extended essay - sina hesseextended essay how does water temperature affect the bioremidiation and...

Extended Essay How does water temperature affect the bioremidiation and biodegradation of an oil spill including the consequences for the respective ecosystem, using the Exxon Valdez and Deepwater Horizon disasters as case studies?

Sina Hesse

Supervisor: Dr Badcock

Student Number: dfs960

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Sina Hesse, Extended Essay, ISZL, Switzerland, 2010

Abstract: Word Count: 298

Oil spills due to human activity are regular incidents, which harm the equilibrium of

ecosystems. Naturally occurring microorganisms (bacteria/fungi) take over the role of

regaining the equilibrium by biodegradation. This essay shows how environmental

factors, mainly water temperature have a large impact on the efficiency of oil degrading

microorganisms.

The Exxon Valdez (1989) disaster in the Arctic and the more recent explosion of the

Deepwater Horizon oil platform in the Gulf of Mexico are two prime examples to explore

this theory. In both cases the respective ecosystems have been exposed to oil spills. In the

Exxon Valdez incident 261 905 barrels of crude oil was discharged into the ocean, the

impact of which is still evident today. During the more recent spill of Deepwater Horizon

in the Gulf 4.9 million barrels of oil were released into the system, but it is already

recovering quickly in comparison.

To investigate the theory that the efficiency of organisms such as Alcanivorax

borkumensis, an oil metabolizing bacterium, is reduced with a decrease in temperature of

the water, I carried out an experiment testing the effect of temperature on the process of

bioremediation. I placed oil sediment and diesel in separate containers of seawater and

kept them at 4°C, and 21°C respectively. The water was provided with oxygen through

pumps and the dissolved oxygen measured. Later the pumps were removed and pH

measured to track bacterial activity. The results indicated that in the warmer water the

organisms appeared to work faster as the oxygen levels decreased more than in the cold

water, and later rose as bacteria possibly died due to lack of food, while in the colder

water the oxygen levels did not increase. As a result it can be assumed that

bioremediation/biodegradation levels are far more efficient with higher water

temperatures.

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Contents Page AIM: .............................................................................................................................................. 5 HYPOTHESIS: ................................................................................................................................... 5

INTRODUCTION: ....................................................................................................................6 Oil Spills ................................................................................................................................... 6 Oil degrading microorganisms ................................................................................................ 6 Ecological effects of oil spills ................................................................................................... 8 Relevance of Topic: ................................................................................................................. 8

METHODOLOGY: ....................................................................................................................9 MATERIALS: .................................................................................................................................. 10 VARIABLES: ................................................................................................................................... 10

Independent Variable: .......................................................................................................... 10 Dependent Variable: ............................................................................................................. 10 Controlled Variable: .............................................................................................................. 10

PROCEDURE: ........................................................................................................................ 11

RAW DATA: ......................................................................................................................... 13 Table 1: Dissolved Oxygen and pH levels for Container A containing seawater, diesel and nutrients at 21 °C. ................................................................................................................. 13 Table 2: Dissolved Oxygen and pH levels for Container B containing seawater, diesel and nutrients at 4 °C. ................................................................................................................... 13 Table 3: Dissolved Oxygen and pH levels for Container C containing seawater, oil sediment and nutrients at 4 °C. ............................................................................................................ 14 Table 4: Dissolved Oxygen and pH levels for Container D containing seawater, oil sediment and nutrients at 21 °C. .......................................................................................................... 14 Table 5: Dissolved Oxygen and pH levels for Container E containing seawater and nutrients at 21 °C. ................................................................................................................................. 15 Table 6: Dissolved Oxygen and pH levels for Container F containing seawater and nutrients at 4 °C. ................................................................................................................................... 15 Table 7: Showing the dissolved oxygen level means for all the containers .......................... 16

DIAGRAMS: ......................................................................................................................... 17 GRAPH 1: SHOWING THE MEAN DISSOLVED OXYGEN LEVELS FOR CONTAINERS COLD SEDIMENT, COLD DIESEL

AND COLD CONTROL, ALL AT 4°C ..................................................................................................... 17 GRAPH 2: SHOWING THE MEAN DISSOLVED OXYGEN LEVELS IN CONTAINERS WARM DIESEL, WARM SEDIMENT

AND WARM CONTROL, ALL AT 21°C ................................................................................................. 18 Figure 6: Container with seawater and diesel at 21°C .......................................................... 19 Visible changes in Warm Diesel. Container A: ...................................................................... 19 Figure 7: Container with seawater and diesel at 4°C ........................................................... 20 Visible changes in Cold Diesel. Container B: ......................................................................... 20 Figure 8: Container with seawater and oil sediment at 4°C ................................................. 21 Visible changes in Cold Sediment. Container C: .................................................................... 22 Figure 9: Container with seawater and oil sediment at 21°C ............................................... 22 Visible changes Warm Sediment. Container D: .................................................................... 23

