2.3. Coral reefs Flashcards
1
Q
What are coral polyps? (4)
A
- tiny, soft animals whic attach themselves to a hard surface in shallow seas where there is sufficient light for growth (photosynthesis)
- => exude calcium carbonate as the grow which form skeletons polyps
- Have small algae (zooxanthelllae) growing inside them there is a symbotic relationship between polyps and algae
- Algae get shelter and food from polyp, polyps grow as algae grows (get food via photosynthesis)
2
Q
7 Conditions for coral reefs to grow
A
- Temperature: between 23C to 25C
- Depth of Water: < 25cm but not exposed to air, below low tide mark
- Salinity: between 32psu and 42psu
- Light: shallow water because algae in coral reefs photosynthesis
- Sediment: minimal as it clogs up their feeding structures and reduces light available
- Wave action: strong wave action which ensures oxygenated water; removes any trapped sediment
- Global distribution: tropical seas between Tropics of Cancer and Capricorn
3
Q
What are the 3 forms of reef?
A
- Fringing reef
- Barrier reef
- Atoll Patch reef
4
Q
6 Characteristics of fringing reef
A
- Near coastline around islands and continents
- Characterised by an outer reef edge capped by an algal ridge
- A broad reef flat
- A sand floored boat channel close to the shore
- Grow sea ward from the land
- Grow around newly formed islands which subside, or sea levels rise relative to land
5
Q
3 Characteristics of barrier reef
A
- Commonly separated from the shore by a wide deep lagoon
- Following a rise in sea level or a drop in the level of the land
- At their shallowest point they can reach the water’s surface forming a barrier
6
Q
Characteristics of atoll (3)
A
- Rings of coral that create protected lagoons
- Usually form when islands surrounded by fringing reefs sink into the sea OR the sea level rises.
- When the island disappears beneath the sea => atoll is formed
7
Q
What are the 3 theories of coral reef formation?
A
- Darwin-Dana
- Murray
- Daly
8
Q
Darwin-Dana theory (5)
A
- An oceanic volcano which emerges from the sea surface and froms an island, becomes colonised by reefs building corals
- The growth of corals begins to form a fringing reef. The island begins to sink slowly. Coral growth continues
- The island continues to sink and a barrier reef is formed with a lagoon between the reef and island. Coral growth is more vigorous
- Eventually the island disappears below the sea surface, leaving an atoll consisting of a ring of small islands
- -> Evidence: submergence takes place in the case of drowned valleys along parts of Indonesia and along the Queensland Coast of Australia
9
Q
Murray theory (5)
A
- Base of the reef consisted of a submarine hill
- Coral grows upon suitable stable submarine platforms with unchanging sea level
- If submarine platforms above sea level => subjected to wave erosion
- After getting a suitable depth of 180 feet, coral polyps start growing to form fringing reefs
- Continuous outward growing of polyps form barrier reefs
- Atolls are formed due to the outward growth of corals in all directions at the top of the submarine platform
10
Q
Daly theory (2)
A
- Rise in sea level is responsible (evidence: rise took place in post glacial times as ice sheets melted due to warm conditions)
- Previous coral reefs provided a base for the upward growth
11
Q
Coral reef management (8)
A
- Damaging fishing practices like dynamiting can be banned. It’s important that this is enforeced or the practices will carry on.
- Have conservation zones, where tourists arent’t allowed or limited amount of tourist can be created
- Areas where coral reef can’t be farmed can be created.
- Fish stocks can be enhanced and quotas imposed on amount being caught.
- Sewage outlets can be moved downstream of coral reefs
- Banning the dropping of anchors on coral reef.
- Reduce the use of fertilisers near coral reefs
- The most important = educating people about: “why coral reefs are important and how we can protect them
