coral reefs Flashcards
two types of corals
tropical corals
deep sea cold water corals
biology of a coral
made up of polyps which are small animals with tentacles and a hard outer shell
zooxanthellae small autotrophic microorganisms that photosynthesis and live inside the polyps tissues
formation of a coral
free floating coral larvae attach to hard surfaces
secrete hard exoskeleton made of calcium carbonate
this protects them from predation
new surface for more larvae to attach to – self sustaining process of reef development
growth rate of tropical corals
0.3-10cm a year
ideal salinity of T corals
40% maximum
30 ppt
ideal Ph of T corals
8.2 - alkaline
ideal temperature for T corals
18 above
ideal: 23 to 25
why don’t corals form at river mouths
the freshwater has a 0.5 ppt salinity which is significantly lower than the optimum salinity for coral growth
why do corals bleach when the salinity lowers?
corals cannot osmoregulate as their echinoderms are sensitive to drops in salinity
how does air limit coral growth?
need the nutrients and oxygen dissolved in the sea water to survive
only grow as high as the lowest tide
ideal acidity of T corals
8.2
alkaline
what happens when excess co2 dissolves in the ocean
CO2 –> H2CO3 –> H+ and HCO3-
Why is ocean acidification damaging for corals?
450 ppm of CO2 = 90% of corals will be surrounded by waters with inadequate aragonite (a form of CaCO3) saturation states
corals grow by placing aragonite crystals on top of each other
these aragonite crystals are formed from the dissociation of HCO3- into CO3- and H+
the CO3- combines with Calcium to make calcium carbonate (CaCO3)
the more it dissociates, the more H+ are released, lowering the ocean’s Ph
what is the maximum coral growth depth?
25 meters
nutrient cycling
live in nutrient poor waters = efficiency of recycling maintains such a diverse ecosystem
– down to s symbiotic relationship between the zooxanthellae and coral polyps