Essay Instructions: SCENARIO: A student has performed the following experiment on coral bleaching
BACKGROUND
Coral reefs are home to millions of animal species and are one of the most diverse and productive ecosystems on Earth. These marine environments are significantly suffering as a result of climate change and human behavior changing the elements of the atmosphere and the oceans from the bygone times of the Industrial Revolution in the 18th century.
Corals have a symbiotic relationship with dinoflagellate protists that exist within vacuoles in coral host cells. The coral is provided with energy needed for photosynthesis in the form of sugars and amino acids. For survival, the dinoflagellate symbionts are supplied with inorganic nitrogen and phosphorus from the host, supporting the productivity of the dinoflagellate symbionts under the conditions, primarily low nutrient, of tropical oceans. The recycling of nutrients enables coral to build vast reef ecosystems found along coastlines, such as the Great Barrier Reef. Alternatively, dinoflagellate symbionts are not conditioned to survive under thermal stress and as a result expel from coral. The manifestation of coral exposed to its thermal tolerance is referred to as ?coral bleaching?. During this process the brown pigmentation of the dinoflagellate symbionts is lost, resulting in the colour change to a vivid white.
The deprivation of nutrition expedites the death of the corals, but it is not coral death alone that is a cause for concern. The timing and extent of coral death and its affect on the reef system are the actual issue. Coral bleaching and the alteration of the extent and timing of coral death impact a number of ecological services. (Done et al. 2003)
Climate change is the most common cause of coral bleaching because the prolonged thermal stress disturbs the photosynthetic process of the zooxanthallae (Maynard et al. 2008). The Great Barrier Reef is the largest continuous reef system in the world and is critical to marine biodiversity, but there have been eight mass coral bleaching events in the Great Barrier Reef since 1979 (Parry et al. 2007). Predictions of coral bleaching in the next 70 years show increasing levels of bleaching and destruction of wildlife and biodiversity until it reaches the level of catastrophic coral death (Jones 2004; Beaumont and Hughes 2002; Parry et al. 2007).
Climate change and global warming studies indicate that sea temperatures in the Great Barrier Reef and similar areas will continue to rise at 1 or 2 degrees Celsius per century and with increasing temperatures, bleaching events will only become more extensive. Exceeding the thermal tolerance of the zooxanthellae has led to coral bleaching in the past. (Hoegh-Guldberg 1999)
Additionally, human activity such as exploitation of marine wildlife, mining, and disturbance of terrestrial environments is a major contributor to global warming speeding up. Thus, human activity is leading to bleaching events and their catastrophic results.
Coral bleaching through both human activity and climate change are causing a devastating impact to reef systems. The extent of damage requires a number of years to recover depending on the level of impact. There are six levels of impact: sub-lethal, very low level, low level, medium level, high level, and catastrophic. At the sub-lethal level, whitening of coral tissue occurs, but without killing the coral tissue. Thus, the sub-lethal level does not require recovery time. At the medium level, many of the visually dominant species are killed, but there are substantial remnants surviving to allow for re-growth, requiring 5 years for the visual appearance to recover and 10 years for the ecological system to recover. Finally, at the catastrophic level, there is massive organism death and, if other characteristics of the ocean are optimal, it will take 10 years for the appearance to be restored and 50 years for the ecology to recover. (Done et al. 2003)
Future scenarios of coral bleaching and their impact vary drastically based on predictions of Parry et al. (2007) and those of Maynard et al. (2008). However, while tolerance to thermal stress may occur and increase over time for some species of coral, there is uncertainty as to the status of other coral. Additionally, predictions of global warming and the contribution of human activity indicate that sea temperatures will only continue to increase. Thus, future decisions and strategies addressing coral bleaching must commence (Weller et al. 2008).
The ecological and economic devastation of coral bleaching is simply too high to rely on corals developing tolerance for high oceanic temperature. The ecological damage includes loss of marine biodiversity through direct loss of coral species and indirect loss of the species that rely on or live on coral reefs (Parry et al. 2007). The economic damage includes damage to fisheries that rely on the fish populations thriving on coral reefs and the tourism industry that is a US$1 billion industry annually for the Great Barrier Reef (Hoegh-Guldberg 1999).
Like plants on earth, coral is fundamental for animal life in the ocean, providing homes to the thousands of species living among coral reefs.
