Benthic macrophyte communities in the Ghar El Melh lagoon (North Tunisia)

Shili, Abdessalem; Trabelsi, E. B.; Maïz, Naceur Ben

doi:10.1652/1400-0350(2002)008[0135:bmcitg]2.0.co;2

Cited by 28 publications

(16 citation statements)

References 2 publications

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“…In the first sector we could observe, in agreement with the literature (Shili et al, 2002), a considerable cover of Ruppia cirrhosa, a perennial seagrass classed in ESG I; this species decreased toward the central part of the lagoon, where it was about equivalent to the covering of Cladophora algae, filamentous opportunistic species classed in ESG II. These latter species became highly dominant in the S-W zone, where R. cirrhosa almost disappeared.…”

Section: Ecological Assessmentsupporting

confidence: 90%

Optical characterization of coastal lagoons in Tunisia: Ecological assessment to underpin conservation

Nourisson

Scapini

Massi

et al. 2013

Ecological Informatics

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Ghar El Melh is a shallow lagoon (average depth of 0.8 m) that has undergone a eutrophication process due to growing human pressures. To obtain a global frame of the ecosystem functioning, an optical and an ecological classification were used in parallel. Downwelling and upwelling spectral irradiances were measured in situ in 22 sampling stations across the water body; then Apparent Optical Properties (AOPs), namely reflectance R(λ) and vertical attenuation coefficient K d (λ) were calculated for each wavelength of visible spectrum, furnishing typical spectra from turbid waters, rich in dissolved and suspended matter. From water samples of the same stations the concentrations of OASs (Optically Active Substances), i.e. Chromophoric Dissolved Organic Matter (CDOM), Non-Algal Particulate (NAP) and Phytoplankton, were assessed. The use of an optical classification for water bodies rich in TSM and CDOM, integrating AOPs and OASs, highlighted a great spatial heterogeneity, well overlapping with hydrology and human impacts patterns. A modified version of the Ecological Evaluation Index (EEI), considering the macrophyte distribution (based on a visual assessment of macrophyte coverage, without quantitative sampling) was then used, highlighting an intermediate ecological condition, despite high water turbidities. The integrated use of both systems thus furnished a complete characterization, rapidly detecting the most impacted sectors and the possible primary causes. The method might be applied as a monitoring procedure in other Mediterranean coastal lagoons, with the aim to adopt a common conservation strategy for these important transitional water bodies.

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Section: Ecological Assessmentsupporting

confidence: 90%

Optical characterization of coastal lagoons in Tunisia: Ecological assessment to underpin conservation

Nourisson

Scapini

Massi

et al. 2013

Ecological Informatics

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“…Green algae are also abundant components in the sediments on the hypersaline Tunisian Shelf (Burollet 1981) and the Tunisian Ghar El Melh lagoon that shows strongly elevated salinities (44% in summer with extreme values of up to 54%; Shili et al 2002). The relationship between elevated salinities and the occurrence of calcareous green algae thus is not clear.…”

Section: Persian Gulf Red Sea Tunisian Shelfmentioning

confidence: 99%

Heterozoan carbonates in subtropical to tropical settings in the present and past

Westphal

Halfar

Freiwald

2010

Int J Earth Sci (Geol Rundsch)

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Water temperature has received considerable attention as steering factor for the genesis of different types of marine carbonate sediments. However, parameters other than temperature also strongly influence ecosystems and, consequently, the carbonate grain associations in the resulting carbonate rock. Among those factors are biological evolution, water energy, substrate, water chemistry, light penetration, trophic conditions, CO 2 concentrations, and Mg/Ca ratios in the seawater. Increased nutrient levels in warm-water settings, for example, lead to heterotrophicdominated associations that are characteristic of temperate to cool-water carbonates. Failure to recognize the influence of such environmental factors that shift the grain associations towards heterotrophic communities in low latitudes can lead to misinterpretation of climatic conditions in the past. Modern analogues of low-latitude heterozoan carbonates help to recognize and understand past occurrences of heterozoan warm-water carbonates. Careful analysis of such sediments therefore is required in order to achieve robust reconstructions of past climate.

