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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

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utilitarian justification for reef conservation
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
    • Compounds to promote bone grafts from stony corals
  • Tourism
  • Food
  • Impact on global climate, carbon exchange
  • Models for scientific study
processes important in reef dynamics what maintains the reef structure
Processes important in reef dynamics – what maintains the reef structure?
  • Symbiotic mutualism (and dissolution of associations)
  • Competition
  • Predation and grazing
  • Disturbance & recovery
questions
Questions:
  • Are symbiotic relationships increasingly disrupted?
  • What are the consequences?
  • How are organisms linked through symbiosis?
  • Are changes reversible?
coral bleaching dissolution of symbiosis
Coral bleaching – dissolution of symbiosis
  • zooxanthellae expelled from tissue
  • polyp can persist – for a while
  • new associations can be formed
  • responses to stresses
a general introduction to symbiosis
A general introduction to “symbiosis”
  • De Bary (1850’s) – “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 dimensions
Symbiosis has many dimensions
  • Form of physical association
  • Types of organisms involved
  • Nature of the exchange or influence
  • Outcomes of the interaction (+, 0, -)
  • Degree of dependence
  • Evolutionary derivation of the association
physical nature of the association
Physical nature of the association
  • Close proximity, but physically independent
  • External contact
  • Internal
what taxa are associated
What taxa are associated?
  • Algae-invertebrate
  • Among animals
  • Bacteria/archaea - animals
outcomes nutrient exchange
Outcomes: nutrient exchange
  • What is the evidence for exchange with endosymbioticdinoflagellates?
  • Experiment: remove zooxanthellae
    • ammonium content of polyp rises
  • For Tridacna clams
    • experimentally enrich with ammonium
    • algal symbiont increases in density
what is the degree of dependence
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
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
How can we evaluate importance?
  • Removal experiments, e.g., cleaner fish
  • Alter background conditions – Chlorella/Hydra experiment
how does heat light disrupt mutualism
How does heat (& light) disrupt mutualism?
  • Symbiodinium is damaged by oxidative stress
coral responses
Coral Responses
  • Polyp responds immunologically
    • Apoptosis & autophagy
  • Zooxanthellae can be expelled
  • Polyp switches to heterotrophy
    • This is a short-term strategy
sensitivity to sst varies
Sensitivity to SST varies
  • Among genotypes of Symbiodinium
  • Among colonies within coral species
  • Between different coral species
  • Geographically for the same coral species
slide22

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
why and what s next
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
competitive dynamics
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
dynamics of predation on coral reef species
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
dynamics of grazing on algal reef species
Dynamics of grazing on algal reef species
  • Urchins 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 algae
  • Indirect effects can become important