The Maldives is famous for many reasons; among these are the magical kingdoms below the waves – the magnificent coral reefs.
The Baa Atoll – a UNESCO Biosphere Reserve – is one of the Maldives’ most renowned regions, comprising 75 islands across three natural atolls, or ring-shaped coral reefs. The shimmering, colourful structures attracting masses of diverse sea creatures naturally also draw snorkellers and scuba divers eager to discover the riches of the ocean. But beyond their beauty, coral reefs play fundamental roles within the ecosystem.
In this three-part series about the coral reef, Emily Wilson, our resident marine biologist, shares her expertise about one of our world’s greatest wonders – and its residents that deserve a closer look.
Insights from our marine biologist:
”Unsung Heroes of the Reef” (Part 1 of 3) by Emily Wilson
Coral reefs cover just one per cent of the seafloor. Yet reefs are rich with diversity, containing one quarter of all life found in our oceans; they are hotspots of activity. The microscopic algae living within corals illuminates each colony with rainbow colours. Every aquatic plant and species of algae breathes oxygen into the oceans, providing a liveable environment for all marine animals, from inhabitants of the sunlit shallows to those of the twilight zone and abyssal planes plunging deep below the ocean’s surface. Through the same reaction, carbon is sucked up from the atmosphere and stored within the organic matter, helping to regulate the Earth’s climate.
These vital coral metropolises, teeming with marine creatures, are thus essential to the functioning of the ocean biosphere. They also provide life-sustaining services to coastal communities and beyond. In addition, the complexity of the calcium carbonate skeleton that the corals secrete provides homes for many ocean-dwelling animals and acts as a wave breaker, subduing the effects of large waves crashing onto the shore.
The tide, however, is sadly turning, with reef ecosystems suffering global decline. It is time to recognise the saviours of our precious ocean hotspots – the unlikely underdogs of coral reef health and resilience. It is now vitally important for us to shift our focus onto some of these unsung heroes.
Unsung Hero #1: The Sponge
Coral reefs are some of the planet’s most dynamic and energetic environments, yet they survive in water of low nutrients – a phenomenon known as “Darwin’s Paradox”. How do the reefs not only survive but, in fact, thrive? Enter the humble sponge.
Simple organism, enormous impact
One of the most basic life forms, an invertebrate with just two cell layers, the sponge or Porifera has undergone millennia of evolution to perfect its porous body form. Each of its thousands of spherical chambers acts as a filter-feeding factory, capturing small food particles in the water’s flow.
To put in perspective just how powerful these filter feeders are, research showed that a sponge 10cm in height and 1cm in diameter contained 2.2 million chambers and pumped 22.5 litres of seawater a day. In this way, sponges are a natural filtration system ensuring corals can flourish in a low-nutrient environment.
The sponge loop
The superhero sponge does more than what meets the eye, forming an intricate web of interactions that helps support the vast abundance of life on coral reefs. Dissolved food particles in the seawater released by corals are readily gobbled up by sponges and recycled into grub for other sea creatures.
To uncover sponges as organic, recycling eco-warriors, scientists released labelled sugars and followed their journey through the food chain. The superhero sponges filtered the sugars and then quickly shed their dead filter cells, producing food for hungry bottom-dwelling creatures. Larger animals, in turn, consumed the bottom-feeders, and the cycle of life roared on.
The sponge as shelter
Sponges serve as a vital component of the reef food web and provide a good home for marine critters.
Reefs are characterised by a wealth of complex food webs and animal interactions. The busyness of the ecosystem means there is high demand for space and resources. This creates a highly competitive environment where organisms utilise other animals as real estate. As a major component of reef infrastructure, sponges are amongst the most widely exploited species for habitat. They harbour an exceptionally diverse array of marine snails, worms, feather stars, crabs, shrimp, and some corals.
Look out for the next article in our ”Unsung Heroes of the Reef” series by Emily, coming soon. Contact us at [email protected] to plan your getaway to our ocean paradise.