Biological Oceanography

(^) Although widely used, the Smith–Mac and its relatives (Petersen, van Veen, Okean,
Campbell, etc., grabs) have been criticized for disturbing the sediment with the
pressure wave that they push downward through the water that can blow away the
sometimes fluffy sediment surface before impact. They also have substantial failure
rates because any small stone or shell bit caught between the scoop edges will allow
sediment to wash out on retrieval. Therefore, they have been largely replaced in recent
work by box corers (Hessler & Jumars 1974, Fig. 13.3b). Several cycles of
modification have brought these to substantial sophistication, and some lighter
designs can be deployed from larger boats as opposed to ships. A stainless-steel box,
25 × 25 or 50 × 50 cm and open at both ends, is driven into the sediment by weights.
Striking the bottom releases a pin holding the lifting bail, which is also attached to a
cable below that passes through pulleys. This cable on retrieval swings a blade down
through the sediment, closing round the curved edge of the coring box. At the same
time a lid is closed over the top of the core to prevent washing. Because the coring
box is open, it has a lesser pressure wave. This is also minimized by very slow final
approach to the bottom. Samples appear to be very slightly if at all disturbed and near-
bottom water is retained over the top, warmed somewhat during passage through
upper layers. Jumars (1975) and others have used box cores to examine the very
small-scale patterns of faunal distribution in deep-sea sediment.
(^) Elaborate sledge samplers have been developed for collecting epibenthos and near-
bottom plankton just above the seabed. For example, the Macer–GIROQ system is a
net with a square-mouth mounted on runners that opens just above the sediment when
the sledge touches down. Above that is a plankton net with a shuttered mouth that also
opens at arrival on the bottom and closes on lift-off. There are fins to hold the sledge
upright (usually) during descent. For detailed description of this and sundry other
benthic gear, see Eleftheriou and McIntyre (2005). Very large and mobile fauna must
be captured with bigger trawl systems, and some very deep-living and active animals
simply are not caught.
(^) Since about 1950 the deep sea floor has been accessible to manned submersibles
and these have grown in sophistication and sampling capability. They can be used to
deploy sensors, corers, scoops, settlement plates, experimental modifications of the
sediment, cameras, and more. More recently, many of these functions can be done
with remotely operated vehicles (ROVs) deployed from ships by cable. With suitable
propulsion and video relay to the operator on deck, these can visit sites at any depth
and serve most of the functions of manned submarines at less expense with risk only
to equipment.
(^) The descriptions and pictures that follow of benthic fauna cannot replace actually
seeing these animals, particularly if you have a chance to see them alive or shortly
after collection. If the chance comes your way to participate in a benthic sampling