The Oceans Are Teeming with Unknown Species

Scientists are finding 2,000 new marine species a year. Why it matters to name and categorize them.


When a group of marine scientists decided to form the World Register of Marine Species in 2007, it only had a small team of 55 researchers from 17 countries, but a grand and ambitious goal: to create a definitive, online, open-access list of all the names for all the living species in the world’s oceans. The endeavor, known by the acronym WoRMS, emerged from the rich soil of another ambitious international project, The Census of Marine Life, which was trying to capture what we know, what we don’t, and what we can never know about life in our oceans.

WoRMS colonized a number of existing registers. Those included the European Register of Marine Species, species registers maintained at the Flanders Marine Institute, and the UNESCO-IOC Register of Marine Organisms (URMO), the first attempt to compile an electronic list of all marine species during the 1990s. URMO’s first version was published on a 3.5-inch floppy disk. WoRMS was a job for an army of taxonomists—or at least a battalion, about 300 all in all today—enlisted to describe, name, and classify marine species.

DUMBO OF THE DEPTHS: The Emperor dumbo (Grimpoteuthis imperator) is about 30 centimeters long. It was recovered from depths of more than 4,000 meters in the North Pacific, and now it finds itself online as part of the World Register of Marine Species, which is trying to create a definitive, online, open-access list of all the names for all the living species in the world’s oceans. Photo credit: World Register of Marine Species.

Now, 15 years on, they’re still at it, continuing the process of listing the species that live in the sea, from the shallowest waters to the deepest rifts, a process that seems almost Sisyphean in scale. There are about half a million names in the database to date, and 2,241 marine species were added last year alone, including the Japanese Twitter mite that, aptly, thrives in cracks in submerged concrete structures, and the Emperor Dumbo, an octopus whose fins resemble the ears of a certain animated elephant. And in 2021, WoRMS started to move forward with a new goal: to complete the register by 2030 as part of the UN Ocean Decade Project.

I spoke with Tammy Horton, chair of the WoRMS steering committee and a researcher at the United Kingdom’s National Oceanography Centre, about why taxonomy is crucial to our ability to understand life in the oceans.

When I think of taxonomy, I think of the work of 18th-century naturalists. I think of Linnaeus. It seems almost old-fashioned. Why should we still be interested in taxonomy?

We’re still trying to find out and catalog all the species that we share our planet with. We haven’t yet finished that job that Linnaeus started. That’s the first reason. And, secondly, we’re at a point where extinctions are on the increase. So, if we’re going to try to analyze and use the data to understand how changes are occurring, we need to be able to reliably say: This is how many of these different species lived here at this time; and this is how many of these different types that are living in this same area now. We can’t do any of that if we can’t describe what the species are.

People say that taxonomy is the foundation science of all biology. Each biologist or ecologist is looking at how different species interact with one another and how they interact with their environment. Putting a name on each of those species is crucial. If you get that wrong, then your science and all the science following afterward is wrong as well.

How did you get into studying taxonomy?

For my Ph.D. I was studying tongue biting isopods, parasites of fish. They look very similar to each other, and they’re not very well studied. So, to identify the animal that I was studying, I had to illustrate it to make sure it was the same species. I spent a lot of time in the Natural History Museum in London, in museums in Paris, and various other marine institutes around the U.K. and Ireland, looking at samples and trying to find out what species it was. And I fell completely in love with taxonomy.

We can’t say how many more species there are to describe. Is it a million or is it 10 million?

WoRMS has been doing this work for about 15 years now. The number of names validated by the register has increased, although only half of the approximately 500,000 species names refer to unique species—the rest are synonyms. What does it mean to “complete” the register?

It means that we want to fill in all the information and have it fully up to date for the known species. And it’s not just about the names. For example, we do not have all the type specimens, which are the representative physical examples of each species, in there. This is really important information. All the species’ names should have a type specimen record, and should have a publication linked, which says this is where this name comes from. And we’re not there yet.

We’re also taking on something a little bit new now. There is such a time lag between a taxonomist like me sitting here with a new species, and getting those species fully described and into the register that they’re sometimes published [in articles] before then. We must find a way to talk about these undescribed species. So, we’re going to start including undescribed [but known] species in the register in the form of temporary names.

How much time might pass between when a sample is collected and it is named, described, and added into WoRMS?

There have been a few papers written analyzing how long it takes from discovery to description and all that. One of the numbers that I remember is, on average, it’s about 21 years. That’s between discovery and description, but I’m not sure how true that is. I would say 10 years. It depends on how much funding the taxonomist has for a particular piece of work. 

Does that mean that there are a bunch of new species just sitting on shelves in museum collections or in labs, waiting to be described?

In many cases, yes. I’ve probably got a number of stuff over there behind me of new species, which I know are new, but perhaps I don’t have the time to describe them because I’ve moved on to another research project. As part of one of my research projects right now, I’m studying animals and crustaceans from an area in the sediments of the deep Pacific. I’m identifying all of them and a lot of them are new. But I may not have the time at the end of the project to describe all those animals because I’ll be moving on to another project to identify other animals. It does take a long time to actually sit down and do the descriptions. And often taxonomists are moved from project to project, doing ecology or identification, and the taxonomy itself happens kind of when they get around to it.

SEA SPIDER: This sea spider was named Austropallene Hodgson in the WoRMS database. Photo Credit: World Register of Marine Species.

How long does it take to do a description?

Well, the taxonomist needs to illustrate the species, describe it—which means they need to write the paper—and then get a paper published.

