1. Lectures 14-15: Coral reefs
Marine Biology
Lectures 14-15: Coral reefs

2. Global distribution of coral reefs

3. Productivity and diversity

4. Structure of coral

5. Coral anatomy

6. Coral anatomy
Zooxanthellae are within the gastrodermal layer lining the gastrovascular cavity.

7. What does the coral animal provide to the zooxanthellae?
Nutrients, especially nitrogen and phosphorus-containing compounds
Carbon dioxide
Location in the photic zone
Protection

8. What do the zooxanthellae provide to the coral?
Organic molecules (carbohydrates, proteins, other organic molecules)
End products of photosynthesis
Radiolabelled C-14 experiments verify this transfer of organic molecules
98% of a coral’s nutrition comes from the zooxanthellae
Oxygen
Aids in calcification

9. Calcification
Active transport of calcium from seawater into epidermal cells of coral occurs.
At peak of calcium deposition, a cell must transport times its own volume.
Calcium carbonate deposition is 14X greater in light than in dark, so role of zooxanthellae proposed to be important
Highest deposition on sunny days at noon.
Mechanism of coupling not well-understood.

10. Calcified coral skeleton

11. Other coral basics
Feeding
Shape vs. depth

12. Role of coral in food web
Primary producers
Primary consumers
Secondary consumers, and up
Detritovores?

13. Factors affecting reef growth
Temperature
Depth
Salinity
Sediment
Wave action
Nutrients

14. Paradox: low nutrients, high productivity
Hypotheses
Efficient coupling between coral and its symbionts
High flow rate of water over reef; integrated amount that flows over the reef is relatively high
Nitrogen fixation by cyanobacteria creates a source of nitrate
Nutrients in particulates are relatively high, and are efficiently sequestered by reef organisms.

15. Reef structure
Reef building
Reef breakdown

16. Types of coral reefs
Fringing
Barrier
Atoll (Darwin’s other theory…)

17. Pacific vs. Atlantic reefs
Differences in diversity
Differences in species composition
Hypotheses to explain these differences

18. Key threats to coral reefs
The scope of the problem
Major threats (explained in some detail)
Coral bleaching
Overfishing
Sewage and other pollutants
Storms
Implications of reef loss