Geoscience Reference
In-Depth Information
8
8
May
July
6
6
1988
4
4
1988
2
2
0
0
1997
−
−
2
1997
−
−
2
0
2
4
6
8
10
0
2
4
6
8
10
Log Individual Volume (
µ
m
3
)
m
3
)
Log Individual Volume (
µ
8
8
1988
June
6
August
6
4
4
1988
2
2
0
0
1997
−
2
−
−
2
1997
−
02468 0 2
02468 0 2
Log Individual Volume (
µ
m
3
)
Log Individual Volume (
µ
m
3
)
FIGURE 9.3.19
Comparison of biomass size-spectra in the planktonic food web of the Mar
Menor between 1988, an oligotrophic state without jellyfishes (open circles, dotted regression
line) and 1997, a eutrophic state that jellyfishes control (filled circles, continuous regression line).
them demands detailed monitoring programs, which are sometimes incompatible with
the accelerated evolution of the lagoon, forced by human-driven activities.
In the case of the Mar Menor, difficulties in the establishment of such
cause-effect relationships have been compounded by the lack of detailed studies
and data on the hydrographic conditions and biological assemblages before most
human interventions. Furthermore, although in recent years the increasing demands
on the Mar Menor coasts have led to the elaboration of
Indicative Plans of Uses of
the Littoral
and distinct evaluations of the environmental impact of human activities
in terms of physical, biological, and human environment, in most cases, only super-
ficial analyses of the marine environment have been made, and they have focused
on satisfying minimum administrative or legal requisites instead of generating the
knowledge required for adequate management.
In any case, the large amount of information compiled during the last 20 years
permits us to establish general guidelines for such cause-effect relationships in order
to draw conceptual models to assign priorities for managerial actions and lines of
research.
Figure 9.3.20
shows a diagram that relates three of the human activities in the
Mar Menor discussed above: the enlargement of the El Estacio Channel, the building
of artificial beaches, and the construction of sport harbors.
13
Many of the conse-
quences of these activities involve potential risks to human use and the local
economy. When the Figure 9.3.20 flowchart was created in 1994, the allochthonous
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