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DISCUSSION: ........................................................................................................................ 23 THE GULF OF MEXICO: ................................................................................................................... 23 FIGURE 1: MAP OF THE OIL SPREAD IN THE GULF OF MEXICO: .............................................................. 25

(WEISENTHAL, 2010) ........................................................................................................ 25

FIGURE 1 SHOWS THE SPREADING OF THE OIL IN THE GULF OF MEXICO AFTER

THE DEEPWATER HORIZON INCIDENT. ......................................................................... 25 Figure 5: Pie chart displaying the fate of the oil in the Gulf of Mexico ................................. 27 Figure 2: Systems Diagram and Food web of the Gulf of Mexico: ........................................ 28

THE ARCTIC SEA:............................................................................................................................ 31 Figure 3: Systems Diagram and Food web for Arctic: ........................................................... 33

FIGURE 4: MAP OF THE OIL SPREAD IN THE EXXON VALDEZ: ................................................................. 34

EVALUATION: ...................................................................................................................... 35 CONCLUSION: ............................................................................................................................... 36

ACKNOWLEDGEMENTS ........................................................................................................ 38

BIBLIOGRAPHY/REFERENCES: ............................................................................................... 39

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Aim:

The aim of this Essay is to investigate the effect of location on oil spills, therefore the

environment and abiotic factors such as water temperature, on the ability of a system to

regain its equilibrium, using the examples of Exxon Valdez (Arctic) and Deepwater

Horizon (Gulf of Mexico)

Hypothesis:

It is expected that the bioremediation and the biodegradation have a higher rate in warmer

temperatures due to the fact that cool water will slow down the microorganisms'

metabolism, and therefore that the tropical system will recover faster than the arctic one.

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Introduction:

Oil Spills An oil spill is a complex liquid petroleum hydrocarbon that is released into the

environment, usually due to human activity. Once crude oil and petroleum are released

into any marine environment both undergo several chemical, physical and biological

changes. Some of the abiological weathering processes include evaporation, dispersion,

sinking, and photochemical oxidation, adsorption onto particulate material, water-in-oil

emulsification and sedimentation. The biological processes are the ingestion by

organisms and degradation by microbes. These processes all occur at the same time and

change the chemical and physical composition of the original crude oil which may affect

the rate of biodegradation. During the first 48 hours of a spill the most important process

is evaporation, in which the low to medium weight components of the oil with low

boiling points volatilize into the atmosphere, resulting in the oil losing up to two thirds of

its original mass. This process is affected by the sea’s temperature, and the solar activity

in the area. (U.S Congress, 05.1991)

Oil degrading microorganisms There are natural oil leaks in the oil storages below the ocean floor, but naturally

occurring bacteria biodegrade the oil. Based on the 1 557 093 barrels (per year) of oil

seeping into the ocean from natural spills, the oceans would be covered in oil slicks

(Minogue, 24.08.10). Biodegradation refers to the natural process during which

microorganisms break down organic molecules into simpler often water soluble,

normally non toxic components. Bacteria take in oxygen and hydrocarbons and release

carbon dioxide into the water. The only component of oil that none of the

microorganisms can biodegrade is tar, resulting in this component ending up either at the

affected shores or at the ocean’s floor (Cleveland, 2010). Bioremediation on the other

hand is adding material, i.e. nutrients such as nitrogen and phosphorus to the environment

to stimulate the growth of microorganisms in the contaminated area, to accelerate the

natural biodegradation process. Bioremediation also includes seeding which is the

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addition of organisms into a system (U.S Congress, 05.1991). Oil degrading

microorganisms usually work together as each organism is specialized in breaking down

a different component of the oil (Schorsch, 25.08.10).

Microorganisms that enable biodegradation and bioremediation function at temperature

ranges from -2 to 35°C, however the rates of biodegradation are faster at higher

temperatures, and are usually found to decrease in lower temperatures. This is due to the

fact that the rate of hydrocarbon metabolism by microorganisms decreases in cold

climates (U.S Congress, 1991). In total approximately 1 500 different types of oil

degrading microorganisms are known. (Schauer, 2010) A microbe called Oleispira

Antarctica for example is specialized to degrading oil in seawater at its freezing point

(Gertler&Golyshin, 28.05.10). The population of naturally occurring marine bacteria

depends on the amount of oil; accordingly their growth in population is stimulated by the

quantity of food and nutrients available. A visible effect of the organisms processing oil

is the water turning cloudy. At the same time the bacteria consume oxygen, hence reduce

the oxygen levels in the water. In the current spill in the Gulf of Mexico clear evidence

for the bacteria’s activity was the decrease of oxygen levels in the water by 30% after a

few days (Biello, 2010).