The worlds largest continuous coral reef system, the Great Barrier Reef, ?could face severe bleaching events every year by the year 2030 [with the] Southern and central sites likely to be severely affected by sea temperature rise with the next 20-30 years? (Hoegh-Guldberg: 1999). It has been concluded that the rapidity and extent of these future climatic changes will result in the complete loss of coral reefs and ecosystems. Without action and the reduction of human impact on the environment, oceanic temperatures will continue to increase, resulting in the diminishment of coral reefs around the world.
AIM: The aim of this experiment is to investigate the affect of the change in sea surface temperature on coral colour. More specifically, the influence of oceanic temperature increase has on the Catalaphyllia jardinei, a species of coral in the Great Barrier Reef. This experimental investigation has been created as a microcosm of the ?real life? global issue.
HYPOTHESIS:
After researching the affects rising sea temperature has on coral, predictions can be determined from previous investigations and outcomes of coral bleaching occurrences. It has been discovered that the optimum temperature range for the Catalaphyllia jardinei (located in the Great Barrier Reef) is between 26 and 28 degrees Celsius. Due to climate change, thus increased sea temperatures the Catalaphyllia jardinei in the Great Barrier Reef has undergone coral bleaching. It was also discovered that global warming, due to human activity, is the main contributing factor of coral bleaching and is predicted to increase in the next century.
With this information the five temperature ranges: 26, 28, 30, 32 and 34 degrees Celsius, have been selected to demonstrate the present/optimum reef temperature and the predicted temperatures if global warming continues other the next century.
The Catalaphyllia jardinei when in sea temperature of 26 degrees Celsius is predicted to have no colour change and continually appear its brown/green colour throughout the experiment. There will be no colour change evident in the experimental tank containing water temperature of 28 degrees Celsius. These two coral specimens are surrounded by water replicating their optimum living conditions and therefore will remain healthy and maintain their natural colour (brown and dark green). At these temperatures the Coral Watch Chart will display the readings at E4 for the lightest area and D6 for the darkest area of the coral
The coral in the 30 degrees Celsius water temperature should appear to discolour after a few days of being submerged in these conditions. This is because the temperature is over the optimum range of the prime Catalaphyllia jardinei living conditions. However, the process of discolouration will be slow and evidence of coral bleaching should not occur until the last day (day 7) of testing. The colours according to the Coral Watch Chart are expected to be approximately E3 and D5 by the end of the 7 days.
The coral situated in the 32 degree Celsius experimental tank should appear to change colour more quickly than the 30 degree tank. This is because the zooxanthellae will be expelled more rapidly under the harsh temperature conditions. Once a collection of zooxanthellae is expelled the coral is provided with less food and energy needed to survive and therefore the bleaching process will continue. The Catalaphyllia jardinei is expected to show bleaching levels of E3 and D4 after the 7 days of testing.
Finally, the experiment tank with 34 degrees Celsius of water temperature will have the greatest affect on the Catalaphyllia jardinei. The harsh temperature conditions replicate those that have demolished reef ecosystems across the world. Therefore, this affect will be evident on the coral in the testing tank. It can be predicted that on day 1 evidence of thermal stress will be evident due to the rapid expulsion of zooxanthellae. The results are predicted to demonstrate high levels of coral bleaching, E2 and D4 on the Coral Watch Chart. As the bleaching process continues the coral will proceed with undergoing more thermal stress and it can be expected that the lightest part of the coral will be E1 and the darkest at D3.
MATERIALS
sand, 5 tanks, 5 thermometers, 5 thermostats, saltwater, indicator strips, 5 coral (Catalaphyllia jardinei), 5 filters
METHOD
1 Set up apparatus (refer to diagram above).
a. Fill each experimental testing tank with water and sand
b. Bury bottom of coral into sand
c. Place thermostat in each experimental testing tank and setting at required temperature
d. Place thermometer in each experimental testing tank to monitor temperature to ensure it remains constant
2 Test the sea water with universal water testing strips to ensure the pH level is 8.5, the specific gravity is 1025 and the nitrate level is <0.025 (ppm). Use solutions to meet requirements.
Regularly monitor the controls listed above.
3 At 1600 hours, describe the water and coral conditions
Select the lightest area, avoiding the tips of branching corals and hold Coral Watch Chart next to selected area.
4 Rotate chart until closest colour match is located.
5 Record the matching colour code along with coral type on the data sheet.
6 Repeat steps 4 to 7 for the darkest area of the coral.
7 Measure the dimension (lengthxwidth) in centimeters and take a photo of the coral in each tank. Note the weather conditions and atmospheric temperature surrounding the tanks.
