A Coral Is Born | Deep Look

Summary

In a stunning natural phenomenon, the Great Barrier Reef's coral species undergo a rare and intricate spawning event that lasts only 30 minutes. This broadcast spawning, triggered by seasonal changes and moon cycles, allows corals to reproduce by releasing sperm and eggs into the ocean. The fertilized eggs develop into larvae, which then settle to form new polyps. However, rising ocean temperatures and coral bleaching are threatening this delicate process, which is vital for marine ecosystems. Scientists are working to replicate these conditions in labs to help restore reefs and protect marine life from climate change.

Takeaways

• 😀 The Great Barrier Reef experiences a unique event once a year, lasting just 30 minutes, during which coral eggs and sperm are released into the water.
• 😀 Coral is an animal, not a plant, and is actually a colony of tiny individual animals called polyps.
• 😀 Polyps secrete calcium carbonate to create their skeleton, which gives coral its structure and anchors it to the ocean floor.
• 😀 Most warm-water corals practice broadcast spawning, where eggs and sperm are released into the water at a precise time based on environmental cues.
• 😀 The gametes (sperm and eggs) float to the surface, where they must meet and fertilize, with only one sperm successfully entering each egg.
• 😀 Once fertilized, coral larvae (planula) begin their search for a stable place to settle, where they will transform into polyps and start growing.
• 😀 Coral polyps absorb algae called zooxanthellae, which provides the corals with nutrition and contributes to their vibrant colors.
• 😀 Polyps can clone themselves, creating more polyps that eventually form large coral colonies and massive reef structures.
• 😀 Coral reefs are vital ecosystems, providing shelter and food for a quarter of marine life, including fish, crustaceans, and sea turtles.
• 😀 Climate change is threatening coral reefs, as warmer ocean temperatures cause corals to expel their algae, leading to coral bleaching and weakened reproductive success.
• 😀 Researchers are working to replicate coral spawning in labs to find ways to help restore coral reefs and ensure their survival in the face of environmental threats.

Q & A

What happens once a year at Australia's Great Barrier Reef?

Once a year, a brief but extraordinary event occurs at the Great Barrier Reef—corals engage in broadcast spawning, where they release their sperm and eggs into the water to fertilize and create new coral larvae.

What is the role of polyps in coral formation?

Polyps are tiny individual animals that make up coral colonies. They secrete calcium carbonate to form the coral's skeleton, which anchors them to rocks or the sea floor, and they also help the coral grow and reproduce.

How do corals manage to reproduce despite their inability to move?

Since corals can't move to find a mate, they practice broadcast spawning, where they release their sperm and eggs into the water to fertilize and create larvae, relying on precise environmental cues like moonlight and water temperature.

What environmental factors trigger coral spawning?

The right month of the year, the light from a waning moon, and the warmth of summer waters all trigger coral spawning. These cues help corals synchronize their reproductive efforts to maximize fertilization success.

What happens after fertilization of coral eggs?

Once the coral eggs are fertilized, they begin to divide and develop into planulae, which are free-swimming larvae that search for a suitable location to settle and grow into new polyps.

What guides the coral larvae to their ideal settling location?

The planulae are equipped with chemical and light sensors that help them navigate the ocean and find a stable, sunlit foundation to settle on, ensuring they have the right conditions to grow.

What is the role of algae in coral health?

Coral polyps absorb algae called zooxanthellae from the surrounding water. These algae provide the corals with nutrition through photosynthesis and contribute to the vibrant colors seen in healthy reefs.

What is coral bleaching, and why does it occur?

Coral bleaching occurs when coral polyps expel their algae due to environmental stress, such as rising sea temperatures. Without the algae, corals lose their vibrant color and become more vulnerable to disease and death.

Why is coral spawning becoming harder to observe?

As climate change causes ocean temperatures to rise, corals are increasingly stressed, and their ability to synchronize spawning efforts diminishes. This makes it harder for eggs and sperm to meet and fertilize successfully.

What efforts are being made to restore coral reefs?

Researchers at the California Academy of Sciences are replicating coral spawning conditions in labs to understand the best ways to grow corals, with the goal of helping scientists restore coral reefs in the oceans.