# Modern diatom in Tunisia as indicators of water chemistry and their use for hydrologic and climatic reconstruction

Leila Ben Khelifa

► To cite this version:

Leila Ben Khelifa. Modern diatom in Tunisia as indicators of water chemistry and their use for hydrologic and climatic reconstruction. 25th International Diatom Symposium, Jun 2018, Berlin, Germany. hal-03947958

HAL Id: hal-03947958

https://hal.science/hal-03947958

Submitted on 19 Jan 2023

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

Public Domain
# MODERN DIATOM IN TUNISIA AS INDICATORS OF WATER CHEMISTRY AND THEIR USE FOR HYDROLOGIC AND CLIMATIC RECONSTRUCTION

<figure><img src="image_1.png" /></figure>

25th International Diatom Symposium
25-30 June 2018 | Berlin | Seminars & Botanical Garden

## Leila Ben Khelifa

Muséum National d'Histoire Naturelle, UMR 7245 MNHN-CNRS MCAM Eq. « Cyanobactéries, cyanotoxines et environnement », 12 rue Buffon, 75231 Paris Cedex 05, France
Email : benkhelifa.leila@bbox.fr

The purpose of this work is to update taxonomic identification of Diatom from Tunisia described in Ben Khelifa, L., 1989, for a better understanding of quaternary diatom occurrence and its implication. In particular, have quaternary *Cerastoderma* lens a marine or a continental origine?

### I. Quaternary Sites location :

<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /></figure>

©Moez Mansoura

<caption>Akarit *Cerastoderma* lens</caption>

<caption>Les Chotts *Cerastoderma* lens</caption>

### II. Modern Sites location with in particular, photos of the diverses biotopes in Wadi El Akarit

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /><figcaption>Hydrothermal sources</figcaption></figure>

<figure><img src="image_21.png" /><figcaption>Metasaline biotopes</figcaption></figure>

<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /></figure>

<figure><img src="image_25.png" /></figure>

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /><figcaption>Modern Akarit biotopes</figcaption></figure>

### II. Diatom assemblages, stenotypic species, autoecological results and paleoecological interpretations

### b. Major Diatom Assemblages in Modern samples of TUNISIA

#### a. Major species

<figure><img src="image_28.png" /></figure>

<figure><img src="image_29.png" /></figure>

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /></figure>

<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

<figure><img src="image_34.png" /><figcaption>Mastogloia dominant in a mesosaline epipelic sample(ST1)</figcaption></figure>

<figure><img src="image_35.png" /><figcaption>Cyclotella meneghiniana and Navicymbula pusilla (EH89)</figcaption></figure>

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /></figure>

<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

<figure><img src="image_40.png" /><figcaption>Several modern hydrothermal samples from the chott area with only two or three species dominant</figcaption></figure>

<figure><img src="image_41.png" /></figure>

<figure><img src="image_42.png" /></figure>

<figure><img src="image_43.png" /></figure>

<figure><img src="image_44.png" /></figure>

<figure><img src="image_45.png" /></figure>

<figure><img src="image_46.png" /><figcaption>Typical holocene assemblage in the Chott area</figcaption></figure>

III. When Diatom allow a detailed paleoreconstruction : in Akarit **Cerastoderma** lens, we can note an evolution from a lagunar environment to a marine one, in Villafranchien time

<figure><img src="image_47.png" /><figcaption>Mastogloia cf. aquilegiae with Achnanthes cf. arenaria are frequent inside the *Cerastoderma* shell</figcaption></figure>

<figure><img src="image_48.png" /></figure>

<figure><img src="image_49.png" /></figure>

<figure><img src="image_50.png" /><figcaption>The most frequent specie in holocene sediment *Denticula elegans* var. *africana* Hustedt is abundant in modern sample EH90</figcaption></figure>

<figure><img src="image_51.png" /><figcaption>Achnanthes brevipes? is very big in fossil sediment</figcaption></figure>

<figure><img src="image_52.png" /></figure>

<figure><img src="image_53.png" /></figure>

<figure><img src="image_54.png" /></figure>

<figure><img src="image_55.png" /></figure>

<figure><img src="image_56.png" /></figure>

Metasaline Assemblage from modern (TN62: C=-(65600µ/cm, pH=9)and fossil samples of the Chott region. *Rhopalodia musculus* occur in very big size and the two *Nitzschia* do not correspond exactly to *Nitzschia graciloides* Hust. And (kütz.)Smith thus more taxonomic work is needed to make sure wether these species are euryhalobous or stenotypic metasaline.

<figure><img src="image_57.png" /></figure>

#### Conclusions

In *Cerastoderma* lens, no thalassic species are observed in the chott area whereas in Akarit, the occurrence of few marine species suggest a tidal influence. However, more *Cerastoderma* lens' samples from the chott regions need to be studied and dated for a definitive response.

<figure><img src="image_58.png" /><figcaption>Eusaline? Marine origin? ; in Akarit *Cerastoderma* lens</figcaption></figure>

<figure><img src="image_59.png" /><figcaption>Eusaline *Synedra crystallina*?</figcaption></figure>

<figure><img src="image_60.png" /></figure>

<figure><img src="image_61.png" /><figcaption>MEB photo for major species occuring in both fossil and modern biotopes</figcaption></figure>

<figure><img src="image_62.png" /><figcaption>Nitzschia denticula or Denticula elegans var. africana</figcaption></figure>

### Thanks to

<figure><img src="image_63.png" /></figure>

<figure><img src="image_64.png" /></figure>

ONM
الديوان الوطني للمناجم
Office National des Mines

<figure><img src="image_65.png" /></figure>

cerege

<figure><img src="image_66.png" /></figure>

CULTURE
LOISIRS
LOISIRS

The euryhalobous specie *Terpsinoe musica* from Akarit *Cerastoderma* lens