Kerkennah Islands Research Articles

Hydrocarbon microseepages in the kerkennah islands, Eastern Tunisia: Integrated surface geochemical and geoelectrical prospecting approaches

Oil exploration is usually carried out using conventional techniques such as seismic reflection and exploratory drilling. However, these techniques are very costly with a high risk of dry holes or failure to find commercial quantities of hydrocarbons. Here we aim to evaluate surface geochemical prospection (SPG) methods which serve as preliminary step to derisk an area by exploring hydrocarbon micro-seeps. This approach helps to identify potential areas of interest when you have limited amount of money to explore a given area. This paper reports on surface gas micro-seepages in the Kerkennah archipelago, part of the Tunisian Pelagian Platform. 33 gas and soil samples were collected on a 1 × 1 km grid over Chergui Island. Both free gas and adsorbed soil gas techniques were used. Free hydrocarbon gas concentrations ranged from 0 to 21 ppm. Adsorbed gases showed concentrations up to 11 ppm. The presence of all light hydrocarbon gas components from methane to pentane, the values of the gas ratios C1/C2, C1/ΣC2+, (C3/C1) x 1000 and C1/(C2 + C3), and the Pixler and triangular diagrams together indicate that these gases are of thermogenic origin and have migrated from subsurface accumulations. Anomalous concentrations of hydrocarbon gases occurred in the middle and west of the study area. Both free and adsorbed gas anomalies have the same planar shape and form linear anomalies with a NW-SE trend. This orientation corresponds to that of the major fault system affecting the Kerkennah archipelago. Subsequent independent VES surveys and re-interpreted seismic lines confirmed the presence of a surface fault as suggested by the surface gas anomalies. In conclusion, our study has confirmed the presence of thermogenic hydrocarbon gas microseepage to the surface. The gases are interpreted to have migrated to the surface along faults. SPG methods were thus able to identify active hydrocarbon migration and can be considered as a useful low-cost approach to hydrocarbon exploration.

Study of microbial communities and environmental parameters of seawater collected from three Tunisian fishing harbors in Kerkennah Islands: Statistical analysis of the temporal and spatial dynamics

Surface seawater, collected from three fishing harbors during different seasons of the years 2015, 2016 and 2017, were assessed for physico-chemical analyses. Results showed that seawater was mainly polluted by hydrocarbons and some heavy metals. Microbial communities' composition and abundance in the studied harbors were performed using molecular approaches. SSCP analysis indicated the presence of Bacteria, Archaea and Eucarya, with dominance of the bacterial domain. Illumina Miseq analysis revealed that the majority of the sequences were affiliated with Bacteria whereas Archaea were detected at low relative abundance. The bacterial community, dominated by Proteobacteria, Bacteroidetes, Planctomycetes, Cyanobacteria, Firmicutes, Actinobacteria and Chloroflexi phyla, are known to be involved in a variety of biodegradation/biotransformation processes including hydrocarbons degradation and heavy metals resistance. The main objectives of this study are to assess, for the first time, the organic/inorganic pollution in surface seawater of Kerkennah Islands harbors, and to explore the potential of next generation marine microbiome monitoring to achieve the planning coastal managing strategies worldwide.

Mesembryanthemum crystallinum L.: A potential invasive plant in Tunisia

Biological invasions are considered as one of the most serious threats to the biodiversity. Mesembryanthemum crystallinum L. (Aizoaceae) is reported invasive in many regions over the world. This paper aim to monitor its distribution in the Kerkennah islands and update its invasive status. Field surveys, performed during May 2022, were achieved to record M. crystallinum occurrences and generate the plant distribution map. Field monitoring reveals that M. crystallinum is widespread and has the ability to grow in a broad range of disturbed habitats. The plant distribution pattern show that it often forms dense stands which allow it to inhibit the growth of other plants. Concidering its behaviour M. crystallinum should be considered as a potential invasive plant in Tunisia which requires the implementation of an appropriate management plan.

