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Coral/algal Reefs IV

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

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Coral/algal Reefs IV

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  1. Coral/algal Reefs IV Variation and Alternative States

  2. Variation in Florida Keys corals, 2005

  3. Brandt, M. E. 2009. The effect of species and colony size on the bleaching response of reef-building corals in the Florida Keys during the 2005 mass bleaching event. Coral Reefs 28:911-924. • Background • Summer & fall, 2005 – high SST in ne Caribbean • Mass bleaching documented • Methods • Monitor corals for 191 colonies in permanent quadrats

  4. Bleaching was correlated with heating

  5. Bleaching prevalence varied among spp

  6. Bleaching incidence varied with colony size

  7. Why and what’s next? • Symbiont “clades” vary genetically • Corals can switch • Symbiodinium communities can vary across environmental gradients • Degree of flexibility is debated • Hosts (corals) also vary • Different fluorescent proteins for protection • Different abilities in heterotrophy • Coral structure affects the light environment

  8. Will coral reefs respond to fast climate change? • Climate shifts • More peak temperature events • More extreme temperature events • Physiological response? • Evolutionary response?

  9. Competitive dynamics • Exploitation competition (for light) • Upright, branching corals can shade massive corals • Encrusting algae can spread over corals • Interference competition (for space) • External digestion by some corals • “Sweeper” tentacles for some species • Hierarchy of competitive dominance • Algae easily overgrow most corals • Among corals Pocillopora is nastiest

  10. Mix of coral polyp and algae

  11. Algal overgrowth

  12. Shading by Sargassum, chemical effects

  13. Herbivores on algae

  14. Dynamics of predation on coral reef species • Coral-feeding fish are present but usually not devastating • Territorial damselfish create safe zones (up to 60% of surface area) • Coral-feeders have their own predators • Starfish, such as “Crown-of-Thorns” can be problematic • Population “outbreaks” can damage living corals

  15. Dynamics of grazing on algal reef species • Urchins are major consumers (e.g., Diademaantillarum) • Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals) • Grazing can suppress competitively dominant algae (>90% removal) • Indirect effects can become important

  16. Evidence for herbivorous fish indirectly helping corals R = redband parrotfish S = ocean surgeonfish Burkepile & Hay, 2010, PLoS One, 5 (e8963)

  17. Mangrove /Mangal A tropical and subtropical boundary community

  18. Questions: • Why are trees found in some ocean boundaries? • Aquatic/terrestrial • salt/freshwater • What are the characteristics of these ecosystems? • How is mangal important to marine ecosystems?

  19. Definitions: • Mangrove • A type of tree that tolerates variation in inundation and salinity • Mangal • A community (set of species) on the marine fringe • Dominated by a special set of salt-tolerant trees • Includes many other, associated species, both of terrestrial and marine origins

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

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

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