Sailing the Lower Midnight… – The Uncharted Frontier of Modern Deep-Sea Exploration

A photograph of the not-so-friendly, and frankly scary-looking, footballfish, a deep sea-predator from the anglerfish family.What lies 5,000 metres Below Sea Level?

It’s cold down there.  Icy cold.  It’s dark.  Pitch black, in fact.  And the crushing pressures make the deepest parts of the oceans into some of the most hostile places on our planet.  The lowest of the low.  The deepest of the deep.  Only three human explorers ever made it down there.  As a brand new wave of deep-sea exploration begins, we look at the mysterious world where marine scientists will be diving into…

 

A geographical map showing the location of the Anton Dohrn sea mount and a computer 3D relief model showing its underwater elevation off the coast of Scotland.
The Anton Dohrn seamount is is an isolated underwater volcanic guyot, located in the northeast Atlantic Ocean, about 200 kilometres off the west coast of Scotland, which was discovered in the late 1950s.

Deep-Sea Exploration

Scientists have used robotic submersibles to dive more than 2,000 metres beneath sea level and explore four sea mounts, just off the west coast of Scotland.  The amazing footage revealed the vast coral reefs, and an array of crustaceans and fish living in the cold, dark waters.  And many of the species they found are believed to new to science.

The Deep Links project team is a collaboration between Plymouth University, the University of Oxford, the Joint Nature Conservation Committee and the British Geological Survey.  The team spent six weeks at sea onboard the RSS James Cook.

Of the four underwater mountains they explored, the biggest is the Anton Dohrn.  At 1,700 metres tall, the Anton Dohrn seamount would dwarf Ben Nevis, which peaks at an altitude of 1,344 metres above sea level.  And yet, the Anton Dohrn is totally submerged.

The Anton Dohrn is thought to be between 40 and 70 million years old.

Scientists say until now these unique habitats have been little explored.

 

Sailing Down to the Lower Midnight

We take a dive down to the deepest of ocean waters…

An infographic diagram comparing the altitudes of some of the highest mountains on Earth, with the depths of the Mariana Trench.
Comparing the Altitude of the Highest Mountains with the Deepest Ocean Regions  Source: Deepseachallenge.com

Sunlight Zone

Down to 200 metres, this is the Sunlight or Epipelagic zone. Most oceanic life happens here, in the warmer surface waters, where it’s a balmy 12 to 20°C.

DEPTH 0 metre.
PRESSURE 1 atmosphere.

PRESSURE EQUAL TO 1 kilogram on your fingernail.

This zone is exposed to the surface, and receives enough light for photosynthesis to occur.

 

The Twilight Zone – Yes, it’s Real!

Between 200 and 1,000 metres down. With depth, sunlight fades to pitch-darkness and temperatures plunge. It can be around 13°C down to just 4°C.  This is the Twilight or Mesopelagic zone.

DEPTH 888 metres.
PRESSURE 89 atmospheres.

PRESSURE EQUAL TO 89 kilograms on a single fingernail.

Photosynthesis is stunted here, due to insufficient light penetration.  At about 500 metres, oxygen is greatly depleted.

 

A diagram showing the Pelagic and Benthic divisions of the Earth's oceans.
Source: The Oceans.Weebly.com

Midnight Zone

Down 1,000 to 4,000 metres.  Midnight or the Bathypelagic zone.  Feels like 4°C.  Bioluminescence produced by the animals here is the only light.

DEPTH 3,953 metres.
PRESSURE 393 atmospheres.

PRESSURE EQUAL TO 393 kilograms on a single fingernail.

At this point, the ocean is pitch black, and many organisms have adapted by becoming bioluminescent.  Many animals here survive on a substance called “marine snow” – a combination of dead or dying organisms, protists, fecal matter, and other inorganic silt (sand, rock, etc.)

 

The Lower Midnight

We have reached the Lower Midnight.  Between 4,000 and 6,000 metres.  It’s nearly freezing here.  This is the Lower Midnight or Abyssal zone.  Most of the ocean floor is found within this range.

DEPTH 5,996 metres.
PRESSURE 595 atmospheres.

PRESSURE EQUAL TO 595 kilograms on a single fingernail.

Few creatures manage to survive the extremely cold waters, and the complete lack of light.

 

The Trenches

We have reached the Trenches or Hadal zone.  6,000 metres plus.  Temperature is just above freezing.  Food is scarce, but new life is still found in this harshest of harsh environment.

DEPTH 8,294 metres.
PRESSURE 823 atmospheres.