8 Record data in logbook/journal. Print photo and include in results table.
9 Repeat steps 2 ? 10 for 7 days recording all data in logbook/journal.
RESULTS:
TANK at 26 degrees Celsius:
day 1 - day 7: All results were E4 and D6
TANK at 28 degrees Celsius:
day 1 - day 7: All results were E4 and D6
TANK at 30 degrees Celsius:
day 1 - day 3: E4 and D6
day 4: E4 and D5
day 5: E3 and D5
day 6: E3 and D4
day 7: E3 and D4
TANK at 32 degrees Celsius:
day 1 - day 3: E4 and D5
day 4: E3 and D5
day 6: E2 and D3
day 7: E2 and D3
TANK at 34 degrees Celsius:
day 1 - day 2: E2 and D4
day 3 - day 4: E1 and D4
day 5: E1 and D3
day 7: E1 and D2
DISCUSSION:
The raw and processed data collection has determined if the variation in sea suface temperture during a seven day period has an affect on the Catalaphyllia jardinei. From the results it can be seen that altering the surrounding temperature of the coral affects the extent and rate at which coral bleaching occurs. The correlation between temperature and coral bleaching increase can be seen from the trends apparent in the graphs (Graph 1(a-f)
Catalaphyllia jardinei in the experimental tanks containing salt water at 26 and 28 degrees Celsius displayed no indication of coral colour alteration for seven days of monitoring. Evidently, the readings from the Coral Watch Chart remained at E4 and D6 throughout the experiment. These constant trends can be seen in Graph 1 (a) and Graph 1(b), as well as the final comparison graph (Graph 1 (f). According to Appendix 1 (journal), the seawater also appeared clear throughout the seven days. Therefore, no zooxanthellae were expelled from the Catalaphyllia jardinei as expulsion results in murky water.
Graph 1 (c) represents the trend of the experimental tank containing seawater at 30 degrees Celsius. The coral remained a healthy colour, E4 and D6 the first three days of the experimental investigation. However, the graph illustrates evidence of a slight colour change according to the Coral Watch Chart after the third day. The brown colouration of the Catalaphyllia jardinei turned lighter on day 4 and later the green area became lighter on day 5 (refer to Table 1 (a), Photographic Coral Bleaching Comparison). This colour change has been a result of loss in the dinoflagellate symbionts that provide the coral with energy. Further loss in DS results in continuous colour change throughout the experiment until the coral has become E3 and D4 according to the Coral Watch Chart.
The Catalaphyllia jardinei in the tank at 32 degrees Celsius looses its original healthy colour after 24 hours. The coral started with hue codes of E4 and D6 however, the brown area of the coral reduced to D5. The colour remained steady for 3 days before the green colour reduced to E3 on day 4. Further signs of coral bleaching occurred with both brown and green areas of the colour becoming lighter which then remained steady again on days 6 and 7. The rate of alteration of colour is highlighted on Graph 1(d). The photographs in Table 1 (a) indicate that the seawater appeared to be cloudy on day 3. Therefore, an increase of zooxanthellae expulsion occurred on this day making the water murky.
The final experimental tank at 34 degrees Celsius for 7 days shows the lowest hues according to the Coral Watch Chart. The results in Graph 1 (f) show the averages of the coral colour codes with this temperature producing the lowest mean. After the first 24 hours (day 1) the results indicate hues lower than any shade of the previous temperatures, E1 and D2. This experimental tank also appeared the cloudiest throughout the experiment with brown pigmentations apparent in the water due to excessive loss in dinoflagellate symbiont. The diminishment of this substance is also the cause for the colour change to a vivid white. This has been a result from the deprivation of nutrients DS provides coral.
QUESTIONS:
1. With the information provided write a CONCLUSION for this experiment.
MUST: Identify trends and relationships in the collected data
Interpret and analyse collected data showing links to the THEORETICAL concept.
Give VALID conclusions, based on correct interpretation of the results with an explanation and compare to similar or related experiments.
Make judgements and draw conclusions
Relate to Global Issue (Climate change/global warming)
Relate to the future
2. INCLUDE THREE HEADINGS: Strengths, Weaknesses and Improvements in a table format that evaluate the experimental design.
MUST: Critically evaluate the experimental design giving detailed weaknesses and offer detailed, relevant improvements to the given design.
This report must use sophisticated and scientific language.
Year 12 Final Experiment Standard
