Human Effects on Natural Threats

The process of coral bleaching appears horrifying. Imagine an entire plain of multicoloured coral turning ghostly white all at once. According to the National Geographic (2010), the Caribbean has lost around 90 percent of its coral reefs, with half of all the corals lost due to bleaching (National Oceanic and Atmospheric Administration, 2014).

“When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.”

– National Oceanic and Atmospheric Administration, National Ocean Service, ‘What is coral bleaching?’ –

The actual process of bleaching, however alarming in the way it makes coral change so drastically, does not actually kill the coral, as the definition by NOAA above states.

A simple graphic explaining coral bleaching. (
A simple graphic explaining coral bleaching. (

Coral bleaching occurs naturally when environmental conditions change, such as an increase in water temperatures (National Geographic, 2010). Like an aircraft forced to dump excess weight in an emergency, coral polyps evacuate the symbiotic zooxanthellae that live inside them. The measure does seem extreme, but there is evidence to suggest that bleaching could be a sly way of ensuring the coral’s own survival in the long run: by expelling algae that will not be able to withstand whatever environmental changes that elicited the bleaching, the coral make room for algae that could be more hardy than their previous zooxanthellae residents (National Geographic, 2010). Although the process is geared to help the coral survive, it it does make the coral more vulnerable to perishing (NOAA, 2014), along with ridding it of the colourful, life-giving zooxanthellae that reside in the coral polyps and provide energy for the coral through photosynthesis.

With human-driven climate change showing no signs of stopping, it is expected that coral bleaching will continue at an increasingly unhealthy rate. And to make matters worse for the coral of the Great Barrier Reef and other reefs around the world, another threat looms large: the crown of thorns starfish.

The a swarm crown of thorns starfish amidst bleached coral.(
A swarm of crown of thorns starfish amidst bleached coral. (

The menacing-looking crown of thorns starfish (or COTS, for short), unlike coral bleaching, really is as scary as it looks, and it is obvious from the first glance how the COTS got its name. The COTS is a large species of starfish, often reaching sizes of up to a full metre across, armed with anything from 7 to 23 arms bristling with venomous spines.

A starry pufferfish (Arothron stellatus), one of the few living things brave enough to take on a mature COTS. (
A starry pufferfish (Arothron stellatus), one of the few living things brave enough to take on a mature COTS. (

The COTS also has very few natural predators once it has reached maturity (although it probably has some of the weirdest predators, such as the Starry Pufferfish and the Triton’s Trumpet snail, seen devouring a COTS here). COTS larva, on the other hand, are more vulnerable to being consumed by a wider range of aquatic life, anything from crustaceans to fish (ARKive, n.d.).

Seemingly to counter this, female COTS can carry up to 60 million eggs at once (ARKive, n.d.). Multiple starfish also coordinate their spawning (just like coral do) to increase reproductive success. COTS populations can also see sudden growth spurts known as outbreaks. The sheer number of eggs one female carries means that even small populations of starfish can quickly repopulate and far exceed their previous numbers and spells disaster for coral.  (ARKive, n.d.)

COTS outbreaks have been naturally occurring on the Great Barrier Reef every so often (Great Barrier Reef Marine Park Authority, n.d.). However, once again due to human-related factors, a natural process now runs rampant and out of control. As with eutrophication (discussed in the post immediately prior), COTS outbreaks are affected by nutrients in the water. A study on the decline of coral cover in the Great Barrier Reef conducted by De’ath, Fabricius, Sweatman and Puotinen (2012) states that “water quality affects the frequency of COTS outbreaks in the central and southern GBR (Great Barrier Reef)”. What these scientists found is that nutrient-rich waters facilitated the growth of phytoplankton, which the larva of COTS feed and thrive on. Coupled with the already impressive reproductive capabilities of the starfish and the increasing frequency of outbreaks (De’ath et al., 2012), and it is clear that human activity is worsening the situation for the Reef.

Tourism, Shipping and Industry

The featured image you see just above is that of Airlie Beach, Queensland. Voted 34th in a lineup of the 100 Best Towns in Australia by Australian Traveller in 2009, the exclusive town, home to just over one thousand permanent residents, lives and breathes tourism, much like the rest of the Great Barrier Reef.

