Illustration: Rebecca Kelly
The deep sea is the last unexplored place on earth. Ellen Nugent takes the plunge.
A LITTLE under 150 years ago, the HMS Challenger set out on a voyage that would set in motion a time of global deep-sea discovery. This expedition gathered evidence of life in the deepest ocean regions, and research continues today in order to fully understand the biodiversity and adaptions of deep-sea life. The deep sea begins 200 metres below the surface of the ocean. Extending to depths of over 10,000 metres in areas such as the Mariana Trench, the deep sea forms the largest environment on earth.
This domain is immense, but what has prompted the flood of research into its depths since the Challenger’s travels? The deep sea contains numerous unique habitats and life forms, providing an unparalleled opportunity for research and use of deep-sea resources. The use of deep-water fishing has become more widespread with the improvement of fishing technology, allowing us to compensate for declines in shallow-water fish populations.
“Scientists don’t yet fully understand the adaptions of deep-sea creatures that allow them to withstand such pressure”
The deep sea also contains valuable mineral deposits: mining operations are in place to supply metals such as nickel, copper and cobalt, which are required in developing countries. Deep-sea oil and gas reserves would contribute to the global fossil fuel demand: frozen methane, a potential energy source, is present in the deep sea in vast quantities. It’s clear from these few examples alone that deep-sea resources pose countless advantages to human activity. This is not including the scientific research into the unique geological structures, or biological and chemical features of deep-sea life and environments.
For every 10 metres we descend below the ocean surface, pressure increases by 14.5 pounds per square inch (psi). At its most shallow, life in the deep sea must survive the crushing weight of 290 psi. In the Mariana Trench, life exists despite the crippling stress of more than 15,000 psi. Creatures in the deepest reaches of the ocean have somehow adapted to survive, and flourish, in these unimaginable conditions.
“Hydrothermal vents provide valuable minerals used by humans and aquatic creatures alike”
Scientists don’t yet fully understand the adaptions of deep-sea creatures that allow them to withstand such pressure. It is thought that chemical stabilizers in the cells of these creatures prevent high pressure from affecting their body structure, such as trimethylamine oxide – which is also responsible for the distinctive smell of fish. Research into this phenomenon is laborious, as it is difficult to replicate high-pressure environments in which to study samples from the deep sea.
An incredible ability to withstand pressure is only one of the interesting adaptions of deep-sea life. Hydrothermal vents provide valuable minerals used by humans and aquatic creatures alike, but these vents can reach temperatures of 400°C – just right for certain species of shrimp. Elsewhere, deep-sea life survives at 0-3°C, in depths untouched by light.
The biological processes that allow life to thrive in such dark conditions are also fascinating. Deep-sea creatures produce bioluminescence from light-producing ‘photophores’. Species such as aquatic worms and squids release glowing particles to attract a mate, and certain fish species use their photophores to eradicate their silhouettes, hiding them from predators.
Fish such as the anglerfish, also use their bioluminescence to light a small, flesh ‘lantern’ before them, attracting prey in the dark abysses of the deepest seas. We’ve only scratched the surface of the many amazing features of undersea life – glowing sharks hunt near sea squirts concealing cancer-killing bacteria, while miniscule plankton float in total darkness, serene in one of the least inhabitable conditions on earth.
The deep sea, and all its wonderful (and often incredibly hideous) inhabitants are in danger, however. You’ve heard all the dangers of climate change to our oceans mentioned before, and the dangers posed by increasing oceanic temperatures and acidity. It should be mentioned, however, that the current decrease in deep-sea oxygen due to climate change would do serious damage to the amazing creatures mentioned above. Very few of them would benefit from a decrease in oxygen, and those species that thrive would be mostly jellyfish.
“Glowing sharks hunt near sea squirts concealing cancer-killing bacteria, while miniscule plankton float in total darkness, serene in one of the least inhabitable conditions on earth”
Humans tend to leave a trail of destruction behind wherever they go, and our forays into the deep sea are no exception. We have over-fished our surface waters to such an extent that we must harvest the fish of the deep sea – how long will it be until we have plundered its depths of all it has to offer? Fish stocks, valuable substances, even scientific samples – we steal from the deep ocean without restraint, often using destructive and wasteful techniques. Humans have so many inventive ways of polluting the deep sea, including the millions of tonnes of waste we dump into the ocean every year.
What can we do to remedy the problem? Is it already too late? The deep sea has so much potential for scientific discovery and research, and so many resources that we can make use of. It’s been established that humankind isn’t very careful about how it gets these resources, but perhaps there is the opportunity to make use of different technologies? There is opportunity for restoration in certain areas: deep-sea fish stocks will increase over time if overfishing is prevented, but resources such as valuable minerals were formed over many thousands of years.
Efforts to repair the damage we have already done will be costly, and will likely be slow and face much resistance. It is important that efforts to protect and repair deep-sea environments are supported and understood. We must also continue our fight against climate change, and humankind’s neglectful attitude towards the world we live in, on a local and global scale. If nothing else, do it for a future where the deep sea is more than an exclusive jellyfish club.