An underwater nightmare: Global warming and coral disease

Transcription

1 An underwater nightmare: Global warming and coral disease Half of all coral reefs in danger, experts warn global warming cited; U.S. warns of major event in Caribbean Caribbean coral suffers record die-off World's coral reef loss 'an underwater holocaust' Friday, March 31, 2006 WASHINGTON (AP) -- A one-two punch of bleaching from record hot water followed by disease has killed ancient and delicate coral in the biggest loss of reefs scientists have ever seen in Caribbean waters.

2 THERMAL STRESS INDUCES PATHOGENIC EFFECTS OF VIBRIO SPECIES ON INDO- PACIFIC AND CARIBBEAN SYMBIOTIC REEF BUILDING CORALS Jane McClanahan & Dr. James Cervino Department of Biological and Health Sciences Pace University

3 Questions to answer What is the coral-algal symbiosis? What are threats are disrupting the symbiosis? How is global warming affecting coral disease?

4 Goals of our research Determine if heat stress causes symbiotic algae cells to become immunocompromised Identify the cell death pathways of Vibriobacteria infected zooxanthellae Compare amounts of apoptotic cells from Vibrio-infected zooxanthellae to controls Identify possible heat-induced toxins produced by Vibrio

5 Coral reefs are the most climatically sensitive ecosystems on the planet Reef health can be used as an indicator of rising seasurface temperatures

6 Why are corals important? Biodiversity Coastal protection Economic value Fish protein

7 Biodiversity 4,000 species of fish 800 species of hard coral

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9 1-2C Above the warmest summer average Rising Seawater Temperatures Great Barrier Reef left more than 30 percent of the reef destroyed.

10 Today, 65% of the worlds reefs are dying due to temperature stress, diseases and chemical pollution (US Coral Reef Task Force, NOAA)

11 Corals: plant or animal? a little bit of both! 1 millimeter of LIVING animal tissue on top of massive calcium carbonate (limestone) skeleton thousands of polyps form a colony Stings prey (zooplankton) with tentacles Non-mobile, can t escape stress such as predators or disease

12 What is Zooxanthellae? Reef-building coral animals have single-celled plants living within their tissues..why? Single-celled plant (algae) living within the coral tissues uses energy from the sun for photosynthesis Products of photosynthesis, such has glucose and oxygen, are used by the coral (AN EXTRA SOURCE OF FOOD) Zooxanthellae use coral waste products (nitrogen, CO2) for photosynthesis Like a self-sufficient recycling system Algae helps coral to deposit skeleton Almost all the coral s color comes from the zooxanthellae

13 Zooxanthellae: coral s solar power

14 Coral Reef Disease

15 Coral diseases: what is known? Out of 18 coral diseases known, pathogens have been identified for 4 of them: Yellow Band Disease: vibrio spp, shellfish pathogens Black Band Disease Sea fan disease: aspergillosis soil fungus White plague (bacteria), affects 18 diff spp, 1 cm/day White pox: sewage pathogen (human gut)

16 Yellow Band Disease 9/ /1997 BBD 3/1996 2/1997 Yellow Band

17 Vibrio-induced Yellow Band Disease Infection caused by 4 Vibrio bacteria species Causes yellow lesions Effects the zooxanthellae directly, not the coral host Higher rate of infectivity at higher temperatures Same group of bacteria in Pacific and Caribbean

18 Yellow-band causing Vibrio bacteria

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20 Yellow band disease causes the destruction of zooxanthellae in-situ

21 100 Coral Mortality Temperature C

22 What are the cell death mechanisms when corals are subjected to thermal stress and infected with shell-fish Vibrio pathogens?

23 Bacterial Mat & Zoox Healthy Zooxanthellae lysis Fragmented degenerate zoox Titlyanov (1996). Healthy Internal structures Begin to shrink PCD in zoox described in Dunn et al., (2001). PCD? Apoptosis (Dunn et al. 2002) Bacterial Lysis Fragmented Degenerate Alga

24 CL The effects of Vibrio on zooxanthellae Starch crystals Shrinkage Transmission Electron Microscopy CL S C-W AC Cl v N N S After Vibrio 24 hrs Control 24 hrs Apoptosis Special thanks Marine Biological Lab Woods Hole MA.

25 Why does the Yellow Band infection intensify with temperature? How does temperature affect the zooxanthellae? Does temperature stress make zooxanthellae more susceptible to infection?

26 Presentation at the 106 th General Meeting May 24, 2006 VIBRIO INFECTION INTENSIFIES FOLLOWING THERMAL STRESS ON ZOOXANTHELLAE CLADE SPECIES IN CULTURE and in THE PACIFIC ANEMONE STICHODATYLA SP. J.M. Cervino1, Pace University, New York NY J.M. McClanahan2, Pace University, New York NY E.A. Lorence3, Pace University, New York NY F. Thompson4, Universidade Estadual de Campinas, BR T.J. Goreau5, Global Coral Reef Alliance, Cambridge MA R.L. Hayes6, College of Medicine, Howard University, Washington D.C.

27 Our results Specific species of symbiotic zooxanthellae are the targets of Vibrio infection Temperature weakens the immune system of algae, which affects growth Lower cell division Lower densities Lysed apoptotic cells

28 Implications ID which zoox are most susceptible to infection ID usual zoox-host partnerships Prediction of which coral species will be affected by Yellow Band

29 What can we do to reduce stress on corals? Influence policy makers to immediately address the significant impacts that heat-trapping carbon emissions have on coral reefs in the tropics

30 Black Band Disease Affects major reef builders Linked to pollution Caused by a consortium of bacteria Grows in a slimy mat over the coral surface

31 Sea Fan Disease Caused by Aspergillosis, a soil fungus Deforestation and excavating cause the soil fungus to be washed down rivers and into the ocean onto the reef environment

32 White Plague Caused by a bacteria Affects 18 different species of coral Often mistaken for bleaching

33 Thermal Bleaching The most severe threat to corals worldwide

34 Global warming is causing thermal bleaching on a massive scale The Great Barrier Reef has suffered severe damage

35 What is bleaching? When temps exceed 1-2C above the summer average Zooxanthellae are expelled Lack of pigment in tissue makes it become translucent, skeleton becomes visible Coral starves from lack of energy Immune system is weakened, coral becomes more susceptible to pathogens

36 Thermal bleaching Healthy, with pigment Bleached no zooxanthellae

37 Corals worldwide suffer from bleaching Bonaire, 2001 Fully Bleached

38 For more information about coral reef disease contact James Cervino, PhD Biological and Health Sciences Dept.