The Stages of Whale-Fall Ecosystems.
For the most part, the nutrients found in the depths are supplied by a steady steam of organic debris falling down from shallower waters. It's not much, but it tends to be enough to sustain the sparse and barren depths. But every now and then, something much larger sinks to the seabed. It draws life from miles around to gather for a feast to last for decades. It is known as a whale-fall.
Whale-fall ecosystems support an abundance of life in waves of successive communities. The carrion of the whale is first stripped of all its flesh by larger scavengers, like Greenland sharks. Once all the flesh is gone, and any debris in the sediment has been hoovered up by opportunists like ghost sharks, bacteria break down the bone lipids to produce energy that supports an ecosystem of life around the carcass.
It is thought that whale-falls may have been the crucial stepping stone that allowed deep-sea species to colonise the sea floor.
Occasionally, a whale carcass will sink to the seabed, and can support a complex biological community for up to 50 years.
Most nutrients in the deep sea are supplied by a steady stream of organic debris, known as marine snow.
Mobile scavenger stage
Lasts 4 months - 2 years
When the carcass comes to rest on the sea floor, the first organisms to arrive at the scene are 'mobile scavengers' - these are the larger ocean wanderers, including hagfishes and gigantic sleeper sharks. Whale-falls attract such an abundance of life because their nutrient content is equivalent to 2,000 years worth of marine snow, providing a rich supply of nutrients concentrated in one small area.
The flesh and soft tissue can support this community of scavengers for up to 2 years. After that time, all that's left are bones, and chunks of organic material buried in the sediment.
The hagfish makes use of four pairs of thin sensory tentacles around their mouths in order to seek out the whale carcass. Once there, they use two rows of sharp tooth-like structures to burrow down into the carcass. They are also able to tear off chunks and deliberately tie their long tails into knots. This increases the force of their bites by creating torque.
Lasts around 2 years
In this 2nd phase of the whale-fall community, mollusks, worms and crustaceans feed on any blubber that remains. As whale-falls are so rare, nothing goes to waste, so the opportunists will spend 2 years burrowing into the surrounding sediment in search of leftovers.
Commonly called the zombie worm or bone-eating worm, this variety of polychaete worm bores away at the bones of the whale carcass. It does so in order to reach the lipids that are sealed away within the bones. Osedax worms rely on these lipids for nutrients. They were first discovered at a whale-fall site in 2002, inhabiting the bones of a decomposition gray whale on the sea floor nearly 10,000 feet (3,000m) deep.
Lasts 10 - 50 years or more
The final stage can last for decades. Only the bones remain. At first look, you might think it impossible for any substantial community of organisms to thrive from bare bones sitting on the sea floor. However, the ecological diversity of species found during the sulfophilic stage is greater than any other deep sea community.
The sulfophilic stage gets its name from the process of chemosynthesis, during which specialised bacteria break down the lipids present in the bones to produce sulphides.
The presence of sulphides allows other organisms to thrive here, including dense mats of bacteria, mussels and tube worms. More than 30,000 organisms can sometimes be found on a single skeleton.
Life at Cold Seeps
Cold seeps are areas of the ocean floor where hydrogen sulphide, methane, and other hydrocarbon-rich seepage occurs. Through a number of process, the chemicals support a biome of highly specialised creatures that live around these cold seeps.
The Open Ocean
The open ocean is an entirely different world to the benthic zone of the sea floor. The endless blue stretches away in all directions, while the black abyss hangs gaping below. Currents are stronger here. There is no shelter to be found, and food is hard to come by.
The Deep Sea Floor
Deep sea life must choose whether to live on the bottom at the benthic zone, or to brave the expansive open ocean of the pelagic midwater zone. These two groups of organisms could not be more different, but which is a more effective way of life?
Deep Sea Coral Reefs represent areas of astounding biodiversity. Lush cold water coral and sponge gardens thrive in the icy waters. An expanse of colourful coral structures blooming out of the sea floor, providing important habitats for deep-dwelling life.
Deep Sea Food Web
The exact nature of the deep sea food web is still not fully understood, but advancements in technology and research in recent years have granted us a greater understanding of how these separate settlements of life are interconnected as one. Let’s take a closer look at the food web of the deep sea.
Deep Sea Zones
Experience what it's like to delve down in a submersible into the deep sea. Scroll down to dive gradually deeper through the successive zones of the ocean.
Deep Sea Symbiosis
Nowhere on Earth are creatures more uniquely adapted to relying on others than in the deep sea - a world of darkness, cold, and intense pressure. Let’s dive in, and take a closer look at the incredible role of symbiosis in the deep sea ecosystem.
Bioluminescence in the deep sea is a natural phenomenon present in many deep dwelling species. The twinkling, flashing, pulsating lights are the result of a chemical reaction that produces light energy within the body of an organism.
Plastic in the Ocean
The main threats seen in our oceans are species loss, habitat degradation, and changes in ecosystem function. Human activities causing a rise in extinction rates has lead to a decrease in biodiversity, particularly in coral reefs, 88% of which are threatened by excessive CO2 emissions.
Brine Pools in the deep sea appear to be biological dead-zones in the ocean, and yet an astounding abundance of ocean life can be found lining the shores of these toxic lakes. Mussels, hagfish, crabs and even sharks frequent these isolated hotspots to hunt.
Occasionally, a whale carcass will sink to the seabed, where it will support a complex biological community for up to 50 years. Deep sea creatures gather here to make the most of the concentrated store of nutrients, from giant sharks to tiny but fascinating bacteria.
In the deep sea, no energy is produced by photosynthesis. Instead, chemosynthetic bacteria have adapted to convert the chemicals expelled by deep sea vents into the energy needed for life to flourish.