By Naomi Krauzig (GEOMAR)

As the research vessel METEOR heads north toward Germany, the CTD Lab has become quiet.

For the past four weeks, the CTD rosette (named after the three core variables it measures: conductivity, temperature, and depth) has been one of the busiest instruments on board. Day and night, it disappeared beneath the waves and returned with information about the entire water column.

Now the final station has been completed and the CTD rosette has been stored away for the last time. It feels like the right moment to reflect on a tool that has accompanied generations of oceanographers -and on a ship that has done the same.

Introduced in the 1970s, Conductivity-Temperature-Depth (CTD) systems revolutionized ocean observation by providing continuous measurements throughout the water column. When METEOR III entered service in 1986, the CTD was already the workhorse of physical oceanography. In the 1990s, it gained a trusted companion: the Lowered Acoustic Doppler Current Profiler (LADCP), capable of measuring ocean currents from the surface to the seafloor.

Aboard METEOR, the CTD rosette now also carries a suite of additional sensors measuring oxygen, chlorophyll, turbidity, photosynthetically active radiation, nitrate, and even particles and plankton through an Underwater Vision Profiler. At the same time, its Niskin bottles collect seawater samples for analyses of oxygen, nutrients, salinity, and other properties, providing a detailed picture of the water column.

During M219, this classic CTD/LADCP system helped us reveal some of the hidden “highways” of the tropical Atlantic. Along the 11°S section off Brazil, a key location for monitoring the Atlantic Meridional Overturning Circulation, CTD measurements identified distinct water masses through their temperature, salinity, and oxygen signatures. At the same time, the LADCPs captured the currents carrying them: the warm, northward-flowing North Brazil Undercurrent in the upper ocean and the colder, southward-flowing Deep Western Boundary Current nearly two kilometers below.

Further north, along 23°W, we crossed the equator and encountered one of the strongest subsurface currents in the world ocean: the Equatorial Undercurrent. Hidden just beneath the surface, this powerful eastward-flowing jet transports enormous amounts of water, heat, oxygen, nutrients, and carbon across the Atlantic: roughly one hundred times the discharge of the Amazon River!

While these observations allow us to investigate water masses, currents, and the circulation of the tropical Atlantic, they also carried an additional meaning for many on board.

For four decades, CTD rosettes have been lowered from the deck of METEOR III in every ocean of the world, helping scientists understand complex ocean processes, monitor changes, and train generations of oceanographers. During more than 11,940 days at sea, thousands of stations have been completed from her deck. Countless students, technicians, crew members, and scientists have contributed to these observations, and many have built their careers around the data collected aboard this vessel.

To take part in the final cruise -and the final CTD cast- of METEOR III was a privilege. Over the course of this voyage, it became impossible not to notice the connection many people have with this vessel. For some, METEOR has been a second home for years. Colleagues became lifelong friends, sometimes even family, and countless memories were made during deployments, watches, and transits at sea. The research vessel, the discoveries, and even the familiar CTD rosette hold a special place in many hearts.

As we pack the last equipment and the laboratories become emptier, it is difficult not to wonder what comes next. METEOR IV will soon continue the tradition, equipped with new capabilities and ready to tackle the scientific questions of the coming decades. New technologies will undoubtedly expand how we observe the ocean, yet some traditions are likely to endure.

https://www.oceanblogs.org/m219/2026/06/27/no-cruise-without-a-ctd/

By Joelle Habib (Laboratoire d’Océanographie Villefranche)

When I was a kid, I wanted to be a photographer. I still do, actually. But somewhere along the way, science intervened, and it gave me something I never expected: the chance to be an underwater photographer. Not the National Geographic kind who chases polar bears or waits weeks for a penguin to do something interesting. My subjects are smaller. Much, much smaller. I get to photograph the invisible life of the deep ocean, the tiny animals and sinking particles that most people never know exist. And the camera I use to do it descends to 6000 meters below the surface.

This instrument is called the UVP, or Underwater Vision Profiler. On this cruise, we deployed a UVP6 attached to the CTD rosette, profiling down to 4000 meters depth. The instrument activates automatically once its pressure sensor detects it is moving downward, takes up to 20 pictures per second all the way to the bottom of the cast. But before we talk about what the UVP gives us and why it matters, we need to talk about what it actually photographs: zooplankton and particles.

