Shining a Light on How Deep Ocean Creatures Communicate

Marine biologist David Gruber journeys to the deep sea to investigate how marine life that live in total darkness generate light to exchange information. Now he says he’s learning how to talk back.

Written by Ian Evans Published on Read time Approx. 6 minutes
David Gruber descends in the Deep Rover, one of two submersibles carried by the research vessel Alucia.Alucia Productions

It’s often remarked that we know more about the surface of Mars than we do about the bottom of the sea. David Gruber, a marine biologist and an associate professor at Baruch College in New York, is trying to change that one expedition at a time.

Gruber, a National Geographic emerging explorer, and his team are studying marine life in the deep ocean that communicate by generating their own light, a phenomenon called bioluminescence. While bioluminescence is rarely found on land, where there is plenty of sunlight, Gruber says it’s “the norm” at depths of 3,000ft (950m) or more. Bioluminescence allows schooling fish to stay together, warn of predators and attract mates. By recording their light patterns, Gruber hopes to better understand exactly how these creatures communicate with each other. For his upcoming expedition he wants to take this understanding one step further, and use lights to talk back.

Oceans Deeply caught up with Gruber in between two separate week-long expeditions on the Alucia research vessel to the Alcatrazes Archipelago off the southeastern coast of Brazil and the Fernando de Noronha Archipelago that lies 220 miles (354km) off the country’s northeastern coast.

Oceans Deeply: Can you give us an overview of this trip to Brazil, and your research on bioluminescence there?

David Gruber: Bioluminescence is one of the focuses of my research – really the goal is to use technology in a way that is noninvasive to try to understand the animals and try to learn more about them. So, we’re using a whole suite of new technologies to try to understand these marine animals, some of them bioluminescent. One of the beauties of this research vessel is that it has two submarines that are capable of diving down to 1,000 meters, or over 3,000 feet.

One of the things we’re trying to answer is how to study this environment that has been barely studied by humans, and when we do go down there, how do we study the environment in a way that doesn’t intrude on the animals living down there. You can imagine that these animals are going 24/7 without light – they’re encased in constant darkness in their environment. So, one of the things we’re trying to do is go down with low-light cameras and not go down there with big lights blaring and blind all of these animals that are barely getting a photon of light.

In terms of bioluminescence, it is such a massive phenomenon in the deep ocean – estimates are that 70–90 percent of animals down there have the capability of producing light. It is very rare up on Earth – we know of only a few animals, like fireflies, in the terrestrial environment. Almost every [deep ocean] creature has this ability to flash, blink, excrete bioluminescence.

It’s such a big ocean that if I am going to a remote place off the coast of Brazil I can’t really get good intel on what creatures will be there. And on this trip, we came across this creature called a pyrosome – these pelagic tunicates [marine invertebrates] – and they were incredibly bioluminescent. We encountered eight or 10 of these, and we were imaging them, and then I went back and realized that there have barely been any studies on them in the past 30 years. So we picked up this animal that had almost been forgotten by science in the past 30 years. Who knows what we’re going to bump into when I go back next week.

Oceans Deeply: What does it look like when you go down and you see these pyrosomes in the deep sea?

Gruber: They’re beautiful – they’re kind of like these hollow tubed animals. They look like a hollow tube but they’re colonial animals [made up] of hundreds or thousands of little zooids. Each one of these little zooids has a little brain and a little heart, and they will pump in one direction, which forms a funnel and they can go up and down.

There are two ways in which their bioluminescence can be stimulated. One is to shine a light on them, and they automatically are phonetically tactic, so if they see light they will immediately flash back. Since there are thousands of little animals, once the bioluminescence is stimulated, it’s like a wave that goes across the whole animal that starts at the point where they’re disturbed and then migrates out through the whole animal and then slowly diminishes again. It’s just an absolutely beautiful display and incredibly bright.

I went back into the literature and found this description from 1850 – another scientist that had bumped into these almost 200 years ago. To reencounter this animal that had almost been forgotten, and to reexamine it, to be inspired by the people who saw this back in the 1850s and now to approach it with all of our fancy tools – what more things can we learn from it?

Oceans Deeply: You’re using technology to monitor flashes and patterns. What exactly are you trying to do with that?

Gruber: For my research team, photographs are data for us, and if we photograph these animals’ bioluminescence with the right kind of camera, we can go back and heavily analyze their communication patterns and work to decipher the algorithm that they’re using or the patterns to their flashing. Are different kinds of flashes used in different scenarios? There are some fish, like flashlight fish, that we’re examining and recording for things like leader-patterns in them; are there ways that animals use bioluminescence to lead their school? Are there ways that, if we could decipher these bioluminescent patterns, we could start flashing back and figure out this language that they’re communicating with? We’re at the really early stages, but it’s a form of communication. We can heavily study the kinetics and patterns of the light; the question is, can we communicate back, and we don’t know yet.

Oceans Deeply: Have you tried?

Gruber: We’re trying. Using flashes to stimulate [the animal], and now, with the recording we’re just on the second part of the trip going to start some playback mechanisms. It just depends, because every time we go on one of these dives we come across a new suite of animals, so we have to encounter it and record the patterns, and then have the playback necessary, all in the same dive, and we haven’t put all of those pieces together yet.

Oceans Deeply: What are the challenges of finding these animals and photographing their bioluminescence?

Gruber: Well, there is an element of danger in asking our sub pilots to turn off all of their light in mid-dive. We have to be somewhere where the submarine is stable enough that we can ride in complete darkness, and that is a challenge. And the other challenge is getting the animal in focus. Imagine being in a dark room with a little light drifting around the room, and you’re running around in the dark trying to image that light, and you’re trying to focus your camera but you don’t have a reference point except that light.

Oceans Deeply: Why do you think it’s important to study these animals?

Gruber: We rely on other organisms for so many things: for our food, for our air, and I see that we have separated ourselves from the other species, besides maybe dogs and cats, and there are so many millions of other species out there and we’re all interconnected. We all share DNA. There are so many similarities between how we operate and how these animals operate, and I am just fascinated by life and all of its many forms and beauty.

It’s a bit like, why do you go to the Metropolitan Museum of Art? That’s why I like to go to the bottom of the oceans; it is complete beauty, artistry, fascination and every time there is something new. At the same time, it’s just fascinating to think that we’re connected to these animals, and we originated in the deep sea. We share DNA, we share replication mechanisms with these animals. It makes me think about people who want to go live on Mars – why would anyone want to go live on Mars when we have this amazing ocean that is largely unexplored and largely unvisited, whereas the surface of Mars, we know that it is a hostile, not very interesting biological place.

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