OTZ Instruments and Cameras

Twilight Zone Explorer (or TZEx)

The movement of carbon through the ocean twilight zone plays a major role in regulating the Earth’s climate—yet scientists don’t yet understand exactly how this cycle works. 

In order to figure out how much carbon the twilight zone removes from the atmosphere, the OTZ team has designed a new submersible system called the Twilight Zone Explorer, or TZEx. The system is built on an existing French profiling float, a type of submersible instrument that can change its buoyancy at will. By inflating and deflating an onboard oil bladder, It can sink into deep water, stay there for a fixed time, and then rise back up again.

Using a set of high-resolution cameras, TZEx will record the movement of carbon-rich debris called  "marine snow" as it sinks through the twilight zone. In doing so, it will give researchers new insight into the movement of organic carbon through the zone, helping them figure out the exact impact it has on global climate.


The small amount of light that reaches the twilight zone plays an important role in governing the rhythms and pulses of life. This light cues animals when to migrate, helps them hide, and much more. 

Instruments that can measure these barely perceptible levels of light are notoriously expensive and difficult to handle, however, so there are currently few direct measurements of light in the twilight zone. To fill those gaps in knowledge, the OTZ team is working with researchers at MIT to create low-cost, easy-to-use radiometers. Once deployed, these tools will let virtually any of the team’s underwater vehicles become an ultra-sensitive light sensor.

High-Volume eDNA Sampler

Searching for rare and often elusive creatures in the ocean twilight zone comes with some challenges. The zone is enormous, has no “landmarks” scientists can use to navigate, and exists in near-total darkness. To get around these limitations, the OTZ team is developing a new approach that uses environmental DNA (eDNA) to identify animals that have passed through the zone, shedding genetic material in their wake.

The team captures that genetic material using new high-volume eDNA samplers. These devices can be attached to any underwater vehicle, and pump hundreds of liters of seawater through a series of filters to collect biological material. By analyzing that DNA in the lab, scientists can reveal traces of even the rarest animals.

ISIIS Camera System

WHOI’s new In-situ Ichthyoplankton Imaging System (ISIIS) captures incredibly detailed images of tiny animals called zooplankton, plant-like phytoplankton, jellies, and small fish. The system takes 14 shadowgraph images of organisms that pass through it each second, producing a huge amount of data on the natural behavior of miniscule creatures in the twilight zone. ISIIS is towed behind a ship on a small, commercially-available Stingray “sled,” which also holds sensors that measure depth, oxygen, salinity, temperature, and other water characteristics.

Data collected by ISIIS will be essential for understanding how plankton fit into the ecosystems of the twilight zone and the ocean as a whole. These microscopic organisms form the base of many ocean food webs, play a key role in producing oxygen, and in some cases, remove carbon dioxide from the atmosphere, helping to regulate Earth’s climate. In spite of their importance, however, marine plankton communities are not well understood—in part because the ocean is vast, and plankton communities vary widely by location and over time.


Sharks and other large fish are among the most iconic animals of the open ocean. Our team suspects that they are also surprisingly active hunters in the twilight zone, but little is known about where they dive to find food, how often they dive, and how long they stay at depth. 

Thanks to small, accurate ROAM satellite tags, WHOI scientists will be able to track these predators in three dimensions as they move through the twilight zone over months or years. ROAM tags, which are attached directly to the backs of sedated animals at the surface, are both smaller and more accurate than any other tracking tags in current use. They can also transmit data back to shore via satellite at the end of each deployment, giving researchers a first look at where these predators are in relation to physical, chemical, and biological processes that create hot spots of activity in the twilight zone.