Chapter 14: Coral Reefs

Overview of Coral Reefs

• Coral reefs are often described as walls of mouths.
• Comprised mainly of stony corals using calcium carbonate to form their skeletons.
• Coral structures are made up of polyps, each capable of feeding.

Nutrient Acquisition

• Corals live in low-nutrient environments but maintain themselves through:
  • Symbiotic relationship with zooxanthellae (algae/dinoflagellate) living in coral tissues.
  • Zooxanthellae photosynthesize, providing nutrients to corals.

Coral Reef Structure

• Coral reefs are found on the continental shelf where sunlight can reach.
• The structure is built from calcium carbonate, contributing to limestone formation.
• Reefs provide habitats for various marine organisms.

Coral Classification

• Belong to the phylum Cnidaria.
• Polyps secrete protective exoskeletons (coralites).
• Corals can be solitary or colonial, with colonial forms forming reefs.
• Types of corals include hermatypic (reef-building, symbiotic) and ahermatypic (non-reef-building).

Reproduction

• Corals release gametes simultaneously, possibly influenced by moon phases.
• Fertilized zygotes develop into planular larvae which settle to form new colonies.
• In poor conditions, corals may produce bailout polyps to find new living spaces.

Coral Competition and Defense

• Coral reefs are competitive environments with corals fighting for space.
• Corals use tentacles, mesenterial filaments, and toxins for defense.
• Some corals grow to shade competitors or use dissolved organic matter for nutrition.

Nutritional Sources

• Corals capture prey with tentacles and stinging cells.
• Zooxanthellae provide photosynthetic byproducts, oxygen, and aid in waste removal.
• Mesenterial filaments produce digestive enzymes to absorb nutrients.
• Low nutrient environments are ideal to prevent algae overgrowth.

Importance of Coraline Red Algae

• Coraline red algae bind and stabilize reef rubble.
• They are crucial for the structural integrity of reefs.

Coral Types and Ecology

• Reefs present diverse ecological niches.
• Types of corals include encrusting, plate-like, branching (staghorn, elkhorn), and massive types.
• Coral reefs are complex ecosystems with producers, grazers, feeders, and top predators.

Conclusion

• Coral reefs are vital marine ecosystems, providing habitat and complex food webs.
• Understanding coral structures, reproductive strategies, and competition can aid in reef conservation efforts.