Calcification:

Question 1

What is the process of calcification?

Answer 1

Deposition of CaCO3 at base of coral polyp

Question 2

What is the purpose of calcification?

Answer 2

Continuous growth of skeletal structures

Question 3

Who are the key players in calcification?

Answer 3

Coral polyps and symbiotic zooxanthellae

Question 4

How do ions get into the coral?

Answer 4

Passive diffusion: Ca2+ and HCO3- from seawater

Question 5

What is the path of these ions into the coral?

Answer 5

Ectoderm -> mesoglea -> calicoblastic layer -> calicoblastic fluid

Question 6

What happens in the calicoblastic fluid?

Answer 6

Complex interactions of dissolved inorganic carbon

Question 7

How does pH play a role in the calcification process?

Answer 7

Active removal of H+ ions from calcifying fluid to create favourable conditions for CaCO3 precipitation

Question 8

What is the role of Ca2+ ATPase in the calcification process?

Answer 8

Active transport of Ca2+ into the calicoblastic fluid

Question 9

What is the effect of the active transport of Ca2+ into the calicoblastic fluid?

Answer 9

Increases Ca2+ concentration in the calcifying fluid, decreases H+ concentrations

Question 10

What is the relationship between Zooxanthellae and corals?

Answer 10

Symbiotic relationship where the Zooxanthellae live in the gastrodermic tissues of the coral

Question 11

What is the benefit of the symbiotic relationship for coral?

Answer 11

Zooxanthellae, through producing amino acids, glucose, and other essential molecules, provide the coral with up to 70% of their needed energy

Question 12

What effect does the symbiotic relationship have on calcification in coral?

Answer 12

Up to 10X more CaCO3 deposition in corals that have zooxanthellae compared to those that don’t as it provides them with more energy for this process

Question 13

What is light-enhanced calcification?

Answer 13

Increased calcification due to photosynthesis

Question 14

What is the mechanism for light-enhanced calcification?

Answer 14

Excess energy from Zooxanthellae supports H+ removal and pH regulation

Question 15

What is the additional benefit of light-enhanced calcification?

Answer 15

Photosynthesis removes CO2 from calcification site

Question 16

What is the significance of the day-night cycle of symbiosis?

Answer 16

Daytime: zooxanthellae photosynthesise = energy provided for coral growth, calcification, H+ removal
Nighttime: corals respire, producing CO2 and nitrogenous waste = zooxanthellae use these products for their own energy

Question 17

What effect does thermal stress have on corals?

Answer 17

Causes bleaching in corals

Question 18

What effect does thermal stress have on zooxanthellae?

Answer 18

Breakdown of photosystems, production of ROS’s = expulsion of zooxanthellae

Question 19

What are the consequences of Zooxanthellae expulsion?

Answer 19

Loss of photosynthetic energy supply, impaired pH regulation, stops calcification process

Question 20

What is the corals defense to zooxanthellae expulsion?

Answer 20

Production of fluorescent pigments to try and protect the remaining zooxanthellae
- If recolonisation within 7-10 days does not occur, corals die