Environmental and Physical Factors Affecting the Diversity and Distribution of the Ichthyoplankton in an "Inverse Estuary", the Sine Saloum (Senegal)

For several decades, the rainfall deficit experienced by the Sahelian
zone has strongly disturbed the West African estuarine ecosystems and in
particular the Sine Saloum estuary in Senegal. The most obvious changes
of the environment are unquestionably the inversion of the salinity
gradient, the hypersalinization of the upstream zones, and the
associated mangrove degradation. Underlying these peculiarities, a key
question motivated and served as a common thread in this thesis: have
these environmental changes affected the estuary’s ecological function
of nursery for fishes? By looking at components such as the larval
diversity and community structure, transport of larvae in and out of the
system, and feeding value of the sea surface microlayer, this thesis
gain knowledge on a variety of important and complementary
environmental/physical factors influencing the diversity and
distribution of the ichthyoplankton; thereby the nursery quality of this
estuary for fishes. Importantly, knowledge gain in this thesis is not
only relevant in the West African regional context, but also throughout
the dry tropics as it is expected that such transformations are on their
way or will be in the near future for several estuaries (Pagès and
Citeau, 1990; Ridd and Stieglitz, 2002). In that sense, the Sine Saloum
served as a case study for understanding and estimating future changes
in estuaries vulnerable to similar environmental transformations.