The Metahaline Environments of the Red Sea and the Persian Gulf
83
salinity metahaline bodies (por, 1975a). The northern tip of the Red Sea, in the
Gulf of Suez, reaches even today salinities of over 44%0. It is now generally
accepted that during the Würm Glacial, the salinity of the Red Sea was even
higher.
The shores of the Red Sea have many lagoon environments with salinities
exceeding that of the open sea. Along the Sinai coast several such lagoons have
been investigated more or less thoroughly: Ras Matarma; EI Bilaiyim; the
mangrove lagoons ofNabq; the pool ofDi Zahav (Dahab) (see Map. 2).
The shallow Persian Gulf has salinities reaching 40%0 in the offshore waters.
Along the southern coast, the Trucial coast, the salinity of the shallow shores
reaches 50%0. In some lagoons values of even 70%0 are reached.
Along with the evaporation-induced high salinity, considerable fluctuation of
temperatures in these metahaline environments also occurs. In some lagoons of
the northern Red Sea, winter temperatures of 10° C have been measured. Even in
the Persian Gulf sabkhas, winter temperatures of 15° C alternate with 40° C in the
summer. The metahaline species are, therefore, adapted to minimum temperatures which are very much below tropical values. The adaptation to high salinity
and low temperature can be considered together as apreadaptation to successful
migration into the Suez Canal. Some of the above-mentioned environments and
their biota, especially species also known in the Suez Canal, will be briefly presented below.
The Gulf of Suez. There are no comprehensive studies on the environments of
this Gulf. With salinity increasing from 41 %0 at the entrance of the gulf (maximum
60 m deep), to 44%0 at the northern tip, and the decrease of minimum winter
temperatures from south to north, reaching a low 15-16° C, there is a gradual
depletion of the tropical fauna. Coral reefs are found only in the southern sector
of the Sinai coast. In the northern two-thirds of the coast, corals are adventive,
young colonies i.e. coral communities instead of coral reefs (in the sense of Wainwright, 1965). The species diversity of the corals also decreases. This depletion is
probably due not only to high salinity and low winter temperatures, but also to
recurrent and catastrophic low tides which expose and kill the corals (Bannwarth,
1913) and to high turbidity. It goes without saying that many of the animals
dependent on a flourishing coral reef do not reach the northern end of the Suez
Canal.
From the many species of rock-living sea urchins of the Red Sea only two
species, Diadema setosum and Echinometra mathaei reached the northern end of
the Gulf of Suez according to James and Pearse (1969) Lawrence (1973) reported
that these two species are more resistant to low temperatures than Echinothrix
calamaris and Tripneustes gratilla, species which do not reach the Gulf of Suez.
Even the widespread and common brittle star of the Red Sea, Ophiocoma scolopendrina, does not reach the Gulf of Suez (James and Pearse, 1969). The molluscs of
the Bay of Suez, near the opening of the Suez Canal, have been well investigated
since the times of Isse1, Vaillant, Fischer, and Fuchs. The resulting data show
c1early that the molluscs of the Canal represent an even more impoverished
version ofthe Bay ofSuez assemblage.
-
It is unfortunate for our subject that so little is known about the northern Gulf
of Suez. However, it is evident that its environment is a first hurdle which the
83
salinity metahaline bodies (por, 1975a). The northern tip of the Red Sea, in the
Gulf of Suez, reaches even today salinities of over 44%0. It is now generally
accepted that during the Würm Glacial, the salinity of the Red Sea was even
higher.
The shores of the Red Sea have many lagoon environments with salinities
exceeding that of the open sea. Along the Sinai coast several such lagoons have
been investigated more or less thoroughly: Ras Matarma; EI Bilaiyim; the
mangrove lagoons ofNabq; the pool ofDi Zahav (Dahab) (see Map. 2).
The shallow Persian Gulf has salinities reaching 40%0 in the offshore waters.
Along the southern coast, the Trucial coast, the salinity of the shallow shores
reaches 50%0. In some lagoons values of even 70%0 are reached.
Along with the evaporation-induced high salinity, considerable fluctuation of
temperatures in these metahaline environments also occurs. In some lagoons of
the northern Red Sea, winter temperatures of 10° C have been measured. Even in
the Persian Gulf sabkhas, winter temperatures of 15° C alternate with 40° C in the
summer. The metahaline species are, therefore, adapted to minimum temperatures which are very much below tropical values. The adaptation to high salinity
and low temperature can be considered together as apreadaptation to successful
migration into the Suez Canal. Some of the above-mentioned environments and
their biota, especially species also known in the Suez Canal, will be briefly presented below.
The Gulf of Suez. There are no comprehensive studies on the environments of
this Gulf. With salinity increasing from 41 %0 at the entrance of the gulf (maximum
60 m deep), to 44%0 at the northern tip, and the decrease of minimum winter
temperatures from south to north, reaching a low 15-16° C, there is a gradual
depletion of the tropical fauna. Coral reefs are found only in the southern sector
of the Sinai coast. In the northern two-thirds of the coast, corals are adventive,
young colonies i.e. coral communities instead of coral reefs (in the sense of Wainwright, 1965). The species diversity of the corals also decreases. This depletion is
probably due not only to high salinity and low winter temperatures, but also to
recurrent and catastrophic low tides which expose and kill the corals (Bannwarth,
1913) and to high turbidity. It goes without saying that many of the animals
dependent on a flourishing coral reef do not reach the northern end of the Suez
Canal.
From the many species of rock-living sea urchins of the Red Sea only two
species, Diadema setosum and Echinometra mathaei reached the northern end of
the Gulf of Suez according to James and Pearse (1969) Lawrence (1973) reported
that these two species are more resistant to low temperatures than Echinothrix
calamaris and Tripneustes gratilla, species which do not reach the Gulf of Suez.
Even the widespread and common brittle star of the Red Sea, Ophiocoma scolopendrina, does not reach the Gulf of Suez (James and Pearse, 1969). The molluscs of
the Bay of Suez, near the opening of the Suez Canal, have been well investigated
since the times of Isse1, Vaillant, Fischer, and Fuchs. The resulting data show
c1early that the molluscs of the Canal represent an even more impoverished
version ofthe Bay ofSuez assemblage.
-
It is unfortunate for our subject that so little is known about the northern Gulf
of Suez. However, it is evident that its environment is a first hurdle which the