The secret garden

Zhou Fang

Zhou Fang， vice president and secretary general of the Film and Television Branch of China Pacific Society， is also the founder and chief director of the professional underwater documentary Diving Round the World. Moreover， her underwater photography has appeared in nationwide roadshows many times. Having filmed many shark subjects， she is known as “the girl chasing sharks round the world”. In addition， she was elected as one of the “Ten Most Beautiful Hunan Women” in 2016. The underwater documentary Looking for Whale Sharks produced by her won the second prize in Hunan TV Micro Film Competition. As a director， she also shot underwater documentaries such as Diving Round the World and Underwater China.

China， a mysterious country with a 5000-year-old civilization， boasts many rivers， lakes and vast territorial waters. However， the underwater beauty of China is barely known to people. This book demonstrates China’s submerged civilization and hidden fabulous cultural treasures to the world， enables more people to realize and discover China’s rich underwater culture， and presents China’s particular beauty to the world.

Underwater China

Zhou Fang

Beijing Science and Technology Press

January 2021

158.00 （CNY）

If there exists the power to shake the earth， it would be the power of the ocean. The ocean not only has a huge reserve of treasures， but it also gestates mysterious species. Despite having explored the ocean for thousands of years， human beings know less than 1% about it. Coral reefs， as the rainforests of the ocean， compose special “secret gardens” together with many other marine lives. So， let’s move on to the undersea world to explore mysterious and magnificent “gardens”！

Coral polyps

The secretions of countless coral polyps form the exoskeletons of coral， the main architect of the secret garden. All kinds of corals have been shaped since coral polyps have multiplied on these bones for generations. The polyps living in colonies are tiny. Being polyp-shaped， they have mouths on the top， which are surrounded by many small tentacles. Those tentacles are used to catch tiny creatures in the ocean. And it is those tiny creatures that made the most beautiful artworks in the seabed.

Polyps extending their tentacles

Coral polyps fluorescing

Laying eggs

While the reflection of the bright moon appears on the seemingly calmsea， underneath， the miracle of life is silently taking place. Receiving the instruction of the sea， coral polyps give birth to new life soundlessly. Like stars， the gushing coral eggs condense into a brilliant Milky Way. Under the boundless starry sky of the seafloor， the “starlight hunters” have been there for a long time. Patiently， they wait for the sea party to have a high-protein feast.

An adventure of life is bound to happen tonight.

Acropora laying eggs

Modes of reproduction

Corals reproduce in a very strange way. Presently， in tropical and temperate waters around the world there exist about 800 species of corals. As animals， corals are either hermaphroditic or gonochoric. Hence， ways of coral reproduction can also be classified into sexual reproduction and asexual reproduction. The so-called sexual reproduction means that the eggs and sperms encounter each other and become fertilized eggs， which will later develop into planulae with certain swimming abilities. A few hours or days later， if the planulae find a suitable place on the seabed" for growing， it will settle down and gradually develop into coral polyps （hydranth）， reproducing asexually then. Asexual reproduction can be divided into budding and division. Through asexual reproduction， polyps with the same genetic material increase their number continuously. For instance， through asexual reproduction， the most common acropora will constantly reproduce itself and form a colony after developing into a single polyp from being a fertilized egg. However， some other polyps will form individual corals.

The planula of corals

Zoantharian with shrinking hydranth

A coral larva attached

to a solid surface

Hermatypic corals

Corals are divided into hermatypic corals and ahermatypic corals regarding their ecological value. Just as the name implies， hermatypic corals are coral reef makers. Living as symbiosis with zooxanthellae in euphotic zone with shallow water， they like sunbathing best. Nevertheless， if you believe hermatypic corals are all about looks and are harmless you’ve been fooled by them.

For example， bubble vesicle corals will blow bubbles during the day， looking chubby and cute. However， when night comes， the seemingly soft “air sac” （cyst） slowly retracts to expose solid bones. Into the darkness the stinging fleshy tentacles reach out， trying to catch various plankton that swim by.

Bubble vesicle coral in the day

Most hermatypic corals possess a commonality that they obtain nutrients from both self-trophic and heterotrophic sources. In the daytime， when sunlight irradiates to the seabed through the water， bubble vesicle corals gain nutrients and energy from the photosynthesis of symbiotic zooxanthellae to maintain the growth of calcareous bones. The bulged cysts resemble blown-up-bubbles， permitting zooxanthellae to fully absorb sunlight and maximize the photosynthesis efficiency. After the nightfall， bubble vesicle corals pack up their bubbles to expose their bones. In this way， the stinging fleshy tentacles can flex their muscles and sway freely rather than struggling to forage among the bulging cysts. The bubble vesicle corals sedulously stretch out， unfold， contract and curl their tentacles repeatedly， aiming to capture plankton in the current to endlessly offer themselves food and energy.