Coral Reefs Flashcards
What kind of waters do coral reefs grow in
Oligotrophic waters
What is the Order name for hard corals
Hexacorallia
What is the Order name for soft corals
Octocorallia
What percentage do coral reefs cover of the global ocean surface and roughly what proportion of known fish species do they host
<0.1% and a quarter of all known fish species
What are hermatypic corals
Reef building corals
What are ahermatypic corals
Non-reef building corals
What phylum do corals belong to?
Cnidaria
What three classes do coral belong too
Hydrozoa, Scyphozoa, Anthozoa
Where are coral reefs distributed?
Tropical and equatorial between tropics of Capricorn and Cancer, i warm oceanic waters
What is optimum coral water temperature
23-25C
Why are corals not found on western continental coasts
Coriolis gyre brings cold water into coastal region - East Africa has a fringing reef, West Africa does not
Why are they not found on major river outflows?
High turbidity, smothering, cold water and low salinity
What is an endosymbiotic relationship
An endosymbiont is any organism that lives within the body or cells of another organism. Usually the relationship is mutualistic and one tends to benefit or need the other.
How does is endosymbioisis relevant to corals
Corals are comprised of two partner organisms; an animal (cnidarian) and a unicellular alga (dinoflagellate in the genus Symbiodinium). The outer membane of the Symbiodinium spp. leaks and benefits the coral polyp. The alga is non motile and fragile so depends on the polyp for structural support.
Name 12 features of a coral polyp
Basal plate; Coenosarc; Theca; Gastrodermis; Gastrovascular Cavity; Septum; Digestive Filament; Mesoglea; Mouth; Tentacle; Nematocyst; Epidermis
What is a nematocyst
A small capsule containing an ejectable thread that causes a sting
What is the epidermis
Outermost layers of skin
What is the Coenosarc
Common body of the polyp colony
What is the Mesoglea
Translucent jelly like substance containing muscle fibers and nerves
What is the theca
The walls surrounding the calyx, (calcium carbonate cup that coral sits in)
`Explain the calcification process
- Calcium from sea water in coelenteron moves into Calicoblastis gastrodermis. 2. Active calcium transport into Calicoblastis epidermis. 3. This turns into Ca^2+ and then Calcium Carbonate in the organic membrane. 4. CO2 from metablism in Calicoblastis epidermis moves into Zooanthellae but also turns to bicarbonate and then Calcium carbonate in organic membrane. 5. CACO3 into Carbonic acid and calcium carbonate, then Bicarbonate converted into CO2 and move to Zooanthellae.
How do corals reproduce asexually
Fragmentation folloing an event such as a storm; Colony fission; Budding
What is colony fission
Colony splits into two or more during early developmental stages.
What is Budding
Asexual reproduction - young polyp grows out of an adult - can divide longitudonally - polyp broadens and divides; or Transversely - one forms from mouth region another from base region
Explain sexual reproduction of corals
Corals release eggs and sperm and fertilized eggs develop into ciliated larva, which drift and settle.
What is the problem with spawning reproduction?
Vulnerable to catastrophic event and can smother corals
What are brooders
Eggs fertilized internally and the ciliated larva develops inside the polyp.
What are broadcasters
Release eggs and sperm into the water column for fertilization
What factors affect the timing of spawing (possible 8)
- Sea temperature, .2. Lunar cycle. 3. Day length. 4. Irradience. 5. Wind and currents .6. Rainfall. 7. Chemical stimuli. 8. Latitude
What is the effect of latitude on breeding
Higher latitudes have shorter breeding seasons
What is monopodal growth
Trunk formed by younger polyp growing on top of an older polyp
What is sympodal growth
Young polyp grows at the edges of older polyp
What is dychotomic growth
Symmetric division of polyps
What are the typical zones of reef zonation from the Lagoon to the Deep water
Back reef; Reef flat; Reef crest; Branching coral zone; Mixed Coral zone and Massive coral zone, (within the forereef); Deep forereed and Platycoral zone
Put into order these types of coral based on resistance to wave energy from low wave energy to high: Massive, Mushroom, Branching, Pillar, Encrusting, Tabular
Branching- Pillar - Tabular - Massive - Encrusting - Mushroom
What is the substratum of the lagoon like
Sandy
What sort of flora and fauna can be found in reef lagoons
Seagrasses, eg, Syrungodium spp. Nursery for reef fish. Benthic organisms like echinoderms, holothuroidae (sea cucumbers). Juvinile sharks and rays
What is the physical characteristics of the reef back
Limited water movement, turbid water and lower diversity
What sort of organisms found at the reef back
Massive corals, eg. Porites spp., Giant Clam, Tridacna spp. And soft corals, (Octocorallaria
What is the physical characteristics of the reef flat
Low tide shallow water, possible exposure
What is the dominating coral type at the reef flat
Branching coral, eg Acropora spp
What organsims other than coral would you expect to find at the reef flat
Fish - Damsel fish, butterfly fish, Surgeon Fish, Parrot Fish.
Invertebrates- Bivalves, gastropods, crustaceans, porifera.
What are the physical characteristics of the reef crest and reef front
reef crest shallow with high wave action - often no corals as often exposed
What is coral distribution like from reef crest to reef front
Reef crest exposed frequently - often no corals. Moving down reef front characterized by faster growing corals and massive and encrusting corals.
What corals are adapted to lower light levels
Slow growing flat tabular corals
Give a natural threat to coral reef systems
Grazing pressure from urchins and Crown of thorns starfish - Acanthaster planci
Give an anthropogenically induces threat to coral reef ecosystems
Coral bleaching - through loss of zooxanthellae - linked to higher water temperature and light damage
