Characteristics, Distribution + Formation of Fringing Reefs, Barrier Reefs + Atolls

Question 1

What are the general characteristics for all coral reefs?

Answer 1

• underwater ecosystems, made up of large amounts of coral, held together by a calcium carbonate skeleton, that create a suitable envi to support a wide variety of wildlife
• marine animals called polyps, which attach to rocky surfaces, produce calcium carbonate skeleton, helping to form reef
• polyps have a symbiotic relationship w zooxanthellae, in which polyps provide zooxanthellae w shelter, whilst zooxanthellae photosynthesis + produce O2 + glucose for polyps

Question 2

What are the characteristics of fringing reefs?

Answer 2

• attached to, or runs closely parallel to, shoreline, + can be separated by a shallow backreef or narrow lagoon
• shallowest + youngest type of reef

Question 3

What are the characteristics of barrier reefs?

Answer 3

• also run parallel to coastline, but are completely separate from shore by a wide, deep lagoon (can be 30-70m deep + kms wide)
• much larger + older than fringing reefs
• e.g. GBR supports a high biodiversity, inc 1,500 fish species, 400 coral species, 30 species of marine mammals + endangered species (e.g. green sea turtle)

Question 4

What are the characteristics of atolls?

Answer 4

• ring shaped reef, surrounding a lagoon, that’s formed from a subsided volcanic island
• isolated in open ocean + often lower + more fragile

Question 5

Describe the distribution of coral reefs.

Answer 5

• found in tropical + sub-tropical regions bc require certain conditions to grow + survive

Question 6

Describe the formation of coral reefs.

Answer 6

• in 1942, Darwin explained process of reef formation through his subsidence theory = proposed coral reefs grow upwards from submerging features
  
  • e.g. a coral reef begins to grow around edge of a newly formed volcanic island, which over time is replaced by a barrier reef, as reef continues to grow whilst volcanic island either starts to sink or sea lvl rises
  • eventually, volcanic island fully submerges, + only a ring shaped reef remains to form an atoll
• but, Murray challenged Darwin, suggesting coral reefs can also form on submerged gyotts w/o a volcanic island