EXOTIC SPECIES AND LESSEPSIAN MIGRATION OF PLANKTON IN LEBANESE WATERS,
LEVANTINE BASIN, EASTERN MEDITERRANEAN
Sami Lakkis
1*
and Raymonde Zeidane
2
1
Section of Oceanography, Faculty of Sciences, Lebanese University, Beirut, Lebanon
* slakkis@inco.com.lb; slakkis@ul.edu.lb; www.ul.edu.lb
2
Laboratory of Plankton and Marine Ecology, NCMS / LNCSR, Batroun, Lebanon
Abstract
The plankton community in the Levantine Basin is relatively poor in biomass and high in diversity. 35% of the local species are found in
the Red Sea, and 65% are present in the western Mediterranean. The majority of the exotic species encountered off Lebanon are Lessepsian
migrants of Indo-Pacific and Erythrean origin. However, several species that inhabit either in the Mediterranean and the Red Sea before
the opening of the Suez Canal have their geological history back to the Miocene era and Tethys Sea. The Aswan High Dam and deepening
of Suez Canal have enhanced hydrological changes in the entire Levantine Sea and induce a continuous migration process. This
phenomenon leading to the “Tropicalization” of the Levantine Basin is an index of certain global climate change.
Keywords : Exotic species, Levantine Basin, endemism
Rapp. Comm. int. Mer Médit., 37,2004
384
Introduction
The Eastern Mediterranean, and in particular the Levantine Basin,
are highly oligotrophic water bodies. Furthermore, their temperature
and salinity are the highest in the entire Mediterranean. These hydro-
logical characteristics are similar to those of the Red Sea. The opening
of the Suez Canal enhance the migration process between the two
marine environments, particularly from the Red Sea into the Mediter-
ranean. An estimated 400-500 marine species were introduced into the
Levantine Basin(1) and many planktonic species established perma-
nent populations along the Levantine coast(2,3). Some other exotic
species may reach the area, not only through the Canal pathway, but
through human activity, namely with ballast water. The fauna and ?ora
of the Eastern Mediterranean, belong to the Atlanto-Mediterranean
type, with certain tropical and subtropical affinities. Studies of the
Levantine plankton before the opening of the Suez Canal in 1869 were
scarce and poorly known. Considering this gap of knowledge, it is dif-
ficult, even impossible, to ascertain whether species occurring both in
the Levant and in the Red Sea may be considered exotic. However, we
concur (1,4) that several Mediterranean endemic species inhabited the
Tethys Ocean.
In this paper we try to define the exotic species found in the Leba-
nese waters, from Indo-Pacific origin and from other remote seas.
Methods and Material
Qualitative and quantitative series of samples for both phytoplankton
and zooplankton were taken monthly or seasonally, from 1970 up to
2002, at several inshore and offshore stations along the coast of Leba-
non between 33°52 N-35°29 N and 34°30 N-35°50 E. Major hydro-
logical profiles were collected simultaneously with vertical and surface
plankton net hauls. Taxa were identified to species. Long-time series of
plankton and hydrological data were published in previous works (5,6).
Results
Several exotic species of Indo-Pacific and Erythrean origin have
been introduced into Levantine Basin through the Suez Canal. Several
other species were introduced by ballast water of vessels coming from
remote seas. Possibly, up to 50% of these species adapted themselves
to the new environment where they established permanent populations.
We estimate that 35% of the species recorded in the Lebanese waters
are also present in the Red Sea(7, 2) (Table 1).
Some Indo-Pacific species in the Levantine Basin have been men-
tioned or recorded in the western Basin; these exotic species have
been probably introduced through the Gibraltar strait rather than the
Suez Canal pathway.
The complete list of the exotic species found in Lebanese waters was
given in a previous work (3). Some of these introduced species may
develop and overcome other species to became an invasive species.
This is the case of the scyphomedusa Rhopilema nomadica, which
appeared in the late 1980s and replaced the previously common
Rhizostoma pulmo. This stinging species injures swimmers and dam-
ages fishingnets. The main exotic species are given in Table 2.
Conclusion
Lessepsian migration is a continuous phenomenon. Most of the exot-
ic species establish permanent populations, some became invasive.
Most of them remain confined to the Levantine Basin; few reach the
Aegean Sea, Ionian and Adriatic. Fewer still reach the western Basin.
The increasing number of exotic species is due to the hydrological
changes taking place in the Levantine Basin, namely, the rise of tem-
perature and salinity, and also due to the global climatic change.
References
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Table 1. Number of plankton species commonly found in Lebanese
waters and Red Sea.
Table 2. Major exotic species found in Lebanese waters during the last
decades.