Towards the identification of wild African date palms in Kerkennah Islands from Tunisia by morphometric and genetic analyses

Wild relatives constitute an invaluable resource for crop breeding and are key components to understand their domestication history. Date palm is one of the oldest fruit crops, cultivated for millennia for its nutritional value and major economic and symbolic role. Two strongly differentiated gene pools have been recognized as the Western gene pool in North Africa and the Eastern one in the Middle East. Although a wild population has been proposed in Oman for the Eastern genetic pool, no wild date palm from the Western one has been yet described. In Tunisia, the date palms of Kerkennah archipelago consisted of spontaneous uncultivated individuals that are promising candidates for putative wild date palms. Morphometric tools were applied to 1140 date palm seeds of 69 Kerkennah accessions and compared to previously defined reference morphotypes. The genetic diversity of Kerkennah accessions was also compared to date palm populations and three Phoenix species using 18 nuclear microsatellite and one chloroplastic minisatellite markers. Morphometric analyses of Kerkennah accessions revealed genotypes with round-shaped seeds, characteristic of wild Phoenix species. Genetic analyses showed that Kerkennah's date palm belonged to the Western gene pool and exhibited a larger diversity and allelic richness than the western cultivated ones, proving that they are more probably wild than ferals. Altogether, our results strongly suggest that the spontaneous date palms growing in the harsh environment of the Kerkennah archipelago are wild populations. This unique heritage long-time preserved from anthropogenic pressure, is likely to contain some of the ancestral genetic diversity that would be of great value for breeding and provides new information for the discovery of the origins of the date palm.

Ethnobotanical and on farm genetic surveys of fig (Ficus carica L.) genetic resources in Kerkennah islands.

Fig tree (Ficus carica L.) is characterized by a wide genetic diversity in Tunisia although it is considered as a secondary species. In Kerkennah islands, despite several biotic and abiotic stresses, local population has conserved the fig germplasm. This species is very well suited to the harsh environments. In order to enhance on farm conservation of fig genetic resources and to have inventory of related traditional knowledge (TK), a global survey was conducted among a wide range of stakeholders and local governmental agencies in Kerkennah archipelago. For this purpose, prospections were done during two successive years covering the totality of the islands. A total of 9 locations and 26 sub-locations were visited. Twenty four farmers were solicited. Surveys have taken into account sex, age of farmers, predominant agricultural activities of farmers, field area, fig cultivated varieties, land management, traditional knowledge, production and its use, source of incomes and marketing of production. Participatory Four Cell Analysis (FCA) allowed the classification of fig cultivars regarding the threat level of loss and the adequate manner of conservation. Results of this study showed that it is imperative to pay particular attention to threatened and rare cultivars. Hence, the importance to conserve such diversified germplasm. On farm conservation program is a suitable alternative for such region for preservation of traditional knowledge, cultivars rehabilitation and a sustainable agriculture.

Isolation and characterization of a newly naphthalene-degrading Halomonas pacifica, strain Cnaph3: biodegradation and biosurfactant production studies.

A newly marine Halomonas pacifica strain Cnaph3 was isolated, as a naphthalene degrader and biosurfactant producer, from contaminated seawater collected in Ataya's fishing harbor, located in Kerkennah Islands, Tunisia. Chromatography flame ionization detector analysis revealed that 98.8% of naphthalene (200mg/L) was degraded after 7days of incubation, at 30g/L NaCl and 37°C. Strain Cnaph3 showed also a noticeable capacity to grow on a wide range of aliphatic, aromatic, and complex hydrocarbons. Interestingly, strain Cnaph3 showed a significant potential to produce biosurfactants in the presence of all tested substrates, particularly on glycerol (1%, v/v). Electrospray ionization analysis of the biosurfactant, designated Bios-Cnaph3, suggested a lipopeptide composition. The critical micelle concentration of Bios-Cnaph3 was about 500mg/L. At this concentration, the surface tension of the water was reduced to 27.6 mN/m. Furthermore, Bios-Cnaph3 displayed interesting stabilities over a wide range of temperatures (4-105°C), salinities (0-100g/L NaCl), and pH (2.2-12.5). In addition, it showed promising capacities to remove used motor oil from contaminated soils. The biodegradation and biosurfactant-production potential of the Halomonas sp. strain Cnaph3 would present this strain as a favorite agent for bioremediation of hydrocarbon-contaminated sites under saline conditions.