A variety of activities on the Great Barrier Reef allow for close contact with marine life. (Wings Diving Adventures, n.d.)
A variety of activities on the Great Barrier Reef allow for close contact with marine life. (

Tourism on natural sites such as the Great Barrier Reef is excellent in a variety of ways. First and foremost, it brings the curious tourist into direct and intimate contact with nature. Such close contact, whether it is with a gigantic humpback whale on the Great Barrier Reef, or a smaller-scale encounter with some fish swimming near shore, elicits a sense of awe and closeness with nature in humans that cannot be felt any other way.

Beyond the emotional benefits for the individual tourist and the educational value of such close experiences with nature, tourism in the Great Barrier Reef is an excellent source of revenue for the Australian Government. Take, for example, the Environmental Maintenance Charge (EMC) that is levied on tourists visiting the Great Barrier Reef. Racking up to a modest $3.50 for tourists spending more than three hours on the Reef (Great Barrier Reef Marine Park Authority, n.d.), it is only when the total number of tourists visiting the Reef is factored in that the financial contributions of tourism on the Great Barrier Reef becomes obvious. According to the GBRMPA, more than a million people visited the Reef in 2013 alone (GBRMPA, n.d.).

However, the sheer volume of people visiting the Great Barrier Reef cannot be without consequence.
A coastal settlement on Airlie Beach. Tourists here can swim, hike through the jungles or take part in canoe trips out into the Reef.  (

With all that diving, snorkeling, boating and yachting come the challenges of keeping wildlife safe from dangers such as the slicing blades of outboard motors and collisions with boats and ships. Tourists more often than not also spend full days on the Reef, if not more, and this inevitably results in litter and human waste. One example is greywater, which is used water that has not come into contact with toilet waste, according to the Singapore’s Public Utilities Board (2014) definition. Another is bilgewater, defined by the Merriam-Webster online dictionary (n.d.) as water that collects in the bilge of the ship, its bottommost part. Such anthropogenic substances are of concern to the GBRMPA, which maintains several pages on “Responsible Reef Practices”, with one section specifically set aside to address the proper handling and disposal of these substances.

Greywater, bilgewater and other unwanted waste products will not only cause harm in the form of pollution when introduced into marine environments like the Great Barrier Reef, they also upset delicate biological processes.

A simple diagram detailing the process of eutrophication, in which algae blooms due to excess nitrogen and phosphorus compounds and thus block out sunlight, take up oxygen and foul waters. (
A simple diagram detailing the process of eutrophication, in which algae blooms (due to excess nitrogen and phosphorus compounds) block out sunlight, take up oxygen and foul waters. (

For example, certain substances can provide nutrients that rapidly accelerate eutrophication, a process that occurs in both freshwater and marine ecosystems when unusually large amounts of nutrients (such as phosphates or nitrates) are added introduced into water bodies (United States Geological Survey, 2014). According to Smith, Joye and Howarth (2006), eutrophication can lead to “dramatic changes in the composition and structure of aquatic food webs” through the explosion of populations of algae (see graphic above). Such nutrient enrichment is also partly to blame for population increases in the crown of thorns starfish (Acanthaster planci) that is widespread along the Great Barrier Reef and devours coral voraciously (GBRMPA, n.d.). This particular threat will be discussed in greater detail in a later post.

The effects of eutrophication in any body of water is sickeningly obvious. (
The effects of eutrophication in any body of water are sickeningly obvious. (

Another human activity that is detrimental to the Great Barrier Reef is coal mining. Just this year, the Australian government approved the creation of the largest coal mine in the country: the Carmichael Project. Valued at a whopping $5 billion and expected to create more than 5,000 jobs once underway, this approval will allow the Indian mining company Adani to dig up roughly 60 million tons of coal every year from Galilee Basin, Queensland, transport it to Abott Point port and ship it to India for use in coal-fired powerplants.

