Coral Reefs Flashcards
What are nematocysts
they are used to capture prey, and as defense and to compete for space
the polyp is enclosed in calcium carbonate created by the coral
Hermatypic corals
reef builders
normally contain zooxanthellae, symbiotuc photosynthetic dinoflagellates
restricted in distrubution by water temperature and water quality
Ahermatypic corals
do not build reefs
may not contain zooxanthellae
not restricted by water temp and quality
coral reefs are groups of _____ ______ interconnected by ___ ______ __ ______
coral polyps
thin layers of tissue
they share a _______ ______ and _________ __________ due to the fact that the entire colony came from _________________________
nervous system and digestive connection
one original polyp that reproduced asexually
each polyp continues to ______________________ so the colony continues to grow _______
lay down new CaCO3 beneath beneath the polyp body
upward
what is the zooanthelae symbiotic relationship with the coral
- the zooxanthellae provide organic molecules to the corals
- the corals provide carbon dioxide, nitrogen and phosphorus for the zooxanthellae
some corals can produce ________________ to capture ___________________
sheets of mucous
zooxanthellae or detritus
what are mesenterial filaments
extensions in the gut wall used for feeding
conditions required for reef growth
- hard substrate
- Light optimal
- Narrow temperature range
- Low sediment load in water
- Low pollution
- Narrow range of pH
How do corals reproduce asexually
buds grow from a single polyp
How do they reproduce sexually
creation of a planula larvae that is able to ride on the water currents to a new environment
Where the corals at
mostly found on contenential shelves, near islands or on seamounts due to the light/depth dependency
Temp requirements
- hermatypic only tolerate low temps
- can only reproduce if over 68d F
- high temps for optimal growth
- above 86 bad
What does coral stress cause
“bleaching”: an expulsion of zooxanthellae from the coral polyp
makes the coral white and KILLS it
What causes bleaching
poor water quality
increased sediment in water column
wave stress
low salinity
disease
- El Nino, Hurricanes
Salinity requirements
35 ppt
not near rivers
why wave action bad
suspends sediments in the water, settles on corals, reduces water clarity - reduces photosynthesis
Tall vs flat
tall: shallow areas due to intense competition for space and light
wide ; deeper areas to capture as much light as possible
what else builds reefs?
coralline algae
cnidarians
sponges
Bryozoans
Fringing Reefs (moana)
- simplest and most common
- narrow stripes along the shore in tropical waters
- consist of an inner reef flat and an outer reef slope
- steep, not exposed to air
- high growth, more species on the slope and the crest
- high wave action
Barrier reef
- grow along along or farther from the shore
- lagoon between the shore and the reef
waves wash sediment onto the back reefs slope reducing coral growth - small islands called keys or cayes
- more growth in crest or just below on the fore-reef
The largest reef in the world
The Great Barrier Reef in Australia
- length of reef structures: 1200 miles
- width: 10-200 miles
what is an Atoll
a circular reef structure surrounding a central lagoon
when do Atolls form
when a volcanic island is formed:
over time, weathering and geologic activity lowers the level of the island till it disappears below the waters surface, leaving only the outer band of coral surrounding a lagoon
two largest atolls
Maldives (Indian ocean)
Marshall islands (pacific)
Coral reef ecosystems foodchain is based on
Zooxanthellae located in the body of the corals
What do Cyanobacteria do for the reef organisms?
they fix nitrogen, making it available to the organisms that feed on them
what part of corals do reef organisms feed on?
the corals themselves
mucous
eggs
larvae
how do reef organisms deter predation?
- release toxic or foul tasting chemicals
- produce hard (spikey?) structures
- Coralline algae grow in a very thin encrusting form that is difficult to feed upon
Competition methods
- grow fast and upright to maximize reproductive ability
- grow slow and huge to outcompete others in the long run
- sting each other
