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Coral Reefs and Climate Change Drew Harvell Ecology and Evolutionary Biology Cornell University
Disease is a major community structuring agent in the ocean • Coral diseases-- eg Acropora spp over 90% mortality mid 1980s • Tropical urchins-- eg Diadema over 90% mortality mid 1980s well documented keystone effect of disease • Temperate urchins • Lobsters, other crustaceans, oysters, abalone
Sea Urchin (Diadema antillarum) Die-Off • started in January, 1983 • population density reduced by 97% in one year (Lessios 1988) • current population density still <3.5% of 1983 (Lessios 1995) • major community shifts on coral reefs • coral to algae dominated • unidentified water-borne pathogen Photo by P. Humann
Ocean diseases and climate warming: explosive mix • corals at upper thermal limits, eg bleaching • pathogens can rapidly evolve new • temp tolerances • pathogens evolve much more rapidly • than coral • anthropogenic activities increase • stir in more new emergent pathogens
White Band Disease of Corals • Acropora cervicornis dominated Caribbean Coral Reefs • from 1950-1970—disappeared thereafter • Mass mortality from White Band Disease in Belize in 1986 • First time in 3,800 years (Aronson & Precht 1997)
Warming Oceans Can Facilitate Pathogens • Black band disease of coral increases in summer • Aspergillosis of coral grows faster at peak summer temperatures • Perkinsus of oyster moved to Maine when winter temps warmed in the 90s • Coral bleaching likely facilitates disease Florida Keys: 63% died during warm El nino
Seafan-aspergillus epizootic 1- Impact in the Keys 2- SpatialEcology 3- Resistance to Disease
Aspergillosis of Sea Fans ~ Dynamics in the Florida Keys ~ • Are there disease hotspots correlated with water quality? • Prevalence: number of infected individuals • Virulence: damage from disease • water quality: temperature, nitrates, chlorophyll a, etc. • Can sea fans fight back? • chemical resistance • Could chemicals from soft corals have biomedical applications? • anti-bacterial compounds (Jensen, Harvell, Wirtz, Fenical 1996) • antifungal compounds (Kim, Kim, Harvell, 2000)
Death of a Diseased Coral Alisa Alker
Seafan Disease Monitoring • Permanent Transects • Established June 1997 • Currently 8 sites along the Florida Keys • Three 25 m transects per site • Parameters measured • Colony height (cm) • % infected individuals: Prevalence • % colony damage: Severity • Dead
June 1997: Hi prevalence, variable severity-- compromised resistance more important than transmission? Kim and Harvell in press
New disease and force of infectionMortality Hotspots-- indicator of disease process scale?
Seafan Corals: Impact of a Fungal Disease Aspergilli cause diseases in immune compromised hosts. Is resistance of seafans compromised? K.Kim photo
Seafan Resistance to Aspergillus • Antifungal chemicals • Hyperplastic tumors • Melanization response NSF, NOAA
8 6 4 2 20 25 30 35 40 Aspergillus sydowii:optimal temp is hot Growth Rate (mm/d, ±SE) Temperature (˚C) Alker et al
20 15 10 5 Antifungal Activity in Gorgonian Corals (Kim et al, 2000) Minimum Inhibitory Concentrations (mg/ml) increasing activity Pseudopterogorgia acerosa Pseudoplexaura wagenaari Pseudoplexaura flagellosa Pseudoplexaura porosa Pseudopterogorgia americana Gorgonia ventalina Plexaura kuna Eunicea succinea Pseudopterogorgia bipinnata Plexaura flexuosa Plexaura homomalla Pterogorgia citrina Briareum asbestinum Erythropodium caribaeorum Pseudopterogorgia rigida Plexaurella grisea Plexaurella nutans Muricea atlantica Muriceopsis flavida Pterogorgia guadalupensis
Your Test • Will the fungus cause seafan exinction? • Need to know: coral mortality rate, longevity, recruitment rate… • …it could because mortality hi, long-lived, and no repro • Is climate warming a threat to corals? • BIG THREAT • Where might new coral diseases come from? • Aquaculture, land, ballast shipping, existing pathogens • Can seafans fight back? • Rapid induction (4-8 days) • Antifungal chemicals, melanin (purpling), gorgonin tumors • Will seafans evolve to be more resistant? • Maybe, clonal variation for selection to act on.
Predation Predation Abiotic Factors Abiotic Factors Competition Competition Disease Corals Corals Diseases in Marine Communities~ Changing Perspectives ~