Rheological investigations of water-soluble polysaccharides from the Tunisian brown seaweed Cystoseira compressa

Rheological characteristics of a sodium alginate and a fucoidan extracted from the brown seaweed Cystoseira compressa harvested from Kerkennah island (Sfax, Tunisia) were investigated. Steady-shear flow and dynamical viscoelasticity were evaluated to describe physicochemical properties of the GulA-rich alginate (ManA/GulA, M/G = 0.77) and highly-ramified fucoidan in semi-diluted media depending on polymer concentration, shear rate, temperature, added mono- (KCl and NaCl) and divalent (CaCl2) salts. Alginate solutions exhibited shear-thinning behavior, with a temperature-dependent behavior highly correlated to the power-law model and the Arrhenius relationship. The results showed strong thixotropic and polyelectrolyte properties, influenced by addition of monovalent and divalent cations. The dynamic rheological characteristics showed a fluid-like viscoelastic behavior (tan δ > 1) whereas the critical overlap concentration C* and specific polymer constant ks were respectively 11 g.L−1 and 4.4 using Williamson model. Fucoidan solutions displayed a shear-thinning behavior with a low viscoelasticity character influenced by temperature and monovalent salts. The flow and viscoelastic characteristics of polysaccharides were described by the Ostwald model.

Notes on the distribution and phylogeography of two rare small Gerbillinae (Rodentia, Muridae) in Morocco: Gerbillus simoni and Gerbillus henleyi

Even though Gerbillinae rodents represent an important part of the mammalian fauna in North Africa, many gaps remain in our understanding of the distribution, ecology, evolution, and systematics of some lesser known species in this family. We present in this study the most recent findings on two of these species. The first species, Gerbillus simoni Lataste, 1881, is a short-tailed, small gerbil, endemic to North Africa. In Morocco, it is present only in a small area in the northeast, where it has not been caught since 1970. In 2014, we captured a small gerbil in this region that was identified as G. simoni based on morphology and molecular data (cytochrome b gene sequencing). This study represents the first genetic characterization of G. simoni in Morocco and the first one outside Tunisia. Populations from Morocco and Tunisia (mainland and Kerkennah Islands) show very little genetic differentiation. The second species, Gerbillus henleyi de Winton, 1903, is a long-tailed small gerbil that lives in the Sahel and North Africa with an extension to the Middle East. In Morocco, this species was only known in the southwest. Between 2014 and 2015, we have captured four gerbils in the northeast of the country, which were confirmed genetically and morphologically as belonging to this species. This represents an extension of its known distribution of about 370km to the northeast of the country. These new Moroccan specimens form a distinct lineage. High genetic diversity is observed throughout the geographic range of G. henleyi, suggesting the existence of several cryptic species.

Auto-centered development and indigenous technics: Slaheddine el-Amami and Tunisian delinking

ABSTRACTUntil his early death in 1985, at age 51, the Tunisian agronomist Slaheddine el-Amami carried out a path-breaking research program at what was then the Centre de Recherche et de Génie Rural. He wrote technical studies ranging from the agricultural capacities of the unjustly-marked-as-barren Kerkennah Islands, to possibilities for drip irrigation, to attempts to quantify the energy use of Tunisian agriculture, to a wide-ranging investigation of indigenous hydraulic systems. There is little explicit mention in this work of a then-dominant strand of heterodox Arab and Third Worldist social science – the emphasis on delinking, or removal from Western commodity, technical and financial flows. Yet through an examination of his work in the context of the delinking paradigm, as put forth by scholars like Samir Amin, Fawzy Mansour and Mohamed Dowidar, I show the use and need for independent agronomic expertise to be deployed within analytical paradigms such as delinking, forged by heterodox political economists. Through delinking, countries could proceed on a path of auto-centered development. The possibility and time frame of delinking is necessarily a socio-technical question linked to indigenous capacities, technical and natural, and the social relations with which they are woven. It is also a question of creating and mobilizing a surplus in the agricultural sector. Through examining Amami’s life’s work, I show the use and need for interdisciplinary methods and research programs, which must braid the social and natural sciences – if not simply take threads from each to create a holistic knowledge – in order to arrive at appropriate developmental programs. Such knowledge and programs were appropriate in that they offered ways of working agriculture without capital-intense inputs – thus resolving rather than aggravating current account imbalances and labor surpluses. They also relied on a decentralization of planning, based on the skills and knowledges of the direct producers. In analyzing such knowledge, systematized in the work of Amami, I will also show how moving from underdevelopment to development requires a mélange of knowledges. Crucial and neglected are those knowledges which have been developed to inform sustainable ways of living on land-bases, in order to produce the rural surplus which is the sine qua non of a successful move beyond developmental malaise in the Global South. I will then link this to the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD) Synthesis Report, showing this paradigm’s continuing relevance.

