8.3 coral reefs

Question 1

What is the maximum depth of water where most coral reefs grow?

Answer 1

Less than 25m

Coral reefs are generally found on the margins of continents and islands.

Question 2

Why do corals prefer shallow water?

Answer 2

Because of the tiny photosynthetic zooxanthellae algae that need light

These algae provide coral polyps with up to 98% of their food requirements.

Question 3

What is the minimum salinity level corals can tolerate?

Answer 3

32psu

Corals are intolerant to water with salinity levels below this threshold.

Question 4

What is the optimal temperature range for coral growth?

Answer 4

23-25 degrees Celsius

Reefs do not develop where the mean annual temperature is below 20 degrees Celsius.

Question 5

What happens to corals if they are exposed to air for too long?

Answer 5

They die

Corals are typically found below the low tide mark.

Question 6

How does sediment affect coral reefs?

Answer 6

It clogs their feeding structures and reduces light for photosynthesis

Sediment-rich water has a negative effect on coral health.

Question 7

What type of wave action do coral reefs prefer?

Answer 7

Strong wave action

Strong waves ensure oxygenated water and help remove trapped sediments.

Question 8

True or False: Storm conditions or tsunami waves are beneficial for coral reefs.

Answer 8

False

While strong wave action is preferred, storm conditions can be damaging.

Question 9

Fill in the blank: Coral reefs grow best in water depths of less than _______.

Answer 9

25m

Question 10

What is the relationship between corals and zooxanthellae algae?

Answer 10

Symbiotic

The algae provide food for the coral polyps through photosynthesis.

Question 11

coral reef formation

Answer 11

• Coral reef formation starts with free swimming coral larvae attaching themsleves to any hard submerged surface. They begin to secrete a hard, calcium carbonate skeleton for portection against predation
• As they grow the polyps rely on a symbiotic relationship with zooxanthellae algae which provides the corals with essential nutrients in return
• Over time, the build up of calcium carbonate porvides a new surface for other polyp larvae to attach themselves to. this allows the reef to continuegrowing and develop a self sustaining process.
• the build up of calcium carbonate skeletons into reefs takes hundereds to thousands of years into coral reefs

Question 12

characterisitcs and case study example

Fringing reefs

Answer 12

These are reefs that form around a land mass found very close to the shore in shallow waters. concave platform of coral that is connected but has grown away from th land they do not have a lagoons perating them from land, less than 500m wide
* case study: tahiti, largest island in french polynesia south of pacific ocean
* shiseido blue project: coral restoration

Question 13

charactersitics and case study example

barrier reef

Answer 13

• broader, older and more continuous
• seperated from land by a wide deep lagoon (too deep for corals to survive but made of dead corals)
• 500m away from shore
• casestudy: GBR

Question 14

3 uses of corals

Answer 14

1. Recreational value: tourism industry one of the fastest growing sectors of global economy; coral reefs are a major draw for snorkellers, scuba divers and recreational fishers
2. Coastal protection - coral reefs buffer adjacent shorelines through wave action and the impact of storms
3. New medicines: Corals are already being used for bonegradts and chemical found within several species contian chemicals that appear useful for treating things like leaukemia and skin cancer

Question 15

characteristcs and case study example

atoll reef

Answer 15

consists of a coral rim enirciling a lagoon. circular reefs around an old volcanic island. not found at continental coastlines, as they need a circular reference to grow around.
case study example: bikini
* grounds for operation crossroads: US nuclear testing program. native bikini islanders were forcibly relocated in 1946 and were promised they could return once it was safe. however decades later radiation levels remain dangerously high making resettlement impossible. to this day islands remains larely uninhabited

Question 16

what effects does ocean acidification have on the corals

Answer 16

Increased co2 dissolved in oceans –> carbonic acid lowering pH, weakens coral skeletons and slowing reef growth. Reduces the ability of coral to build their calcium carbonate skeletons. Can cause coral bleaching by making polyps stressed.

Question 17

year, key idea, formation process, supporting evidence, weaknesses

Darwin’s subsidence theory

Answer 17

1846
Key idea: coral reefs form around sinking volcanic islands
Formation process
1. coral forms fringing reefs around a volcanic island
2. island gradually sinks and the reef continues growing upwards, forming a barrier reeef
3. eventually the island submerges, leaving an atoll

Supporting evidence: evidence of deep coral structures in the pacific, matches reef structures found in different locations
weaknesses: does not explain reefs ina reas with no celar evidence of subsidence, no direct proof of gradual sinking in all reef areas

Question 18

year, key idea, formation process, supporting evidence, weaknesses

Murray’s Theory

Answer 18

1872
Key idea: reefs form on submarine hiils or plateaus rather than sinking islands
Formation process
1. coral reefs develop on submerged hills, plateaus or banks that rise from the ocean floor
2. corals grow upwards as conditions allow
3. reefs do not depend on volcanic islands or subsidence

