Midwater research

The largest living space on Earth lies between the ocean’s sunlit upper layers and the dark floor of the deep sea, on average some 4,000 meters below. This vast midwater habitat is home to our planet’s largest ecosystems and its largest animal communities. Midwater species are adapted to a fluid, three-dimensional world without solid boundaries; and they probably outnumber all other animals on Earth. They comprise essential links in the oceanic food web by providing food for important commercial species like tuna and salmon, as well as for whales, turtles, and giant squid. This is a huge planetary resource, yet we know far less about these species than we do about the constituents of any other major habitat.

For more than a century scientists had to study midwater animals indirectly, by towing nets from ships at the surface or by probing the depths with sound. At MBARI, we study midwater animals directly, using undersea vehicles to carry our cameras, instruments, tools and samplers into their deep habitat. This approach, with humans in the real-time control loop, has revolutionized our understanding of midwater ecology and the biology of the animals who live there. These advances are enabled by new technologies; the hardware, software, and methods developed by MBARI engineers, video technicians, and our operations group.

A fundamental aspect of MBARI’s midwater research program is the midwater time series project. For more than 20 years, remotely operated vehicles (ROVs) with high-resolution video cameras have conducted transects through the upper kilometer of the water column at a single site over Monterey Canyon. The data generated by this project includes the identities and abundance of all species encountered, coupled to concurrent measurements of relevant water properties. This is the only data set of its kind in the world and it is immensely valuable by providing a baseline for examining regular seasonal cycling, episodic events like El Niño, and the growing effects of climate change.

Ecological investigations encompass a wide range of research projects. One of the most striking aspects of exploring the midwater habitat has been discovering the unexpected profusion and diversity of gelatinous animals. We have documented their diversity, described many new taxa, tracked their ecological niches in the community, and investigated their behavior patterns. An overall goal of these efforts is to accurately trace and quantify the passage of organic carbon from primary production at the surface, through the complexities of the midwater community, to the animals that live on the deep seafloor.

The behavior patterns of deep-sea animals have long been a subject of mystery and speculation. Because of the access provided by MBARI’s ROVs, detailed observations of the behavior of these animals have become possible for the first time. The value of this new kind of information is that it allows a much better understanding of the complex ecological interactions between species.

Bioluminescence evolution and chemistry – Understanding the origins, generation, and evolution of bioluminescence is a critical pathway for investigating the most widespread form of communication on Earth.

Midwater ecology group

The reward of regular investigations of midwater ecology with an ROV is a radically new perspective on the deep sea. Many of MBARI’s most stunning discoveries have come from the time-series data of midwater ROV surveys. We have logged thousands of hours surveying and describing the deep waters of the ocean.

Zooplankton biodiversity group

The ocean’s midwater zone is dominated by gelatinous predators such as ctenophores, siphonophores, and hydromedusae. Researchers contend that these gelatinous groups will become increasingly abundant as the ocean changes.


Upper-ocean systems
Acoustical ocean ecology
Acoustic instruments
Acoustic fingerprinting
Acoustic community ecology
Acoustics in the news
Biological oceanography
Global modes of sea surface temperature
Krill hotspots in the California Current
Nitrate supply estimates in upwelling systems
Chemical sensors
Chemical data
Land/Ocean Biogeochemical Observatory in Elkhorn Slough
Listing of floats
SOCCOM float visualization
Periodic table of elements in the ocean
Biogeochemical-Argo Report
Profiling float
Interdisciplinary field experiments
Ecogenomic Sensing
Genomic sensors
Field experiments
Harmful algal blooms (HABs)
Water quality
Environmental Sample Processor (ESP)
ESP Web Portal
In the news
Ocean observing system
Midwater research
Midwater ecology
Deep-sea squids and octopuses
Food web dynamics
Midwater time series
Respiration studies
Zooplankton biodiversity
Seafloor processes
Revealing the secrets of Sur Ridge
Exploring Sur Ridge’s coral gardens
Life at Sur Ridge
Mapping Sur Ridge
Biology and ecology
Effects of humans
Ocean acidification, warming, deoxygenation
Lost shipping container study
Effects of upwelling
Faunal patterns
Previous research
Technology development
High-CO2 / low-pH ocean
Benthic respirometer system
Climate change in extreme environments
Station M: A long-term observatory on the abyssal seafloor
Station M long-term time series
Monitoring instrumentation suite
Sargasso Sea research
Antarctic research
Geological changes
Arctic Shelf Edge
Continental Margins and Canyon Dynamics
Coordinated Canyon Experiment
CCE instruments
CCE repeat mapping data
Monterey Canyon: A Grand Canyon beneath the waves
Submarine volcanoes
Mid-ocean ridges
Magmatic processes
Volcanic processes
Explosive eruptions
Hydrothermal systems
Back arc spreading ridges
Near-ridge seamounts
Continental margin seamounts
Non-hot-spot linear chains
Eclectic seamounts topics
Margin processes
Hydrates and seeps
California borderland
Hot spot research
Hot-spot plumes
Magmatic processes
Volcanic processes
Explosive eruptions
Volcanic hazards
Hydrothermal systems
Flexural arch
Coral reefs
ReefGrow software
Eclectic topics
Submarine volcanism cruises
Volcanoes resources
Areas of study
Bioluminescence: Living light in the deep sea
Microscopic biology research
Open ocean biology research
Seafloor biology research
Automated chemical sensors
Methane in the seafloor
Volcanoes and seamounts
Hydrothermal vents
Methane in the seafloor
Submarine canyons
Earthquakes and landslides
Ocean acidification
Physical oceanography and climate change
Ocean circulation and algal blooms
Ocean cycles and climate change
Past research
Molecular ecology
Molecular systematics
SIMZ Project
Bone-eating worms
Gene flow and dispersal
Molecular-ecology expeditions
Ocean chemistry of greenhouse gases
Emerging science of a high CO2/low pH ocean