Chapter 14Part 1

Coral Reefs

ClassificationBiology

DiversityFeeding/Nutrition

Coral Classification

• Domain: Eukaryota• Kingdom: Animalia• Phylum: Cnidaria (Hatschek, 1888)

• Class: Anthozoa (Ehrenberg, 1831)

Scleractinian Corals

• Calcium carbonate skeleton (CaCO3)• Polyps• Symbiodinium sp. (zooxanthellae)• Hermatypic –

– Contain Symbiodinium– Reef-building

• Ahermatypic– Most do not contain Symbiodinium– Not reef-building

Coral Classification

Coral Biology

Figure 14-2. Cutaway view of one of the polyps in a coral colony and of the calcium carbonate skeleton underneath.

coenosarc

Coral Biology• Radial symmetry• One opening (mouth)• Gastrodermis – tissue

lining stomach• Septum – increase

stomach lining area and contain reproductive cells

• Basal plate - calciferous ring with 6 supporting radial ridges. The ridges grow vertically and project into the base of the polyp.

This drawing depicts the basic anatomy of a hard coral polyp. Artwork Credit: NOAA/Gini Kennedy

Calcium Carbonate Skeletons• CO2 + H20 H2CO3

– (carbonic acid – weak acid)• H2CO3 H+ + HCO3

- – (carbonate ion)

• H+ ion helps to neutralize by combining with OH- to form H20

• Carbonate ion will also:• HCO3

- H+ + CO32- (bicarbonate ion)

• Ca2+ + CO32- CaCO3

• TAKES ENERGY – Where does it come from?

Coral Polyps

Most corals are made up of hundreds to hundreds of thousands of individual coral polyps like these. The tissue is only millimeters thick.

Day

Night

Porites astreoides

Symbiodinium photo by S. R. Santos

Symbiodinium (zooxanthellae) are found in the gastrodermal layer of tissue in the coral at densities greater than 1 million per square inch

Symbiodinium Classification

• Domain: EukaryotaKingdom: ChromalveolataSuperphylum: AlveolataPhylum: DinoflagellataClass: DinophyceaeOrder: SuessialesFamily: BlastodiniaceaeGenus: Symbiodinium

(Freudenthal, 1970)

http://www.eol.org/pages/91312

Symbiodinium• Endosymbionts of cnidarians and giant clams• Provide corals up to 100% of energy for survival

and reef-building– Corals provide wastes that Symbiodinium uses for

photosynthesis.– Symbiodinium provides corals products of

photosynthesis for food• Acquired by corals

– Ingestion by planula– Transmission from mother to daughter colony

through asexual reproduction– Ingestion by coral especially after “bleaching”

Symbiodinium Diversity

Symbiodinium ecological diversity

LaJeunesse, 2001

Typical Coral Growth Forms

Caribbean Corals

Porites astereoides – A4aMontastrea faveolata – B1

Siderastrea siderea – C3 or B5a

Gorgonia ventalina –B1

Acropora palmata – A3

Porites furcata – A4, B1, C4

Indo-Pacific Corals

Acropora hyacinthus

Acropora formosa

Acropora sp. mix

Herpolitha limax

Acropora humilis

Platygyra sp.

Porites sp.

Acropora formosa and Porites sp.

Acropora sp. in the Pacific

Reef Building Corals: Pacific

Coral Nutrition and Feeding

Mesenterial filaments secrete digestive enzymes, corals can also use mucus nets, or absorb DOM from the water

Coral Nutrition and Feeding

Coral Nutrition and Feeding

Love-Hate Relationship with Sunlight

• Necessary for photosynthesis by Symbiodinium• Must protect itself against excess sunlight to avoid “bleaching,” or more accurately, “paling” of Symbiodinium cells • Coral skeleton scatters light to increase absorption when fewer pigments available (Enriquez et al. 2005)

Use of sunlight

GBR1997-1998One of worst

bleaching events in history

Love-Hate Relationship with SunlightProtections against too much sunlight

• Photoprotection• Pigments, pathways of photosynthesis, others

• Coral pigments• Movement of Symbiodinium cells • Diversity of Symbiodinum cells on a single colony

Kemp et al 2008

• Global climate change and coral bleaching– Warmer oceans + high light = stressed Symbiodinium and coralsAND possible death of corals from loss of

Symbiodinium

Coral Bleaching

lh3.ggpht.comwww.ncar.ucar.edu

Coral bleaching video

Coral bleaching

42% of coral cover of GBR lost