An aerial view of Galilee Basin in Queensland, Australia, site of the Carmichael Project. (Photograph by Andrew Quilty/Greenpeace/AAP) (
An aerial view of Galilee Basin in Queensland, Australia, site of the Carmichael Project. (Photograph by Andrew Quilty/Greenpeace/AAP) (

This multifaceted project also has a wide range of potential effects on the reef. Dredging of up to five million tons of seabed to prepare for coal carrying ships as well as the possibility of coal carriers running aground (as in the case of the Chinese-registered Shen Neng 1) are some of the more obvious effects. However, some of the longer term effects of the Carmichael project include exacerbating the existing problem of coral bleaching, a harmful process that is accelerated by climate change, fueled in part by coal-fired powerplants. As such, the Carmichael Project does not only result in far-reaching ramifications for the Great Barrier Reef, but all marine life in general as well. It does not make it any better that the Carmichael project, though facing fierce opposition from environmental advocacy groups like Greenpeace, is expected to churn out coal for sixty whole years.

Case Studies: Accidents

The saying goes that mistakes are the stepping stones to success. Correcting a mistake results in learning acts as a preventative measure of sorts against similar mistakes in the future.

Sadly, some mistakes only require a single occurrence to cause irreparable damage. This post covers two mistakes that have seriously affected the Great Barrier Reef and the creatures that reside on it.

Salvage work begins on the Shen Neng 1. (The Courier-Mail, 2012)
Salvage work begins on the Shen Neng 1. (

The first Case Study of an accident on the Great Barrier Reef is the case of the Shen Neng 1, a Chinese-registered bulk coal carrier. The massive ship ran aground on Douglas Shoal in the Great Barrier Reef on the 3rd of April, 2010, gouging out a massive 115,000 square-metre section of the reef (and doing moderate damage to other parts of the reef) before spewing its load of coal into the clear waters (Great Barrier Reef Marine Park Authority, 2011). Nine days elapsed before the stricken vessel was finally refloated on 12th April, 2010. Though the salvage efforts were valiant, they could not reverse the effects of the ship’s grounding.

As compiled in the GBRMPA’s Shen Neng 1 Grounding Impact Assessment, the damage caused by this one mistake is beyond extensive. Along with the damage caused by the ship physically running aground, chemicals were also introduced into the reef in this totally avoidable accident.

An example of such harmful chemicals is antifoulant paint from the Shen Neng’s hull. Antifoulant paints are engineered specifically to be toxic to sea life so as to prevent the attachment of such animals to the ship’s hull (known was ‘fouling’, which explains the naming for this kind of paint). This paint was scraped clean off the ship as it slammed into Douglas Shoal (GBRMPA, 2011). In addition, more than three tons of fuel from the Shen Neng 1 leaked into the waters of the Reef, coupled with roughly 5,000 litres of oil dispersant (which does not reduce the toxicity of the fuel). Fuel oil is also slow to be degraded by native marine microbes, which means that the toxicity of the oil remained long after the actual incident.

The crippled Shen Neng leaks oil. (The Courier-Mail, 2012)
The crippled Shen Neng leaks oil. (

Given the grievous physical damage to the Reef as well as the lingering toxicity from substances originating from the Shen Neng 1, this is one mistake that cannot be allowed to happen again.

The second Case Study involves a lesser known accident on the Great Barrier Reef. This time, it involved the US Marine Corps, two AV-8B Harrier jump-jets and and four bombs.

Two Harrier jump-jets of the US Marine Corps. (, n.d.)
A pair of Harrier jump-jets of the US Marine Corps. These remarkable close-support jets can takeoff and land vertically like helicopters. (

In the year 2013, as a lead-up to exercise Talisman Sabre, two Harriers on a training mission were faced with an unexpected problem: the presence of a civilian vessel in target area around Townshend Island for their training bomb drop. Unable to complete their drop and low on fuel, the pilots of the jets were forced to jettison two 500 pound GBU-12 munitions, along with two other inert dummy bombs, into the ocean. This was done as the bombs would seriously hamper the Harriers’ ability to land safely.

The GBU-12 bombs were, thankfully,  eventually recovered following their discovery by an Australian warship (the two dummies were left where they fell, since they posed no threat to the Reef and would mean risking dangerous diving conditions to retrieve). Should the GBU-12s have exploded, each 500 pound weapon, engineered to completely annihilate tanks and other armoured targets, would have had enough strength to do considerable damage to the Reef. Fortunately, unlike the Shen Neng 1, this accident did not have a chance to leave a lasting impression.

