Structure, fonctionnement, évolution des communautés benthiques ...

tel-00009359, version 1 - 1 Jun 2005
Chapitre 3 - Fonctionnement du réseau trophique benthique de la Grande Vasière
muddy bank and the offshore station, but the SI value in September was in the range of the values
calculated for the central ‘Grande Vasière’ stations. Two different seasonal patterns were observed:
except for F, the water column stratification appeared to be weak in late April-early May, surface-tobottom
temperature differences were less than 1°C, with a thermocline at ca. 20 m in A, B and G,
versus 40 m in C and D (Fig. 2). In September, the water column stratification was well established
(∆T ranging from 4°C in G to 7°C in D, but only 3°C in F); the thermocline depth varied from 30 to 50
m depending on the stations.
Table 2. Tide coefficient, mean (± SD) bottom-water daily temperature (°C), salinity, current velocity
(cm.s -1 ; 1.6 m off bottom) and stratification index (according to Tagushi, 1982) of the water column in
April-May (Sp) and September (Su) 2002.
Station A B C D E F G
Season Sp Su Sp Su Sp Su Sp Su Su Sp Su Sp Su
Tide coefficient 110-112 46-52 111-109 38 64-56 38-41 80-72 48-41 64-55 103-107 69-73 49-43 58-63
Temperature
(°C)
Salinity
Mean current
velocity (cm.s -1 )
Stratification
index (SI)
10.59
(0.01)
35.23
(0.01)
11.75
(3.71)
11.42
(0.01)
35.43
(0.00)
7.15
(3.64)
10.91
(0.10)
35.33
(0.04)
12.46
(3.97)
11.19
(0.05)
35.37
(0.02)
6.01
(2.32)
10.85
(0.05)
35.28
(0.03)
9.21
(3.50)
181
11.48
(0.02)
35.44
(0.00)
8.17
(5.27)
11.21
(0.05)
35.41
(0.02)
8.32
(4.28)
81.5 109.3 102.0 146.2 66.5 150.8 80.3 159.5 128.7 198.8 197.7 89.7 144.6
11.50
(0.04)
35.46
(0.01)
11.20
(5.32)
11.81
(0.03)
35.48
(0.00)
11.97
(5.00)
10.39
(0.02)
34.97
(0.02)
12.20
(6.67)
12.87
(0.15)
35.15
(0.02)
13.30
(4.60)
11.31
(0.01)
35.48
(0.00)
5.40
(2.58)
12.21
(0.04)
35.46
(0.00)
7.80
(2.63)