Supporting evidence: coral reefs are found on plateaus (eg bahamas), some reefs occur without clear volcanic origins
Weaknesses: does ot explain atoll formation in the middle of deep ocean basins, fails to explain why reefs maintain a circular shape

Question 19

year, key idea, formation process, supporting evidence, weaknesses

Daly’s Glacial control theory

Answer 19

1915
key idea: sea levels dropped during the ice age, exposing platforms for coral growth
Formation process
1. During the ice age, sea levels were lower, exposing submarine platforms
2. corals colonized these platforms
3. as sea levels rose after glaciation, corals continued growing upwards

supporting evidence: supports modern evidence of past sea elvel changes, can explain some of the reef formations in non volcanic regions

weaknesses: does not fully explain deep ocean atolls, relies on ice age sea level changes which may not apply to all reefs

Question 20

3 political problems in managing coral reefs

Answer 20

1. Successful management depends on local communities, but many policies are top down and do not consider traditional knowledge or livelihoods
2. Many marine protected areas (MPAs) lack funding and staff to enforce fishing bans and conservation measures
3. Lack of coordinated global policies for reef conservation

Question 21

2 economic problems in managing coral reefs

Answer 21

1. Coral reef tourism generates $36 billions per year - economic output tends to outweigh reef protection for most government priorities
2. Balancing conservation and economic activities like fishing, tourism and coastal development is difficult

Question 22

2 social problems in managing coral reefs

Answer 22

1. In Singapore, 60% of reefs have been lost to land reclamation projects
2. Parrot fish popular in carribean cusine however are known as ‘lawnmowers of the ocean’ as they eat algae on corals. overfishing leads to unchecked growth of algae, smothering corals and blocking sunlight for photosynthesis

Question 23

4 environmental problems in managing coral reefs

Answer 23

1. Sediment runoff leads to flocculation and sedimentation with nutrients like nitrates from soil causing eutrophication of the algae, blocking sunlight from corals
2. more intense storms and rising sea levels can physically damage reefs and alter the conditions which the corals require for survivial
3. rising sea temp causes coral bleaching, weakening reefs and makinf them more vulnerable to disease
4. increased co2 lower pH, making it more difficult for corals to build their calcium carbonate skeletons

Question 24

how does it work, +ve, -ve, case study example w facts

water quality improvement plan

Answer 24

strategies to reduce pollution from agricultural runoff, sewage and industrial waste, improving water quality for coral reefs
+ve
* reduces eutrophication, preventing excessive algae growth that harms corals
* improves ecosystem health
-ve
* limited to specific regions
* requires continuous monitoring and enforcements

Queensland, Australia: 2050 water quality improvement plan aims to reduce nitrogen levels from agricultural sources - inorganic nitrogen reduced by 4.3%

Question 25

# how does it work, +ve, -ve, case study example w facts marine protected areas (MPAs)

Answer 25

designated regions where human activities are regulated to conserve marine ecosystems and biodiversity +ve: * protects marine life and habitats from overfishing and destructive fishing practices helps restore * maintain fish populations * preserves biodiversity -ve: * can restrict economic activities like fishing, affecting local communities * enforcement and funding challenges GBR MPA covers 344 400 km2 protecting 3000 coral reef species

Question 26

coral restoration projects: eg New Haven Koh Tao

Answer 26

Structural restoration through building coral nurseries and artificial reefs in controlled environments then moving them to degraded reef areas. Passive restoration focueses on reducing or eliminating sressors to allow natural recovery eg MPAs to mitigate threats like overfishing +ve * projects give education and training for people so they can keep going * collaboration with local authorities in influenceing policies -ve * not much global difference to climate issues which cause i eg ocean acidificiation * physical restoration is expensive and requires high amount of regular maintenance

Question 26

# how does it work, +ve, -ve, case study example w facts Sustainable fishing practices

Answer 26

regulations to prevent overfishing and destructive fishing methods like dynamite fishing and cyanide fishing +ve * maintains fish populations for long term sustainability * reduces habitat destruction -ve * difficult to enforce in open waters * fishermen may resist restrictions due to economic independence GBR: seasonal closures and fishing limits implemented to restore fish populations

Question 27

reducing greenhouse gases through the world community (eg Paris agreeement)

Answer 27

global agreements and initiatives to reduce co2 emissions and slow climate change which affects coral reefs through ocean acidification and temp rise +ve * addresses long term threats like coral bleaching and ocean acidification * global cooperation can create significant impact -ve * difficult to enforce as some countries do not comply * slow progress in reducing emissions Paris agreement: aims to limit global warming to 1.5C to reduce coral bleaching risks