Species Spotlight: Mammals

If what the National Geographic and numerous history books state is true, it is this writer’s opinion that ancient mariners either really missed their girlfriends a lot or had the worst eyesight ever to have mistaken the dugong for mermaids.

A dugong chows down on sea grass meadows as a pilot fish follows. Dugongs are the only marine mammal that feed solely on sea grass. Photo by Barry Ingham. (The Habitata Advocate, n.d.)
A dugong chows down on sea grass meadows as a pilot fish follows. Dugongs and manatees are the only marine mammals that feed solely on sea grass. Photo by Barry Ingham. (

Classified as Vulnerable to Extinction by the IUCN Red List, Dugongs (Dugong dugon) are herbivores that graze on sea grass. Closely related to the elephant, dugongs actually do grow tusks. However, only the tusks of male dugongs ever break the skin to become visible. Dugongs also closely resemble another species of marine mammal: the manatee. One way to distinguish these two very similar-looking animals is the tail. Dugongs possess fluked tails which look much more like the tails of a whale or dolphin as compared to manatees, which have paddle-shaped tails. Herds of these creatures have been observed, sometimes numbering into the hundreds, although dugongs normally are found in mother-offspring pairs.

A Humpback Whale mother plays with its calf (Great Barrier Reef Liveaboards, n.d.)
A Humpback Whale mother plays with its calf. (

Along with dugongs, the Great Barrier Reef is host to a variety of whales and dolphins, including the humpback whale (Megaptera novaeangliae). These awe-inspiring creatures have the perhaps the largest appendages in the animal kingdom, with their flippers reaching up to five metres in length. The unique patterns on their tails can be used to identify individual whales, especially when they engage in the signature behaviour that has earned these whales their name. When diving to feed on plankton or small fish, humpback whales will dive and arch their backs (hence the name), causing their tails to surface high above the water. Returning to the surface, humpbacks may also breach, driving their 20-30 ton bodies clear out of the ocean in a spectacular display.

Another interesting aspect of humpback whale behaviour is the phenomenon of ‘escort whales’, as seen in this video here. Escort whales are male humpbacks that follow and aggressively defend any female that allows them to follow. Thought to be a form of courtship gesture, humpbacks are also known for their hauntingly beautiful whale songs.

Species Spotlight: Fish, Sharks and Rays

When the exceedingly popular animation Finding Nemo was released, it brought viewers into a world of brightly coloured fish, comparative to the varieties and hues one would see on the actual Great Barrier Reef.

A clownfish in its anemone home, as photographed by Wolcott Henry (National Geographic, n.d.)
A clownfish in its anemone home, as photographed by Wolcott Henry (

Of the close to 2,000 different species of fish on the reef, perhaps the most famous of them all is the Clown Anemonefish, Amphiprion percula. However, it is the closely-related False Anemonefish, Amphiprion occellaris, who are the stars of Finding Nemo, going on an amazing adventure through hostile waters fraught with danger. Still, perhaps what is more amazing is what happens daily on the great barrier reef on what has come to be known as ‘cleaning stations’.

What seems like a dangerous job for this small cleaner wrasse is actually a common occurrence on many reefs, where predators like this White Tip Reef Shark literally 'park' on the seafloor to be cleaned. (PBase, 1980)
What seems like a dangerous job for this small cleaner wrasse (the yellow fish just below and to the right of  the shark’s dorsal fin) is actually a common occurrence on many reefs, where predators like this White Tip Reef Shark literally ‘park’ on the seafloor to be cleaned. (

Cleaning stations, prevalent in the Great Barrier Reef and in other reefs around the world, are sites where Cleaner Wrasse (Labroides dimidiatus) and other species of similar wrasse attend to clients of all shapes and sizes who gather for cleaning. Like something out of a scene from yet another animated film about underwater life, cleaning stations are reminiscent of the underwater ‘whale wash’ of Shark Tale, minus the music and not exclusive to whales. Here, all predatory instincts are thrown aside as sharks, rays and all manner of fish arrive to be cleaned by the wrasse. In this mutually beneficial symbiotic relationship (explained in this YouTube video), the fish are cleaned of parasites by the wrasse, who consume these parasites as food.