If you have ever watched SpongeBob SquarePants, you already know a zooplankton. Sheldon J. Plankton, the tiny villain who is perpetually trying to steal the Krabby Patty formula, is one. And funnily enough, the most abundant zooplankton across all the world’s oceans, is indeed this small crustacean: the copepod.

Here is the basic idea: a plankton is any organism that drifts with the ocean currents rather than swimming against them. If it photosynthesizes like a plant and contains chlorophyll pigments, it is a phytoplankton. If it is an animal, it is a zooplankton. A jellyfish is a zooplankton, just a very large one. Zooplankton graze on phytoplankton, on each other, and on anything small enough to eat. Now for the process that connects all of this to climate, to carbon, and to why we are out here on a research vessel in the middle of the equatorial Atlantic: the biological pump.

The biological pump is the ocean’s mechanism for pulling carbon out of the atmosphere and locking it away in the deep sea. Here is how it works: phytoplankton at the surface absorb CO₂ from the atmosphere and convert it into organic matter through photosynthesis. When they die, or when zooplankton eat them, defecate, excrete, and die themselves, all of that organic carbon does not simply disappear. It becomes marine snow! Yes, it snows in the ocean!!! Marine snow consists of a continuous rain of particles, aggregates, fecal pellets, shed exoskeletons, … Every flake of marine snow is a fragment of life that once existed at the surface, now on a one-way journey into the deep. This is the gravitational pump, one of the most important carbon sinks on Earth, and it is one of the pumps that the UVP was built to observe.

Marine snow seen by PELAGIOS (Pelagic In situ Observation System) in the Tropical Atlantic; 23°W; 100 m depth. Photo Credit: Henk-Jan Hoving

So why image and count particles rather than simply collecting water samples or relying on sediment traps? Because the abundance and size distribution of marine particles are two of the major factors controlling biological carbon sequestration in the ocean, and traditional methods cannot capture them at high resolution throughout the water column. Vertical profiles of particle images can reveal the processes that determine particle size, type, and distribution, and combined with information on carbon content and sinking velocity, they provide high-resolution information on how the biological pump operates at depth. The UVP allows for the remote collection of large datasets on particle abundances and their size distributions, enabling much higher spatial and temporal resolution than traditional methods. But particles are only one part of the story, the UVP also tracks zooplankton and their daily migrations: every night, zooplankton rise from the deep to feed near the surface, then sink back down before dawn, actively carrying carbon into the deep ocean in their own bodies. Without imaging tools like the UVP, this active carbon flux is nearly impossible to quantify.

Each image you see here was taken in complete darkness, somewhere between the ocean surface and 4000 meters below. The UVP6 illuminates a tiny volume of water, with a single red flashing light, capturing only the particles and organisms that happen to drift through that small window at that exact moment.

The instrument captures everything larger than 100 micrometers, roughly the width of a human hair. In the images you will see two types of things: fuzzy, irregular blobs of varying sizes: Marine snow aggregates. And more defined, structured shapes, sometimes with appendages, antennae, or transparent shells. Those are the zooplankton.

Every image is a small portrait of a world that already existed long before we had the tools to see it. I am so lucky I am able to see parts of that hidden life in this lifetime.

Counting Snowflakes in the Darkness of the Deep Ocean

Far below the ocean’s surface—where sunlight disappears, pressure skyrockets and temperatures plunge—some of the strangest animals on the planet have evolved to survive. Transparent heads. Glowing bodies. Needle-like teeth. Tentacles that seem straight out of science fiction.

And yet, these bizarre sea creatures are very real. 

An estimated one million deep-sea species remain undiscovered. In fact, many deep-sea creatures have only been seen a handful of times because their habitats are so vast and difficult to explore.

Here are seven ocean animals that prove our blue planet can be just as strange as outer space.

1. The Vampire Squid

Despite its dramatic name, the vampire squid does not want to suck your blood. This deep-sea animal earned its spooky reputation because of its dark color, glowing eyes and cloak-like webbing stretched between its arms. 

Unlike many squid species, vampire squid don’t actively chase prey. They have the ability to match the density of surrounding seawater to avoid constantly swimming by hanging suspended or drifting. They then use long, filament-like appendages to feed on “marine snow”—tiny drifting particles of organic material. 

To avoid predators in the darkness, vampire squid rely on bioluminescence. Light-producing organs, called photophores, help them blend into faint light filtering down from above. When threatened, photophores near the tips of their arms create bursts of light that may confuse or distract predators long enough for the squid to escape. 