Distribution of the plankton assemblages during the winter and summer along the southern coast of the Kerkennah Islands (Tunisia, Eastern Mediterranean Sea)

AbstractWe studied the distribution of microphytoplankton, ciliates and mesozooplankton in relation to environmental factors in the coastal waters around the Kerkennah Islands. Diatom species were more abundant in winter, representing 74% of the total microphytoplankton abundance, whereas dinoflagellate abundance was higher in summer (58%). Naked ciliates dominated during the winter (73%) and loricate ciliates dominated during the summer (67%). Copepods were the most abundant mesozooplankton group present during the entire period of study, comprising 93%–98% of the total mesozooplankton community. The results indicate that (i) species distribution differed significantly between winter and summer, (ii) environmental factors such as temperature, salinity and nutrients influenced plankton assemblages; and (iii) the highest abundance of several pollution indicator species was due to direct exposure to the polluted coast of Sfax and the effect of tidal asymmetries generating nutrient‐rich inputs from the city.

Introduction of a New Potential Invader into the Mediterranean Sea: The Indo-PacificAvrainvillea amadelpha(Montagne) A. Gepp & E.S. Gepp (Dichotomosiphonaceae, Ulvophyceae)

The Indo-Pacific species Avrainvillea amadelpha (Montagne) A. Gepp & E.S. Gepp is reported for the first time from the Mediterranean Sea (Kerkennah Islands, Tunisia). The species is considered as introduced and invasive in the Hawaiian Archipelago. The Mediterranean specimens are studied and the reproductive structures are described and illustrated here for the first time. The possible origins and vectors of this introduction and the risk of propagation of the species in the Mediterranean Sea are discussed.

New insights into the stratigraphic, paleogeographic and tectonic evolution and petroleum potential of Kerkennah Islands, Eastern Tunisia

This work presents general insights into the stratigraphic and paleogeographic evolution as well as the structural architecture and the petroleum potential of Kerkennah Islands, located in the Eastern Tunisia Foreland, from Cenomanian to Pliocene times. Available data from twenty wells mostly drilled in Cercina and Chergui fields are used to establish three lithostratigraphic correlations as well as isopach and isobath maps in order to point out thickness and depth variations of different geological formations present within our study area; in addition to a synthetic log and isoporosity map of the main carbonate reservoir (the nummulites enriched Reineche Member). The integrated geological study reveals relatively condensed but generally continuous sedimentation and a rugged substrate with horsts, grabens and tilted blocks due to the initiation and the individualization of Kerkennah arch throughout the studied geological times. Furthermore, a relationship was highlighted between the evolution of our study zone and those of Sirt basin, Western Mediterranean Sea and Pelagian troughs; this relationship is due to the outstanding location of Kerkennah Islands. The main Bou Dabbous source rock is thicker and more mature within the central-east of the Gulf of Gabes indicating therefore the southeast charge of Reineche reservoir which shows NW-SE trending tilted block system surrounded by normal faults representing the hydrocarbon migration pathways. Besides, the thick Oligo-Miocene formations deposited during the collapse of the Pelagian block caused the maturation of the Ypresian source rock, while the Pliocene unconformity allowed basin inversion and hydrocarbon migration.

Control, energy management and performance evaluation of desalination unit based renewable energies using a graphical user interface

Renewable energy sources coupled to desalination unit offers a promising prospect for covering the fundamental needs of power and water in isolated regions. In this context, this study aims to control a reverse osmosis desalination unit powered by renewable energy sources and hydrogen storage situated in the Kerkennah islands (Tunisia). The hybrid system is made up of two wind turbines, a photovoltaic generator, a fuel cell and an electrolyzer. In order to ensure an optimum exploitation of the produced energy, a novel power management algorithm is developed to control the different energy flows exchanged among the system components. This algorithm determines the reference powers of the fuel cell, the electrolyzer and the desalination unit in seven operation modes, and supervises the fill levels of fresh water and hydrogen tanks. The daily simulation of the desalination system with the proposed algorithm for any month of the year and the annual simulation of the energy supervision algorithm are carried out by new graphical interfaces. These interfaces facilitate the simulation and display the different curves describing the hybrid system behavior. The simulation results show that the proposed control strategies provide good installation autonomy and improve the system stability under varying load power demand.

