Coral reefs are home to a quarter of all marine species, so it is fitting that they are the focus of Blue Planet II’s third episode. Exploring the vast array of different marine life that live here – from green turtles and bottlenose dolphins, to manta rays, octopuses, and parrotfish – the episode will demonstrate how these different creatures have adapted to survive in these underwater mega-cities. However, rising temperatures are having a devastating impact on the world’s coral reefs, so undertaking measures to halt the effects of coral bleaching has never been more crucial.
Explore our latest collection about the coral reef environment below:
Coral reefs are one of the most productive ecosystems on the planet, with primary production rates compared to that of rain forests. Benthic organisms release 10-15% of their gross organic output as mucus that stimulates microbial metabolism, and as a result coral reef microbes grow up to 50 times faster than open ocean communities.
Coral reefs are also ‘choral’ reefs, with many fishes producing specific sounds for courtship and spawning rituals. New research is even showing that larval reef fishes may use these sounds emanating from coral reefs to navigate during migration.
Manta rays are one of the most charismatic species of rays, but there has been uncertainty around their taxonomy for some time. Not anymore, however: scientists have recently discovered that manta rays are, in fact, a type of Mobula ray, or “devilray”. As a result, all types of manta ray have been reclassified as devilrays, and the genus Manta, has been removed from existence.
Female southern blue-ringed octopuses don’t need wingmen (tentacle-men?) to help them find potential mates. They choose to go it alone, having evolved to be able to smell male octopuses. What’s more, it’s possible they are able to mask their own scent to potentially disguise themselves from unwanted suitors.
Green turtles are endangered marine herbivores that break down food particles, primarily sea grasses, through microbial fermentation. However, the microbial community and its role in health and disease are still largely unexplored; by studying stranded and wild turtle populations in the Great Barrier Reef, we can learn more about this method of digestion.
Even though tiny little planktonic copepods live in the depths of coral reef waters, scientists have discovered that their diets are largely made up of terrestrial plants, such as tropical or subtropical plants located around Sanya Bay, China. It’s even been suggested that pollen could be food-of-choice for copepods.
On the coral reefs of New Caledonia, a recent study found that the fish that live there have come up with a series of tactics to repel their main predator, turtle-headed seasnakes. Blennies and gobies focused their attacks on snakes physically entering their nests, whereas damselfish attacked passing snakes as well as nest-raiders. The fish most commonly bite the snakes to deter them, although damselfish and blennies also slap snakes with their tails.
Today coral reefs are suffering from numerous pressures. Industrial pollution, shoreline alterations, diseases of corals, and over-extraction of fish, invertebrates, and even the limestone rock itself, have all contributed to the demise of about one third of the world’s reefs. More recently, climate change, notably a rise in sea temperature, has led to coral bleaching and then the death of component corals. Increased CO2 in the atmosphere has also been recorded as leading to the disruption of shoaling behaviour in fish.
With rising global temperatures leading to coral bleaching and endangered reefs, you’d think that would be all these undersea mega-cities have to be concerned about. But their residents aren’t making life easy either! Corallivorous snails eat and purposely damage coral reefs in sporadic, large-scale attacks that scientists refer to as ‘plagues’, ‘invasions’, or even ‘population outbreaks’, indicating the level of destruction these snails wreak on coral. Certain snails have also adapted to be able to burrow into sand on coral reefs, further damaging their coral home.
Corals rely on photosynthesis to form the basis of tropical coral reefs. High sea surface temperatures driven by climate change can cause coral bleaching, leading to declines in coral health. However, not all species of coral struggle with increasing temperatures so much, due to a thermo-tolerant adaptation to protect against coral bleaching.
Images: 1) Coral Reef by marcelokato. 2) Underwater by marcelokato. 3) Fish by joakant. 4) Swimming by Pexels. 5) Clown fish by Pexels. All public domain via Pixabay.