Another bacterium that is specialized in highly efficient oil-degrading is Alcanivorax

borkumensis, which lives solely on oil, and dies after having consumed all the oil in its

surroundings. Alcanivorax Borkumensis was first found in 1998, from a sample taken

from an island (Borkum) in the North Sea and is most seawater tolerant amongst those

organisms, hence most effective in natural sea water (Schauer, 2010). Oil degrading

microorganisms can present up to 80 % of the bacteria population in oil-contaminated

areas (Brooijmans, 2009). During an oil spill Alcanivorax is at the top of the food chain

based upon the abundance of food (oil). Some animals, such as small crustaceans prey

on the bacteria which helps inhibiting uncontrollable growth of the population, but to

balance the equilibrium it can take months to years (Schorsch, 2010). Rob Condon from

the Bermuda Institute of Ocean Research fears an enormous growth in the Jellyfish

population in the Gulf of Mexico as they too eat the bacterium (Condon, 2010).

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Ecological effects of oil spills

Oil has an obvious negative effect on wildlife and habitat. It reduces the plumage of

birds, makes them less buoyant, thus reducing the insulating ability, and making the birds

more unprotected to temperature changes. The oil also impairs the birds’ flying abilities,

and therefore makes them very vulnerable to predators. While the birds attempt to

remove the oil from their feathers they ingest the oil, which may cause kidney damage,

flawed liver function and irritation of the digestive system. As a result this might cause

dehydration and metabolic imbalances. Most birds that are affected by oil spills die

unless humans intervene. Marine mammals are affected by the oil film floating on the

ocean as they are forced to surface for breathing. They show similar symptoms as birds.

The oil may coat the fur of the sea otters and seals, and therefore reduces its insulation

ability, thus resulting in hypothermia. The entire food chain of an ecosystem is harmed by

an oil spill through the oil floating on the ocean´s surface, thus limiting the sunlight

penetration and consequently reducing photosynthesis of phytoplankton and other marine

plants. The decreasing fauna and fatalities due to the oil can have an overall effect on the

food web and its links, disturbing the system equilibrium.

Relevance of Topic: My research was relevant as it helps us to understand the influencing factors, i.e.

environmental ones to the equilibrium of a system in the event of an oil spill, be it human

induced or natural spills. Furthermore it may lead to finding adequate reactions towards

those situations, depending on the respective ecosystem. It allows us to understand the

site of a spill as a system hence it helps us to try to minimize the impact on the system

and the fragile food webs and possibly even offers new ways of supporting and

enhancing the natural process of biodegradation.

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Methodology:

I compared the bacterial activity in the containers with different oils, one of which was

diesel, and the other oil sediment. I compared each oil variety at the two different

temperatures: 4 and 21°C and measured the pH levels (which were meant to get more

basic with bacterial activity) and dissolved oxygen (which should decrease due to

bacterial activity). According to my research the bacteria should “burn” the oil, and

therefore visibly decrease the amount of oil present. I was also expecting more of the oil

to disappear in the warmer containers.

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Materials: 3 liters of aquarist sea water (simulated sea water)

o This sea water was ‘treated’ with ‘living stones’ which means that the

stones come from the ocean, and are kept wet at all times, resulting into

containing a mix of naturally occurring sea water bacteria.

7 beakers with a capacity of 500 ml

4 pumps (3 with power cord, 1 with battery)

4 meters of white pipe

7 oxygen disperser for salt water

10 ml of Micro-and Macro-Nutrient Hydrofertilizer

o Main Ingredients :

1.8% nitrogen, 1.8% soluble phosphate, 2.3% soluble potassium

oxide

100 ml of oil sediment from the bottom of an oil container

100ml of Diesel fuel for cars

3 T-connection pieces

Variables:

Independent Variable:

- Type of oil

o sediment

o diesel

- Temperature

o 21°C

o 4°C

Dependent Variable:

- Dissolved Oxygen (mg/l)

- pH

Controlled Variable:

- Amount of sea water (500 ml)

- Amount of nutrients (2 drops)

- Amount of oil (10 ml)

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Procedure:

1. Place the aquarium seawater in a bucket, and prepare one of the pumps by

connecting it to the electricity, and then connecting the pipe to the pump.

2. Place an oxygen disperser to allow the water to dissolve the oxygen on the end of

the pipe.

3. Place the ends of the pipe with the oxygen disperser in the bucket of seawater to

keep it oxygenated and keep the bacteria alive.

