Why researchers are racing to study the world’s ocean

Posted on July 21, 2025 in News

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Did you know that the ocean produces approximately half of the world’s oxygen? Or that key medicines have come from ocean discoveries, like a painkiller found in a sea snail?

With this comic, we explore some of the cool things scientists do know about the ocean and what dwells inside of it.

Hi! I'm Noelle Bowlin. I run an ecosystems monitoring program for NOAA. My expertise is in larval fish ecology. Most fish species live at the surface as larvae, or baby fish. As they grow into adults, they may stay near the surface, or they may migrate to the other ocean zones. Illustration of a Noelle Bowlin, a Black woman wearing a lab coat holding a marine creature in a jar. Below are illustrations of various fish.

The open ocean is made up of five vertical zones
sunlit zone/epipelagic surface to 200m (660 feet)
twilight zone/mesopelagic 200m to 1000m (660ft to 3300 feet)
midnight zone/bathypelagic 1000m to 4000m (3300ft to 13100 feet)
abyssal zone/abyssopelagic 4000m to 6000m (13100ft to 19700 feet)
hadal zone/hadalpelagic, or the trenches 6000m to 10994m (19700-36070 feet)
An illustration of the different ocean zones gradually becoming darker blue with a rocky bottom.

SUNLIT ZONE or EPIPELAGIC.
Light Bright.
Temperature Variable, from 97°F (36°C) to 28°F (-2°C).
Pressure 1-20 atmospheres.
The bulk of photosyntesis in the world occurs at and near the surface of the ocean. This is where larval fishes get their start! They're tiny and they have tiny mouths. So they need lots of food gathered in one place.
Illustration of marine organisms and small fish in light blue water with the sun shining above.

You get small organisms like plankton in swarms, feeding on phytoplankton at the surface ... which attracts predators like anchovies, sardines, and mackerels ... which attracts even larger predators. With these high densities of food, you get a lot of schooling organisms in the epipelagic.
Illustration of a whale next to small fish and magnifying glasses over plankton and photoplankton.

TWILIGHT ZONE or MESOPELAGIC (or midwater).
Light Dim.
Temperature Variable.
Pressure High, 20-100 atmospheres.
Organisms in the mesopelagic often have big eyes to detect what little light gets down here. The cockeyed squid has one big eye (to pick up dim light from the surface) and one little eye (to pick up bright biolumiescent flashes in the depths). Two of the most abundant families of fishes live in this zone lanternfishes & lightfishes (also known as bristlemouths).
Illustration of a cockeyed squid and a cartoon version of Noelle Bowlin explaining why it has different sized eyes. There are also illustrations of a lanternfish and a light fish.

Half of the fishes in this zone migrate to the surface at night ... and back down during day. It's the largest migration on earth, and it happens every single day! This region acts as a huge carbon sink. It plays an important role in transferring carbon from the surface to the deep ocean.
An illustration of the sun above the water and fish migrating towards the surface and then back down to the deeper, darker zone.

MIDNIGHT ZONE or BATHYPELAGIC.
Light None.
Temperature Cold.
Pressure Very high, 100-400 atmospheres.
If you could see, you would see very fine particles all around, moving very slowly. This is marine snow falling down from the zones above. Marine snow can fall for weeks before reaching the sea floor. My favorite animal in the abyssal zone is the stoplight loosejaw.*
*It also lives in the twilight zone!
Illustration of marine snow, very fine particles under magnification and a cartoon version of Noelle Bowlin pointing to a stoplight loosejaw, which is a dark gray fish with sharp teeth and red spots under its eyes.

Compared to the zones above, the density of organisms drops off. They encounter each other less frequently, which leads to interesting adaptations. For example When an anglerfish male finds a female, the male fuses to the female! "There are a lot of fish in the sea, but it's a big sea," Bowlin says.
An illustration of higher concentration of fish at the top of the ocean and fewer fish as it gets deeper and darker. There is also an illustration of a male anglerfish fusing to a female anglerfish and a cartoon version of Noelle Bowlin.

ABYSSAL ZONE or ABYSSOPELAGIC.
Light None.
Temperature Very cold. Near freezing.
Pressure Very high, 400-600 atmospheres.
The average depth of the ocean is about 4000 meters. Only in certain places in the world does the ocean floor dip into the abyssal zone. Marine snow continues to fall.
An illustration of the ocean floor dipping against a dark blue background with marine snow.

You don't get high densities of organisms in this zone. The ones that are here typically have very small eyes. They invest in their other senses. Creatures here are gelatinous to withstand the high pressures. "This zone is where we find the dumbo octopus, the deepest dwelling octopus!" Bowlin says.
An illustration of a cusk eel, which is dark grey and has small eyes. There is also a cartoon version of Noelle Bowlin raising her arms toward an orange dumbo octopus.

Life still exists at these extreme environments. A lot of organisms here rely on marine snow for nutrients. Nutrients accumulate on the sea floor, regardless of depth. In some places, hydrothermal vents emit heat and gases that provide fuel for life.
An illustration of a pinkish snailfish, giant isopod and tripod fish along with conical hydrothermal vents emitting heat and gases.

There's increasing interest in harvesting marine resources these days. Deep sea mining, fishing in the twilight zone, and laying internet cables on the sea floor are among the ways in which we use our oceans. It's important that scientists continue to study the ocean so that we can understand the impact we have on our shared planet.
Illustration of two ships at the top of the ocean on a starry night with long cables reaching down deep to the dark ocean floor.

Angela Hsieh for

This comic was written and illustrated by Angela Hsieh, based on reporting from Berly McCoy. It was art directed by Emily Bogle and edited by Rebecca Ramirez.

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