There are a number of reasons why it takes a long time sometimes, but essentially it depends on the work of the taxonomist: Have they got the time and the funding to make the description? And also, does the new species belong to a group of species that have been well studied in recent years? If yes, then it will likely be described sooner than a species which is only represented by one or two specimens, or belonging to a group of very diverse and poorly known species, since the taxonomist has to compare each new species against all those already known.

But if there was plenty of funding and the taxonomist had no other work to do, and there were plenty of specimens and from a well-studied taxon, then it should take just a few months. My most recent new species [a deep-sea amphipod from the Amathillopsidae family] was described during lockdown and took less than a year from collection to publication. It was collected July 20, 2020 and published April 14, 2021. So, it can be done relatively quickly!

How many species do you think are still unknown?

I added six species just yesterday to WoRMS and I’m sure other editors are adding new species each day. We add on average 2,000 species per year. But we can’t say within an order of magnitude how many more species there are to describe. Is it a million or is it 10 million? And that’s a very, very difficult and contentious debate in marine science. Because until we actually catalog everything, and get to a point where we do know everything, then it’s very difficult to say how many unknown species there are. And perhaps that is even unknowable.

But we can use what we do know to make estimates, and that’s what people have done in the past. There have been a number of scientific papers written which have attempted to make those estimates of how many unknown species there are. There was one written by WoRMS back in 2012.  And they said between 700,000 and almost 1,972,000 species are expected in the world.

We’re revisiting that paper right now and updating that. We’re going to make another estimate soon.

Taxonomy is the foundation of biology. If you get the name wrong, then all the following science is wrong.

Are there areas of the world where you think the unknown or undescribed species might be clustered?

Yes, there are areas of the world which are less well studied, like the deep sea. That is due to logistical and technical reasons, because it’s quite hard to get there and quite hard to collect the animals. And in the tropics, there’s huge amounts of biodiversity that is understudied, not really because of difficulty of accessing the environment, but because there is much higher diversity there. And a lot of it is cryptic diversity. It’s either well-hidden physically, or you can have two or more species that look so similar that you think there’s one. When we study them in really great detail and use molecular methods to differentiate them, then we’ll realize that it’s perhaps a complex of five or more species, but they all look exactly the same. So, there’s that. Plus, institutes in the tropical regions globally sometimes don’t have the means to do as much marine biological work that perhaps the marine stations in the Global North have had. That has provided an imbalance in our understanding of the regions as well.

Some of the deep sea is now being drilled for oil. And areas of the ocean in tropical zones are also being targeted for oil and gas exploitation, as well as for destructive fishing practices like dredging. How do you balance this need to collect specimens so that you can have a full picture of life in the oceans in the face of an ongoing, and even accelerating degradation of those environments?

We’re working as quickly as we can, because, as you say, the environments are being degraded, and we still haven’t described the biodiversity of those environments. So, we’re collecting for the future study of those environments. That is the benefit of working with museums really. You collect the animals, and they never ever dispose of those samples; they are retained in perpetuity, which explains the 21 years from collection to description. So, in that sense, it doesn’t matter how long it takes. But in another sense, it does matter because we’re losing information we can feed back into how to manage our environments. So, we have to work quite closely with the industries that are exploring these environments.

And there are a lot of industries that look at and use the deep sea and open ocean. There is fishing, but also mineral extractions, and oil and gas explorations as well. And, yes, drilling, for oil. Many people will be aware of the [Deepwater] Horizon incident in the Gulf of Mexico. And that incident really showed the need for baseline understanding of biodiversity in the deep sea, because we needed to be able to look and compare what had happened before and after the Horizon incident. Generally, our understanding of biodiversity in the deep sea is: We know that there’s a huge amount more we need to know.

I’m wondering how marine biologists developed these kinds of relationships with these oil companies. I imagine that the technology might have something to do with it.

Absolutely. Whether they’re sitting in an oil field doing explorations, they have all this technology on site ready to use, and they’re mostly using it for mapping oil platforms and inspecting their well heads. But we recognized that we could use their cameras and do surveys of the area and undertake all sorts of exciting scientific projects, all using their technology.

That’s so interesting. I wonder, though, considering the degree at which that industry is destroying these habitats, how do you walk that line as researchers? If they’re exploring in fragile areas, and you say there are, I don’t know, 1,000 unique species in this area, and if you drill, you will destroy them, what happens then?

I mean, if that’s what we say, then that’s what we say. We don’t have to like it. And we don’t have to agree with what they’re doing. But the science that we provide, the datasets that we analyze, and the results that we give, they go to both industry and policymakers. It is the same data. You can have a personal opinion, like “I’d rather you really didn’t go there because it’s going to destroy everything.” And that may well be the case, you know. But that’s why we provide the data to policymakers and government, too, so that policymakers can put in place the frameworks to prevent things from being destroyed. Because we’ve shown them the data that says that’s going to destroy it. So that’s why we work with policymakers and governments as well as industry.

Is there anything that can speed up the process? Like new technologies?

Taxonomy is going digital. We have microscopes where we can take images and we can do very advanced scanning of specimens, and you can do all this fantastic digital processing and imaging. Museums are heading to the full digitization of their [sample] collections. If you think about it, maybe decades into the future there will be a physical representation, but also a digital twin of the museums where you can look through all the collections and visualize the specimens without actually having to go there. And there’s so many new, exciting technologies coming including computer vision. All the facial recognition technology that we already use is going to be used for taxonomy and for identification tools. If we can digitize the specimens, we can then use computer vision and artificial intelligence to analyze them. And add that to molecular barcoding, which can place specimens closest to their nearest relatives and identify them in that way. We’re moving taxonomy into a completely new world.

Lead collage created using images from the World Register of Marine Species.

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