Sanctuary Integrated Monitoring Network
Greater Farallones National Marine Sanctuary
Urchin and crab
Deep ocean urchin and crab. Photo: MBARI
In the deep waters of the Gulf of the Farallones National Marine Sanctuary lie unique organisms and dramatic geological features. Less than 80 kilometers (50 miles) offshore, the steep continental slope descends into the deep sea to depths beyond 200 meters (660 feet) with the deepest parts of the sanctuary exceeding 2,000 meters.

The deep sea is the largest habitat on earth and is home to many relatively unknown biological communities. It is only in the past two decades that better technologies have allowed humans to view previously unseen areas: the development of camera-equipped remotely operated vehicles (ROVs) and manned submersibles provide a new window on this world.

In the "old" days, exploration of deep-sea life involved dragging a net along the bottom or through the open water. Delicate animals such as jellies came back to the ship damaged beyond recognition. Today, ROVs have substantially increased our knowledge because they allow us to observe animals in their natural habitat and better understand how they interact with each other and with their environment.

There are two major habitats in the deep sea: Deep-sea life is adapted to dark, cold, high-pressure and low-oxygen conditions. Compared to the relatively shallow water habitats (less than 200 meters) along the California coast, food is generally scarce at depth. Some animals adjust to these harsh conditions, making use of a habitat few others can tolerate; it reduces competition for food and their chances of being eaten.

Organisms have adapted in a variety of ways. Natural light penetrates to only about 300 meters, so marine plants, which need sunlight, are absent below this depth. Because it is dark, many animals don't have the ability to see; others have extraordinarily sensitive eyes to pick up what little light is available. Many deep-sea organisms make their own light - a chemical reaction called bioluminescence. Bright displays of light may be used to communicate, attract mates, create confusion (and thus avoid a predator) or lure food.

Primnoid coral (Narella sp.), blackcoral (Trissopathes pseudotristicha), and feather star (Florometra serratissima) on the Davidson Seamount at 2669 meters. Credit: NOAA/MBARI 2006

Enteroctopus dofleini (giant pacific octopus) on Rittenburg Bank floor. -85m, 9 deg. C

The cold water slows an animal's metabolism. Most deep-sea animals move very slowly, and some employ special enzymes to deal with this unique environment. Slow metabolism may account for the long lives of deep-sea organisms, including certain rockfishes that can live for more than 200 years. Other animals, like sea cucumbers, carry high levels of unsaturated fat in their cell walls to maintain membrane fluidity in this cold, high-pressure environment.

Food is generally limited in the deep sea, so finding it and capturing it is more difficult. Many animals feed on an array of discarded biological material called "detritus," which rains down from above as a result of the activities of animals in shallower water.

Whatever these animals discard or shed provides food that sinks to the seafloor for scavengers and mud-feeding organisms like brittle stars and sea cucumbers. On occasion, large "food falls," like dead whales or dead kelp, sink from above, attracting large numbers of animals that come to take advantage of the bounty.

Human Interaction
It is essential to monitor human impacts on the ocean so that we can understand how our activities change our environment. A clear understanding of these effects can help resource managers and policy makers develop sound conservation strategies.

Conservation and management issues affecting sanctuary resources in the deep sea include seabed disturbance, non-sustainable fishing and radioactive waste.


Experts from many different fields - biologists, geologists, chemists, engineers and physical oceanographers - all study the deep sea, seeking to understand how the ocean works.

This work is important for many reasons; the size of the deep sea (covering 63 percent of the earth's surface) means that we should know as much as possible about this ecosystem. Scientists strive to understand how deep-sea animals are different from shallow-water species and what adaptations they have developed in response to the deep ocean's unique environment.

The deep sea may also provide economic opportunities. Cancer-fighting drugs developed from sea sponges or other marine organisms may some day provide new pharmaceuticals. Researchers are also investigating the seafloor for new forms of energy. However, one of the best reasons to study the deep sea may be simple curiosity about all the amazing creatures and geological features hidden in its depths.