biological diversity and tropical forests in tunisia - PART

By far the most serious problem threatening Lake Ichkeul is a series
of 6 dams being constructed on all 5 of the main rivers flowing into the
lake. The dams will severely reduce the freshwater input to the lake,
resulticg ic lower summer water levels and increased influxes of seawater.
Significant increases ic salinity will kill off much of the Potamogeton
and Scirpus that currently attract waterfowl. If no mitigation actions
are taken, the habitat value will drop sharply, with serious ramifications
for macy species of birds and the natural integrety of the national park.
Hollis ( 1986) recommended five possible schemes for ameliorating the
effects of the dams. None of the actions has been due to indecision by
responsable agents and a lack of finances for the projects. The
recommended actions include filling the Djoumine marsh; installing a weir
or slaice at Oued Tinja to control water flow; building dykes to reduce
the area of the lake, thus reducing salinity; and reservoir releases when
the lake is below 10 cm ASL.
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3.3.1.2. Lake Bizerte
Lake Bizerte is cocnected to, and lies northeast of, Lake Ichkeul.
The lake area is aboat 13,000 ha and fluctuates slightly with the tides.
Water ic Lake Bizerte is saline, but during winter and spring, water
enterieg from Lake Ichkeul through Oued Tinja lowers the salinity to
slightly less thac that of seawater (35 g/l). A t its deepest po2ct the
lake is 12 m deep and most of the lake is deeper thac 2 m. The adjacent
terrair is gectly andulating with a low marsh on the east side.
A. Vegetatioc
Most of the shoreline has been cultivated or developed. In the marsh
at the east sidi the parts that have not been cultivated or developed
support halophile vegetation. Marine flora totals 145 species (~aouli
1980). The number of species decreases close to Oued Tinja due to the
lower salicity, bat marine Phacerogames such as Zostera marina and Ruppia
maritime cac be foacd. Other marine Phanerogames growing in the lake
icclude Zostera coltii betweec 0.5 m and 1 m deep (especially on the north
side) end Cymodocea codosa at dapths between 1 and 2 m. Algaes found in
the shallow waters include:
Chlorophyceaes :
Ulva lactuca
Entermorpha compressa
Chaetomorpha linum (rare)
Cladophora prolifera (rare)
C. laetevirecs
Caalerpa prolifera
Pheophyceaes:
Cystoskirs abmtacifolia
Dictyota abrotanifolia
Dicty~pteris polupodioides
Padica pavoria ( rare)
Rhodophyceaes:
Lithohamnium fruticulosum
L. lenormandi
Jania rubens (rare)
Corralina officinalis
Laurencia papillosa ( rare)
Gracilaria confervoides (rare)
Posidonia oceanica
Acetalbularia mediterranea
Halimedia tuna