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

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Coral/algal Reefs III

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Coral algal reefs iii

Coral/algal Reefs III

The future?


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 hoegh guldberg

Coral bleaching (Hoegh-Guldberg)


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


What is exchanged

What is exchanged?


What are the outcomes of symbiotic associations

What are the outcomes of symbiotic associations?

  • Recipient


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


Bleaching occurs with high sst

Bleaching occurs with high SST


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


Variation in florida keys corals 2005

Variation in Florida Keys corals, 2005


Coral algal reefs iii

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


Bleaching was correlated with heating

Bleaching was correlated with heating


Bleaching prevalence varied among spp

Bleaching prevalence varied among spp


Bleaching incidence varied with colony size

Bleaching incidence varied with colony size


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


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