- Scientists compiled all known population genetics studies of deep sea ecosystems, finding a paucity of research.
- The researchers warn that human impacts like pollution, fishing, and mining are encroaching further into deep sea areas faster than scientists are studying them.
- They say more research will enable stakeholders to protect vulnerable ecosystems.
We know very little about the deepest parts of the ocean – and are disturbing them faster than we’re learning about them, according a study published this week in Molecular Ecology.
To see just how big this knowledge gap is, researchers at Oxford University conducted a survey of all known population genetics studies of deep sea invertebrates. Population genetics is the study of the differences between and within populations, and helps scientists understand how groups of plants and animals evolved and how they may respond to environmental changes.
The researchers discovered that there have been 77 papers published on this topic in the last 33 years. Of these, just nine looked at areas deeper than 3,500 meters – which comprise about half the planet’s surface.
Additionally, the researchers focused on invertebrates. They say what while invertebrates comprise the bulk of wildlife at the bottom of the deep sea, research of the last few decades has been aimed instead on vertebrates like fish, as well as animals living in unusual ecosystems like hydrothermal vents.
A lack of basic information
The relative few studies they found on the population genetics of deep sea invertebrates shine a valuable, if dim, light on an otherwise unknown expanse. They indicate the animals that live in the deep may be about as genetically diverse as shallow-water species, and that some populations are distinct and isolated from each other even in small areas.
But that’s pretty much it. The researchers write that there is a lack of even basic ecological information for all but a few species.
According to Christopher Roterman, co-author and postdoctoral researcher in Oxford’s Department of Zoology, the researchers “found it concerning that so few studies accounted for the largest ecosystem on the planet. Only nine studies for half the planet and only two for a quarter of it.”
Roterman told Mongabay that their findings indicate populations may be structured differently in the deep, and that current research methods may not be effective in their study.
“In terms of the actual data, our review revealed a picture of high connectivity within species over large distances (100s-1000s of miles), but revealed population structure (low connectivity) with depth, suggesting a stratification of some species into sub-populations separated by a few hundred meters of depth – which may reflect adaptation to changing conditions as you go deeper – i.e. changes in
temperature, pressure, food availability or oxygen availability. In some cases this population separation amounts to the populations being designated as separate, but superficially identical species,” Roterman said. “We also revealed that the use of some genetic markers may not be very useful for inferring patterns of demographic change over recent history, suggesting that newer methods should be used.”
The importance of protecting the deep
Roterman and his colleagues say study and protection of deep sea ecosystems is important for many reasons. For one, the deep sea could represent “a potential larder for biotechnology and biomedical research,” he said, and is a “key cog in the machinery of how the planetary ecosystem maintains dynamic equilibrium.”
“Large-scale disruption of the deep-sea, while very remote to us at present could have long-term negative consequences unless we manage to learn more about how these deep-sea communities function and are structured,” Roterman said.
In addition to unveiling the secrets of deep sea ecosystems, the researchers say investment in genetics studies will help stakeholders more effectively manage and protect marine diversity and resources as human impacts on the deep intensify.
“These studies have the power to influence the way that stakeholders are
able to manage sustainably deep-sea resources,” Roterman said. “While deep-sea animals do not make up a large part of our diets at present (although consumption is higher in Asia), biomass harvesting is getting deeper and deeper. These population genetic studies therefore can have a direct impact on food supply and are important.
“However we also noticed that little work has been done on species that are habitat forming – such as sponges and deep-water corals. These animals are much like the trees in rainforests and host a variety of other species, some of which are commercially harvested. Population genetic information can therefore be crucial in the setting up of marine protected areas (MPAs) that provide oases from human activity that can lead to greater productivity in the areas that are open to human harvesting.”
Ever-increasing human impact
They warn that despite this lack of knowledge and exploration of the deep, human activities are leading to ever-greater impacts. For instance, microplastics can now be found in the deepest, most remote reaches of the ocean. Commercial bottom-trawling fishing is tearing through ancient, deep sea ecosystems, turning them into “faunal deserts.” And about 1.8 million square kilometers – an area about the size of Libya – has been allotted for potential exploration and extraction of metals.
“Today humans have an unprecedented ability to [affect] the lives of creatures living in one of the most remote environments on earth — the deep sea,” Roterman said in a statement. “At a time where the exploitation of deep sea resources is increasing, scientists are still trying to understand basic aspects of the biology and ecology of deep sea communities.”
Roterman calls for more research of the deep sea, saying it will help us figure out how its ecosystems may respond to disturbance and how best to protect them.
“Population genetics is an important tool that helps us to understand how deep sea communities function, and in turn how resilient they will be in the future to the increasing threat of human impacts.” Roterman said. “These insights can help governments and other stakeholders to figure out ways to control and sustainably manage human activities, to ensure a healthy deep sea ecosystem.”
Roterman said fishing is currently the activity having the biggest impact on deep sea communities. But he warns that metals mining may soon become the bigger threat.
“What may start off in relative terms, as a pin-prick on the seafloor, may rapidly expand before the long-term detrimental effects are fully understood,” he said.
“What we don’t know at present is how human activities and climate change will affect these populations in the future, but history tells us that we shouldn’t be complacent.”
Technological advances could further study at a lower cost
Getting good data from 5,000 meters down can be a tricky and costly undertaking. Roterman says this is due to the high cost of specialized sampling equipment, as well as the large volumes of fuel required to travel out into the open ocean far from the coast where deeper areas tend to be.
“For this reason, there are few studies that span most of the abyssal plains and the hadal trenches,” Roterman said. “Until now, human impacts in these areas have been restricted to pollution (rubbish, microplastics industrial and nuclear waste), but large-scale mining pilot studies have begun that could result in large areas being heavily disturbed.”
But the researchers say advances in technology may help population geneticists learn about the denizens of the deep more cheaply, easily, and quickly. They point to the increasing availability of autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) that are already at work mapping and sampling the ocean’s depths. And development of “next-generation sequencing” technologies over the past five years means geneticists are able to get more information from fewer individuals, lowering the costs associated with collecting them from the deep.
“Next-generation sequencing allows us to scan larger and larger portions of an animal’s genome and at a lower cost,” Michelle Taylor, co-author and senior postdoctoral researcher in Oxford’s Department of Zoology “This makes deep sea population genetic studies less costly, and for many animals, the sheer volume of data these new technologies create means they can now be studied for the first time.”
But, Taylor urges, haste is of the essence.
“We cannot bury our heads in the sand and think that people are not going to try and exploit resources in the deep sea, so science needs to catch up.”
- Taylor, M., & Roterman, C. N. Invertebrate population genetics across Earth’s largest habitat: the deep-sea floor.
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