4. Take pipes and cut of 6 pieces of the pipe, each 4cm long, and attach them to the

pump, and the T-connector

5. Cut 7 pieces of 50cm each of the pipes, and attach them to the other ends of the T-

connector, and connect the spare one to the battery pump

6. Now prepare the 7 beakers by placing 500ml of simulated sea water in each of

them

7. Attach the pumps to the electricity, and place one extension cable in the fridge

and attach one of the electronic pumps to this extension cable

8. Place the two drops of Nutrients in each of the beakers.

9. Label the beakers according to the tables (A,B,C,D,E,F)

10. Place beaker E in the fridge, together with beaker C and B

a. Beakers F and E are the control beakers that only contain the water and the

Nutrients

11. Leave Beaker A, D, and E outside the fridge to keep them at room temperature.

12. Place the oxygen dispersers in the water and fix the pipes so that all beakers get

oxygen.

13. Switch on the oxygen pumps

14. One beaker outside the fridge is going to be a spare as both pumps will have to

use a T-connection to keep the amount of oxygen the same in all the beakers, but

the measures for this beaker are irrelevant.

15. Now take a measure of dissolved oxygen using the Lab Quest and the dissolved

oxygen probe.

16. Record the measurements in the data tables, taking 3 trials for each of the beakers

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17. Add 10 ml of the oil sediment in containers C and D

18. Add 10 ml of Diesel in containers A and B

19. Stir the content of all containers to allow the bacteria to mix with the oils and

diesel.

20. Take three measurements using the dissolved oxygen probe for each container,

every day for 11 days.

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Raw Data:

Table 1: Dissolved Oxygen and pH levels for Container A containing seawater, diesel and nutrients at 21 °C.

Container A

Result Dissolved Oxygen (mg/l) pH levels

Day Measurement 1 Measurement 2 Measurement 3 Measurement 1 Measurement 2 Measurement 3

1 6.2 6.3 6.2

2 6.2 6.3 6.2

3 6.3 6.3 6.3

4 6.3 6.3 6.3

5 6.3 6.3 6.3

6 6.3 6.3 6.3

* 7 4.0 3.9 3.9 7.5 7.6 7.6

8 1.2 1.5 1.3 7.9 7.9 7.9

9 0.3 0.2 0.3 7.5 7.5 7.5

10 0.8 0.8 0.8 8.0 8.0 8.0

11 0.7 0.8 0.8 8.0 8.0 8.0

* = this day the oxygen pumps were removed, and I started to measure pH

Table 2: Dissolved Oxygen and pH levels for Container B containing seawater, diesel and nutrients at 4 °C.

Container B



1 6.4 6.4 6.3

2 6.4 6.4 6.5

3 6.4 6.5 6.4

4 6.3 6.4 6.5

5 6.4 6.3 6.5

6 6.3 6.4 6.1 * 7 2.8 2.9 3.0 8.2 8.1 8.3

8 2.0 2.6 2.4 8.3 8.3 8.3

9 2.4 2.5 2.3 7.4 7.3 7.2

10 1.3 1.0 1.4 8.3 8.4 8.3

11 1.1 1.0 1.1 8.4 8.2 8.3


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Table 3: Dissolved Oxygen and pH levels for Container C containing seawater, oil sediment and nutrients at 4 °C.

Container C



1 6.2 6.1 6.2

2 6.3 6.4 6.4

3 6.5 6.4 6.3

4 6.3 6.4 6.3

5 6.4 6.5 6.2

6 6.4 6.5 6.3

* 7 6.5 6.2 6.1 8.1 8.1 8.1

8 2.4 2.5 3.1 8.3 8.3 8.3

9 2.4 2.7 2.3 7.3 7.3 7.3

10 1.5 1.4 1.2 8.4 8.4 8.3

11 1.2 1.1 1.3 8.5 8.4 8.3


Table 4: Dissolved Oxygen and pH levels for Container D containing seawater, oil sediment and nutrients at 21 °C.

Container D

Result Dissolved Oxygen (mg/l) pH levels Day Measurement 1 Measurement 2 Measurement 3 Measurement 1 Measurement 2 Measurement 3

1 6.1 6.0 6.1

2 6.3 6.6 6.0

3 6.3 6.3 6.3

4 6.3 6.3 6.3

5 6.3 6.3 6.3

6 5.5 6.3 4.4

* 7 4.1 4.0 3.9 7.5 7.5 7.5

8 1.0 1.5 1.5 7.9 7.9 7.9

9 0.3 0.2 0.2 8.0 8.0 8.0

10 1.0 1.0 0.8 8.3 8.3 8.2

11 0.9 0.9 0.9 8.1 8.1 8.0


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Table 5: Dissolved Oxygen and pH levels for Container E containing seawater and nutrients at 21 °C.