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“…This counteracts the effects of a reduction of the load from the land. Several authors have suggested increasing the water exchange between the lagoon and the sea as a measure to improve the water quality in the lagoon (Shili et al, 2002;Moussa et al, 2005). The present investigation and model scenarios show that the water quality at the boundary can not be ignored.…”

Section: Coastal Boundary Concentrationsmentioning

confidence: 59%

“…A biomass over 5 g C m -2 or about 15-17 g dry weight m -2 has been selected to represent areas with well-established vegetation with meadows of Ruppia. It is then possible to compare the simulated vegetated area with those having 80-100% cover during the 1999-2000 investigation by Shili et al (2002).…”

Section: Sensitivity To Nutrient Load Boundary Concentrations and Fimentioning

confidence: 99%

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Model analyses of the future water quality of the eutrophicated Ghar El Melh lagoon (Northern Tunisia)

et al. 2009

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Ghar El Melh (Northern Tunisia) is a shallow eutrophicated lagoon (total surface area 35.6 km 2 ) which was one of the primary sites within the MELMARINA project. It is connected to the Mediterranean through a dredged opening and receives untreated sewage from two towns and a catchment of 131 km 2 . During the past decade the lagoon's water quality has deteriorated and vegetation has changed. Ruppia sp. has diminished and green macroalgae (mainly Cladophora sp.) has increased. Frequent resuspension of fine alluvial sediment has reduced both water transparency and angiosperm (Ruppia sp.) vegetation cover. Flash floods during winter deliver most of the load of sediment and nutrients from the catchment to the lagoon. Options for restoring the angiosperm cover in the lagoon have been analysed using a model system developed for the main part of the lagoon consisting of a 2-D hydrodynamic model coupled to an ecological model. The ecological model includes a combined description of eutrophication and sediment transport with rooted vegetation (Ruppia sp.), benthic macroalgae, benthic microalgae, phytoplankton and suspended matter and nutrients. A separate sediment module includes pools of nutrients, organic carbon and fine sediment. Deposition and resuspension of the sediment pools are dependent on current and wind-generated shear stress. The load of nutrients and fine sediment was estimated through calibrating the model against measured water quality data and sediment deposition rates. The anthropogenic load from July 2003 to July 2004 was 33,000 tonnes fine sediment, 182 tonnes total N and 26 tonnes total P. A net import of sediment and nutrients from the sea was simulated, driven by the relatively high concentrations of suspended matter and particulate-bound N and P measured in coastal Mediterranean water outside the lagoon. Scenario simulations indicate that the lagoon acts as a deposition area for sediment N and P for boundary concentrations down to 50% of the measured concentrations at the coast outside the lagoon. A range of simulations with decreasing load of sediment and nutrients indicate that angiosperm vegetation will slowly recover with loads of 25% of current loads, combined with increased filtration by bivalves which would decrease suspended matter concentrations and increase transparency. Elevated concentrations of suspended matter and nutrients in the sea outside the lagoon are discussed in relation to a 30-year flash flood of the Mejerda River in February 2003. Coastal erosion as well as nutrients and sediment delivered by this river probably account for a general elevation of these concentrations close to the coast.

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Benthic macrophyte communities in the Ghar El Melh lagoon (North Tunisia)

Cited by 28 publications

References 2 publications

Optical characterization of coastal lagoons in Tunisia: Ecological assessment to underpin conservation

Optical characterization of coastal lagoons in Tunisia: Ecological assessment to underpin conservation

Heterozoan carbonates in subtropical to tropical settings in the present and past

Model analyses of the future water quality of the eutrophicated Ghar El Melh lagoon (Northern Tunisia)

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