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M. Ahmed and V. Barale
19.2 Lagoon and Coastal Waters of Northeastern Africa
The coastal waters of northern Egypt are under the direct impact of the Nile river
outflow (Barale and Larkin 1998). Although the river plume is unlikely to have
maintained the same impact on the pelagic zone it must have had, in the era preceding
the 1963 closure of the Aswan High dam, its influence on the coastal zone is still (or
perhaps is again, according to Nixon 2003) a major feature of the area. The lagoons
bordering the Nile river delta are all located by the plume impact area, and represent
hotspots of great environmental and socio-economic significance. Four of them, i.e.
the Lakes Maryut, Edku, Burullus and Manzala, are deltaic water bodies, while a
fifth one is the non-deltaic Lake Bardawil (Fig. 19.1).
The four lagoons situated in the Nile river delta are shallow basins (depth < 3 m,
with an average depth of ∼1 m) of brackish waters. Lake Maryut is artificially enclosed and has long been without a major connection to the sea. Lakes Edku, Burullus
and Manzala display typical lagoon characteristics, are separated from the Mediterranean by low-lying, narrow coastal sand barriers, and are connected to the sea by
protected channels. The latter are vital for dozen of species of fish that depend on the
lakes for at least part of their life cycle, and constitute the only inlet/outlet available
for thousands of commercial fishing boats that operate in the lakes. The deltaic lakes
receive much of their freshwater input from irrigation drains located along the southern, eastern, and western margins. The fifth lagoon, the non-deltaic Lake Bardawil,
is situated away from the Nile delta region, in northern Sinai. Contrary to the other
lagoons of the area, this large, somewhat deeper, hypersaline water body does not
have any freshwater inflow, and communicates only with the Mediterranean Sea.
Like other Mediterranean lagoons, those of northern Egypt originated as a result
of changes in sea level, combined with neotectonic land subsidence. In the Nile
river delta lagoons, bottom sediments are composed of plant- and shell-rich muds
and sandy silts, whereas the Bardawil lagoon displays sand-size sediments mixed
with evaporates (Levy 1974). In general, the coarsest sediments are found near the
openings toward the sea, where current velocities are largest, and the finest sediments are in the innermost reaches, where drains are located and current velocities
approach zero. Biological processes contribute significantly to production of carbonate sediments through formation of mollusk shells, ostracod and foraminiferal
tests (Bernasconi and Stanley 1994). In fact, according to the trophic state index
suggested by Carlson (1977), the lagoons can be considered eutrophic during the
entire year. The lagoon margins are bordered by extensive marshes rich in aquatic
macrophytic plants.
The ecosystem in these coastal water bodies is controlled by the interaction of natural and anthropogenic factors. Ongoing natural processes, including barrier erosion,
channel siltation, land subsidence and rising sea level, as well as the prevailing sedimentary processes, have induced substantial changes in the lagoons’ environment
(Ahmed et al. 2000). Human activities, such as inlet engineering works, reclamation of water areas, wastewater discharge, salt paning, fishing, hunting of water
birds and recreation, aggravated by the lack of effective and consolidated management practices, continue to have a major impact on the lagoons’ ecological balance
M. Ahmed and V. Barale
19.2 Lagoon and Coastal Waters of Northeastern Africa
The coastal waters of northern Egypt are under the direct impact of the Nile river
outflow (Barale and Larkin 1998). Although the river plume is unlikely to have
maintained the same impact on the pelagic zone it must have had, in the era preceding
the 1963 closure of the Aswan High dam, its influence on the coastal zone is still (or
perhaps is again, according to Nixon 2003) a major feature of the area. The lagoons
bordering the Nile river delta are all located by the plume impact area, and represent
hotspots of great environmental and socio-economic significance. Four of them, i.e.
the Lakes Maryut, Edku, Burullus and Manzala, are deltaic water bodies, while a
fifth one is the non-deltaic Lake Bardawil (Fig. 19.1).
The four lagoons situated in the Nile river delta are shallow basins (depth < 3 m,
with an average depth of ∼1 m) of brackish waters. Lake Maryut is artificially enclosed and has long been without a major connection to the sea. Lakes Edku, Burullus
and Manzala display typical lagoon characteristics, are separated from the Mediterranean by low-lying, narrow coastal sand barriers, and are connected to the sea by
protected channels. The latter are vital for dozen of species of fish that depend on the
lakes for at least part of their life cycle, and constitute the only inlet/outlet available
for thousands of commercial fishing boats that operate in the lakes. The deltaic lakes
receive much of their freshwater input from irrigation drains located along the southern, eastern, and western margins. The fifth lagoon, the non-deltaic Lake Bardawil,
is situated away from the Nile delta region, in northern Sinai. Contrary to the other
lagoons of the area, this large, somewhat deeper, hypersaline water body does not
have any freshwater inflow, and communicates only with the Mediterranean Sea.
Like other Mediterranean lagoons, those of northern Egypt originated as a result
of changes in sea level, combined with neotectonic land subsidence. In the Nile
river delta lagoons, bottom sediments are composed of plant- and shell-rich muds
and sandy silts, whereas the Bardawil lagoon displays sand-size sediments mixed
with evaporates (Levy 1974). In general, the coarsest sediments are found near the
openings toward the sea, where current velocities are largest, and the finest sediments are in the innermost reaches, where drains are located and current velocities
approach zero. Biological processes contribute significantly to production of carbonate sediments through formation of mollusk shells, ostracod and foraminiferal
tests (Bernasconi and Stanley 1994). In fact, according to the trophic state index
suggested by Carlson (1977), the lagoons can be considered eutrophic during the
entire year. The lagoon margins are bordered by extensive marshes rich in aquatic
macrophytic plants.
The ecosystem in these coastal water bodies is controlled by the interaction of natural and anthropogenic factors. Ongoing natural processes, including barrier erosion,
channel siltation, land subsidence and rising sea level, as well as the prevailing sedimentary processes, have induced substantial changes in the lagoons’ environment
(Ahmed et al. 2000). Human activities, such as inlet engineering works, reclamation of water areas, wastewater discharge, salt paning, fishing, hunting of water
birds and recreation, aggravated by the lack of effective and consolidated management practices, continue to have a major impact on the lagoons’ ecological balance