T he oceans encompass habitats
ranging from highly productive
coastal regions to lightless,
high-pressure, and low-temperature
deep-sea environments. The benthic
(bottom-living) species that reside
within the sediments in these habitats
form one of the richest species
pools in the oceans and perhaps on
Earth. Even though 70.8% of the
earth is covered by oceans, and most
ocean floor is covered by sediments,
there is still much to learn about
biodiversity in marine sediments. The
major reasons for the gaps in knowledge
are logistics and effort. Approximately
65.5% of the planet is
covered by ocean that is greater than
130 m in depth (i.e., the approximate
depth limit of the continental
shelf) and is accessible only by submersibles
or remote-sampling gear.
Even the remaining shallow areas
(i.e., approximately 5% of the earth's
surface) present challenges in terms
of ship availability and cost, as well
as loss of experiments and ship time
to weather.