It’s the mystery of whale sharks that makes them remarkable. How can an animal so big be among the least-known on Earth? The fact is, we have no idea how important they really are and we probably never will. For the Samu-Bajau, sea people of far southeast Asia, they have always known. For the rest of humanity, we need to learn quickly, or else we jeopardise our own survival. But this means thinking differently. We need to understand the importance of what, at first glance, seems like unexceptional behaviour on their part.
Conveyors of ecosystem energy
The size, demeanour and behaviour of whale sharks in a three-dimensional and nutrient-poor world, means they have a disproportionate impact on our lives. Like manta rays and blue whales, they transfer(of nutrients) the thing that sets animals apart from plants, is that they can move. Some of the biggest migrations on Earth every day, are the movement of insects like caterpillars, from the stem of a plant to a leaf and back, before turning into butterflies and transferring the energy elsewhere. Large-scale migration of grazing animals and migratory songbirds moves More, amplify and concentrate nutrientsEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More. The intensity and precision by which they do this, we cannot begin to estimate. They do it in specific places, as they have done practically forever. Like all animals, they are a barometer for climate. Their sustained presence and actions soften weather extremes and make even local areas, a better overall climate for living.
The intensely nutrient-poor waters in parts of eastern Indonesia would remain so, if it weren’t for whale sharks. Because of their size and mobility, they can reach places where the sun’s energy is captured fastest by marine algae (plants). By consuming vast quantities of the extraordinarily energy-rich prey that feeds on the algae they help kick-start amplificationAmplification (of nutrients and energy). Animals consume plants and other animals and in doing so, reintroduce important energy-containing nutrients back into the environment, at even higher concentrations and in patches. Amplification of energy is driven by migration and happens at every scale, from insects moving daily in and out of your vegetable patch, to African wildebeest herds and the seasonal More ecology (when lots more animals pile on). Then throughout the season, they continuously recycle and maintain those processes. They produce vast amounts of waste, which enables congregations of other animals to find benefit.
Food producers & climate regulators
These processes, when scaled up to about 150,000 whale sharks in the Indo-Pacific (maybe as many as half a million globally before declines) have consequences for our climate too. When carbon is trapped by ocean algae it risks release into the atmosphere. Where we really need it, is inside food chains. The seasonal amplification of food systems by animals is what ecosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More are all about. With the Sun’s energy locked inside those processes, it is exactly where we need it. This is how balance was maintained for millions of years. It led to the rise of humans, by providing us with food. Stable climate is a byproduct of healthy ecosystems.
Climate management, therefore, isn’t just about removing carbon. Neither is it simply about eating fish or not eating fish. It’s about making sure carbon is where it needs to be, to feed stable ecosystems.
But the scale of impact from whale sharks isn’t just in immediate time and place. It’s even greater, when you consider it’s been going on for hundreds of millions of years. Long before human civilisation, whale sharks were laying the foundations for our evolution. Maintaining evolutionary processes is, according to some school of thought, the only unifying definition of restoration or ‘rewilding.’ This is why.
Today, whale sharks matter every bit as much they did back then. But the customary beliefs of people like the Sama-Bajau, that we avoid harm by protecting them, are more important now than ever before. Because today, whole nations depend on protecting whale sharks to help rebuild lost ocean ecosystem integrity.
A rare insight in Saleh Bay
We cruised overnight for about 50 miles into Saleh Bay on the island of West Nusa Tenggara in Indonesia. This 2,000 km2 bay is separated from the Flores Sea by two narrow channels about 30m deep. It may be one of the few places in eastern Indonesia with resident populations of Whale Sharks [1]. The bay itself is 200-300m deep in places and is like an inland sea. It gathers nutrients from the surrounding volcano sides, turning green and growing full of planktonA soup of micro-organisms. Usually refers to all the zooplankton and algae in the ocean but can also be used to describe tiny insects in the atmosphere (see aerial plankton). More.
Vertical migration
Whale sharks forage almost continuously, though they are suspected to feed for about 8-hours a day. They come to the surface at night and dive deeper during the day. In the morning in Saleh Bay you can see bright blue sapphire copepods near the surface. Crystal structures in their bodies reflect blue light, which the whale sharks are adapted to see. They disappear by about 11am. We are glimpsing the top of a band of plankton from the ocean’s middle layers that oscillates up and down each day like a pendulum.
“The largest living space on Earth is the mid-water zone and of all places on the planet, is the least explored”
Dr Rob Ballard, Woods Hole Oceanographic Institute
The ecology of Saleh Bay
Saleh Bay covers 2,000 km2 and has two narrow entrances on its northwest corner. The clue to its importance is in its geography. Being oriented northwest to southeast, it runs parallel to the monsoon trade winds. These blow in opposite directions in the wet and dry seasons.
