biological diversity and tropical forests in tunisia - PART

3.3.1.6. Thyna Salt Ponds
Just south of Sfax, and 270 km south of Tunis, are the Thyna salt
ponds. The salt ponds are part of the ecological unit of the Gulf of
Gabes coast, but are described separately here because they also qualify
as a marine lagoon. The east side of the lagoon borders the sea and the
two are only separated by an embankment. Before the embankment was
constructed, the area was an kntertidal zone. The salt ponds are
continuously being extended toward the south. In 1984 there were 860 ha
sectioned off from the sea, although not all of it was in operation for
salt production (van Dijk 1986). The salt ponds are shallow (most less
than 1 m deep, all less than 3 m) with sandy and muddy bottom substrates.
A. Vegetation
Sparse halophile vegetation (~alocnemum, ~rthrocnemum) occurs at the
edges of the salt ponds, but there is almost no submergect vegetation ic
the ponds. In the less saline sections there is abucdact phytoplankton
a~d algae.
B. Fauna
Mammals. Red fox and sand rat have been observed (Van Dijk 1986)~ but
they are not likely to occur in large numbers.
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Birds. The close proximity to the sea makes Thyna a good high tide
resting place for many species of waterfowl and waders and several species
also nest there. Most of the birds listed for the Gulf of Gabes (figure
4) cac also be observed at Thyna.
August , 1987 :
The following species were observed in
Black-necked grebe
Littl* egret
Spoonbill
Flamingo
n Shelduck
Oystercatcher
Avocet
Kentish plover
Little stint
D~nlin
White-winged black tern
C. Influences
Turnstone Black-headed gull
Redshank Mediterranean gull
G reenshank Lesser black back
Marsh sandpiper Herring gull
Curlew sandpiper c Slender-billed gull
Black-tailed godwit Gall-billed tern
Bar- tailed godwi t n Commm tern
Curlew Black tern
Black-winged stilt n Little tern
Ruff Sandwich tern
n = Nesting Birds
The ponds were created for commercial salt productioc, so there is
freqae~t macipulation of water levels and equipment operatioc. Nests can
be flooded or crashed by this activity, but the salt ccmpany's guardians
protect adult birds from poaching and harassment. Ac adjacect ph3sphate
plact acd an olive oil refinery discharge affluects ict3 the sea.