The Ocean

I have always wondered what it is like to go under the ocean and swim with the fishes. With a sense of curiosity and fascination with the life that thrives beneath the surface of the ocean, I took my first dive at Bunaken Island, Indonesia.

Exploring the beauty of the underwater world in Bunaken, Indonesia

Beneath the surface of the ocean lies a world very different from ours. The ocean animals come in every shape and size. Some creatures are microscopic, while others are massive. Some are beautiful, others are strange looking. Some are unsurprising, others have odd habits and peculiar abilities. Living amongst these fascinating creatures are the ocean producers. They inhabit the zone closest to the surface of the ocean as they need sunlight to make food through photosynthesis. These include seaweeds, marine algae and seagrasses; though only seagrasses are categorised as plants.

Different species live together in an underwater ecosystem that is linked through complex relationships. For example, a marine ecosystem like the coral reef hosts a copious array of lives that depend on each other for survival.

Photography by: Michelle Ng

Importance of the coral reef

The ocean is indeed so amazing. I took interest in the coral reef because they play an important role in marine ecosystems and is a great source of biodiversity. They protect the land from harsh weather, provide a home and food for a large variety of marine life. Besides, they are very pretty and colourful to look at.

Zooxanthellae, algae and seagrasses are the main types of producers in the coral reef ecosystem. Corals have a mutually beneficial symbiotic relationship with microscopic algae called zooxanthellae that live in the coral tissue. These algae are a coral’s primary food source and give them their colour. In return, the coral gives the algae a home, and the carbon dioxide it needs through respiration. Corals shelter some parts of the oceans from ocean waves, allowing seagrasses to take root. In return, seagrasses trap fine sediments and particles from both land and water, keeping the water clear for corals reefs to develop nearby.

Sponges and sea anemones are common inhabitants of coral reefs. Sponges anchor themselves on coral skeletons and provide shelter to these animals. They are known for their commensal relationship with fish, shrimp, crabs and other small animals. These small animals live in the sponges but provide no benefit to the sponge itself. On the other hand, sea anemones are recognised for their mutually beneficial symbiotic relationships with anemonefish, which is better known as clownfish. The clownfish protects the anemone from predators such as the butterflyfish, while the tentacles of the sea anemone guard the clownfish and their eggs from enemies.

Effects of human activities on the coral reef ecosystem and ways to protect our underwater ecosystem

Since coral reefs grow mostly in shallow water near the shore, they are extremely vulnerable to the effects of human activities, both directly and indirectly. Climate change is one of the greatest global threats to the coral reef ecosystem. This change is mainly due to greenhouse gases derived from human activities. As the underwater ecosystem is linked through complex relationships, harm to the coral reefs could have ripple effects on the entire ecosystem that depends on them.

Increase in greenhouse gases in the atmosphere causes atmospheric pressure and the seawater temperatures to rise. When ocean temperature rises, the corals stress out and expel the algae living in them. The coral thus loses its main food source, becomes white, and is more vulnerable to diseases. This condition is called coral bleaching.

During my dive, I noticed that some of the corals were indeed bleached. That made me think hard. Have my actions caused harm to the ocean? What can I do to stop this?

The ocean is so important to us. Many of the ocean’s fishes and plants depend on healthy coral reefs. We can all do our part by reducing the emissions of greenhouse gases to help conserve our underwater ecosystem.

Written by Michelle Ng
Illustrations by Daphne Lim