Continuing with the somehow inevitable links to film, another famous (or perhaps infamous) example of biodiversity on the Great Barrier Reef are the many different kinds of sharks (more than 300 species reside on the Reef, according to Diving Cairns, a dive trip operator located that makes frequent trips to the Great Barrier Reef). Though it is highly likely that none of these sharks will ever attack a boat full of fishermen (or, maybe they will), their reputation undoubtedly precedes them. Ranging from the elusive Reef Sharks (such as the White Tip Reef Shark pictured above) to the dangerous yet strangely alluring Great White Shark (Carcharodon carcharias) of Jaws fame, captured here by a diver on the Great Barrier Reef, sharks never cease to enthrall and intrigue.

A ray photographed by the author at the Melbourne Sea Life Aquarium.
A ray photographed by the author at the Melbourne Sea Life Aquarium.

Closely related to sharks are rays. These encompass the stingray, a specimen of which was involved in the tragic death of Australian icon Steve Irwin, and the majestic Giant Manta Ray (Manta birostris). Capable of growing to a massive seven metres from wingtip to wingtip, Manta rays are only just beginning to be understood by science. One of the two species of Manta rays identified, the Giant Manta is pelagic, meaning that they often cross oceans in extended trips of incredible distances. This nature makes them hard to monitor as an IUCN Red List Vulnerable species. However, their popularity with divers, given their docile nature (and the fact that they seem pretty OK with being approached, as seen in this video) is seen as encouraging in helping to preserve this awesome creature from extinction.

Species Spotlight: Coral

Forming the backbone of the reefs all around the world are the rainbow-coloured, plant-like creatures known as coral. Coming in all shapes and sizes, with every imaginable colour in between, corals are essential to the continued existence of any reef, and these remarkable creatures, closely related to jellyfish and anemones, start their lives in an equally remarkable way.

In this video (BlueWorldTV, 2013), underwater photographer Jonathan Bird manages to record the systematic release of coral reproductive material at night. With military precision, huge batches of eggs and sperm are released all at once into the seawater. These massed releases are a part of a survival strategy, where safety in numbers increases the chances of one of the gamete bundles, as Bird calls them, will progenate the next generation of coral.

Once fertilised, the gamete bundles settle on the seafloor. Now called polyps, the individual cells form colonies, using limestone to create skeletons to support themselves or as a means of defense by shaping them into sharpened spines known as spicules. Colonies grow when their constituent polyps undergo cell division, and colonies that meet merge to form even larger colonies. Each polyp, though sometimes possessing its own brightly coloured tissue, can also take on colours from algae (known as zooxanthellae) that they host within their bodies. These algae provide nutrients for the polyp, although there are also coral species that feed on plankton and even small fish.

Spicules of various species of coral, photographed by scientists under a scanning electron microscope. (Wikipedia, 2012) (Click to Enlarge)
Spicules of various species of coral, photographed by scientists under a scanning electron microscope. (

Coral are basically split into two distinct types: soft coral and hard coral. Soft corals are the fashioniastas of the reef, with vibrant colours of pinks and oranges. Besides their spicules, soft coral lack a proper skeleton and are thus gelatinous, swaying in the ocean currents while their polyps wave their tiny, feathery tentacles in the water. Given their soft texture, soft corals are easy targets for predators, but they will not go down without a fight. Certain species of soft corals secrete foul-tasting chemicals or poisons while others resort to spiny spicules as defense mechanisms.

Red Sea Fingers coral, Alcyonium glomeratum. (Kenmare Bay Diving, 2010) (Click to Enlarge)
Red Sea Fingers coral, Alcyonium glomeratum. (

Hard coral, on the other hand, are slightly different. These types of coral create hardened limestone skeletons for themselves, eventually forming colonies of millions of individual polyps. Unlike their soft coral cousins, which can double or even triple the size of their colonies annually, hard coral generally manage a modest one to one-and-a-half centimetres of growth per year. They are the true building blocks of the reef and, given time, can reach truly massive sizes.

Photographer Dano Pendygrasse photographs's Ian Drysdale inspecting a bed of Staghorn hard corals. (Pendygrasse, n.d.) (Click to Enlarge)
Photographer Dano Pendygrasse photographs’s Ian Drysdale inspecting a bed of Staghorn hard corals. (

Both types of coral are fundamental to a substantial portion of the world’s marine biodiversity. Although covering less than one percent of the world’s seafloor, coral reefs support around one quarter of all the world’s marine species.

