Periphytic diatom communities in tributaries around Lake Ichkeul, northern Tunisia: A preliminary assessment

Abstract

An initial inventory of diatom biodiversity at 12 sites draining into Lake Ichkeul, northern Tunisia, was performed in summer 2014, together with the characterisation of metal pollution status by analysing trace metal concentrations to determine Water Quality Indices. The maximum values of Fe, Mn, Sb, Zn, Cu and Pb were all below the national and international standard, except for Fe in Hammam Ben Abbes thermal spring and Sb in Wadi Tinja, indicating that the surface water of the Ichkeul basin was largely acceptable. Diatom community composition and specific descriptors, including quantification of morphological alterations and mortality, were used to diagnose environmental stress. High abundances of Achnanthidium minutissimum (Kützing) Czarnecki were observed at the Fe-rich site, which could reflect a response to metal contamination. Diatoms were stressed mostly by the influence of temperature and salinity, which drove species composition and increased mortality. Further research is required on the ecology of diatoms in Ichkeul thermal springs. The use of diatoms as indicators of ecosystem health in the Ichkeul area requires additional knowledge of diatom diversity in the ecoregion.

Keywords: ecosystem, freshwater, thermal springs