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
zooxanthellae
live within the polyp tissue
autotrophic and photosynthetic
in exchange for exclusive access to nutrients (N2 + P)
waste produced by the coral fertilizes the algae
importance of nitrogen
most important
retain nutrient very efficiently
as unlike free floating algae – they don’t loose nitrogen to the water
used for DNA and protein synthesis
three types of reefs
fishing reef - very close to shoreline and not separated by a lagoon, vert shallow
barrier reef - parallel to coastline but not attached as its separated by a lagoon
atolls - ring shaped far from land
zooplankton
microscopic prey that consume phytoplankton
primary autotrophic producer
corals digest zooplankton
from upwelling – ocean acidity causes stratification of surface waters so less transfer of carbon between the surface and deep sea - less transfer of biomass for coral uptake
coral services
provide food and shelter for fish
which are constantly excreting ammonia which are then absorbed by corals and the algae
threats to coral ecosystems
drainage basin schemes
land clearance
desalination plants
eutrophication
climate change
drainage basin schemes
urban development and deforestation
wash slit into the sea
corals are sessile – cannot move in search for food
use tentacles to catch zooplankton which can be smothered by slit
murky waters also block photosynthesis
land clearance
led to freshwater run off which alters the salinity of the water
desalination plants
discharge will have detrimental affects
salinity and temperature increase
accumulation of metals and toxic chemicals
conc build up in poor flushing areas (lack of strong currents)
causes bleaching of corals
eutrophication
algal blooms from cyanobacteria and microcystic bacteria
block sunlight and deplete oxygen dissolved in the water – outcompete the other species
causing coral bleaching
climate change
causes ocean acidification and mass scale bleaching
co2 sequestration is a natural process – co2 + h2o –> h2co3 + H+ ions –> co3- + H+ ions
issue: excess of co2
h2co3 dissociates almost immediately into its ions – an excess co2 lowers the ph by increasing the hydrogen ion concentration making it more acidic – this natural system allows calcium to combine with carbonate ions to make calcium carbonate – corals use a form of calcium carbonate known as aragonite to make their exoskeleton
when there is an excess co2 – the ocean stratifies as the warmer waters are harder for the wind to mix with strong deep ocean currents to allow the transfer of carbon to the deep ocean – this lack of infusion of carbonate rich waters causes the surfaces waters saturate with co2 – support less phytoplankton and photosynthesis – impacting the whole food web as uptake of co2 slows
what type of organism are corals
calcifying
