the role of zooxanthellae in the thermal tolerance of corals
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The Role of Zooxanthellae in the thermal tolerance of corals. Emily Wanerka Juliet Blass. Key Words. Acclimatization – an organism’s response to changes in its environment Temperature change in our case - PowerPoint PPT PresentationTRANSCRIPT
THE ROLE OF ZOOXANTHELLAE IN THE THERMAL TOLERANCE OF CORALS
Emily WanerkaJuliet Blass
KEY WORDS
Acclimatization – an organism’s response to changes in its environment Temperature change in our case
Zooxanthellae – photosynthetic algae that live in coral tissues forming a symbiosis with the coral
Coral Bleaching Climate Change
ABOUT THE AUTHORS Ray Berkelmans
-Australian Institute of Marine Science (1999 – present)
-climate change and coral reefs Madeleine J.H. van Oppen
- Australian Institute of Marine Science (program leader 2005 – present)
-Research scientist-Marine molecular ecology
BACKGROUND INFORMATION Projected increases
in temperature due to global warming are a major threat to coral reefs.
Survival depends largely on the corals’ ability to acclimatize
Algal symbiosis between coral reefs and zooxanthellae
Heat stress results in bleaching of corals, and can lead to death of the coral
PURPOSE Investigate the role of
zooxanthellae in the thermal tolerance of corals
Necessary to understand whether symbiont change will affect the level of thermal tolerance in corals, with anticipated increases in sea surface temperatures in near future
Average seawater temperatures predicted to increase 1-3°C over the next 100 years
EXPERIMENTAL DESIGN Acropora millepora –a widespread Indo-
Pacific hard coral species Three different populations of A. millepora
were studied 22 colonies from North Keppel Island
(coolest) 22 colonies from Davies Reef (middle temp) 22 colonies from Magnetic Island (warmest) Location of Study: Magnetic Island Control: Native colonies from each location
GEOGRAPHY OF STUDY
REGIONAL TEMPERATURES
Figure 2. Average daily temperatures at Magnetic Island, Davies Reef and Halfway Island (approximately 15 km from North Keppel Island) for the warmest austral summer months. Data are averages of 48 readings per day over 15 years (Magnetic Island) and 10 years (Davies Rf and Halfway Is) and were averaged over the reef flat (0 m at LAT) and slope (5 m at LAT). A 10 day smoothing function is applied to indicate the general trend in summer temperatures. Temperatures differences between Halfway Island and Nor th Keppel Island are less than 0.1 8C based on an 18 month period when loggers were deployed at both sites (data not shown).
Obtained Results
RESULTS Thermal tolerance
among native populations was strongly linked with location
Relative thermal sensitivity was demonstrated by contrasting and significantly different patterns of zooxanthella density
Reduced algal density did not affect the thermal resistence of the individual corals associated
Increased tolerance only proven with type D
STRENGTHS/WEAKNESSES Strengths
Keppels results support adaptive bleaching hypothesis
Temperatures recorded in 3 areas every half hour
Transplants - highly regulated (depths etc) Weaknesses
- Method of symbiont change not certain (shuffling, switching)
- Davies – Inconsistent with link between acclimatization and location
FURTHER STUDY Cell Biochemistry of the coral proteins Temperature limits in sustaining coral life,
and biological changes of coral in response to changing temperatures
Physiological characteristics of zooxanthella Process of Symbiont Change
REFERENCES http://data.aims.gov.au/staffcv/jsf/external/view.jspx;js
essionid=22A9E673BB4E173F062BBB20915F2B3E?partyId=100000290
Berkelmans, Ray, and Madeleine J.H. Van Oppen. "The Role of Zooxanthellae in the Thermal Tolerance of Corals: a ‘nugget of Hope’ for Coral Reefs in an Era of Climate Change." Proceedings of The Royal Society B (2006): 2305-312. PubMed. 8 June 2006. Web. 17 Feb. 2011.
http://www.aims.gov.au/docs/publications/waypoint/001/headlines-01.html