Heavy metal concentrations in Liza aurata (Risso, 1810) captured from the Kerkennah Islands (Gulf of Gabes) and associated health risks

Heavy metal concentrations in Liza aurata (Risso, 1810) captured from the Kerkennah Islands (Gulf of Gabes) and associated health risks

The southernmost record of Felimida elegantula (Philippi, 1844) (Gastropoda: Nudibranchia)

The southernmost record of the Mediterranean nudibranch Felimida elegantula (Philippi, 1844) is reported here. A single specimen, with a colour pattern that hampered an easy morphological identification, was collected at the Kerkennah Islands (Tunisia). DNA-barcoding analysis (with the cytochrome c oxidase subunit I genetic marker) unambiguously confirmed its identification, and radular and anatomical features conformed with those previously described. With this record, the chromatic polymorphism of F. elegantula is demonstrated to be extremely large and the known range of the species is extended to the African coast of Tunisia.

Compositional variability of the aerosols collected on Kerkennah Islands (central Tunisia)

The aim of the present study is to investigate the seasonal variability of the aerosol concentrations and origins in central Tunisia. Four field campaigns were carried out in 2010/2011 to collect air-suspended particles on the Kerkennah Islands. The elemental composition (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Pb, Ni, V, and As) of the particles collected in summer (June and July), autumn (September and November), winter (February and March), and spring (April and May) is determined by X-ray fluorescence analysis.Examination of the enrichment factors (EF) of all elements indicate that Al, Fe, Si, Ca, Ti, Mn, and Cr are mainly derived from soil sources, whereas Na and Cl are mostly of marine origin. Other elements such as K and Mg or S and P have multiple origins (Marine/crustal and crustal/anthropogenic, respectively). Finally, V, Cu, Ni, As, and Pb appear to be produced by anthropogenic activities.Based on the inter-elemental correlations, the mass concentrations of mineral dust (MD), sea-salt (SS) and anthropogenic (non-crustal and non-marine) sulfates (NSS) are quantified. MD, SS and NSS display significant inter-seasonal differences: on the one hand, MD and SS are the highest in spring and the lowest in winter, probably because of the seasonal change in meteorological conditions. On the other hand, NSS and Cu concentrations are above their autumn and winter values in spring and summer, which suggests the existence of a common source of the combustion type for these two pollutants.

Impact of Geographical Isolation on Genetic Differentiation In An Insular Population of the Carpet ShellRuditapes decussatusin the Mediterranean Basin

ABSTRACT Genetic variation was investigated using allozymes, cytochrome c oxidase subunit I, internal transcribed spacer region 1, and microsatellite markers in mainland and insular populations of the carpet shell Ruditapes decussatus from the western and eastern Mediterranean Basin. Five morphometric parameters and weight of valves were also used to study the distribution of variation within and among populations. The species is characterized by a relatively high inter- and intrapopulation morphological and genetic variability. The highest values of percent polymorphism and heterozygosity (allozyme and microsatellite data) were found in the sample from Kerkennah Island. The occurrence of higher levels of genetic variability in insular population is probably because this population inhabit marginal environment characterized by temporal-ecological instability. The genetic heterogeneity analysis demonstrates a certain amount of genetic differentiation among local populations of R. decussatus with a relative...

Factor driving heterotrophic dinoflagellate in relation to environment conditions in Kerkennah Islands (eastern coast of Tunisa)

Factor driving heterotrophic dinoflagellate in relation to environment conditions in Kerkennah Islands (eastern coast of Tunisa)

Optimal sizing of stand-alone photovoltaic/wind/hydrogen hybrid system supplying a desalination unit

The real penetration of renewable energy sources (RES) under varying weather conditions required an optimal sizing of hybrid renewable power generation systems. The present paper proposes a methodology based on iterative technique, to perform the optimal sizing of a stand-alone hybrid photovoltaic/wind/hydrogen system supplying a desalination unit which feeds the area’s inhabitants with fresh water. The methodology aims at finding the optimal technical–economic configuration among a set of systems components. Taking into account the models of the main hybrid system components and the hourly meteorological data and load profile for any site located worldwide, the recommended algorithm gives all possible configurations that can completely cover the fresh water requirements of isolated consumers. Afterward, the optimal configuration is predicted on the basis of the minimum initial investment cost. A case study is conducted to analyze a hybrid project, which is designed to supply a seawater desalination unit installed on the Kerkennah islands located in the south of Tunisia.

Seasonal and daily fluctuation of diatoms during spring tide periods in Kerkennah Islands

Seasonal and daily fluctuation of diatoms during spring tide periods in Kerkennah Islands