Seafloor
The ocean floor, or benthos of the Sanctuary, provides a diversity of habitats for
bottom-dwelling organisms, as well as those that forage but do not necessary dwell there, such as
gray whales. We learn about habitats of the seafloor using several tools including remote sensing
devices, bottom sampling and underwater video.
The remote sensing tools use acoustics or sound to
produce data that is processed into imagery for interpretation of substrate, depth, and features
on the seafloor. Common remote sensing tools include side scan sonar and multi-beam sonar.
Interpretation of remote sensing data is verified using seafloor samples or underwater video.
Using this information we classify the habitats of the sanctuary by substrate type, depth, slope,
relief and morphology. As we gather information on the composition of benthic communities, we also
associate these with the habitat information. Bottom samples and underwater video provide us
information on the benthic communities inhabiting the Sanctuary.
The seafloor of the Sanctuary encompasses over 3,300 square miles. To date we have mapped only
about 35 percent of the seafloor, so we still know relatively little about the habitat and benthic
communities in the Sanctuary. Each year we conduct more seafloor mapping and habitat classification,
and studies to learn about benthic community composition. In the past few years, we used our side
scan sonar mapping data to select likely targets for underwater viewing of deep sea corals and
sponge, and verification of the side scan data interpretation. Using a remotely operated vehicle
(ROV) equipped with a video camera, we were able to video tape the seafloor and benthic communities.
We did indeed find both soft and hard corals, as well as several species of sponge!
Prior to remote sensing, a common tool for seafloor mapping was to take soundings and bottom
samples. Maps of the Sanctuary seafloor have been created using these data to provide preliminary
information about the seafloor. These methods are antiquated and provide only spot data that must
be extrapolated for areas between the samples. From these data, and the remote sensing data we have
collected, we have a picture that will be improved upon with detailed knowledge over time. Benthic
habitats in the Sanctuary range from sand and mud bottoms, to pebble, cobble and bedrock, from
depths extending from the intertidal to 1,477 meters (4,800 feet) in the Quinault Canyon.
Within the Sanctuary boundary are the heads of three submarine canyons, Nitinat, Juan de Fuca and Quinault
from north to south, and troughs of the Juan de Fuca Canyon extend throughout the northern portion
of the Sanctuary. Sand waves, from less than a meter tall to several meters tall have also been
documented. As we gain knowledge about the habitat and the benthic communities, we will be able to
study the associations between the two, allowing us to predict communities where we have not yet
explored, slowly allowing us to piece together a picture of the ocean floor.
Contact for page content: Robert Steelquist
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