Container E



1 6.1 6.2 6.3

2 6.3 6.3 6.3

3 6.3 6.3 6.3

4 6.3 6.3 6.3

5 6.3 6.3 6.3

6 6.3 6.3 6.3 * 7 2.8 2.7 2.8 7.8 7.8 7.8

8 2.0 2.1 1.9 7.9 7.9 8.0

9 0.3 0.3 0.3 8.0 8.0 8.0

10 0.8 0.8 0.7 8.0 8.0 8.0

11 0.6 0.6 0.6 8.0 8.0 8.0


Table 6: Dissolved Oxygen and pH levels for Container F containing seawater and nutrients at 4 °C.

Container F



1 6.3 6.4 6.3 2 6.4 6.3 6.4 3 6.4 6.3 6.3 4 6.3 6.4 6.4 5 6.4 6.4 6.4 6 6.4 6.4 6.4

* 7 2.6 2.6 2.6 8.2 8.2 8.2

8 2.6 2.3 2.2 8.3 8.3 8.3

9 1.4 1.5 1.4 8.0 8.0 8.0

10 1.5 1.2 1.3 8.0 8.0 8.0

11 1.1 1.2 1.1 8.1 8.0 8.0


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Table 7: Showing the dissolved oxygen level means for all the containers

Mean Value (mg/l) Warm Diesel Cold Diesel Cold Sediment Warm Sediment Warm No oil Cold no oil

Days a B C D E F

1 6.23 6.36 6.16 6.06 6.20 6.33

2 6.23 6.43 6.36 6.30 6.30 6.36

3 6.30 6.43 6.40 6.30 6.30 6.33

4 6.30 6.40 6.33 6.30 6.30 6.36

5 6.3 6.40 6.36 6.30 6.30 6.40

6 6.30 6.26 6.40 5.40 6.30 6.40

* 7 3.93 2.90 6.26 4.00 2.76 2.60

8 1.33 2.33 2.66 1.33 2.00 2.40

9 0.26 2.40 2.46 0.23 0.30 1.43

10 0.80 1.23 1.36 0.93 0.73 1.33

11 0.76 1.06 1.20 0.90 0.60 1.13


This table shows that the trends in the cold and the warm water were also visible in the

control containers which may show that the temperature was the main influence on the

oxygen levels.

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Diagrams:

Graph 1: Showing the mean dissolved oxygen levels for containers Cold Sediment, Cold Diesel and Cold Control, all at 4°C

This Graph shows that at day 7, or for container C at day 8 after the oxygen pumps were

removed, the oxygen levels are starting to drop. It is also visible that the mean never

drops below one.

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11

Dis

solv

ed

Oxy

gen

(m

g/l)

Days

Cold Diesel

Cold Sediment

Cold Control

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Graph 2: Showing the mean dissolved oxygen levels in containers Warm diesel, Warm sediment and Warm Control, all at 21°C

In this graph it is visible that the mean dissolved oxygen levels also drop at day 7, and

that the means go well below the one mg/l. It is also visible that all values start to

increase after day 9, showing that the bacteria’s activity has either decreased or they have

died due to lack of food. (This pattern is also visible in the control container, which may

be due to the fact that some oil may have entered the container)

0

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11

Dis

solv

ed

oxy

gen

(m

g/l)

Days

Warm Diesel

Warm Sediment

Warm Control

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Figure 6: Container with seawater and diesel at 21°C

Visible changes in Warm Diesel. Container A: Container A contained sea water and Diesel, and was at 21 °C . It is well visible that

there is no more Diesel floating on the surface. The water has turned a light yellow from

the degrading oil, and contains a few floating sediments that are the leftovers from the

oil.

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Figure 7: Container with seawater and diesel at 4°C

Visible changes in Cold Diesel. Container B: This is the diesel at 4°C. There is clear visible evidence that there is still a layer of Diesel

that coats the water. It appears the bacteria worked slower at the 4°C of the fridge.

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Figure 8: Container with seawater and oil sediment at 4°C

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Visible changes in Cold Sediment. Container C: This is oil sediment, at 4°C . It is visible that some of the oil was spread along the sides

of the container due to the bubbler. There is some sediment at the bottom of the

container, and a thin coating of oil on the water.

This also shows that some of the oil sediment was on the sides of the container, though a

film of oil is still visible in the water. Preventing this might have been a possible

improvement.

