Ben Othman, H., Pringault, O., Louati, H., Hlaili, A. S., & Leboulanger, C. (2017). Impact of contaminated sediment elutriate on coastal phytoplankton community (Thau lagoon, Mediterranean Sea, France). J. Exp. Mar. Biol. Ecol., 486, 1–12.
Résumé: Effects of sediment-released contaminants and nitrogen were assessed on phytoplankton communities sampled from Thau lagoon (France, Mediterranean Sea) and one close offshore marine station. Phytoplankton was exposed to sediment elutriate (seawater containing a mix of metals, organic chemicals, and nutrients) or to ammonium enrichment for four days using immersed microcosms exposed to natural conditions of light and temperature. Functional (production – respiration balance) and structural (taxonomy and cell densities) responses of the phytoplankton community were assessed. In the lagoon, both treatments stimulated phytoplankton growth, compare to controls. Conversely in the offshore station, the phytoplankton growth was stimulated only with the sediment elutriate addition. In offshore and lagoon stations, both treatments caused a shift in the taxonomic composition of the phytoplankton. Proliferation of potentially toxic diatoms and dinoflagellates resulted from the addition of elutriate. Correspondence analysis determined that phytoplankton from the offshore station was more sensitive to both treatments compared to the lagoon community. According to daily production and respiration balance, lagoon community metabolism remained heterotrophic (P < R) for all treatments, whereas only transient shifts to net autotrophy (P> R) were observed in the offshore community. Direct toxicity of contaminants released from sediment, if any, was therefore masked by nutrient enrichment effects, whereas indirect evidence of contaminant pressure was highlighted by changes in community composition and metabolism. (C) 2016 Elsevier B.V. All rights reserved.
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Cozzoli, F., da Conceicao, T. G., Van Dalen, J., Fang, X., Gjoni, V., Herman, P. M. J., et al. (2020). Biological and physical drivers of bio-mediated sediment resuspension: A flume study on Cerastoderma edule. Estuar. Coast. Shelf Sci., 241, 106824.
Résumé: Predictive models accounting for the effect of bioturbation on sediment resuspension must be based on ecological theory as well as on empirical parametrization. The scaling trend of individual metabolic and activity rates with body mass may be a key to the mechanistic understanding of the observed patterns. With this study we tested if general size scaling rules in bio-mediated sediment resuspension may apply to a broad range of physical contexts for the endobenthic bivalve Cerastoderma edule. The effect on sediment resuspension of populations of C. edule differing by individual size was measured across physical gradients of current velocity and sediment composition in terms of fraction of fine particles. C. edule were able to enhance the resuspension of sediment containing silt, while they had scarce effect on the resuspension of coarse sediment. The effect of bioturbation was maximal at intermediate current velocity, when the hydrodynamic forcing is not strong enough to overcome the abiotic sediment resistance but it is able to suspend the bioturbated sediment. Although differences in sediment silt content and intensities of hydrodynamic stress have a relevant influence in determining the bioturbators individual contribution to sediment resuspension, the observed mass scaling trend is consistent across all treatments and close to theoretical expectation for size scaling of individual metabolic rates. This observation supports the hypothesis that the contribution of individual bioturbators to sediment resuspension is directly related to their energy use. Therefore, the proposed approach allows the formulation of expectations of biotic contribution to sediment resuspension based on the general size scaling laws of individual energy use.
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Goni-Urriza, M., Moussard, H., Lafabrie, H., Carré, C., Bouvy, M., Sakka Hlaili, A., et al. (2018). Consequences of contamination on the interactions between phytoplankton and bacterioplankton. Chemosphere, 195, 212–222.
Résumé: Sediment resuspension can provoke strong water enrichment in nutrients, contaminants, and microorganisms. Microcosm incubations were performed in triplicate for 96 h, with lagoon and offshore waters incubated either with sediment elutriate or with an artificial mixture of contaminants issued from sediment resuspension. Sediment elutriate provoked a strong increase in microbial biomass, with little effects on the phytoplankton and bacterioplankton community structures. Among the pool of contaminants released, few were clearly identified as structuring factors of phytoplanktdn and bacterioplankton communities, namely simazine, Cu, Sn, Ni, and Cr. Effects were more pronounced in the offshore waters, suggesting a relative tolerance of the lagoon microbial communities to contamination. The impacts of contamination on the microbial community structure were direct or indirect, depending on the nature and the strength of the interactions between phytoplankton and bacterioplankton. (C) 2017 Elsevier Ltd. All rights reserved.
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Lafabrie, C., Garrido, M., Leboulanger, C., Cecchi, P., Grégori, G., Pasqualini, V., et al. (2013). Impact of contaminated-sediment resuspension on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea). Estuarine Coastal and Shelf Science, 130, 70–80.
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Pringault, O., Lafabrie, C., Avezac, M., Bancon-Montigny, C., Carré, C., Chalghaf, M., et al. (2016). Consequences of contaminant mixture on the dynamics and functional diversity of bacterioplankton in a southwestern Mediterranean coastal ecosystem. Chemosphere, 144, 1060–1073.
Résumé: Contamination of coastal environments is often due to a complex mixture of pollutants, sometimes in trace levels, that may have significant effects on diversity and function of organisms. The aim of this study was to evaluate the short-term dynamics of bacterioplankton exposed to natural and artificial mixtures of contaminants. Bacterial communities from a southwestern Mediterranean ecosystem, lagoon and the bay (offshore) of Bizerte were exposed to i) elutriate from resuspension of contaminated sediment, and ii) an artificial mixture of metals and herbicides mimicking the contamination observed during sediment resuspension. Elutriate incubation as well as artificial spiking induced strong enrichments in nutrients (up to 18 times), metals (up to six times) and herbicides (up to 20 times) relative to the in situ concentrations in the offshore station, whereas the increases in contaminants were less marked in the lagoon station. In the offshore waters, the artificial mixture of pollutants provoked a strong inhibition of bacterial abundance, production and respiration and significant modifications of the potential functional diversity of bacterioplankton with a strong decrease of the carbohydrate utilization. In contrast, incubation with elutriate resulted in a stimulation of bacterial activities and abundances, suggesting that the toxic effects of pollutants were modified by the increase in nutrient and DOM concentrations due to the sediment resuspension. The effects of elutriate and the artificial mixture of pollutants on bacterial dynamics and the functional diversity were less marked in the lagoon waters, than in offshore waters, suggesting a relative tolerance of lagoon bacteria against contaminants. (C) 2015 Elsevier Ltd. All rights reserved.
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