Preliminary study of hyperbenthos in Heraklion Bay (Cretan Sea)
Department of Environmental Technology and Management,
Institute of Marine Biology of Crete,
P.O. Box 2214, GR 71003 Heraklion,
Figure 1. Lateral and front schematic view
of the hyperbenthic sledge: C1: collector 1; C2: collector 2;
C3: collector 3; P.H.: pressuring house containing the battery
package and the controller; Pn1: plankton net 1; Pn2: plankton net
2; Pn3: plankton net 3; E.M.S.: electro-mechanical opening-closing
system; D1: door 1; D2: door 2; D3: door 3
The hyperbenthos is a term applied to the association of small sized
bottom-dependent animals (mainly Crustaceans) that have good swimming
ability and perform, with varying amplitude, intensity and regularity,
seasonal or daily vertical migrations above the seabed (Brunel et al.,
1978). Beyer (1958) was the first referring to "hyperbenthos"
that has to be used in preference to "suprabenthos", because
the Greek noun benthos should be preceded by a Greek prefix (hyper-),
rather than by its Latin equivalents (supra-, super-).
The terms "hyperbenthos" and "suprabenthos"
are used mainly in temperate and northern seas, whereas
"swarming", "resident" or "demersal
zooplankton" and "benthopelagic plankton" or
"benthic boundary layer fauna" are usually preferred to
designate the same fauna in tropical areas and the deep sea
There has been much taxonomic interest in the hyperbenthos. Most of
the hyperbenthic species are present in much higher densities than in
either the overlaying water layers or in the adjacent sediment and most
of them are not there accidentally. Beyer (1958) discussed the species
found in abundance in the hyperbenthos but which were rare or absent
More recently, there has been recognition of a distinction between
the truly hyperbenthic species and a variety of "visiting" or
"immigrant" animals that can be classified as endobenthic,
epibenthic or planktonic. There has been also increased interest in the
role of hyperbenthos in the functioning of marine ecosystems, mostly
because it has been found that many demersal fish and epibenthic
crustaceans feed, for at least part of their life, on hyperbenthic
animals. Furthermore, there is renewed interest in pre-recruit studies
as many larval and early post-larval fish and crustaceans have a
hyperbenthic phase. On the other hand, studies of benthic-pelagic
coupling related to energy fluxes rarely include samples taken within a
few centimeters above the seabed and may, therefore, underestimate
significantly the flux of particulate organic material (Mees &
The often highly mobile hyperbenthic animals living immediately above
the seabed are only occasionally caught by conventional benthic or
pelagic sampling gears thus a plethora of hyperbenthic sampling devices
have been constructed and used with varying success. The choice of
sampling equipment in use depends largely on local conditions e.g.
size of the ship, power and capabilities of the lifting gear, degree of
exposure, depth, bottom relief and sediment structure and the type of
sample required for the specific research topic under investigation
(Eleftheriou & Holme, 1984).
Most of the published information refers to temperate and cold-water
environments. In recent years there have been considerable development
in hyperbenthic research in the tropics (mostly in coral reef lagoons)
and the deep sea. Nevertheless, Mediterranean Sea hyperbenthic studies
are scarce and limited to the western basin of this enclosed region
referring either to the surf zone or to deep environments (Cartes 1998;
Cartes & Sorbe, 1999; San Vicente & Sorbe, 1999; Cartes et
al., 2001). As far as the Eastern Mediterranean Sea is concerned,
there is total absence of information on hyperbenthic communities. In
the 1990s a number of studies (Karakassis, 1991; Tselepides 1992;
Tselepides & Eleftheriou, 1992; Koutsoubas et al., 1992;
Karakassis & Eleftheriou, 1997) contributed significantly to our
knowledge of the macrobenthic fauna from the Cretan Sea. Even so, our
knowledge of the hyperbenthic fauna remains nil.
In the framework of a multidisciplinary European research project
conducted by the Department of Technology and Management of the Marine
Environment of the Institute of Marine Biology of Crete (I.M.B.C.), a
sampling program of 5 successive cruises of the R.V. Philia has
been performed in the continental shelf and upper slope of Heraklion Bay
(Cretan Sea). The investigation of the hyperbenthic diversity of this
particular area was included among the aims of the project.
Heraklion Bay is situated in the north coast of Crete. Fieldwork
included collection of water column, sediment, plankton and macrobenthic
samples, as well as measurements of physicochemical and hydrographic
parameters. For the collection of hyperbenthic samples, in particular, a
modified three-level towed sledge (see Figure) was used. Technical
characteristics are given in Shand & Priestley (1999).
Preliminary results reveal that the hyperbenthic sledge really
samples a specific fauna. The hyperbenthic samples comprise even
different taxonomic groups comparing to the macrobenthic and
macrozooplanktonic ones. Mysidacea, Cumacea, Amphipoda, Decapoda,
Copepoda and Isopoda are among the most abundant taxonomic groups of the
hyperbenthic habitat of Herakion Bay.
Further analysis to species level will provide new information
on the life cycles and classification of macrofaunal species in
endobenthic, epibenthic, and hyperbenthic ones. Considering that
numerous benthic species -up to now regarded as rare in the area- may
prove to be abundant when proper sampling methodology has been used and
it is expected that results of this project will significantly increase
our knowledge concerning the biodiversity of the benthic environment in
the continental shelf of the Eastern Mediterranean.
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