Ben Othman, H., Lanouguère, É., Got, P., Sakka Hlaili, A., & Leboulanger, C. (2018). Structural and functional responses of coastal marine phytoplankton communities to PAH mixtures. Chemosphere, 209, 908–919.
Résumé: The toxicity of polycyclic aromatic hydrocarbons (PAHs) mixtures was evaluated on natural phytoplankton communities sampled from lagoons of Bizerte (South-western Mediterranean Sea) and Thau (North-western Mediterranean Sea). PAHs induced short-term dose and ecosystem-dependant decreases in photosynthetic potential. Chlorophyll a was negatively affected by increasing PAHs concentrations, together with dramatic changes in phytoplankton community composition. Size classes were strongly affected in the Bizerte compare to the Thau lagoon, with a decrease in nano- and microphytoplankton densities compare to picophytoplankton. In both locations, the diatom Entomoneis paludosa appeared favoured under PAH exposure as evidenced by increase in cell density, whereas autotrophic flagellates and dinophytes were strongly reduced. Smaller cells were more tolerant to exposure to highest PAHs concentrations, with persistent picophytoplankton carbon biomass at the end of the incubations. Apparent recovery of photosynthetic potential, accompanied with a regrowth of chlorophyll a under the lowest PAH doses, coincided with a significantly altered community composition in both lagoons. Furthermore, sensitivity to PAHs was not related to the phytoplankton cell size, and toxicity-induced modification of top-down control by grazers during the experiment cannot be excluded.
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Derolez, V., Bec, B., Munaron, D., Fiandrino, A., Pete, R., Simier, M., et al. (2019). Recovery trajectories following the reduction of urban nutrient inputs along the eutrophication gradient in French Mediterranean lagoons. Ocean & Coastal Management, 171, 1–10.
Résumé: French Mediterranean coastal lagoons have been subject to huge inputs of urban nutrients for decades leading to the eutrophication of these vulnerable ecosystems. In response to new environmental regulations, some of the lagoons have recently been the subject of large-scale management actions targeting the waste water treatment systems located on their watersheds. While the eutrophication of coastal ecosystems is well described, recovery trajectories have only recently been studied. To assess the rapidity and the extent of the effect of the remediation actions, we analysed data from a 14-year time series resulting from the monitoring of nutrients, biomass and the abundance of phytoplankton in the water column of French Mediterranean coastal lagoons covering the whole anthropogenic eutrophication gradient. Following a 50% to 80% reduction in total phosphorus (TP) and total nitrogen (TN) urban loadings from the watershed of hypertrophic and eutrophic ecosystems, the integrative parameters chlorophyll a, TN and TP, provide evidence for a rapid response (1 to 3 years) and for an almost complete recovery, suggesting no hysteresis for the eutrophic lagoon. However, our findings also show that recovery patterns depend on the eutrophication status before remediation and may include feedback responses. The different responses revealed by our results should help stakeholders prioritise remediation actions and identify appropriate restoration goals, especially in light of the targets of the Water Framework Directive (WFD).
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Draredja, M. A., Frihi, H., Boualleg, C., Gofart, A., Abadie, E., & Laabir, M. (2019). Seasonal variations of phytoplankton community in relation to environmental factors in a protected meso-oligotrophic southern Mediterranean marine ecosystem (Mellah lagoon, Algeria) with an emphasis of HAB species. Environ. Monit. Assess., 191(10), 603.
Résumé: The spatial and temporal variation of phytoplankton communities including HAB species in relation to the environmental characteristics was investigated in the protected meso-oligotrophic Mellah lagoon located in the South Western Mediterranean. During 2016, a biweekly monitoring of phytoplankton assemblages and the main abiotic factors were realized at three representative stations. Taxonomic composition, abundance, and diversity index were determined. In total, 227 phytoplankton species (160 diatoms and 53 dinoflagellates) were inventoried. There was a clear dominance of diatoms (62.9%) compared with dinoflagellates (36.8%). Diatoms dominated in spring and dinoflagellates developed in summer and early autumn in Mellah showing a marked seasonal trend. Data showed that the dynamic of the phytoplankton taxa evolving in the lagoon was mainly driven by temperature and salinity. For the first time, a number of potentially toxic species have been identified, including 2 diatoms (Pseudo-nitzschia group delicatissima, Pseudo-nitzschia group seriata) and 5 dinoflagellates (Alexandrium minutum, Alexandrium tamarense/catenella, Dinophysis acuminata, Dinophysis sacculus, Prorocentrum lima). These harmful species could threat the functioning of the Mellah lagoon and human health and require the establishment of a monitoring network. Finally, our study suggests that the observed decrease of the phytoplankton diversity between 2001 and 2016 could result from the reduction in water exchanges between the lagoon and the adjacent coast following the gradual clogging of the channel.
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Fiandrino, A., Ouisse, V., Dumas, F., Lagarde, F., Pete, R., Malet, N., et al. (2017). Spatial patterns in coastal lagoons related to the hydrodynamics of seawater intrusion. Mar. Pollut. Bull., 119(1), 132–144.
Résumé: Marine intrusion was simulated in a choked and in a restricted coastal lagoon by using a 3D-hydrodynamic model. To study the spatiotemporal progression of seawater intrusion and its mixing efficiency with lagoon waters we define Marine Mixed Volume (V-MM) as a new hydrodynamic indicator. Spatial patterns in both lagoons were described by studying the time series and maps of VMM taking into account the meteorological conditions encountered during a water year. The patterns comprised well-mixed zones (WMZ) and physical barrier zones (PBZ) that act as hydrodynamic boundaries. The choked Bages-Sigean lagoon comprises four sub-basins: a PBZ at the inlet, and two WMZ's separated by another PBZ corresponding to a constriction zone. The volumes of the PBZ were 2.1 and 5.4 millions m(3) with characteristic mixing timescale of 68 and 84 days, respectively. The WMZ were 123 and 433 millions m(3) with characteristics mixing timescale of 70 and 39 days, respectively. (C) 2017 Elsevier Ltd. All rights reserved.
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Gaertner-Mazouni, N., & De Wit, R. (2012). Exploring new issues for coastal lagoons monitoring and management. Estuarine Coastal and Shelf Science, 114, 1–6.
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