“Hard Anemone”

An exoskeleton Even though it lies Beneath the animal

II. The Coral Host Some scleractinian coral growth forms

massive branching

plate like

foliaceous columnar

Zooxanthallae participate In a mutualistic Association with encrusting Free-living Corals.

Both members of the association benefit Algae in coral tissue Already present in planula as indicated by the cycling of carbon

(one important nutrient is Nitrogen)

1 III. Coral Reef Community Coral Reef Structure: 3 main types of reef Structure Hard Substrate

Coral rubble Fringing Reef What is the Barrier Reef process by Atoll which reefs Hard Substrate are formed? Consolidation

Hard Substrate

IV. Biogeography of Coral Reefs Darwin first explained how reefs form…. Where do Coral Reefs Occur? Island Fringing Reef

And that Barrier Reef Each type Lagoon Is a stage Atoll In the same process

Calcium Carbonate Original Island

Where do Coral Reefs Occur?

Solar radiation

Temperature

Indo-Pacific Maximum diversity

Atlantic Maximum diversity In areas where mean avg. temp. >20 C Number of Genera Especially where fluctuations are small But not too far above 27 C.

2 V. Physical Factors and Zonation in Coral Reef Communities High temperature, high light (UV), desiccation A. Competition for space between Corals runoff, etc. keep many corals from the reef flat Wave action, major storms control the reef front

Vertical Zonation Of a Fringing Reef Competition video

B. Herbivory by Sea Urchins and Fish

• Extensive fisheries starting in the 1950’s had little additional effect on coral reefs

• However major predators of sea urchin Diadema and herbivorous fish competitors were lost

• From 1982-84 a mass die-off of sea urchins due to a disease reduced populations by 99%

• This was followed by extensive take over of reefs by algae

Hughes, 1994 Hughes, 1994

3 Hughes, 1994

Hughes, 1994

Impact of fisheries Fisheries vs. hurricanes Resilience Roberts C.M. 1995. Role of herbivory Conservation Biology Vol 9: 988-995 Phase shifts

http://www.jamaicachm.org.jm/Article/December2005.asp

What Cellular Events Lead to Bleaching? VII. Climate Change and Coral Reefs

Bleaching Event in the Maldives

Two Alternative Mechanisms

Before During After

4 Temperature fluctuations in the GBR related to the onset of bleaching (arrows)

•The displaced symbiont is inferior to invading symbionts

•Replacement of the resident population in an animal requires depletion of the population (e.g. Hydra with nutritionally inferior and superior strains)

• An alternative strain is available to populate the bleached animal hosts (may be residual or external in origin)

McField (1999) also identifies temperature as the cause of bleaching in Belize during 1995

Hughes et al 2003, Invariant bleaching threshold Science Vol. 301 p 929 leads to massive losses

•bleaching is an ecological gamble in that it sacrifices short-term benefits for long term advantage. This counters conventional wisdom that bleaching is detrimental from all perspectives, and supports the role of symbionts as adaptive agents. Andrew C. Baker Bleaching threshold as a • In rebuttal: there is no guarantee that temperature was the stressor that caused bleaching. broad spectrum of responses •Also, as light energy is critical to coral survival, stressed corals might survive better when transplanted to the more sunlit site and less well after transfer to deep water. leads initially to differential • Baker is unable to distinguish newly invading genotypes from other rare genotypes that are bleaching present in the host and which simply increase in proportion. The latter is a phenotypic change known as acclimatization and as such is restricted in its provision of new genetic combinations for evolution. Hoegh Guldberg et al. Adaptive bleaching response may lead to evolution in some species Acclimatization vs. Adaptation

5 Acidification of the Oceans

Baker et al 2004

Conducted molecular studies of Symbiodinium in corals from reefs differentially affected by 1997-98 ENSO: • in Panama before and after bleaching events • from heat adapted & bleached Persian Gulf to milder Red Sea • severely bleached Kenyan corals to unbleached Mauritius corals

Under this model, Coral reefs would reach a point where maintenance of a coral dominated U.S. phase rather than Coral an algal dominated phase would be Reefs nearly impossible

Annual revenues from reef tourism in Keys is $1.6 billion

Only 6% of the Florida Keys Marine Sanctuary is no take

Purple

Pandolfi et al. 2005. Are U.S. coral reefs on the slippery slope to slime? Pandolfi et al. 2005. Are U.S. coral reefs on the slippery slope to slime? Science #307: 724-1726 Science #307: 724-1726

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