PRESSURE EQUAL TO 823 kilograms on a single fingernail!!

This zone is truly abyssal, and almost completely unexplored by humans. It’s name was derived from Hades, the underworld in greek mythology.

 

A computer-generated bathymetric model showing the complex relief of the Mariana Trench.
The Bathymetric Model of the Mariana Trench  Source: NOAA.gov

11,000 Metres Down…

Stretching for more than 2,500 kilometres (1,500 miles), the Mariana Trench is a very narrow, very deep crack in the ocean floor.  At its deepest, it reaches nearly 11 km (seven miles) down – it is the lowest point in our oceans.

There are more than 20 trenches like the Mariana around the World.  Most are in the Pacific Ocean.  The Mariana Trench is at the juncture where two of the Earth’s tectonic plates are grinding together.

Marine geologists have spent the past five years creating the most detailed survey of the Mariana Trench to-date.  They believe that finding out more about the inner workings of these deep-sea spots is vital, as theories have suggested that they are at the root of the biggest major earthquakes.  The trenches are formed at the boundary of two tectonic plates, where very heavy oceanic crust (in the case of the Mariana Trench, the Pacific Plate) dives underneath lighter continental plate – a process called subduction.

But geologists now think these seismically active zones could play a central role in some earthquakes.

 

A photograph showing just one of the many unfamiliar lifeforms who populate the depth of the oceans: a carnivorous sponge named Chondrocladia lampadiglobus.
Chondrocladia lampadiglobus (or “Ping Pong Tree” Sponge) is a carnivorous demosponge that lives between 2,600 and 3,000 metres deep.  Source: MBARI.org

Exotic Ocean Creatures

The deep sea is the largest ecosystem on Earth.  A certain number of species have been identified, but little is known about their lifestyle.

The Deep Links team found brightly coloured cold-water coral reefs, stretching for many kilometres.  Some of the species were several metres high, while others were thought to be thousands of years old.

They discovered huge sponge gardens crammed with tiny animals, crustaceans, including deep-sea crabs and shrimps, basket stars, sea anemones, and many fish species, including lepidions and chimaeras, which are related to sharks.

On our way there, we might even meet one of these guys (top image)!  Thankfully, the chances are…  It’s so dark down there, you wouldn’t see it coming!

Or… would you?

The Footballfish is a congenial-looking creature that strives in the tropical and subtropical waters of the Atlantic, Indian and Pacific Oceans, at depths of 1,000 metres.

As with other deep-sea anglerfish families, the sexual dimorphism is extreme: the largest globose-shaped females may exceed lengths of 60 centimetres (two feet), whereas adult males do not generally exceed 4 cm (1.5 inches).

A drawing illustration of the spooky scary deep-sea footballfish creature by Swiftheart Studios.
Spooky Scary Footballfish by Swiftheartstudios Source: DeviantArt

Their poor musculature and cumbersome morphology indicate that mature female footballfish are probably poor swimmers and thus largely sedentary, lie-in-wait predators, living in open water, with very few caught below 1,000 m (3,280 feet).

The female football fish are carnivorous and they feed upon other pelagic fish and cephalopods, as well as shrimps and euphausiids, presumably attracted to within striking distance by the footballfish’ luminous lure…  BOOH-YAH!!

 

A 1960s black and white photograph of deep-sea pioneering explorers Piccard and Walsh inside the bathyscaphe Trieste.
Jacques Piccard and Don Walsh on board Trieste, descended to the lowest point in the Pacific ocean in 1960. Source: USN

Race to the Bottom of the Oceans

Only three explorers ever made the epic submarine journey down to the deep Mariana Trench at the bottom of the Pacific Ocean.

On 23rd January 1960, Swiss and American oceanographers Jacques Piccard and United States Navy Lt. Don Walsh made deep-sea exploration history when they reached a record depth of 10,911 metres (35,798 feet) below sea-level aboard the Trieste bathyscaphe.

… and James Cameron – the famous Hollywood director – became the first person in 50 years to make the journey to the deepest place on the planet on 26 March 2012. 

Deep sea research has important implications for the sustainable management of the marine environment.  As humans become increasingly reliant on the marine environment to supply food, building materials, fuel, and soak up carbon in order to slow the progress of human-induced climate change, our increasing use of this environment is starting to affect its ‘normal’ functioning, and the very processes that allow it to provide us with food or fuel.

This research will help address environmental questions of the deep sea, and should help governments and society to ensure the long-term health of the oceans.