Coral Reef Flashcards
what is a reef?
- solid structure made of and by living things
- build upwards
what kind of record do reefs leave?
geological
what were past reefs called?
bioherms - mounds (lens shaped)
biostromes - flat (laterally extensive)
how long have reefs existed for?
450 MY
what were original reefs made of and which Order?
corals
Rugosa
when did modern reef-building corals arise?
triassic in order Scleractinia
where are rugose corals found?
rocky mtn
where is the origin of recent corals?
Tethys Sea
describe Tethy Sea
- shallow large sea
- tropical (warm)
- ancestors of corals today -> since evolved from corals that lived in shallow, warm water then corals today grow in same conditions
describe the Great Barrier Reef
- young
- migrated N to warmer water
- N is the oldest and thickest
- S is youngest and less than 10 MYO
where do coral reefs form?
shallow and warm tropical water
what do coral reefs need?
- bright sunlight for photosynthesis of algal symbionts
- wave or current action for nutrients -> regions of lower turbidity is ideal because clearer the water the more sunlight that will reach algal symbionts
- low turbidity for photosynthesis not to be inhibited
- hard substrate for attachment -> no growth on sand or mud, new gen grow on skeletons of previous gen
what are the main builders of reefs?
scleractinian (hard or stony corals)
what are hard corals also known as?
hexacorals -> feeding tentacles in groups of 6
what kind of grouping do scleractinian’s have?
colonial -> billions of individual polyps make up colony
how many tentacles do soft corals have?
8 or more around moth (octocorals)
describe the soft coral skeleton
either no calcified skeleton, or some small fragments of calcified
skeleton in collagen, or protein skeleton
- don’t provide as much structure to reef as hard corals do
what kind of coral is included in soft corals?
gorgonian corals - fan shaped corals with flexible protein stalk that allows them to reach out into currents
- fan faces the current in order to capture as many nutrients as possible
what are reef-building corals?
hermatypic - build bioherms
what do corals have and how do they get food energy?
- zooxanthellae
- algal symbionts provide coral with food energy to build aragonite skeleton during day
how are prey captured?
nematocysts at night
what kind of polyps are corals?
solitary polyps or colony of polyps
- polyps secrete skeleton of calcium carbonate
what are zooxanthellae?
dinoflagellates
how are dinoflagellates acquired?
from enviro or from parent during larval development
where do dinoflagellates live?
in coral gastrodermis
how do dinoflagellates enter?
through phagocytosis
- intracellular
what is the most common species for dinoflagellates?
symbiodinium
where do zooxanthellae live?
in endodermis - tissue lining gut
what covers the calcium skeleton?
living tissue of coral forms a thin veneer
what do corals capture at night?
plankton
- respire O2, produce CO2 and ammonia
what do corals do during the day?
algae photosynthesize, produce O2, amino acids and sugars
what do algae do?
- Receive CO2 and some NO3 (nitrate) from coral host
- Use sunlight, H2O and CO2 to make organic matter (photosynthesis)
- ‘Leak’ O2, amino acids, sugars to coral host
- Produce carbonate ions (CO3^2-) in host tissue
what do corals do?
Makes CaCO3 [Ca^2+ & CO3^2-] (gets Ca2+ from seawater; carbonate from algal symbiont)
* Secretes CaCO3 (calcium carbonate) as a skeleton
* Produces CO2 by respiration (this is used by the algae)
how does calcification work?
Ca2+ + 2HCO3 ->
Ca(HCO3)2 -> CaCO3 + H2CO3
(calcium + bicarbonate -> calcium bicarbonate -> calcium carbonate + carbonic acid)
how does carbonic acid resolve?
resolves itself into CO2 and water
where does calcium carbonate crystallize?
onto existing aragonite crystals making coral’s hard skeleton
what does calcification enhance?
photosynthesis
what does photosynthesis enhance?
calcification
what does calcification produce and what is it used by?
produces co2 and used by algal symbionts
what does photosynthesis produce and what are they used by?
o2 and sugars and used by coral host
- positive feedback relationship
what are the factors used to enhance calcification?
- Light: Corals grow 14 times faster under light than in the dark.
- calcium uptake is highest at mid-day on a clear sunny day.
- on a cloudy day, the rate is 50% lower,
- in the dark the rate is 90% lower.
- calcium deposition rate rapidly decreases as depth increases. - Temperature: 25-30 degrees C -> shallow water near equator gets warm and stays warm
- Clear water (5-10m depths) -> shallow water allows for better light penetration
- Slightly elevated salinity -> rarely see corals in estuaries bc freshwater inflow there
- Shape (branching grow faster than sphere shaped) -> covering more area to capture more nutrients and sunlight
- Age (younger grow faster than old)
what theory is used to describe how all types of reefs form?
darwin’s theory of how atolls form
what are fringing reefs?
along margin of landmass
limited growth due to runoff from land which generates turbidity (cloudy water = reduced photosynthesis)
what are barrier reefs?
separated from land by lagoon
- grow quite far from land
what are platform reefs?
reef forms flat surface
what are atoll reefs?
landmass submerged
reef encloses shallow lagoon
how come coral isn’t sinking?
land sinks slowly and coral reefs also build slowly so as land sinks the coral reef solidifies
what kind of reefs are found in GBR?
- fringing reefs(N)
- barrier reefs (full length of GBR is barrier reef)
- platform reefs and atolls along whole GBR
in what direction do reefs grow towards?
toward wind and waves and current -> new nutrients come from
what is the advancing edge called?
reef crest
what is below the reef crest?
reef slope -> area of strong wave energy but high nutrients
what is behind the crest protected by?
wind and waves - reef flat
what is a coral bombie?
massive coral head that withstands wave energy
what does spur and groove formation do?
dissipates wave energy
Montastrea annularis zone
lower on reef, strong withstands wave force
Acropora cervicornis zone
reef crest - like breaking since that allows it to reproduce asexually
- helps reproduce better
Elkhorn coral
fast growing in shallow water
- fragment easily storms
- delicate
describe the leeward side of the structure
more lush coral due to less wind stress
away from wind and current
describe the windward side of structure
towards wind and currents
- traps sediment which protects coral
