Coral Reefs

• Built entirely by biological activity • CaCO 3 solubility low above 20 o isotherm • Radioactively labeled Ca absorption low on cloudy days • Global distribution limited by temperature • 70 m is max depth (1-2% surface illumination) • 32-35 ppt salinity range • Limited by sediment & exposure to air (subtidal) • Enhanced by wave action to a point

Terminology/Taxonomy

Hermatypic: Reef building Prop/support Domain: Eucarya Kingdom: Animalia Phylum: Cnidaria (Coelenterata) Class: Anthozoa animal • No medusa stage (only polyp) • All marine • Solitary or colonial • Polar and tropical • Some supported by skeleton • Largest class of Cnidarians Flower Order: Scleractinia Hard Ray or beam

Cnidarian body plan

Two-Way Digestive System

Dinoflagellates

• • • • • • • • Classification is changing: Used to be in Kindom: Protista Now some taxonomists put them in a Kingdom or Phylum : Alveolata (Bauman 2007).

Both fresh water & marine Many are bioluminescent Cause Red Tide Some produce neurotoxins

Pfiesteria

has gotten a lot of press in NC

Zooxanthellae

apparently loose (or they adhere to the cell wall) their flagella when they live in corals.

Zooxanthallae

is a genus among the Dinoflagellata It will loose its flagella and live in the tissue of corals Zooxanthallae exist as endosymbionts in bivalves, other coelenterates & gastropods

Xenia sp.

host with its

Zooxanthallea sp. endosymbiont Zoanthus sociatus

has zooanthallae as

intracellular

endosymbiont and uses photosynthate and feeds on other zooplankton too. Uses autotrophy & heterotrophy (mixotrophic) (Trench 1974) Giant clam (

Tridacna sp.

) both

digests

and uses

photosynthate

from zooxanthallae

Coral reefs found in waters with notoriously low productivity.

Open Tropical Seas produce 18-50 gC/m 2 /yr

(Nybakken 1988) Vs.

Coral reefs :1500-5000 gC/m 2 /yr

(Kohn & Helfrich (1957), Odum & Odum (1955), Johannes et al. (1972) How can this be?

Coral reefs, like tropical rain forests hold on to nutrients. Both exist in nutrient POOR Regions. Zooxanthellae live IN coral polyp tissue, thus their photosynthate (carbon compounds) remains in the tissue and does not diffuse in the surrounding sea water.

Since polyps are predatory, they capture plankton that float in from the ocean and HOLD the nutrients and support the zooxanthellea nutritionally.

Mutualistic Relationship (+/+)

How do the coral & and the

Zooxanthallae

do this?

Mutualism: Host & tenant ?

both must benefit Predation : Predator & prey ?

sometimes “host” digests “tenant’ Parasitism: Host and parasite?

Zooxanthallae use lipids captured by coral for their uses Corals may eject

Zooxanthallae

Changes with species of coral, environmental conditions, and possibly with species of

Zooxanthallea

Lipids constitute 1/3 dry weight of corals (excluding skeleton) Levinton 1982

Food: Plankton Light Photosynthesis by

Zooxanthallae sp.

Carnivory by the coral polyp Carbohydrates to generate ATP Lipids in prey Acetyl -CoA Lipids Saturated fatty acids most common in shallow reefs Unsatured fatty acids increase with depth

Low SA, Few

Zooxanthallae

Large surface area, many zooxanthallae Short tentacles, catch few plankters, many

Zooxanthallae

Long tentacles, catch many plankters, few

Zooxanthallea

Sea level

Fringing Reef

Atoll

formation Time

Barrier Reef

: Larger geologic feature. Pierced by numerous channels “large” lagoon between reef and continent. Ex: Australia, Bahamas

Rate of submergence= S Rate of coral growth=CG If S>CG; guyot is formed

Sedimentation lagoon Low wave action: sediment settles Diminished Coral Growth: Lagoon formation

WIND

High wave action Little sedimentation High plankton abundance (from ocean) High light: Rapid coral & coralline algae growth Balanced by wave destruction

Darwin 1842 Wind & Waves Leeward No surge channels Branching corals Levinton 1982 Windward Surge channels Spur & Buttress Zone

Nybakken 1988

Atlantic vs. Pacific Reefs

Few atolls Many atolls

Corals

36 Genera 62 Species

Corals

80 Genera 700 Species

Acropora sp.

Dominant reef builder 3 species 200 species Same trends for molluscs, crustaceans, fish

Balance of Accretion & Subsidence

160-206 tons CaCO 3 /yr/ha

Acropora cervicornis

Staghorn coral Can grow 10 cm/yr

Montastrea annularis

0.25-0.7 cm/yr • Wave damage • Rapid sea level rise • Boring animals • Sponges • Bivalve molluscs • Polychaetes • Gnawing fish • Echinoderms (Acanthaster sp.) Defecation of CaCO 3 : “Sand”

Complex Species Interactions

•

Direct effects

•

Indirect effects

Algae +

Acropora sp

(fast growing)

Montastrea sp.

(slow growing) Corallivorous Fish Damselfish (Pomacentridae) -

Chaetodon capistratus

Foureye butterfly fish Remove damselfish, coral gets grazed down Return damselfish

Acropora sp

. grows back faster than

Montastrea sp

.

Some Web Sites Crustose coralline red algae (Rhodophyta) http://www.mbari.org/staff/conn/botany/reds /ian/default.htm

Zooxanthellae sp.

http://coralreef.noaa.gov/aboutcorals/coral10 1/symbioticalgae/

References

Bauman, R.W. 2007. Microbiology with diseases by taxonomy. 2 nd Ed. Pearson/Benjamin Cummings Darwin, C. 1842. The structure and distribution of coral reefs. Being the first part of the geology of the voyage of the Beagle. London: Smith, Elder.

Johannes, R. El, et al. 1972. The metabolism of some coral reef communities: A team study of nutrient and energy flux at Eniwetok atoll. Bioscience. . 22:541-543.

Kohn, A., and P. Helfrich. 1957. Primary productivity of a Hawaiian coral reef. Limnol. Oceanogr. 2(3):241-251 Nybakken, J.W. 1988. Marine Biology: An Ecological Approach, 2 nd Ed. Harper Collins NY, NY Odum, H.T., and E.P. Odum. 1955. Trophic structure and productivity of a windward coral reef community on Eniwetok Atoll. Ecol. Monogr. 25:291-320 Ogden, J.c., and P.s. Lobel. 1978. The role of herbivorous fishes and urchins in coral reef communities. Envir. Biol. Fishes 3:49-63.

Trench RK (1974) Nutritional potentials in

Zoanthus sociathus

(Coelenterata, Anthozoa). Helg wiss Merresu 26:174–216