2. The Barreleye Fish

If aliens wore fishbowls on their heads, they might look something like the barreleye fish.

This bizarre fish has a transparent head filled with fluid, allowing us to see its bright green eyes rotating inside its skull. Barreleye fish eyes can point upward to search for prey silhouetted against faint sunlight—or rotate forward when it’s time to feed.

For decades, scientists misunderstood how barreleyes actually looked, likely because damaged specimens lost the transparent tissue around their heads during the collection process. That was the case until researchers at the Monterey Bay Aquarium Research Institute were able to observe one alive.

Barreleyes serve as good reminders that we still have so much to learn about life beneath the waves.

3. The Giant Isopod

Imagine a roly-poly the size of a housecat. That’s basically a giant isopod.

These enormous crustaceans live deep on the ocean floor, up to 7,000 feet down, and they can grow more than a foot long! Their segmented armor, multiple legs and glowing eyes give them a prehistoric appearance—fitting, as the first recorded isopod fossil is more than 300 million years old.

Because food is scarce in the deep sea, giant isopods are built for survival. They can go surprisingly long periods of time without eating—sometimes years—and often scavenge remains that drift down to the floor.

4. The Anglerfish

Few creatures scream “deep-sea alien” more than the anglerfish.

With oversized teeth, expandable stomachs and a glowing lure dangling from its head, the anglerfish looks like something designed for a science-fiction movie. The glowing lure is actually bioluminescence—a natural chemical light used to attract prey in the darkness of the deep ocean.

Anglerfishes hunt using their bright lures to entice fish and crustaceans to draw close. Only females have the lures, however (you go, girl!). They also use this method to attract males.

In a habitat that sunlight never reaches, producing light can mean the difference between survival and starvation.

5. The Dumbo Octopus

Yes, the dumbo octopus is actually named after Disney’s Dumbo. Dumbo octopuses are, in fact, adorable and measure an average of just 8-12 inches in length.

Dumbo octopuses have ear-like fins extending from the sides of their heads that flap through water like tiny wings. They live at extreme ocean depths, 1,000-13,000 feet beneath the surface, making them one of the deepest-living octopus species scientists know about.

Unlike some octopus relatives, dumbo octopuses don’t ink when threatened. With predators limited that far down in the ocean, they don’t possess a defensive ink sack like other octopuses do.

Their cute appearance may seem less alien than some deep-sea creatures but make no mistake: An octopus flying through total darkness thousands of feet underwater is still pretty otherworldly.

6. The Goblin Shark

Nicknamed a “living fossil,” the goblin shark looks unlike almost any other shark species alive today. 

Goblin sharks have semi-translucent skin, and their blood vessels can be seen through it. That’s why the goblin shark may look different colors in photos—sometimes a pale white, grey or pink. Its long, flattened snout and protruding jaws create an unmistakable profile. Even stranger? Those jaws can rapidly shoot forward to snatch prey before retracting again.

The mysterious allure of goblin sharks remains strong, as information is sparse, and photos of the species are extremely rare. Encounters with humans, through observation or accidental catch, are limited. What’s more alien than that!?

7. Gelatinous Deep-Sea Creatures

Some of the ocean’s strangest residents aren’t even solid.

Gelatinous animals include glowing jellies and drifting organisms that appear almost holographic underwater. Some pulse with neon colors. Others trail unbelievably long tentacles. 

Sea jellies date as far back as 500 million years ago—if not longer. They are soft-bodied creatures consisting of at least 95% water, possessing a simple structure and a noticeable lack of almost everything that distinguishes plant from animal—including blood, a heart and a brain. Talk about out of this world!

It’s easy to think of deep-sea creatures as mysteries, but these animals are essential parts of our ocean ecosystem. The deep ocean regulates climate, stores carbon and supports biodiversity on a massive scale. 

Yet much of it remains unexplored.

That’s why Ocean Conservancy is committed to protecting our entire ocean—and all the creatures that dwell there, no matter how mysterious they may be. The truth is, some of the most incredible discoveries on our planet may still be waiting in the dark depths below.

And honestly? That’s way cooler than science fiction!

The post Deep-Sea Animals That Look Like Aliens appeared first on Ocean Conservancy.

Deep-Sea Animals That Look Like Aliens