Salinity is between 28.2 to 28.4 ppt[4], comparatively low compared to open ocean. This lower than average salinity is the result of rainfall with about 60 inches falling in the northwest monsoon between November and April. During this rainy season, nutrients are introduced from the river catchments, which remain inside the bay. This promotes substantial growth of algae which feeds plankton. This sets up conditions for whale sharks which feed on abundant copepods (plankton).
The monsoon variable
This oceanographyThe study of the physical, chemical and biological properties of the ocean. More is reflected in the different distribution of Whale Sharks. It’s this ability of animals to respond and move according to physical changes in our environment that makes them important. They precisely respond to surplus energy and stop systems like Saleh Bay becoming choked with algae. They do this by promoting more plankton growth, while keeping plankton in balance too.
In the southeast monsoon, the winds push surface water west and this sets up a circulation that generates upwelling in the east of the bay. The whale sharks would feed nearer the surface at this time.
During the northwest monsoon, the winds are reversed. Nutrient-poor water from the Flores Sea enters the Bay. River water flows over the top which limits nutrientA substance that contains the raw materials for life. At a chemical level, these are contained inside compounds that are absorbed into the body and essential energy-containing molecules are extracted, so that energy can be transformed into other chemical processes that use the energy for living. More mixing until the wind calms during the doldrum period. Meanwhile, nutrients from the dry season are pushed further downwards, settling nearer the centre of the bay.
The scale, intensity and magnitude of whale sharks’ impact on Saleh Bay
An average 6m whale shark filters 2.8 kg of plankton per hour for 8 hours a day from 600 cubic metres of water per hour (Shark Institute).
At last count, 99 individual whale sharks had been recorded in Saleh Bay. Let’s assume there are 200 whale sharks in total. These animals are filtering 328.5 million cubic metres of seawater annually. This is a staggering 0.15% of the entire volume of Saleh Bay.
This might not sound much but then we’re land-dwellers. We think in two-dimensions where our impact is on most of the land surface. The ocean has a lot of relatively empty space. A large like a whale shark is a massive influence because of its ability to move and consume in a precise manner. They are the top of the pyramid. They help keep the ecosystem in good condition and enable the survival of its local human population.
Ecosystems are regulated from the top down but throughout the food chainA single thread in a food web illustrating the chain of animals that eat each other. At the base of the food chain are small high-energy (fast metabolism) animals and at the other end large low metabolism animals. An example would be whales eating krill that eat plankton that eat algae. Or lions that eat gazelles that eat grass. More [3]. This makes Whale Shark incredibly important for fisheries. The sum total maintains the entire system’s balance. The contribution of hundreds of thousands of whale sharks in our oceans plankton hotspots is essential. Without filter-feeding and other predatory animals, we end up with the risk of algae-ridden dead-zones, such as the sargassum sea.
A call to action for conservation scientists
If we don’t answer the question: ‘why do whale sharks matter?’ we risk devaluing the status and importance of this incredible life-supporting animal. It means revisiting the way we do research. We have to start asking new questions and interpreting answers in the context of whale sharks’ impact on our lives.
Humans have long had a connection to wildlife. People and animals living together was the basis for human civilisation to evolve. Spiritual traditions that protect nature are just as complex as ecosystems. Those cultures are the human embodiment of why protecting animals mattered in the first place.
Today we covet natural science too much at the expense of natural philosophyNatural philosophy concerns itself with the question of 'why' things work [1]. Natural science tries to work out 'how' [1]. Understanding the difference is fundamental to conservation but is largely missing . Natural philosophy has more in kin with ecological wisdom, such as the beliefs, cultures and traditions of first nations peoples all over the world. It embraces an understanding More.
Most people would imagine that the question about why whale sharks matter would be fundamentally important to conservation. But it remains largely unconsidered today. Answering this, surely, would help persuade people to make wise decisions about our use of the marine environment? If we pre-empted research with more of this understanding, we’d make more sense of why we are doing conservation in the first place. It will make us all better custodians and able to justify why we must protect all animals.
Read more in my Atlas of Marine Values of Eastern Indonesia
References
- Farid, M., et al., Evidence of residential area of whale sharks in Saleh Bay, West Nusa Tenggara. IOP Conference Series: Earth and Environmental Science, 2021. 744: p. 012018.
- Asrial, E., et al., Biology and blooms of the edible jellyfish (Crambione mastigophora) in the Saleh Bay, Indonesia. 2015: JBES. p. 356-369.
- Myers, R., et al., Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean. Science (New York, N.Y.), 2007. 315: p. 1846 – 50.