Figure 9: Container with seawater and oil sediment at 21°C

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Visible changes Warm Sediment. Container D: This sediment was at 21 °C.T his container

also shows that some of the oil sediment that

stuck to the side of the container. But it is

also visible that the liquid is very yellow

from the degraded oil. There is also a little

sediment that is floating in the liquid.

In this container also some of the oil stayed

at the sides of the container, but the color

shows that the bacteria worked as the water

is cloudy)

Discussion:

The Gulf of Mexico:

The gulf has an average temperature of 30°C. The area of the spill contains 8 332 species

of plants and animals including 1 461 mollusks, 604 polycheates, 1503 crustaceans, 1 270

fish, 4 sea turtles, i.e. the loggerhead sea turtle, as well as 218 birds species and 29

marine mammals e.g. Bottlenose dolphins. The Gulf of Mexico also contains the

endangered smalltooth sawfish, and concerned species such as the largetooth sawfish.

The animals living near shore such as the sea turtles and the sawfish are particularly

threatened by oil spills (Cleveland, 2010).

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The Gulf of Mexico’s coral reefs, particularly the Staghorn, and Elkhorn coral, can be

affected by the oil spills, either by the sinking oil, or by the oxygen loss in the water due

to the action of Alcanivorax bacteria. It has been found that oil and dispersants if applied

in an oil spill, both harm soft as well as hard coral species. Chronic exposure to toxic oil

sediments can lead to reduction in offspring, and therefore less coral reproduction.

(Guzman, 2010)

Deepwater Horizon was a deepwater drilling rig in the Gulf of Mexico (Tiber field). On

April 20th, 2010 an explosion on the rig caused the death of 11 workers, and produced a

fireball that was visible from a distance of 56 km. The fire could not be controlled, and

on the 22nd of April Deepwater Horizon sank leaving the pipes open, gushing at the sea

floor. This caused the biggest offshore oil spill in the US history. It is assumed that about

4 900 000 barrels of crude oil spilled into the Gulf of Mexico. After a month the oil slick

covered approximately 41 424 km2 (Cleveland, 2010).

25


Figure 1: Map of the Oil Spread in the Gulf of Mexico:

(Weisenthal, 2010)

Figure 1 shows the spreading of the oil in the Gulf of Mexico after the Deepwater

Horizon incident.

26


Ecological Effects of the spill on Wildlife and Habitat

The huge amounts of oil that entered the system of the Gulf caused the equilibrium to

shift, as the input into the system was huge but there was no output to balance it. As the

spill in the Gulf of Mexico is a rather recent event it is difficult to predict the long term

effects that the large amounts of light crude (which is a rather volatile type of crude oil)

that spilled into the gulf may have on the environment and the wildlife (U.S Fish &

Wildlife Service, 2010). However the direct effects of the oil, on a number of species

have been evaluated thoroughly: Data were collected, and the total of dead and visibly

oiled animals found, were recorded. Overall there were 6104 dead birds, 2263 of them

were visibly oiled. 594 dead sea turtles were recorded of which 17 were covered in oil

and 456 pending (had not been clearly identifiable). Mammals including dolphins found

dead were 99, while there were only 9 that were collected alive, but oiled (NOAA, 2010).

The floating oil can contaminate plankton, which may include algae, fish eggs and

invertebrates. Damage in lower trophic levels could cause ecological harm for years. But

the oil also affects scavengers such as bald eagles, raccoons, and skunks due to

consumption of carcasses with bioaccumulation. As oil has the potential to stay in a

system for a considerable period of time, and therefore has long term effect such as

suppression of the immune system, organ damage, and even behavioral change, it takes

the ecosystem a substantial time to reestablish equilibrium (Cleveland, 2010).

The current situation, however looks encouraging says Erik Cordes, five months after the

spill. Cordes has been studying deep marine communities in the gulf, including some

deep-water corals as well as unusual tubeworms which live near natural oil seeps. He

says that when examining these areas, within 32km of the rig, he did not find any visible

impact. But as these sights are at 300 to 500 meters depth it is possible that there is an

impact at the 1000 to 1500 meters depth at which the oil has sunk. Edward Overton also

reports that the oil seems to be degrading and therefore becoming less toxic, thus

minimizing the impact (Service, 2010). Latest data show that approximately only 26% of

the oil spill is left: 25% evaporated, 16% was naturally biodegraded, 8% chemically

dissolved, 5% burned and 3% skimmed and 20% removed (Cleveland, 2010, figure 5).

27


Figure 5: Pie chart displaying the fate of the oil in the Gulf of Mexico

Fate of oil released by the

Deepwater Horizon

Disaster. Source: National

Incident Command Center.

This pie chart shows what

about one quarter was

removed, another quarter

naturally evaporated or

dissolved, one quarter was

dispersed (mainly by natural

means biodegradation),

and only one quarter is left

either afloat or washed up

on beaches as tar.