Diving In: A Brief Look

The first time I came to know about the Great Barrier Reef was through, of all things, a video game.

It was the first game in a series of games featuring the namesake character, Ty the Tasmanian Tiger. Developed by Krome Studios, the very first Ty the Tasmanian Tiger game had a series of levels set in the Great Barrier Reef. These levels were bursting with colour, and as a first-time gamer, I was enthralled by the multitudes of rainbow-coloured fish that swam in schools everywhere I looked. I was thrilled by the coral and the clear waters (although I was much less thrilled by the inexplicably hostile sharks, homing sea mines and oversized groupers, all of which were out to get me).

That was the closest that I would ever get to the Great Barrier reef. That is, until today.

In 2012, a group of scientists began a daring endeavour. Starting from the Great Barrier Reef, the Catlin Seaview Survey, sought to and succeeded in surveying “150km of reef… with [the] SVII Camera, and now 105,000, GPS located, panoramic images are currently being analysed by marine scientists around the globe” (Catlin Seaview Survey, n.d.). Several publicly available images from the survey have been compiled below. (Click on the images for a better look.)

“To scientifically record the world’s coral reefs and reveal them to all in high-resolution, 360-degree panoramic vision.”

– The Mission of the Catlin Seaview Survey –

Working in concert with technology giant Google, the Catlin Seaview Survey was able to bring interactive ‘virtual dives’ to everyone with a working internet connection. Such dives can be accessed on Google Views, as well as the Catlin Seaview Survey site itself. It goes without saying that these virtual dives beat an early 2000’s video game rendering of the Great Barrier Reef by several lightyears.

Still, nothing can quite best the actual experience itself.

According to the Australian Government’s Great Barrier Reef Marine Park Authority (GBRMPA), there were more than one million full-day tourist visits to the Great Barrier Reef from the years 2012 to 2013 (GBRMPA). Note that this figure does not take into account other kinds of trips, such as trips that last less than one day. To accommodate such a massive number of visitors and keep them entertained, facilities such as underwater observatories have been constructed to compliment existing activities such as diving and snorkeling.

But the Great Barrier Reef is much more than just a tourist attraction: it is home to 1,800 species of fish (National Geographic, 2011), along with 134 species of sharks and rays, one third of all the soft corals in the entire world and six of seven endangered turtle species spread out over 2,900 individual reefs. And we’re not even counting the other species of marine mammals (like the dugong), molluscs, starfish and crustaceans (WWF Australia, n.d.).

Beyond being a home for wildlife, the Great Barrier Reef is also inextricably connected to aboriginal people groups who have inhabited its many islands for over 60,000 years. In fact, for these Aboriginal and Torres Strait Islander people, the Reef is more than just a home. Their cultures have long used the reef as a means of survival, for practicing their religion and to further their unique traditions (GBRMPA, 2004).

Torres Islander
Modern Aboriginal and Torres Strait Islander people in Glenelg Shire, Australia (

It isn’t hard to see just how captivating this place is. To put things into perspective, the Great Barrier Reef was so captivating that, even through a video game which barely did justice to its immense natural beauty, it managed to become part of a 10-year-old Singaporean child’s imagination which, until today, still lingers.

Sadly, though memory may remain, the Great Barrier Reef might not.

Going back to the virtual dives I took that were made possible by the Catlin Seaview Survey’s work, I was stunned by the sheer lack of colour. This was not the Great Barrier Reef my video game had promised me, where colour was perhaps the only word that could singly and fully describe its beauty. This Reef was dying, its coral lay strewn about, like bones that had been picked clean by animals, across a lifeless seabed quite devoid of fish. If this trend occurs across all 2,300 kilometres of the Great Barrier Reef, an unprecedented number of marine species will go extinct.

Dead Coral, Lady Elliot Island. (Click to enlarge)
Dead Coral, Lady Elliot Island. (

Extinction is forever. And forever is an unacceptably long time. For us, time is running out, and if we let it slip through our fingers, perhaps the only way we will ever get to see the Reef again, in paltry, sorely lacking fractions of its former glory,  is through video games.