Coral/algal Reefs IVCoral/algal Reefs IV

Variation and Alternative Variation and Alternative StatesStates

Variation in Florida Keys corals, Variation in Florida Keys corals, 20052005

Brandt, M. E. 2009. The effect of species and colony Brandt, M. E. 2009. The effect of species and colony size on the bleaching response of reef-building size on the bleaching response of reef-building corals in the Florida Keys during the 2005 mass corals in the Florida Keys during the 2005 mass bleaching event. Coral Reefs 28:911-924.bleaching event. Coral Reefs 28:911-924.

• BackgroundBackground– Summer & fall, 2005 – high SST in ne Summer & fall, 2005 – high SST in ne

CaribbeanCaribbean– Mass bleaching documentedMass bleaching documented

• MethodsMethods– Monitor corals for 191 colonies in Monitor corals for 191 colonies in

permanent quadratspermanent quadrats

Bleaching was correlated with Bleaching was correlated with heatingheating

Bleaching prevalence varied Bleaching prevalence varied among sppamong spp

Bleaching incidence varied with Bleaching incidence varied with colony sizecolony size

Why and what’s next?Why and what’s next?

• Symbiont “clades” vary geneticallySymbiont “clades” vary genetically– Corals can switchCorals can switch– SymbiodiniumSymbiodinium communities can vary communities can vary

across environmental gradientsacross environmental gradients– Degree of flexibility is debatedDegree of flexibility is debated

• Hosts (corals) also varyHosts (corals) also vary– Different fluorescent proteins for protectionDifferent fluorescent proteins for protection– Different abilities in heterotrophyDifferent abilities in heterotrophy– Coral structure affects the light Coral structure affects the light

environmentenvironment

Will coral reefs respond to fast Will coral reefs respond to fast climate change?climate change?

• Climate shiftsClimate shifts– More peak temperature eventsMore peak temperature events– More extreme temperature eventsMore extreme temperature events

• Physiological response?Physiological response?

• Evolutionary response?Evolutionary response?

Competitive dynamicsCompetitive dynamics

• Exploitation competition (for light)Exploitation competition (for light)– Upright, branching corals can shade Upright, branching corals can shade

massive coralsmassive corals– Encrusting algae can spread over coralsEncrusting algae can spread over corals

• Interference competition (for space)Interference competition (for space)– External digestion by some coralsExternal digestion by some corals– ““Sweeper” tentacles for some speciesSweeper” tentacles for some species

• Hierarchy of competitive dominanceHierarchy of competitive dominance– Algae easily overgrow most coralsAlgae easily overgrow most corals– Among corals Among corals PocilloporaPocillopora is nastiest is nastiest

Mix of coral polyp and algaeMix of coral polyp and algae

Algal overgrowthAlgal overgrowth

Shading by Shading by Sargassum, Sargassum, chemical chemical effectseffects

Herbivores on algaeHerbivores on algae

Dynamics of predation on coral reef Dynamics of predation on coral reef speciesspecies

• Coral-feeding fish are present but Coral-feeding fish are present but usually not devastatingusually not devastating– Territorial damselfish create safe zones Territorial damselfish create safe zones

(up to 60% of surface area)(up to 60% of surface area)– Coral-feeders have their own predatorsCoral-feeders have their own predators

• Starfish, such as “Crown-of-Thorns” Starfish, such as “Crown-of-Thorns” can be problematiccan be problematic– Population “outbreaks” can damage Population “outbreaks” can damage

living coralsliving corals

Dynamics of grazing on algal reef Dynamics of grazing on algal reef speciesspecies• Urchins are major Urchins are major

consumers (e.g., consumers (e.g., Diadema antillarumDiadema antillarum))

• Grazing by herbivorous Grazing by herbivorous fish can be specialized fish can be specialized on algae (more impact on algae (more impact than fish feeding on than fish feeding on corals)corals)

• Grazing can suppress Grazing can suppress competitively dominant competitively dominant algae (>90% removal)algae (>90% removal)

• Indirect effects can Indirect effects can become importantbecome important

Evidence for herbivorous fish Evidence for herbivorous fish indirectly helping coralsindirectly helping corals

R = redband parrotfishR = redband parrotfish

S = ocean surgeonfishS = ocean surgeonfish

Burkepile & Hay, 2010, Burkepile & Hay, 2010, PLoS One, 5 (e8963)PLoS One, 5 (e8963)

Mangrove /MangalMangrove /Mangal

A tropical and subtropical A tropical and subtropical

boundary communityboundary community

Questions:Questions:

• Why are trees found in some ocean Why are trees found in some ocean boundaries?boundaries?– Aquatic/terrestrial Aquatic/terrestrial – salt/freshwatersalt/freshwater

• What are the characteristics of these What are the characteristics of these ecosystems?ecosystems?

• How is mangal important to marine How is mangal important to marine ecosystems?ecosystems?

Definitions:Definitions:

• MangroveMangrove– A type of tree that tolerates variation in A type of tree that tolerates variation in

inundation and salinityinundation and salinity

• MangalMangal– A community (set of species) on the A community (set of species) on the

marine fringemarine fringe– Dominated by a special set of salt-Dominated by a special set of salt-

tolerant treestolerant trees– Includes many other, associated species, Includes many other, associated species,

both of terrestrial and marine originsboth of terrestrial and marine origins

Characteristics: very low wave Characteristics: very low wave action, with silty substrates action, with silty substrates (sometimes sand)(sometimes sand)

Extent: 2/3 – 3 /4 of tropical shores Extent: 2/3 – 3 /4 of tropical shores were fringed with mangal were fringed with mangal