(Cleveland, 2010)

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Figure 2: Systems Diagram and Food web of the Gulf of Mexico:

29


30


Figure 2 shows the systems diagram and the food web for the Gulf of Mexico in order to

illustrate the complexity of this tropical system. Even though only a fraction of the

species from the gulf is present in this food web it is complex, and shows several species

on each trophic level representing the relatively stable system.

31


The Arctic sea:

The Arctic sea has a very cold surface water temperature, which is always near the sea

waters freezing point (-1.8°C in order to freeze). The area of the Arctic contains

endangered marine mammals such as a variety of whales and walruses. The low water

temperature allows only very limited plant growth, the main part of which is

phytoplankton, however their abundance is large. Currents carry the nutrients that the

phytoplankton requires, and in summer they are able to photosynthesize. The Arctic’s

ecosystem is fragile and at an equilibrium that is easy to unbalance, due to the short food

webs, and the cold temperatures, resulting into slow recovery from damage or

destruction. Therefore already small amounts of oil spilled can harm the equilibrium.

Within this system the Exxon Valdez oil spill took place on March 24th in 1989. The

tanker hit ground in Prince William Sound spilling its crude oil contents in the sea. This

resulted in the second largest oil spill in the US History, and a spill of

261 905 barrels of oil. The spread of oil covered around 7km2, but following a storm on

the 27th of March the oil spread over 70 km down the coastline and through the ocean,

resulting into 2,080 km shoreline covered in oil. This spill took place in a pristine

ecologically important area, home of many endangered wildlife species. Thousands of

mammals and hundred thousands of fish and birds died as a consequence of this

enormous oil spill. The Exxon Valdez oil spill trustee council is estimating 250 000 killed

birds, 3 500 Sea otters, 300 Seals as well as 22 Orcas. The ocean floor was coated in oil

sediments, which caused species that live at ground level, such as small worms, and

certain fish and shells to dramatically decrease in numbers having a direct effect on the

connected food chain. Furthermore the oil had a long term effect that destroyed millions

of fish larvae and eggs, and is thought to cause herring and salmon to deform in the

development phase in the eggs years later (Smid, 2005).

Some of the oil persisted beyond a decade in toxic forms and triggered biological

exposures, which had long-term effects on the population levels. Chronic exposures to

32


toxins increased mortality for years. This could be particularly seen with sea otters or

Enhydra lutris who, in the heavily oiled area of the Prince William Sound have not yet

recovered from the disaster. In 1993 the sea otter abundance was at only 50% of the

estimated numbers before the spill, and was continuing to decline in 2001. It is now

estimated to be at 16% of the pre-spill population. A biomarker of an aromatic

hydrocarbon exposure (CYP1A) was detected in the blood samples taken from sea otters

during 1996-98 and even samples collected in 2001. A serum enzyme, gamma glutamyl

transferase, was detected in the bloods, which suggest liver damage in the affected

animals. The observations made suggest that the chronic exposure to oil is a limiting

factor in the recovery of the otters. Comparing levels from 1996, 1998 and 2001 the

impact appears to be slowly decreasing (Ballachey, 2003).

The indirect effect on trophic levels impacted species beyond mortality, increasing

genetic mutations. It also inhibited the recovery of rocky shorelines, and caused a decline

in structural algae, and therefore invertebrates. New data show that species like the

common loon, cormorants, the harbour seal, the harlequin duck, the pacific herring or the

pigeon guillemot could not increase their recovery process from the oil disaster yet. The

bald eagle, black oystercatcher, common murre, pink salmon, river otter and sockeye

salmon on the other hand have recovered from the consequences of the spill, whilst some

species like the Orcas and mussels are still recovering (Cleveland, 2010).

Oil spills have more effects on arctic ecosystems as the oil gets degraded a lot slower at

lower temperatures, and also due to shorter food chains, and the missing or destruction of

one link in these chains can be fatal for the whole food chain. The remaining oil left on

beaches releases toxins that still influence the surrounding species. Most bird species had

not recovered when a study was done in 2001, as the oil still contaminates their food.

From the 17 affected bird species only 4 are starting to recover slowly, 9 are not showing

any signs of recovery, and for another 4 species the situation has even deteriorated (Smid,

2005).

33


Figure 3: Systems Diagram and Food web for Arctic:

Figure 3 shows a systems diagram with a food web of the Arctic to aid to visualize the

fact that the short and less complex food web causes the system to be less stable than

systems in tropical areas.

34


Figure 4: Map of the Oil spread in the Exxon Valdez:

(Cleveland, 2010)

Figure 4 shows the spread of the Exxon Valdez oil spill labeled with dates to show at

which speed the oil spread across the ocean.

