In this blog series, scientists from the Earth Observatory of Singapore (EOS) explore key themes of the documentary series Changing Ocean Asia. In this post, Assistant Professor Kyle Morgan explores the role coral reefs play in ocean health locally and globally and why ocean health is critical for our own survival in the 'Urban Oceans: Super Corals' episode of the docu-series. Watch the episode here.

Did you know that the ocean contributes up to 70 per cent of the world’s oxygen supply?

A healthy ocean relies on healthy marine ecosystems. Coral reefs provide critical habitats that support an abundance of marine species, which is why they are often referred to as the 'rainforests of the ocean'. Coral reefs are crucial areas of biodiversity and provide resources that support livelihoods of coastal communities.

Coral reefs support a diverse marine ecosystem and are often called 'rainforests of the ocean' (Source: Screengrab from Changing Ocean Asia)

The global epicentre of coral diversity is right here in Southeast Asia, in an area known as The Coral Triangle. The Coral Triangle is a geographical area that spans the warm tropical seas between the Philippines, Papua New Guinea, and Indonesia. Within this region, we can find over 70 per cent of the world’s coral species, a huge variety of reef fishes and incredible diversity of other marine organisms.

The Coral Triangle is also a region of very high human population density, and coral reefs provide coastal protection for millions of people by reducing wave energy before it reaches the shoreline, especially during storms. Because coral reefs are such an important marine ecosystem within Southeast Asia, their response to external pressures, such as climate change and increasing human activities, is critical for ocean health and, ultimately, for our own survival.

Within The Coral Triangle there are a number of "urban ocean" areas. These are areas of the coastal seas where marine environments coexist with large urban centres that have a dense human population, urban development, and man-made infrastructure.

In an urban ocean, human activities at the coast can place extraordinary stress on local marine environments, including coral reefs. For example, runoff of terrestrial sediment and nutrients into the ocean reduces water quality and affects the health of coral reefs. A similar effect occurs when large ships disturb fine seafloor sediments – a problem for busy port cities.

Coral reefs provide three-dimensional habitat for fishes and other reef organisms, but to remain the main engineers of these underwater megacities, corals need to be healthy and resilient in the face of climate change and a changing ocean. Corals are also animals themselves and they require a sustainable environment to build and grow. If we lose them, it can take multiple human generations for reefs to build back to their original states.

What is concerning now are the current trends of increasing ocean temperatures, which can cause coral bleaching, as well as the rapid rates of sea-level rise that may inundate some reefs, particularly in urban areas. This is because the high amounts of suspended material (known as turbidity) on many urban coral reefs means that corals typically grow under low-light conditions. If sea level rises faster than the corals can grow, they may no longer receive adequate sunlight. While this makes urban coral reefs vulnerable to the impacts of sea-level rise, it also requires them to learn to adapt and become more resilient to survive.

Coral reefs in urban oceans have developed innovative strategies to adapt to these reduced light and turbid water conditions. Some corals grow laterally along the reef surface to maximise the amount of sunlight they can capture, while others use long extended tentacle-like polyps to capture food particles in the water column to supplement their energy needs. Both adaptations allow corals to tolerate more extreme conditions in the urban ocean, making them more resilient to environmental stress than corals living in pristine conditions. It is because of this inherent strength that these corals are sometimes referred as 'super corals'.

To date, marine research has often focused on the declining health of remote coral reefs found in charismatic locations. But now, more researchers are exploring urban coral reef systems and their physical environments, which are showing signs of resilience to our changing climate system, and which may provide clues to save coral reefs in decline around the world.

It is important to study urban coral reefs so we can better understand the resilience of ecosystems to our changing ocean. We may then start to apply the lessons we have learnt to help protect coral reefs in coastal areas of the world where urbanisation is accelerating, or to help save ocean areas where change is happening faster than adaption can occur.

What we discover from these super corals and their ability to build their own resilience can teach us important lessons on how to protect and preserve more fragile reef systems. Armed with this knowledge, we can reduce coral decline on reefs across Southeast Asia and the globe.

The new documentary series Changing Ocean Asia explores four key themes around the impacts of the changing ocean. Narrated by Dr Sylvia Earle, the documentary also looks at the challenges and solutions that are being explored by scientists at the Earth Observatory of Singapore as well as governments and businesses. 

The series can be viewed from any web browser or wifi-enabled device that offers the Curiosity Stream application or on any one of their partner platforms including StarHub TV Channel 422 in Singapore, Amazon Prime, Apple TV, and other partners globally.