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The concentrations of nutrients and heavy elements in the surface water of the lake Ichkeul, main wadis which feed directly and thermal springs that flow into the lake, are measured to evaluate these chemical elements. There are used to highlight the interactions between these different aquatic compartments of Ichkeul. All metal concentrations in lake water, except Cu, were lower than the maximum permitted concentration for the protection of aquatic life. The results show that the highest concentrations are located in the eastern and south-eastern part of the lake where the polluted water comes from the lagoon of Bizerte through the wadi Tinja as well as from the city of Mateur through the wadi Joumine. The pollution indices and especially the heavy metal evaluation index (HEI) show high pollution specially located at the mouths of wadis and an increase of heavy metal concentrations, as a result of uncontrolled releases of domestic and industrial wastewater. [ABSTRACT FROM AUTHOR]

Lake Ichkeul is considered one of the most significant wetlands in the Mediterranean basin. It serves as a crucial wintering area for numerous western Palearctic birds. A notable decline in species diversity has been observed in the past decade, attributed to excessive water usage for irrigation and the effects of climate change. This study aimed to assess the status of Ichkeul Lake and its catchment through identifying potentially toxic cyanobacteria, and sediment quality. Our first striking finding was that Lyngbya majuscula the dominant potentially toxic cyanobacterium in the lake originated from the Tinja channel. Trace element concentrations in lake sediments exceeded SQG standards which is indicative of rare detrimental effects to biological life. However, the sediment in front of the Tinja channel exhibited high contamination levels of Zn and Cd. These findings call for an urgent need to ensure the ongoing management and conservation of this world heritage site. • Potentially toxic cyanobacteria of Ichkeul Lake and its catchment • Potentially toxic trace elements in the sediment of Ichkeul Lake and its catchment • Lyngbya majuscula , originated from Tinja channel • Trace element concentrations in lake sediments exceeded SQG standards • Alarming detrimental effects to biological life [ABSTRACT FROM AUTHOR]

A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous analysis of 16 PAHs, 12 PCBs and 9 OCPs in sediment. The sample preparation was adapted by modifying the nature of the extraction solvent, the extraction technique and the amount of sediment. The analytical performances were evaluated in terms of accuracy, linearity and quantification limits. The method was validated by the analysis of a reference marine sediment material (SRM 1941b). The obtained concentrations are in good agreement with the certified values with recoveries ranging 60 %-103 % for most of PAHs. Acceptable recoveries are obtained for PCBs, ranging 76 %-131 %, and for OCPs ranging 81 %-137 %. The method was applied to the analysis of sediments from the hydro-system Bizerte Lagoon/Ichkeul Lake (Tunisia). The Bizerte lagoon is mainly contaminated by PAHs whereas the Ichkeul lake is mainly by OCPs. [ABSTRACT FROM AUTHOR]

The European eel (Anguilla anguilla) stock has been declining for the last three decades and today, it is currently listed as endangered. The objective of this study was to quantify the escapement rate of silver eels to obtain an estimate of the future spawners migrating from the southern part of its distribution area in Tunisia. A mark-recapture experiment was conducted in Ichkeul Lake (Tunisia) between December 2013 and February 2014, covering the winter downstream run of eels. The size range of the downstream migrating eels was between 33 and 79 cm with 585.3 ± 156.77 g mean weight. The number of migrating silver eels was estimated to 342 221 (297 956-386 486), corresponding to a biomass of 200.2 (174.3-226.1) t, with a density of 23.55 (20.51-26.6) kg ha-1. The commercial fishing rate was estimated to be 18.8% (16.6-21.5%), which translates into an escapement rate of 81.2% (78.5-83.4%). The ratio current/pristine escapement was 0.69 for the entire migration period. [ABSTRACT FROM AUTHOR]

Purpose: Ichkeul National Park, NW Tunisia, is a UNESCO Biosphere Reserve. Garaet El Ichkeul Lake is known for its seasonal variability in water level and salinity. In recent decades, the waterbody has been affected by the construction of new hydraulic structures. To reduce the impacts of dams and to maintain the sustainability of the ecosystem, a sluice was built at the outlet of the lake, and it operated for the first time in 1996. This paper describes an investigation of recent sedimentation dynamics in Ichkeul Lake, determined by radiometric dating of sediment cores. Materials and methods: A sediment core was collected with a UWITEC gravity corer at the deepest, central part of the lake in August 2009. Specific activities of unsupported lead-210 (Pb) and caesium-137 (Cs) were measured in the core, enabling calculation of recent sediment accumulation rates (SAR). Published radiometric data from nearby sediment cores, collected in 1997 and 1982, provide a comparison. Results and discussion: The measured excess Pb inventory was 5300 ± 500 Bq m, leading to an estimation of constant flux of 165 ± 16 Bq m yr, a value higher than the best estimate for local atmospheric fluxes (123 ± 12 Bq m yr) and the flux estimated from the core collected in 1982 (48 Bq m yr). The Cs inventory was 3550 ± 120 Bq m, two times higher than the historical Cs atmospheric deposition in the area. The Cs profile displayed a distinct peak, but the Cs depth-distribution did not follow the pattern expected from atmospheric deposition. Application of the constant rate of supply (CRS) model, with the reference point method, produced a chronology and SAR values comparable to those found in previous work. The whole Cs profile was quantitatively reconstructed from the historical records of atmospheric deposition, using the system-time-averaged (STA) model. Conclusions: The CRS and STA models provide consistent sediment accumulation results for the whole data set, considering the time resolution of the chronology (~6 years) and analytical uncertainties. Results from cores sampled in 1982, 1997 and 2009 reveal an increasing SAR trend, from ~0.25 g cm yr in the early 1940s to ~0.67 g cm yr at present. In the 13 years since installation of sluice gates at Tinja, SAR in the central Ichkeul Lake has not declined. Thus, if siltation continues at the present rate, shallowing of the lake will seriously affect the hydromorphology and ecology of this important lake. [ABSTRACT FROM AUTHOR]