Choose the correct statements about corals?
A. Corals are invertebrate animals a few millimeter in diameter.
B. Corals are sensitive to heat stress and ocean pH change.
C. Corals provide algae with stable environment, CO\(_2\) and nutrients.
D. Corals bleach to get rid themselves of pathogens.
Show Hint
Coral bleaching is a sign of severe stress, not a healthy cleaning process. It's the breakdown of the vital symbiosis between the coral animal and the algae that gives it color and most of its food.
Step 1: Analysis of Statement A. A coral reef comprises large colonies of small animals known as coral polyps. Each polyp is an invertebrate, usually a few millimeters in size. Statement A is accurate.
Step 2: Analysis of Statement B. Corals have limited environmental tolerances. Elevated ocean temperature (heat stress) and reduced pH (ocean acidification) are significant stressors that can harm their symbiotic relationship with algae and induce coral bleaching. Statement B is accurate.
Step 3: Analysis of Statement C. Corals engage in a symbiotic relationship with microscopic algae called zooxanthellae. The coral polyp offers the algae a protected environment and the substances needed for photosynthesis (CO\(_2\) and nutrients like nitrates and phosphates). Statement C is accurate.
Step 4: Analysis of Statement D. Coral bleaching occurs when corals eject the symbiotic algae residing in their tissues, causing them to turn white. This is a stress response, primarily to heat, not a method to eliminate pathogens. The loss of algae can result in the coral's demise. Statement D is inaccurate.Conclusion: Statements A, B, and C are correct.
