coral/algal reefs iii

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Coral/algal Reefs III. The future?. Utilitarian justification for reef conservation. Therapeutic compounds from marine species Anti- virals from sponges, seagrass Anti-tumor compounds from tunicate, dogfish, bryozoan , sea hares, cyanobacteria , sponge - PowerPoint PPT Presentation

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  • Coral/algal Reefs IIIThe future?

  • Utilitarian justification for reef conservationTherapeutic compounds from marine speciesAnti-virals from sponges, seagrassAnti-tumor compounds from tunicate, dogfish, bryozoan, sea hares, cyanobacteria, spongeCompounds to promote bone grafts from stony coralsTourismFoodImpact on global climate, carbon exchangeModels for scientific study

  • Processes important in reef dynamics what maintains the reef structure?Symbiotic mutualism (and dissolution of associations)Competition

    Predation and grazing

    Disturbance & recovery

  • Questions:Are symbiotic relationships increasingly disrupted?What are the consequences?How are organisms linked through symbiosis?Are changes reversible?

  • Coral bleaching (Hoegh-Guldberg)

  • Coral bleaching dissolution of symbiosiszooxanthellae expelled from tissuepolyp can persist for a whilenew associations can be formedresponses to stresses

  • A general introduction to symbiosisDe Bary (1850s) The living together of different species for an extended period of time.

    Proximity, not outcomes, define symbiosis

    Variation in characterizing some associations, e.g., pollination

  • Symbiosis has many dimensionsForm of physical associationTypes of organisms involvedNature of the exchange or influenceOutcomes of the interaction (+, 0, -)Degree of dependenceEvolutionary derivation of the association

  • Physical nature of the associationClose proximity, but physically independent

    External contact

    Internal

  • What taxa are associated?Algae-invertebrate

    Among animals

    Bacteria/archaea - animals

  • What is exchanged?

    CapabilityDonorRecipientphotosynthesisalgae, bacteriaprotists, invertschemosynthesisbacteriainvertebratesadded nutrientsbacteriamany animalsmethanogenesisbacteria, protistsanaerobic protistscellulose digestionbacteria, protistsherbivores (terrest.)luminescenceVibrio, Photobact.molluscs, fishprotectioncnidariafish

  • What are the outcomes of symbiotic associations?Recipient

    -0+-0amensalismcommensal+parasitismmutualism

  • Outcomes: nutrient exchangeWhat is the evidence for exchange with endosymbiotic dinoflagellates?Experiment: remove zooxanthellaeammonium content of polyp risesFor Tridacna clamsexperimentally enrich with ammoniumalgal symbiont increases in density

  • What is the degree of dependence?Facultative

    Obligate (often has very specialized morphology and life history)

    Symmetry is not necessarily found

  • What is the evolutionary origin of the association?Parasite-host may evolve to be mutualistic

    Predator-prey (coral/dinoflagellate)

    Close proximity may lead to coevolved relationship

  • How can we evaluate importance?Removal experiments, e.g., cleaner fish

    Alter background conditions Chlorella/Hydra experiment

  • Bleaching occurs with high SST

  • How does heat (& light) disrupt mutualism?Symbiodinium is damaged by oxidative stress

  • Coral ResponsesPolyp responds immunologicallyApoptosis & autophagyZooxanthellae can be expelledPolyp switches to heterotrophyThis is a short-term strategy

  • Sensitivity to SST varies Among genotypes of SymbiodiniumAmong colonies within coral species Between different coral species Geographically for the same coral species

  • 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.BackgroundSummer & fall, 2005 high SST in ne CaribbeanMass bleaching documentedMethodsMonitor corals for 191 colonies in permanent quadrats

  • Bleaching was correlated with heating

  • Bleaching prevalence varied among spp

  • Bleaching incidence varied with colony size

  • Why and whats next?Symbiont clades vary geneticallyCorals can switchSymbiodinium communities can vary across environmental gradientsDegree of flexibility is debatedHosts (corals) also varyDifferent fluorescent proteins for protectionDifferent abilities in heterotrophyCoral structure affects the light environment

  • Competitive dynamicsExploitation competition (for light)Upright, branching corals can shade massive coralsEncrusting algae can spread over coralsInterference competition (for space)External digestion by some coralsSweeper tentacles for some speciesHierarchy of competitive dominanceAlgae easily overgrow most coralsAmong corals Pocillopora is nastiest

  • Dynamics of predation on coral reef speciesCoral-feeding fish are present but usually not devastatingTerritorial damselfish create safe zones (up to 60% of surface area)Coral-feeders have their own predatorsStarfish, such as Crown-of-Thorns can be problematicPopulation outbreaks can damage living corals

  • Dynamics of grazing on algal reef speciesUrchins are major consumers (e.g., Diadema antillarum)Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals)Grazing can suppress competitively dominant algaeIndirect effects can become important