1. Coral Structure and Function I

2. Maritime coastal
- greenish
- particulate
Caribbean
- blue
- clear

3. BLUE CLEAR water reflects blue of the sky
water refracts sunlight (more blue light)
no interference from green plants
CLEAR
little particulate matter
few phytoplankton in the water
less dissolved organic carbon

4. PHYTOPLANKTON microscopic algae - flourish in colder ocean waters
live in upper 60m - the PHOTIC ZONE
give local Maritime waters their colour

5. as you descend through water column
lose more and more light
reds go first (lower energy)
gives a bluish cast to everything
much more pronounced locally than in the Caribbean
we have far more photosynthetic organisms in the water
absorb the light (red & blue ) for photosynthesis - leaves green

6. Tropical waters are still very PRODUCTIVE bottom of food chain events
So- the blue colour & clear water of tropics due to few photosynthetic organisms in tropical waters
Tropical waters are still very PRODUCTIVE
bottom of food chain events
primary production
production of organic material from inorganic

8. Primary Production trophic pyramids/webs - find plants at the bottom
use SUNLIGHT energy to fix CO2 into organic molecules
Primary Production
plants consumed by primary consumers etc.
less total biomass as you go up the pyramid
increase size of organism as you go up the pyramid

9. eximine coral reefs ecosytem:
“how does this flourishing ecosystem survive with so few producers - the plants ” ?
clear water, few phytoplankton ???

10. In the reef system primary production is mostly BENTHIC (bottom)
Open ocean (or local Maritime), primary production is mostly PELAGIC (water column)

11. Much of the productivity from corals
Cnidaria - from the Latin “nettle” – a plant
have often been mistaken for plants
attached to a substrate
do not wander about
same colour as many
marine plants
same branched nature
and growth habit

12. were originally classified as plants
by the naturalist John Ray ( )
In 1723, Jean Peyssonel
decided they were animals

13. naturalist John Ellis
a microscope modified for aquatic work
found the animal polyps on many reef organisms
then considered to be animals for a while - with no plant component
improvements in microscopy confirmed their animal nature, with polyps filtering out plankton with their tentacles
subsequent studies showed that the reef is composed of many organisms, as well as the Cnidarians

14. The Royal Society Coral Reef Expedition 1896-1898
Funafuti Atoll (Ellice Islands - Tuvalu)

15. The Royal Society Coral Reef Expedition 1896-1898
Funafuti Atoll (Ellice Islands - Tuvalu)

16. The Royal Society Coral Reef Expedition 1896-1898
Funafuti Atoll
analysis of cores -

17. The Royal Society Coral Reef Expedition 1896-1898
Funafuti Atoll
analysis of cores - mostly:
1. Calcareous red algae
2. Calcareous green algae (Halimeda)
3. Foraminifera (20-40m protists, porous CaCO3 shell)
4. Corals
Top 18m of the core was 80-90% Halimeda

18. Calcareous red algae

19. Calcareous green algae (Halimeda)

20. Foraminifera

21. Corals

22. so where were the primary producers ??
20C - new understanding of trophic pyramids, attention turned to reef productivity
very productive (produce lots of biomass)
lots of life
lots of diversity
productivity couldn’t be due just to the calcareous green and red algae
so where were the primary producers ??

23. Extensive examination of atolls (Eniwetak – Marshall Islands)
lots of encrusting algae on the surface of corals, but also ...
examine corals in more detail
true nature of the Cnidarians
algae growing inside the cells of the coral polyp

24. These algae - ZOOXANTHELLAE
enough algae inside the coral polyp to account for massive primary production
their presence explained the plant-like growth habit of the Cnidarian -
to increase surface area for light absorption
Also explained the colours of the corals

25. 1950s - Tom & Gene Odum
suggested the coral polyp and the alga were in some sort of mutualistic relationship
the polyp itself is a miniature ecosytem
the two organisms exchange nutrients and other benefits
“Trophic Structure and Productivity of a Windward Coral Reef Community on Eniwetok Atoll”

26. Corals are predacious animals - suspension feeders
two main methods of prey capture
nematocysts
mucus

27. extend tentacles - mostly at night
zooplankton are most plentiful (move up from deeper waters)
whole surface of the coral becomes a trap for plankton
paralyze prey
sting with NEMATOCYSTS
trap prey
sticky MUCUS on
tentacles

28. tentacles produce WAVE-LIKE action sweeping the mucus and prey into the mouth
down the pharynx (gullet) to the gastrovascular cavity for digestion

29. tentacles produce WAVE-LIKE action sweeping the mucus and prey into the mouth
down the pharynx (gullet) to the gastrovascular cavity for digestion
prey digested, mucus recycled, solid, undigestible material (eg silt) ejected

30. Tentacles mostly retracted during the day
help corals avoid predation
protect from UV
Corals also get some nutrients from seawater
dissolved amino acids
glucose
inorganics
not usually much, except in locally polluted areas

31. Most scleractinian (stony) corals
structure of the polyps and skeleton of the coral is a simple combination
Most scleractinian (stony) corals
colonies of polyps
linked by common gastrovascular system (coenosarc)
polyp made up of two cell layers
outer epidermis (or ectoderm)
inner gastrodermis (endoderm)

32. non-tissue layer between gastrodermis and epidermis = mesoglea
made of collagen & mucopolysaccharides

33. non-tissue layer between gastrodermis and epidermis = mesoglea
made of collagen & mucopolysaccharides
"lower layer" of epidermis = calicoblastic epidermis
secretes the calcareous external skeleton
"upper layer" of epidermis is in contact with seawater

34. The corallite is the part of the skeleton deposited by one polyp
The skeletal wall around each polyp is called the theca
The coral structure also includes calcareous plate-like structure known as septa

35. One of the epidermal cell types is the cnidocyte
contains organelles called nematocysts
discharge toxic barbed threads
capture zooplankton prey

37. gastroderm cells line the body cavity
capable of phagocytosis (food particles)
contain the intracellular algae
extend into tentacles
zooxanthellae not in direct contact with the cytoplasm of the coral gastroderm cell
zooxanthellae reside inside a vacuole
the symbiosome (animal origin)

38. Much of the food needed by the polyp comes from the SYMBIONT
Many corals have different growth forms - can vary with local environment - light, depth etc.
Local environment affects distribution of the zooxanthellae

39. single-celled alga, with 2 flagellae
Zooxanthellae:
ZOO - animal
XANTHE - gold-coloured
single-celled alga, with 2 flagellae
a dinoflagellate
spherical, um dia
Most dinoflagellates are free-living
unusual group of algae
feeding modes ranging from photosynthetic autotrophy to heterotroph

40. Many dinoflagellate produce toxins
e.g. ciguatoxin causes ciguatera "fish poisoining”
Other toxic dinoflagellates responsible for algal blooms
e.g. red tides (Gymnodinium)
paralytic shellfish poisoining (Alexandrium)

41. coloured tinge to the coral brown to yellow brown
dinoflagellates
chlorophylls a and c
lack chlorophyll b
characteristic dinoflagellate pigments
diadinoxanthin and peridinin
~ 3 x 106 cells/cm2
coloured tinge to the coral
brown to yellow brown