35


Evaluation:

One of the restrictions for the experiment was that I was not able to get actual seawater,

as my school (ISZL) is located in central Switzerland. Therefore I was forced to use

aquarium seawater, normally used for fish tanks. The likelihood of this water containing

one of the over 1500 sorts of oil degrading bacteria was large, as the water was mixed

with “living stones” from the ocean to generate an ocean like climate with

microorganisms and minerals. The simple improvement that could have been made was

to arrange to get seawater directly from the sea.

While the experiment showed relatively clear result, probably those could have been even

more impressive, in case the warm water experiment had been closer to the actual water

temperature of the Gulf of Mexico and the Arctic. Therefore I should have heated one up

to 30°C and cooled the other one down to -1.8°C, to mirror the systems of the Gulf and

the Arctic. It would also have been ideal if I had been able to get the Alcanivorax

borkumensis for my experiment rather than use the aquarist seawater.

A big advantage would have been a bigger time frame to allow the data to show a more

reliable trend. It would also have helped to complete more repeats to ensure that my data

was reliable.

36


Conclusion:

The experiment showed a trend that supports my hypothesis showing differences in speed

of regaining a stable equilibrium of ecosystems based upon biodegradation of oil at

different water temperatures. The clear decrease in the dissolved oxygen is visible as the

bacteria started to use the provided oxygen in the water to biodegrade the oil. In all

containers the decrease is visible, but in container “Warm Sediment” and “Warm Diesel”

(referring to tables 1 and 4), the decrease was more distinct than in the “Cold Sediment”

and ”Cold Diesel” samples (referring to table 2 and 3). Furthermore tables 1 and 4 show

that the dissolved oxygen levels start to increase again at day 10, as the bacteria have now

broken down all the oil that they were capable off, and are therefore not using as much

oxygen, as their population starts to decrease due to lack of food. In tables 2 and 3 on the

other hand there is a slight decrease visible even after day 10, suggesting that the bacteria

are still functioning, and their population is not yet decreasing. A further indication of

bacteria activity could be seen in the visible change: while the oil floated at the surface of

the water at first, the water began to become cloudy during the experiment. After the 10

days there was a slight oil layer on top of the experiments with cold water, whilst for the

warmer water it was gone (see figures 6 and 7). This suggests that the bacteria present are

faster in degrading the oil in the water with higher temperature. This trend could be seen

in all six different experiment setups, however in the warm containers the oxygen had

decreased to 0.3 mg/l and then began to increase back to about 1.0mg/l, whilst the cold

containers only decreased to 1.0mg/l, but never increased again.

The change in the pH which was larger in the warm containers with oil, while the pH of

the containers without oil stayed rather constant. It was visible that

all containers got more basic, which suggests bacterial activity. Like the oxygen results

a higher change in pH in the warm diesel and the warm sediment suggests that the

bacterial activity in the warm water was higher. This supports my hypothesis that

biodegradation is more active at higher temperatures.

37


Overall I can conclude from my research that a system has the ability to regain its

equilibrium after an oil spill. It has proven however to be impossible to breed oil

degrading microorganisms in the amounts necessary to stabilize a system as Prof.

Schauer explained. (Schauer, 25.08.10), hence the ecosystems can only recover from an

oil spill with help of naturally existing bacteria. And as the examples of Exxon Valdez

and Deepwater Horizon clearly show, environmental factors play a major role in

supporting the efficiency of natural biodegradation.

Whereas the Prince William Sound area (Arctic) and the respective wildlife and habitat

still suffers heavily from a spill dating more than 20 years back and oil contamination is

still visible as well as traceable, the majority of the visible oil on the water surface in the

Gulf of Mexico disaster, which discharged more than 20 times as much oil, is already

gone. Hence the conclusion is that in the warm Gulf area, where natural oil spills occur

on regular basis and therefore the population of oil degrading microorganisms is higher,

thus more effective, the impacts of an oil spill are better manageable, however still

substantial for the relevant ecosystem.

Word Count: 3997

38


Acknowledgements

I would like to thank my supervisor Dr. Badcock for her patience. I would also like to

thanks my IB Biology teacher Mr. Thomas who assisted me in finding some of the

crucial materials for my experiment, which was a great help. I also thank Kathy

Stevenson for support. I also thank the shop Aquatrend in Cham, and Florian Mächler

who helped me a great deal. Also Alain Navarrete was a great help in working out the

procedure of my experiment. I also thank Prof. Schauer for his time, and help. I would

also like to thank my mum for encouraging me to keep working and her moral support.

Thank you all very much.

39


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