98
T.Hopner
that even in a sub-area of limited size, the Musallamiya-Dafi Bay system (Saudi Arabia,
north of Jubail), a variety of different habitats can be discriminated: terrestrial desert,
wetland, rocky, sandy and muddy intertidal zone, shallow subtidal area, open water,
coral reefs, islands. An enumeration like this does not point to the narrow mosaic of
small and different biotopes which is typical of the well structured coastline stretches.
Each of the biotopes has its own properties which make them different in coping with
the emissions. In the following text the most typical coastal sub-ecosystems of the Gulf
are enumerated, focusing on the flat coasts in the north, west and south.
We have arranged these sub-systems in the sequence from the lowest to the highest
sensitivity (Table 9.1). The arguments are coastal ecological ones (arguments like visual
sensitivity and others are omitted). The sensitivity index model is based on the coastal
sensitivity scale to oil accidents elaborated by Gundlach and Hayes (1978) on the occasion of the Amoco Cadiz accident (Bretagne, France) of 1978. Criteria were th!,! sensitivity of the biocoenosis, the danger of oil accumulation and the natural recovery potential. When this model is transferred to the sensitivity to a desalination plant, criteria
are sensitivity to the emissions, but not the ability of the ecosystem to dilute the loads.
9.9
How to Use the Sensitivity Index
In the case of an EIA for a special project the number of sub-ecosystems is expected to
be much less, and the remaining categories will be more similar. It is expected that for
a special project several alternative locations will be proposed. Then the sensitivities of
these locations will be assessed and compared. The coast of the United Arab Emirates,
to take an example, exhibits the categories 1, 6 through 8 and 10 through 15 (see Table 9.1), but sub-categories may be added. The sensitivity profile of a given region is
narrower than the profile of a whole sea (like the Arabian Gulf). Normally, a regional
sensitivity assessment will be done and two or more sites within one region will be
compared. A location at an exposed coastal strip under the influence of a coast-parallel
current is less sensitive than a channel-lagoon or shallow bay system. In contrast, a
barrier island/lagoon system is a typical case of peculiar sensitivity to desalination
plants. The considerable residence time of the water, e.g. within the channels and lagoons, means at the same time that the water discharged stays long within the system.
As the salinity gradients show, the influence of the tides is not sufficient to provide
effective flushing. It must be expected that pollutants are deposited within the system
with significant consequences for the ecosystem.
9.10
Effects on the Regional Ecosystem as a Whole
On a geographical map, the Gulf seems to be an enclosed sea with limited exchange
with the ocean. In fact, the exchange is high. A sun-driven current system links the Gulf
strongly to the ocean. The Gulf ocean circulation (Sheppard et al. 1992) is driven by the
evaporation within the Gulf and supported by the prevailing winds. By evaporation,
salinity increases in the northern part up to 40 psu. The heavy water sinks down and
leaves the Gulf as a bottom current. It is replaced by ocean water of about 37 psu which
enters the Gulf as a surface current. The current moves along the Iranian coast while
T.Hopner
that even in a sub-area of limited size, the Musallamiya-Dafi Bay system (Saudi Arabia,
north of Jubail), a variety of different habitats can be discriminated: terrestrial desert,
wetland, rocky, sandy and muddy intertidal zone, shallow subtidal area, open water,
coral reefs, islands. An enumeration like this does not point to the narrow mosaic of
small and different biotopes which is typical of the well structured coastline stretches.
Each of the biotopes has its own properties which make them different in coping with
the emissions. In the following text the most typical coastal sub-ecosystems of the Gulf
are enumerated, focusing on the flat coasts in the north, west and south.
We have arranged these sub-systems in the sequence from the lowest to the highest
sensitivity (Table 9.1). The arguments are coastal ecological ones (arguments like visual
sensitivity and others are omitted). The sensitivity index model is based on the coastal
sensitivity scale to oil accidents elaborated by Gundlach and Hayes (1978) on the occasion of the Amoco Cadiz accident (Bretagne, France) of 1978. Criteria were th!,! sensitivity of the biocoenosis, the danger of oil accumulation and the natural recovery potential. When this model is transferred to the sensitivity to a desalination plant, criteria
are sensitivity to the emissions, but not the ability of the ecosystem to dilute the loads.
9.9
How to Use the Sensitivity Index
In the case of an EIA for a special project the number of sub-ecosystems is expected to
be much less, and the remaining categories will be more similar. It is expected that for
a special project several alternative locations will be proposed. Then the sensitivities of
these locations will be assessed and compared. The coast of the United Arab Emirates,
to take an example, exhibits the categories 1, 6 through 8 and 10 through 15 (see Table 9.1), but sub-categories may be added. The sensitivity profile of a given region is
narrower than the profile of a whole sea (like the Arabian Gulf). Normally, a regional
sensitivity assessment will be done and two or more sites within one region will be
compared. A location at an exposed coastal strip under the influence of a coast-parallel
current is less sensitive than a channel-lagoon or shallow bay system. In contrast, a
barrier island/lagoon system is a typical case of peculiar sensitivity to desalination
plants. The considerable residence time of the water, e.g. within the channels and lagoons, means at the same time that the water discharged stays long within the system.
As the salinity gradients show, the influence of the tides is not sufficient to provide
effective flushing. It must be expected that pollutants are deposited within the system
with significant consequences for the ecosystem.
9.10
Effects on the Regional Ecosystem as a Whole
On a geographical map, the Gulf seems to be an enclosed sea with limited exchange
with the ocean. In fact, the exchange is high. A sun-driven current system links the Gulf
strongly to the ocean. The Gulf ocean circulation (Sheppard et al. 1992) is driven by the
evaporation within the Gulf and supported by the prevailing winds. By evaporation,
salinity increases in the northern part up to 40 psu. The heavy water sinks down and
leaves the Gulf as a bottom current. It is replaced by ocean water of about 37 psu which
enters the Gulf as a surface current. The current moves along the Iranian coast while