1 The African Marginal and Enclosed Seas: An Overview
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On average, the Mediterranean Sea is poor in nutrients, with consequent low
phytoplankton biomass and primary production. Oligotrophy increases from west
to east. Primary production in the open sea is considered to be phosphorus-limited,
rather than nitrogen-limited as in most of the world’s oceans. By contrast, a rich biodiversity characterizes the Mediterranean ecosystem: the fauna and flora are among
the richest in the world, with over 10,000 marine species recorded, highly diverse
and with a large proportion (28 %) of endemic species. No species disappearances
have been reported, but changes in species composition and richness have occurred in
some areas (with some species showing alarming trends, as in the case of the bluefin
tuna, Thunnus thynnus in particular, due to overfishing of a stock already threatened).
The introduction of exotic species – such as that of tropical species from the Red
Sea, which occurred after the Suez Canal opening
5 – is a growing concern. Large
populations of marine mammals (e.g. the fin whale, Balaenoptera physalus) have
been documented, while other species are in danger (e.g. the monk seal, Monachus
monachus, is critically endangered; the marine turtles Caretta caretta and Chelonya
midas are listed respectively as threatened and endangered).
The state of the Mediterranean’s open waters is generally good, but coastal areas
are subject to various environmental problems, including eutrophication and heavy
metal, organic and microbial pollution. Land-based activities (urbanization, industry and agriculture, particularly in the north-west) are the main sources of pollution.
About 30 % of the ever-increasing population of Mediterranean countries, approximately 150 million people, lives on the coast. Adding to the resident population, each
year the Mediterranean Sea is also host to 150 million tourists. Population density,
almost 100 people per km
2 , twice that of the region as a whole, and related economic activities place a high pressure on coastal zones. Since the Mediterranean Sea
is essentially oligotrophic, eutrophication is limited to near-coastal sites that receive
enhanced nutrient loads (of anthropogenic nature) from rivers, or direct discharges of
untreated domestic and industrial wastewaters, and to adjacent open waters. However,
this is expected to worsen, together with the occurrence of harmful algal blooms.
Oil shipping is also a growing concern, since of the 2000 cargos that sail in the
Mediterranean at any given time, about 250–300 are oil tankers, transporting 400
million tons/year of petroleum products (i.e. 30 % of world traffic). This large traffic
gives rise to about 1 million tons/year of illegal oil discharges at sea (i.e. 20 % of the
total oil pollution in the oceans).
1.5 Red Sea
The Red Sea is a semi-enclosed tropical basin, bounded by northeastern Africa,
to the west, and the Arabian Peninsula, to the east (Fig. 1.5). The elongated and
narrow-shaped basin extends between the Mediterranean Sea, to the north-west, and
5 A phenomenon known as the Lessepsian Migration, after Ferdinand de Lesseps, the engineer who
oversaw the Canal’s construction.
17
On average, the Mediterranean Sea is poor in nutrients, with consequent low
phytoplankton biomass and primary production. Oligotrophy increases from west
to east. Primary production in the open sea is considered to be phosphorus-limited,
rather than nitrogen-limited as in most of the world’s oceans. By contrast, a rich biodiversity characterizes the Mediterranean ecosystem: the fauna and flora are among
the richest in the world, with over 10,000 marine species recorded, highly diverse
and with a large proportion (28 %) of endemic species. No species disappearances
have been reported, but changes in species composition and richness have occurred in
some areas (with some species showing alarming trends, as in the case of the bluefin
tuna, Thunnus thynnus in particular, due to overfishing of a stock already threatened).
The introduction of exotic species – such as that of tropical species from the Red
Sea, which occurred after the Suez Canal opening
5 – is a growing concern. Large
populations of marine mammals (e.g. the fin whale, Balaenoptera physalus) have
been documented, while other species are in danger (e.g. the monk seal, Monachus
monachus, is critically endangered; the marine turtles Caretta caretta and Chelonya
midas are listed respectively as threatened and endangered).
The state of the Mediterranean’s open waters is generally good, but coastal areas
are subject to various environmental problems, including eutrophication and heavy
metal, organic and microbial pollution. Land-based activities (urbanization, industry and agriculture, particularly in the north-west) are the main sources of pollution.
About 30 % of the ever-increasing population of Mediterranean countries, approximately 150 million people, lives on the coast. Adding to the resident population, each
year the Mediterranean Sea is also host to 150 million tourists. Population density,
almost 100 people per km
2 , twice that of the region as a whole, and related economic activities place a high pressure on coastal zones. Since the Mediterranean Sea
is essentially oligotrophic, eutrophication is limited to near-coastal sites that receive
enhanced nutrient loads (of anthropogenic nature) from rivers, or direct discharges of
untreated domestic and industrial wastewaters, and to adjacent open waters. However,
this is expected to worsen, together with the occurrence of harmful algal blooms.
Oil shipping is also a growing concern, since of the 2000 cargos that sail in the
Mediterranean at any given time, about 250–300 are oil tankers, transporting 400
million tons/year of petroleum products (i.e. 30 % of world traffic). This large traffic
gives rise to about 1 million tons/year of illegal oil discharges at sea (i.e. 20 % of the
total oil pollution in the oceans).
1.5 Red Sea
The Red Sea is a semi-enclosed tropical basin, bounded by northeastern Africa,
to the west, and the Arabian Peninsula, to the east (Fig. 1.5). The elongated and
narrow-shaped basin extends between the Mediterranean Sea, to the north-west, and
5 A phenomenon known as the Lessepsian Migration, after Ferdinand de Lesseps, the engineer who
oversaw the Canal’s construction.