82
The Suez Canal
indicate that reproduction in the Canal should be considered to be the rule rather
than the exception.
Schellenberg (1928), analyzing a very diversified collection of Amphipoda,
wrote that the populations in the Canal do not differ in fertility and in size from
the populations outside the waterway. The same is true for the harpacticoid
copepods, analyzed by Por and Marcus (1972).
The size problem has been mentioned in passing by Fox (1929). He set out to
inquire whether the high salinity has a stunting effect on the Canal anirnals. The
results of Fox indicate that the specimens living in the Canal are not smaller than
their conspecifics living in the open sea. In some cases, such as the sea cucumber
Synaptula reciproquans, the ascidian Phallusia nigra and the grey mullet Mugil
cephalus, sizes are even greater than usual. No author ever reported having found
specimens sm aller than usual, or individuals deformed or deleteriously developed
in any sense. One can, therefore, assurne that the Canal populations live within
their eco-physiological range. The populations living in the Canal reproduce
normally, and are not dependent on occasional reinforcements coming from outside. The species living in the Canal are preadapted to the conditions which they
encountered and there was no need for an adaptative process, or for appearance
of "physiological races", nor of new genetic combination or subspecies. The Red
Sea species inhabiting the Canal have behind them a long history of adaptation to
high salinities in many different sites oftheir zoogeographical range.
2.9 The Metahaline Environments
of the Red Sea and the Persian Gulf
To understand the success of the Red Sea species in the settling of the high
salinity waters of the Suez Canal, one must for a moment raise the curtain over a
much larger scene, that of the Western Indian Ocean. The hot desert shores of
Arabia, the horn of Africa, and Persia shelter a wealth of semi-isolated litt oral
basins, with higher-than-sea salinities. If these basins are deep and permanently
water-filled, they are termed "Ghor" or "Sharm". If they are shallow and periodically or permanently reduced to salt swamps, they are called "Sabkha". Evaporation may reach such high values as 300 cm/year.
In all these environments marine biota live, adapted unilaterally to high salinities. It is in a sense a hyper-eurhyalinity as opposed to the much better-known
amphi-euryhalinity ofthe estuarine organisms.
The term metahaline, as proposed by Por (1972), covers environments of high
salinity which are still inhabited by marine biota, fulfilling all their life-cycle in the
respective basin. The marine hyper-euryhaline organisms of this type are consequently called metahaline organisms. The upper limit of the "Metahalinicum" has
to be sought over 70%0 when through CaC0 3 precipitation the physico-chemical
properties of the water change. The metahaline organisms are replaced there by
amphieuryhaline organisms, many of which necessarily reproduce outside the
high salinity basin.
At times, especially at low eustatic levels, whole portions of the adjacent seas
of the Indian Ocean-the Red Sea and Persian Gulf----could turn into high-
The Suez Canal
indicate that reproduction in the Canal should be considered to be the rule rather
than the exception.
Schellenberg (1928), analyzing a very diversified collection of Amphipoda,
wrote that the populations in the Canal do not differ in fertility and in size from
the populations outside the waterway. The same is true for the harpacticoid
copepods, analyzed by Por and Marcus (1972).
The size problem has been mentioned in passing by Fox (1929). He set out to
inquire whether the high salinity has a stunting effect on the Canal anirnals. The
results of Fox indicate that the specimens living in the Canal are not smaller than
their conspecifics living in the open sea. In some cases, such as the sea cucumber
Synaptula reciproquans, the ascidian Phallusia nigra and the grey mullet Mugil
cephalus, sizes are even greater than usual. No author ever reported having found
specimens sm aller than usual, or individuals deformed or deleteriously developed
in any sense. One can, therefore, assurne that the Canal populations live within
their eco-physiological range. The populations living in the Canal reproduce
normally, and are not dependent on occasional reinforcements coming from outside. The species living in the Canal are preadapted to the conditions which they
encountered and there was no need for an adaptative process, or for appearance
of "physiological races", nor of new genetic combination or subspecies. The Red
Sea species inhabiting the Canal have behind them a long history of adaptation to
high salinities in many different sites oftheir zoogeographical range.
2.9 The Metahaline Environments
of the Red Sea and the Persian Gulf
To understand the success of the Red Sea species in the settling of the high
salinity waters of the Suez Canal, one must for a moment raise the curtain over a
much larger scene, that of the Western Indian Ocean. The hot desert shores of
Arabia, the horn of Africa, and Persia shelter a wealth of semi-isolated litt oral
basins, with higher-than-sea salinities. If these basins are deep and permanently
water-filled, they are termed "Ghor" or "Sharm". If they are shallow and periodically or permanently reduced to salt swamps, they are called "Sabkha". Evaporation may reach such high values as 300 cm/year.
In all these environments marine biota live, adapted unilaterally to high salinities. It is in a sense a hyper-eurhyalinity as opposed to the much better-known
amphi-euryhalinity ofthe estuarine organisms.
The term metahaline, as proposed by Por (1972), covers environments of high
salinity which are still inhabited by marine biota, fulfilling all their life-cycle in the
respective basin. The marine hyper-euryhaline organisms of this type are consequently called metahaline organisms. The upper limit of the "Metahalinicum" has
to be sought over 70%0 when through CaC0 3 precipitation the physico-chemical
properties of the water change. The metahaline organisms are replaced there by
amphieuryhaline organisms, many of which necessarily reproduce outside the
high salinity basin.
At times, especially at low eustatic levels, whole portions of the adjacent seas
of the Indian Ocean-the Red Sea and Persian Gulf----could turn into high-