials, such as

Enis 16

the sensors, were very expensive, and cheaper options needed to be explored. Time was also a

limiting factor. The time range allotted for the project did not allow for a large number of groups

to be tested. If more time was given, more groups and treatment types could have been tested.

One last limiting factor was the plants ability to stay alive. The range of pH levels that could be

tested were limited, due to the plants sensitivity to pH changes and pH threshold. Levels beyond

these thresholds could not be tested because the plant would not be able to survive the process.

Time, cost, space, and the plants ability to stay alive all limited the scope of the project.

Some assumptions had to be made when running the experiment. The first assumption is

that the transfer of O2 between the water and the air was minimal and equal for both groups of

plants. A second assumption was that other types of plants will be likewise effected by the

increase in the pH level of the ocean. Thirdly, it was assumed that at the beginning of

experimentation, each plant was equally healthy and strong. The last set up based assumption

was that there were no other acids in the water except CO2, allowing the pH to CO2 conversion

chart to be used. Some assumptions were made about the materials as well. It was assumed that

the materials received were exactly the same as the advertised materials. The sensors were

assumed to work as expected, and it was assumed that the Arduino code for the pH sensor

worked properly and accurately. Assumptions were made about the plants, environment, and

materials used throughout the project.

12.2 ARDUINO CODE /*

# This sample code is used to test the pH meter Pro V1.0.

# Editor : YouYou

# Ver : 1.0

# Product: analog pH meter Pro

# SKU : SEN0169

*/

#define SensorPin A0 //pH meter Analog output to Arduino Analog Input 0

#define Offset 0.00 //deviation compensate

#define LED 13

#define samplingInterval 20

#define printInterval 800

#define ArrayLenth 40 //times of collection

int pHArray[ArrayLenth]; //Store the average value of the sensor feedback

int pHArrayIndex=0;

void setup(void)

{

pinMode(LED,OUTPUT);

Serial.begin(9600);

Serial.println("pH meter experiment!"); //Test the serial monitor

}

void loop(void)

{

static unsigned long samplingTime = millis();

static unsigned long printTime = millis();

static float pHValue,voltage;

if(millis()-samplingTime > samplingInterval)

Enis 17

{

pHArray[pHArrayIndex++]=analogRead(SensorPin);

if(pHArrayIndex==ArrayLenth)pHArrayIndex=0;

voltage = avergearray(pHArray, ArrayLenth)*5.0/1024;

pHValue = 3.5*voltage+Offset;

samplingTime=millis();

}

if(millis() - printTime > printInterval) //Every 800 milliseconds, print a numerical, convert the

state of the LED indicator

{

Serial.print("Voltage:");

Serial.print(voltage,2);

Serial.print(" pH value: ");

Serial.println(pHValue,2);

digitalWrite(LED,digitalRead(LED)^1);

printTime=millis();

}

}

double avergearray(int* arr, int number){

int i;

int max,min;

double avg;

long amount=0;

if(number<=0){

Serial.println("Error number for the array to avraging!/n");

return 0;

}

if(number<5){ //less than 5, calculated directly statistics

for(i=0;i<number;i++){

amount+=arr[i];

}

avg = amount/number;

return avg;

}else{

if(arr[0]<arr[1]){

min = arr[0];max=arr[1];

}

else{

min=arr[1];max=arr[0];

}

for(i=2;i<number;i++){

if(arr[i]<min){

amount+=min; //arr<min

min=arr[i];

}else {

if(arr[i]>max){

Enis 18

amount+=max; //arr>max

max=arr[i];

}else{

amount+=arr[i]; //min<=arr<=max

}

}//if

}//for

avg = (double)amount/(number-2);

}//if

return avg;

}