coral reef

Question 1

location

Answer 1

tropical and sub-tropical
shallow, warm and clear seawater
great barrier reef - australia’s east coast (2600 km)
deep sea corals found throughout world’s oceans, from tropical to polar regions

Question 2

characteristics of corals

Answer 2

Some have a calcium carbonate skeleton (hard corals)
Some have symbiotic algae (zooxanthellae)
Some build reefs (hermatypic) and some don’t (ahermatypic)
All corals are polyps with tentacles surrounding a mouth

Question 3

what are the limiting factors for corals?

Answer 3

temperature
depth
light
sedimentation
salinity
air exposure
energy 
nutrients

Question 4

what’s the optimal temperature?

Answer 4

between 23&25 (hermatypic)

cannot drop below 18

Question 5

light

Answer 5

Mutualistic association with endosymbiotic algae (zooxanthellae) which photosynthesize and provide nutrition for coral

Question 6

what impact can sedimentation have on coral reefs?

Answer 6

often correlated with freshwater input

Leads to increased turbidity (decreased water clarity) which reduces photosynthesis

Clogs coral feeding structures

Corals can remove small amounts of sediment using mucus and cilia but cannot handle heavy sedimentation

Question 7

what’s the range of salinity corals can tolerate?

Answer 7

corals can only tolerate a narrow range of salinity (32-35 ppt)

A large influx of freshwater will kill corals

Question 8

air exposure

Answer 8

corals can only survive short, infrequent periods of air exposure

Mucus can prevent desiccation for an hour or two

Coral reefs are therefore limited by the level of the lowest tide

Some species can withstand exposure

Question 9

energy

Answer 9

moderate amounts of energy are best

Too much energy can damage corals while too little energy results in sediment build up

Hurricanes affect coral reefs

Wave action provides oxygenated, nutrient rich seawater for corals

Question 10

nutrients

Answer 10

coral reefs are in low nutrient areas but are very productive ecosystems

Question 11

substrate

Answer 11

Three distinct habitats/substrates
1.Reef (living corals)

2. Rubble (dead and broken corals)
3. Sand (dead, digested corals & algae)

Question 12

anatomy of a reef

Answer 12

Reef flat

Reef crest

Outer reef

Question 13

formation of a coral reef

Answer 13

Fringing reef
- Anchored to land, typically quite young, in the shallows of a mountainous island

Barrier reef
- Reef growing parallel to the coast, separated by a lagoon

Atoll
- Circular, continuous reef without a central island and a central lagoon

Question 14

biodiversity

Answer 14

Most diverse marine ecosystem

Comparable to tropical rainforest biodiversity

More than 25% of marine fish species live in coral reefs

Question 15

current state of the coral reefs

Answer 15

25% of reefs have already been lost

Mass bleaching event in 97/98 alone killed ~16% of the worlds reefs

66% are under serious threat

33% are at elevated risk of extinction

All corals may be threatened by extinction by mid-century

Question 16

human impacts

Answer 16

Aquarium & souvenir trade

Overfishing and destructive fishing

Tourism

Pollution

Climate change & coral bleaching

Coral diseases

Plagues of predators/invasive species

Question 17

coral bleaching

Answer 17

Gradual loss of color as corals lose symbiotic zooxanthellae

Zooxanthellae provide ~90% of coral nutrition

Corals starve when they bleach

Bleached corals can recover but will die if stresses persist

Question 18

mangroves locatio

Answer 18

Distributed across tropical and subtropical intertidal forests

Most mangroves found in South East Asia

Question 19

mangroves requirements

Answer 19

Substrate: prefer fine grained substrate (mud) but can grow on sand, rock, or coral

Temperature: greater than 20c but no less than 16c, not cold resistant

Salinity: mangroves are salt tolerant

Energy: low, shores must be free of strong wave action and tidal current

Sediment: anoxic and waterlogged, but mangroves have aerial and shallow roots to obtain oxygen

Biomass, productivity, biodiversity: high

Question 20

mangroves significance

Answer 20

Act as nurseries for many species

Protected ecosystem for adults of many species

Buffer coasts from hurricanes and storms

Reduce erosion of coast and siltation of water

Plants can absorb nitrates and phosphates, cleaning up and restoring water near the shore

Question 21

mangrove human impact

Answer 21

Oil spills

Charcoal and timber industries

Input of pesticides and fertilizers

Clearing of thousands of hectares of forest to create man-made shrimp ponds for shrimp aquaculture industry

Coastal development

Climate change

Warming

Sea level rise

Question 22

mangrove restoration

Answer 22

Locals using their own natural resources

Planting new mangroves

Education and awareness

Question 23

invertebrates: giant clam adaptations

Answer 23

microstructures called ocelli that help get sunlight to the algae
produces metabolic waste products, which serve as a second nutritional source

Question 24

invertebrates: christmas tree worms

Answer 24

feathery tentacles - radioles- part of respiratory system=> external gills covered with hairlike cilia that help the filter-feeding worm trap plankton and pass the food down to its mouth.

Question 25

vertebrates: sea snake

Answer 25

• flattened and oar-like tail=> allows sea snakes to propel themselves through the water more effectively.
• salt glands and nostrils located at the top of their snouts to breathe more efficiently.

Question 26

vertebrates: lionfish

Answer 26

• red and white stripped color- camouflage
• ability to remain practically motionless in the water
• venom glands

Question 27

what are the stresses that impact coral reefs?

Answer 27

changes in water temperature,
increased UV radiation,
ocean acidification, 
variation in salinity, 
sedimentation, 
disease,
toxins