Coral Reef Processes (powerpoint)

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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


Order:
Scleractinia

Hard

Ray or beam

Domain:
Eucarya

Kingdom:
Animalia

Phylum:
Cnidaria

(
Coelenterata
)

Class:
Anthozoa


Flower

animal


No medusa stage (only polyp)


All marine


Solitary or colonial


Polar and tropical


Some supported by skeleton


Largest class of Cnidarians



Two
-
Way Digestive System

Cnidarian

body plan

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

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


Zooxanthallae

exist as
endosymbionts

in

bivalves, other coelenterates & gastropods

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),

J
ohannes 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

Food: Plankton

Carnivory

by the

coral polyp

Lipids in prey

Light

Photosynthesis by

Zooxanthallae

sp.

Carbohydrates to generate

ATP

Acetyl
-
CoA

Lipids

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

Levinton

1982

Saturated fatty acids most common in shallow reefs

Unsatured

fatty acids increase with depth

Long tentacles, catch many

plankters
, few
Zooxanthallea

Short tentacles, catch few
plankters
,

many
Zooxanthallae

Large surface area, many
zooxanthallae

Low SA,

Few

Zooxanthallae

Atoll
formation

Sea level

Fringing Reef

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


WIND

Sedimentation

Low wave action: sediment settles

Diminished Coral Growth:





Lagoon formation

High wave action

Little sedimentation

High plankton abundance (from ocean)

High light:




Rapid coral & coralline algae growth


Balanced by wave destruction

lagoon

Darwin 1842

Levinton

1982

Wind & Waves

Windward

Leeward

Surge channels

Spur & Buttress Zone

No surge channels

Branching corals

Nybakken

1988

Atlantic vs. Pacific Reefs

Few atolls Many atolls


Corals



Corals


36 Genera




80 Genera


62 Species




700 Species




Acropora

sp.

Dominant reef builder

3 species 200 species

Same trends for
molluscs
, crustaceans, fish

Balance of Accretion & Subsidence

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
.)


160
-
206 tons CaCO
3
/yr/ha

Defecation of CaCO
3
: “Sand”

Complex Species Interactions


Direct effects


Indirect effects

Algae

+

-

Corallivorous

Fish

-

Acropora

sp
(fast growing)

Montastrea

sp.
(slow growing)

Damselfish (
Pomacentridae
)

-

-

-

Remove damselfish,

coral gets grazed down


Return damselfish

Acropora

sp
. grows back faster

than
Montastrea

sp
.

Chaetodon

capistratus

Foureye

butterfly fish

http://www.mbari.org/staff/conn/botany/reds
/ian/default.htm

Crustose

coralline red algae (
Rhodophyta
)

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

Zooxanthellae

sp.

Some Web Sites

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

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