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Featured Picture: Staff scientist Samuel Georgian takes a turn piloting the ROV Beagle (Marine Applied Research and Exploration) during an expedition off the coast of California.

The Last Frontier

“There is, one knows not what sweet mystery about this sea, whose gently awful stirrings seem to speak of some hidden soul beneath…”

            -Herman Melville (Moby-Dick)

The deep sea is the largest environment on the planet, yet remains almost completely unexplored. Hundreds of years ago, scientists weren’t even sure that it was possible for life to exist in the dark and cold depths of the ocean. As it turns out, the deep-sea is teeming with an astonishing variety of life, much of it very different and bizarre compared with shallower habitats. With the advent of new technology, the past fifty years have seen an incredible awakening of interest – and amazing discoveries – in the deep sea. For many scientists, it is the ‘sweet mystery’ of the unknown that makes the deep sea such a strong siren call.

Why Explore the Deep Sea?

While scientists often become deep-sea explorers out of a sense of curiosity and wonder, there are also practical reasons to explore this remote and inhospitable world. Life in the deep oceans exists against all odds: vibrant ecosystems flourishing in complete darkness, frigid temperatures, and extraordinarily high pressure. Some truly bizarre creatures have evolved under these tough conditions, from sharks straight out of nightmares to the terrifying giant isopod. The wacky nature of many deep-sea organisms captures our imaginations, but often leads to important scientific discoveries as well.

Life is both weird and beautiful in the deep ocean. Here, a Schaefer’s Anglerfish (Sladenia shaefersi) uses modified fins to walk along the seafloor in search of prey. Photo courtesy of NOAA.

In 1977, scientists crammed into a submersible called Alvin discovered abundant life growing around a hydrothermal vent, upending everything we thought we knew about life on this planet – and potentially others. Hydrothermal vents form when extremely hot and mineral rich fluids are released through fractures in the seafloor. Entire communities of deep-sea species rely on these vent fluids as their sole source of energy, one of the only ecosystems on the planet that does not ultimately rely on sunlight. Finding life in these extreme and unusual environments gives us hope that we may one day find life on other planets – perhaps even with in own solar system ­– and gives us clues where we should look.

While finding an entirely new type of ecosystem is rare, scientific expeditions to the deep sea frequently discover new species. For example, one study estimated that about 30% of species observed during expeditions to seamounts were completely new to science! Finding new species improves our understanding of evolution and how ecosystems function. They can also be directly beneficial to humans by providing new chemical compounds with important pharmaceutical or scientific uses. Deep-sea organisms have already provided us with novel compounds used to develop anti-inflammatories, cancer treatments, nerve regeneration treatments, and antifungal agents. Notably, a chemical from a hydrothermal vent Archaea organism improved our ability to replicate DNA. Advances in DNA replication are a key component of rapid viral testing, including those being developed for the COVID-19 virus that is sweeping the planet.  

Sulfide chimneys at a hydrothermal vent at the Urashima vent site. The energy-rich fluids being vented into the water column support an entire system of life not found anywhere else on the planet. Photo courtesy of NOAA

Exploring the Incredible Requires Incredible Technology

The deep sea is challenging to explore. Surveying these remote environments generally requires the use of large oceanographic vessels coupled with technology that can handle a highly pressurized, dark, and cold environment. Early approaches, including dredging, box coring, and towed camera arrays, are limited in their capabilities but are still used today because they are inexpensive and easy to operate. However, modern deep-sea exploration is increasingly being conducted with an impressive array of futuristic robots, sensors, and satellites.

One of the biggest innovations in deep-sea research was the introduction of submersibles that allow for direct exploration of the seafloor. Submersible vehicles come in several varieties, each having different capabilities to survey, record, and sample the seafloor. Human occupied vehicles (HOVs) carry a small team of scientists that can directly view and study the seafloor, remotely operated vehicles (ROVs) are piloted from a ship via a long cable, and automated underwater vehicles (AUVs) operate independently according to a pre-programmed mission. Each of these vehicles, along with ships, airplanes, and satellites, can carry a suite of sophisticated sensors that can measure almost anything: the shape of the seafloor, the chemical composition of seawater, the type of sediment found on the bottom, and even the amount and type of microbes present. Improved satellite capabilities have also given rise to telepresence-enabled expeditions that broadcast the video feed from ROVs in real time around the world, allowing anyone to participate in these exciting  discoveries from the comfort of their living rooms.

The remotely operated vehicle (ROV) Hercules explores the San Juan Seamount. Photo courtesy of Ocean Exploration Trust.

Protect What We Find

Perhaps the single most important reason to explore the deep sea is so that we can protect it. Despite being so remote from humans, our activities still represent a considerable risks to these fragile habitats and most deep-sea habitats lack adequate protection. Carbon emissions, pollution, seafloor mining, and overfishing all threaten the existence and health of deep-sea ecosystems. In many cases, we may lose species before they have been named; entire ecosystems before we have even discovered them. Imagine if we had mined all of the world’s hydrothermal vents before 1977, never uncovering the incredible biological riches that exist there. Exploration of the deep sea is a critical first step towards ensuring that we adequately safeguard these wonderful – and wacky – ecosystems.