France - The Mediterranean Lagoons
309
Table 13.1. Nutrient concentration (mean and range for the observation period) in main Corsican and
Languedocian lagoons
N-NH4
N-N0 3
N-N0 2
P-P0 4
N/P
(mg/l)
(mg!1)
(mg/l)
(mg/l)
(molar)
Thau
Mean
0.054
0.097
0.041
6.05
1986-1987
Min.
0.013
0.027
0.013
004 (Feb)
Max.
0.144
0.213
0.058
17.7 (May)
Mauguio
Mean
0.106
0.217
3.1
1990
Min.
0.014
0.055
0.09 (Sep)
Max.
00456
0.508
1404 (Dec)
Prevost
Mean
0.027
0.01
0.052
2.8
1975
Min.
0.013
0.001
0.016
0.3 (Jul)
Max.
0.062
0.035
0.116
10.3 (Jan)
Berre
Mean
0.03
0.06
0.024
0.027
11.87
1989-1992
Min.
0.001
0
0.001
0.002
1.1 (Jun)
Max.
0.194
0046
0.04
00407
35.5 (Apr)
Diana
Mean
0.026
0.092
0.003
0.019
9.9
1981
Min.
0
0
0
0
0.1 (Jun)
Max.
0.052
0.266
0.026
0.046
27.6 (Apr)
Urbino
Mean
0.019
0.066
0.001
0.011
14.3
1981
Min.
0
0
0
0
0.1 (Jun)
Max.
0.049
0.319
0.001
0.018
91.2 (Apr)
Biguglia
Mean
0.01
0.138
0.006
0.026
23.67
1981
Min.
0
0
0
0
0.20un)
Max.
0.038
00499
0.043
0.132
1760ul)
Mediterranean
0
0.265
0
0.011
16
Sea
freshwater environment and the sea. Variability is therefore maximal.
Here, the effects of desiccation, temperature and salinity variations lead
to large-scale mortalities. The water's edge is therefore a privileged site
for the development of floating or attached macrophytes that thrive on
this organic matter.
From these characteristic features several questions arise: (1) What is
the impact of a given eutrophication event on the systems? (2) What can
be considered as man-made eutrophication: pollution from land (agriculture, industry, urbanization) or pollution in the water itself (intensive
fish and shellfish farming)? (3) How can seasonal, annual and pluriannual variations inherant in the ecosystem be distinguished from the
effects of man-made eutrophication?
To answer these questions, we have chosen two different paths of
investigation: (1) comparative studies of diversified and little polluted
lagoons of the Corsican coasts which are neither overexploited, nor close
to urban or industrialized areas, and which represent various degrees of
eutrophication; and (2) studies of the effects of artificially induced eutrophication at one of these sites.
309
Table 13.1. Nutrient concentration (mean and range for the observation period) in main Corsican and
Languedocian lagoons
N-NH4
N-N0 3
N-N0 2
P-P0 4
N/P
(mg/l)
(mg!1)
(mg/l)
(mg/l)
(molar)
Thau
Mean
0.054
0.097
0.041
6.05
1986-1987
Min.
0.013
0.027
0.013
004 (Feb)
Max.
0.144
0.213
0.058
17.7 (May)
Mauguio
Mean
0.106
0.217
3.1
1990
Min.
0.014
0.055
0.09 (Sep)
Max.
00456
0.508
1404 (Dec)
Prevost
Mean
0.027
0.01
0.052
2.8
1975
Min.
0.013
0.001
0.016
0.3 (Jul)
Max.
0.062
0.035
0.116
10.3 (Jan)
Berre
Mean
0.03
0.06
0.024
0.027
11.87
1989-1992
Min.
0.001
0
0.001
0.002
1.1 (Jun)
Max.
0.194
0046
0.04
00407
35.5 (Apr)
Diana
Mean
0.026
0.092
0.003
0.019
9.9
1981
Min.
0
0
0
0
0.1 (Jun)
Max.
0.052
0.266
0.026
0.046
27.6 (Apr)
Urbino
Mean
0.019
0.066
0.001
0.011
14.3
1981
Min.
0
0
0
0
0.1 (Jun)
Max.
0.049
0.319
0.001
0.018
91.2 (Apr)
Biguglia
Mean
0.01
0.138
0.006
0.026
23.67
1981
Min.
0
0
0
0
0.20un)
Max.
0.038
00499
0.043
0.132
1760ul)
Mediterranean
0
0.265
0
0.011
16
Sea
freshwater environment and the sea. Variability is therefore maximal.
Here, the effects of desiccation, temperature and salinity variations lead
to large-scale mortalities. The water's edge is therefore a privileged site
for the development of floating or attached macrophytes that thrive on
this organic matter.
From these characteristic features several questions arise: (1) What is
the impact of a given eutrophication event on the systems? (2) What can
be considered as man-made eutrophication: pollution from land (agriculture, industry, urbanization) or pollution in the water itself (intensive
fish and shellfish farming)? (3) How can seasonal, annual and pluriannual variations inherant in the ecosystem be distinguished from the
effects of man-made eutrophication?
To answer these questions, we have chosen two different paths of
investigation: (1) comparative studies of diversified and little polluted
lagoons of the Corsican coasts which are neither overexploited, nor close
to urban or industrialized areas, and which represent various degrees of
eutrophication; and (2) studies of the effects of artificially induced eutrophication at one of these sites.