Vol. 35 – 2009 - Ecologia Mediterranea - Université d'Avignon et des ...

HANADI ISMAÏL, HUSSEIN ABOU-HAMDAN, AHMAD KOUBAYSSI, STÉPHANIE FAYOLLE, GABY KHALAF, ARLETTE CAZAUBON, JACQUES HAURY
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High values for conductivity and TDS for all
studied stations are linked to high imputs of
organic compounds and mineral nutrients in
these sations. However, conductivity and TDS
content in were lower in L1 and L4 than in L2
and L3. Thus L2 and L3 are much more mineralized
than L1 and L4: (Tables 1a, b).
Nitrate concentrations are high but below the
permissible limit in drinking water (Nisbet &
Vernaux 1970 – EU requirements), except for
station L2 where values exceeded 50 mg/L.
Phosphate and nitrite increased also considerably
in station L2 which is more severely
polluted than the other stations. The direct
discharge of domestic wastes and sewage, and
Figure 2 – Temperature, Velocity and Depth in the different stations
(L1, L2, L3 & L4) at each sampling month.
the proximity of the main road contribute to
anthropogenic inputs elevating the measured
physical and chemical parameters in site L2.
The substrate granulometry was finer at L3
and L4 (fine = 95%, coarse = 5%) than L1
(fine = 45%, coarse = 55%) and L2 (fine
= 55%, coarse = 45%) which, together with
the high level of physical and chemical variables
favoured the developpement of plants,
such as macroalgae and phanerogams.
Biotic variables
Macrophytic richness
Twenty seven taxa including hydrophytes,
helophytes and terrestrial species were
observed at the four stations (Table 2). The
taxonomic richness differed among the stations:
9 taxa at L1, 9 taxa at L2, 22 taxa at L3
and 19 taxa at L4. This was mainly due to the
greater helophytes and terrestrial taxonomic
richness at L3 (11 and 8 taxa) and L4 (7 and
5 taxa) than at L1 (3 and 1 taxa) and L2 (6
and 0 taxa).
The hydrophytes species were more numerous
at L4 (7 taxa) and L1 (5 taxa) than L2 and
L3 (3 taxa for each one).
However, five taxa were common to all stations
(Cladophora sp., Vaucheria sp., Lemna
minor L., Glyceria plicata (Fries) Fries and
Phalaris arundinacea L.). Some taxa were
specific to one station like Chara sp. at L1,
Myriophyllum spicatum L., Potamogeton crispus
L., Potamogeton pectinatus L. at L4 and
Veronica anagallis-aquatica L., Galium
aparine L., Lactuca serriola L. and Urtica
dioica L. at L3.
Except in station L1, the taxonomic richness
varied according to the season. The number
of taxa is higher in spring and summer at all
stations. Except for the dry period (total disappearance
of the hydrophytes), richness in
L1 was relatively stable during seasons (Figure
3).
The station L2 was characterized by the
absence of terrestrial species and the stability
of the number of hydrophyte over the seasons
(Figure 3). However we noticed the disappearance
of Lemna minor L. during the winter.
The number of the helophytes presented a
maximum during spring and decreased during
other seasons with the disappearance of
Apium nodiflorum L. Lag., Cyperus eragrostis
Lam., Cyperus longus L., and Phalaris arun-
ecologia mediterranea – Vol. 35 – 2009