1063-0740/01/2702- $25.00 © 2001
Russian Journal of Marine Biology, Vol. 27, No. 2, 2001, pp. 121–124.
Original Russian Text Copyright © 2001 by Biologiya Morya, Moshchenko.
Sedimentation, or the settling of suspended particles
through the water column due to gravity, is a funda-
mental mechanism that provides for the transport of
matter from trophogenous areas to bottom communi-
ties [1, 6]. At the same time, suspended particulate mat-
ter also exerts a negative inﬂuence because it may both
bury benthic organisms and cause problems for their
ventilation and other life processes by littering their ﬁl-
tering apparatuses. Only a few animals are adapted to
survive under heavy siltation; therefore, the amount of
suspended particulate matter should be recognized as
one of the most important factors controlling the abun-
dance and distribution of benthic organisms. Some ani-
mals, such as the hydroids, absolutely lack any proper
mechanisms of sediment rejection and are cleaned of
settling suspended matter only by the force and pattern
of hydrodynamic action. Thus, in the evaluation of the
inﬂuence of sedimentation on benthic abundance and
distribution, we should take into account not only the
amount of suspended particulate matter, but also its
behavior near the bottom, i.e., sedimentation and resus-
pension. Modern optical and labeling methods [3–5, 7]
are not useful for biologists studying the distribution of
benthic ﬂora and fauna, because they are either
extremely expensive or very laborious.
The aim of this paper is to describe a rather simple
modiﬁcation of the cylindrical sediment trap method.
This method makes it possible to evaluate both the
amount of suspended particulate matter settling from
the water column onto the bottom and its behavior in
the near-bottom area.
MATERIAL AND METHODS
At present, the most widespread method of quanti-
tatively assessing the ﬂux of settling particles is the
method of cylindrical sediment traps [1, 6, 7]. To obtain
accurate data, the sediment traps must be strictly cylin-
drical, because it has been shown in experiments and
using models that funnel-shaped devices do not sufﬁ-
ciently trap the suspended particulate matter and bottle-
shaped ones trap too much. The opening should be
more than 4.5 cm in diameter because traps with
smaller diameters trap too many hydraulically light
fractions, and the ratio of the trap height to the diameter
of the opening should be less than 5. The collecting efﬁ-
ciency of such traps approaches 100% [1, 2].
The ﬂux of water and particles continuously passes
through the trap placed in the moving medium. It does
not inﬂuence the settling of particles, but it may
strongly modify the velocity of the ﬂux measured, even
with the trap design requirements noted above .
Therefore, in the case of a strong horizontal current, the
trap becomes an artiﬁcial separation surface, and a
calm zone appears within it. Under these conditions,
the amount of sediment settled on the trap bottom is
really the highest possible measure of sedimentation
rate . Thus, the velocity of the current is an important
factor inﬂuencing the amount of settled matter, and the
trap may be used to evaluate turbulence [6, 7].
If we take a trap with nonstandard proportions, for
example, with a height-to-diameter ratio of less than 1,
the amount of sediment captured under turbulent water
conditions is less than that caught by the standard trap.
This makes it possible to estimate the resuspension
intensity, i.e., the behavior of suspended particulate
A Study of Sedimentation and Resuspension
in the Near-Bottom Boundary Layer Using Cylindrical Traps
in Hydrobiological Investigation
A. V. Moshchenko
Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, Vladivostok, 690041 Russia
Received February 22, 2000
—An inexpensive and convenient method for marine biological investigation of the sedimentation in
the immediate proximity of biological objects on the seabed is considered. The method is a modiﬁcation of the
widespread method of cylindrical sediment traps [1, 6]. It makes it possible to analyze the amount of suspended
particulate matter passing within the near-bottom boundary layer and the processes of sedimentation and resus-
pension. Its application is illustrated by the results of investigation of the inﬂuence of some processes taking
place in the near-bottom layer on the distribution of scleractinian corals in a reef off Dao-Chao Island (Baity-
long Archipelago, the Gulf of Tonkin).
near-bottom boundary layer, sedimentation, resuspension, cylindrical sediment traps