coral reefs

Question 1

two types of corals

Answer 1

tropical corals
deep sea cold water corals

Question 2

biology of a coral

Answer 2

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

Question 3

formation of a coral

Answer 3

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

Question 4

growth rate of tropical corals

Answer 4

0.3-10cm a year

Question 5

ideal salinity of T corals

Answer 5

40% maximum
30 ppt

Question 6

ideal Ph of T corals

Answer 6

8.2 - alkaline

Question 7

ideal temperature for T corals

Answer 7

18 above
ideal: 23 to 25

Question 8

why don’t corals form at river mouths

Answer 8

the freshwater has a 0.5 ppt salinity which is significantly lower than the optimum salinity for coral growth

Question 9

why do corals bleach when the salinity lowers?

Answer 9

corals cannot osmoregulate as their echinoderms are sensitive to drops in salinity

Question 10

how does air limit coral growth?

Answer 10

need the nutrients and oxygen dissolved in the sea water to survive
only grow as high as the lowest tide

Question 11

ideal acidity of T corals

Answer 11

8.2
alkaline

Question 12

what happens when excess co2 dissolves in the ocean

Answer 12

CO2 –> H2CO3 –> H+ and HCO3-

Question 13

Why is ocean acidification damaging for corals?

Answer 13

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

Question 14

what is the maximum coral growth depth?

Answer 14

25 meters

Question 15

nutrient cycling

Answer 15

live in nutrient poor waters = efficiency of recycling maintains such a diverse ecosystem
– down to s symbiotic relationship between the zooxanthellae and coral polyps

Question 16

zooxanthellae

Answer 16

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

Question 17

importance of nitrogen

Answer 17

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

Question 18

three types of reefs

Answer 18

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

Question 19

zooplankton

Answer 19

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

Question 20

coral services

Answer 20

provide food and shelter for fish
which are constantly excreting ammonia which are then absorbed by corals and the algae

Question 21

threats to coral ecosystems

Answer 21

drainage basin schemes
land clearance
desalination plants
eutrophication
climate change

Question 22

drainage basin schemes

Answer 22

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

Question 23

land clearance

Answer 23

led to freshwater run off which alters the salinity of the water

Question 24

desalination plants

Answer 24

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

Question 25

eutrophication

Answer 25

algal blooms from cyanobacteria and microcystic bacteria
block sunlight and deplete oxygen dissolved in the water – outcompete the other species
causing coral bleaching

Question 26

climate change

Answer 26

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

Question 27

what type of organism are corals

Answer 27

calcifying