74
The Suez Canal
same species are as widespread and dominant as 50 years ago. Por and Marcus
(1972) reach the circumstantial conclusion that the benthic copepods inhabiting
the Canal in 1902, when the pump plankton ofHerdman was collected (see above)
belonged to an essentially similar association as found today. From the two
studies by Lipkin (1972a, b) it appears that the main water plant populations have
also been constant since the list of Lyle and RendIe (in Fox, 1926) and Lami
(1932), not to speak of Beets (1953). It is worthwhile to notice that we have no data
prior to 1924 concerning the water-plant population of the Suez Canal. It is
evident that at the time of Keller and of Krukenberg there was no Halophila
stipulacea in the Canal and the advance ofthe macrophytic algae (besides perhaps
Cladophora) was only beginning.
W. Steinitz (1929) considered the possibility of some species having later disappeared from the Canal waters. Gohar (1954) even implies that in the very first
years of the Canal conditions were more propitious for settling of benthic animals
since "the deposition of mud had not gone so far as to impede the settlement of
plants and animals on the bottom". Taking up this theme Thorson (1971) considers that the "bottom which was fairly clean ... in 1869 (!) now consists of an
increasing layer of gelatinous mud".
Probably most of the presumed cases of species' disappearance can be attributed to two circumstances: (1) unequal collecting (different sites, different methods, different seasons); (2) reduction of numbers owing to successional phenomena. W. Steinitz for instance gives the case of Brachidontes variabilis which was
frequent in the Canal, but in the collections of the Cambridge Expedition it had
become rare. He thought the same had happened to Mactra olorina. However,
both molluscs are still very frequent in the Canal system. How little one can rely
on the fortuitous lack or sparsity of a species in a collection can be shown by two
examples: Gruvel (1936) found numerous populations of Branchiostoma lanceolatum in the Canal: the Cambridge Expedition, less than ten years before did not
report one specimen. The same author reports the tectibranch gastropod N otarchus savignyi as being characteristically associated with Halophila, everywhere in
Lake Timsah. This species does not appear in O'Donoghue's list (1929) based on
the Cambridge collections, and Barash and Danin (1972) even believe that their
record (under the name of Bursatella leachi savigniana) is the first report from the
Suez Canal.
Only one instance given by W. Steinitz seems to be a ca se of a possible retreat
or even disappearance: the rock-boring Pholas dactylus reported as very frequent
by Keller and subsequently by Tillier and Bavay was not found by the Fox
Expedition in 1924 "although a special search was made in the Canal banks". The
sandstone slabs were found "riddled with holes presumably made by aboring
mollusc but neither living molluscs nor shells were found within" (Fox, 1926,
p.29). Fox suggests "oil from ships" as one possible explanation for this disappearance. That especially in the artificial canal sectors, pollution and the Canal
widening project could exterminate whole populations of sessile animals seems a
reasonable assumption.
Succession also changed the quantitative appearance of some species. For
instance, the intertidal levels were at an early stage inhabited only by Balanus
amphitrite and Brachidontes variabilis. At the present, several other species have
The Suez Canal
same species are as widespread and dominant as 50 years ago. Por and Marcus
(1972) reach the circumstantial conclusion that the benthic copepods inhabiting
the Canal in 1902, when the pump plankton ofHerdman was collected (see above)
belonged to an essentially similar association as found today. From the two
studies by Lipkin (1972a, b) it appears that the main water plant populations have
also been constant since the list of Lyle and RendIe (in Fox, 1926) and Lami
(1932), not to speak of Beets (1953). It is worthwhile to notice that we have no data
prior to 1924 concerning the water-plant population of the Suez Canal. It is
evident that at the time of Keller and of Krukenberg there was no Halophila
stipulacea in the Canal and the advance ofthe macrophytic algae (besides perhaps
Cladophora) was only beginning.
W. Steinitz (1929) considered the possibility of some species having later disappeared from the Canal waters. Gohar (1954) even implies that in the very first
years of the Canal conditions were more propitious for settling of benthic animals
since "the deposition of mud had not gone so far as to impede the settlement of
plants and animals on the bottom". Taking up this theme Thorson (1971) considers that the "bottom which was fairly clean ... in 1869 (!) now consists of an
increasing layer of gelatinous mud".
Probably most of the presumed cases of species' disappearance can be attributed to two circumstances: (1) unequal collecting (different sites, different methods, different seasons); (2) reduction of numbers owing to successional phenomena. W. Steinitz for instance gives the case of Brachidontes variabilis which was
frequent in the Canal, but in the collections of the Cambridge Expedition it had
become rare. He thought the same had happened to Mactra olorina. However,
both molluscs are still very frequent in the Canal system. How little one can rely
on the fortuitous lack or sparsity of a species in a collection can be shown by two
examples: Gruvel (1936) found numerous populations of Branchiostoma lanceolatum in the Canal: the Cambridge Expedition, less than ten years before did not
report one specimen. The same author reports the tectibranch gastropod N otarchus savignyi as being characteristically associated with Halophila, everywhere in
Lake Timsah. This species does not appear in O'Donoghue's list (1929) based on
the Cambridge collections, and Barash and Danin (1972) even believe that their
record (under the name of Bursatella leachi savigniana) is the first report from the
Suez Canal.
Only one instance given by W. Steinitz seems to be a ca se of a possible retreat
or even disappearance: the rock-boring Pholas dactylus reported as very frequent
by Keller and subsequently by Tillier and Bavay was not found by the Fox
Expedition in 1924 "although a special search was made in the Canal banks". The
sandstone slabs were found "riddled with holes presumably made by aboring
mollusc but neither living molluscs nor shells were found within" (Fox, 1926,
p.29). Fox suggests "oil from ships" as one possible explanation for this disappearance. That especially in the artificial canal sectors, pollution and the Canal
widening project could exterminate whole populations of sessile animals seems a
reasonable assumption.
Succession also changed the quantitative appearance of some species. For
instance, the intertidal levels were at an early stage inhabited only by Balanus
amphitrite and Brachidontes variabilis. At the present, several other species have