MOLECULAR ANALYSIS OF GYRODINIUM INSTRIATUM EXCYSTMENT CELL USING FTA TECHNOLOGY

Abstract Gyrodinium sp. (BgT3C2) strain isolated from a resting cyst in sediment from Bougrara lagoon (Tunisia) was used to investigate the utility of FTA Technology for the protection and purification of nucleic acid. We have used FTA cards to obtain the sequence of the LSU rDNA D1-D2 region from very low concentrated BgT3C2 strain culture. Nucleotide sequence analysis supported and confirmed identification of BgT3C2 strain to Gyrodinium instriatum. Keywords : Biotechnologies, Genetics, Phytoplankton. Introduction Using molecular approaches revolutionised the identification and taxonomic of the organisms with their genetic characterization, mostly based on nuclear ribosomal DNA marker

What are the potential drivers of blooms of the toxic dinoflagellate Karenia selliformis ? A 10-year study in the Gulf of Gabes, Tunisia, southwestern Mediterranean Sea

International audienceWe report on a 10-year study of the dynamics of toxic dinoflagellate Karenia selliformis at 20 stations along the nearshore of the Gulf of Gabes (Tunisia) in relation to environmental variables. Dinoflagellates and K. selliformis have dominated the phytoplankton community and K. selliformis blooms have taken place since 2001. Phytoplankton groups showed significant variability among sampling sites, but did not vary significantly from year to year. Redundancy analysis revealed that salinity, nitrate and phosphorus significantly explained the variability of the main phytoplanktonic groups namely, diatoms, dinoflagellates, cyanobacteria and euglenoids, while K. selliformis exhibited a specific pattern. Because of the wide variability in K. selliformis abundance, we tested the influence of environmental variables on its presence/absence using a generalized linear mixed-effect model (GLMM). K. selliformis occurrence had a positive relationship with nitrate and a negative one with total phosphorus. The different spatial gradients of these two chemical variables led to spatial differences in K. selliformis development prevalent near touristic areas. Temperature was also retained in the GLMM and since it rose over the 10 years of the study, it likely supports the expansion of K. selliformis. The discrepancies between model predictions and observed occurrences suggest that consideration of other sources of environmental forcing may improve our understanding of the determinism of K. selliformis dynamics. Our study may be useful in the management of this ecosystem so as to plan for the best disposal options in the treatment of urban and industrial wastes in the gulf's coastal waters

Prokaryotic Diversity and Dynamics during Dinoflagellate Bloom Decays in Coastal Tunisian Waters

International audience(1) Background: Harmful algal blooms (HABs) can negatively impact marine ecosystems, but few studies have evaluated the microbial diversity associated with HABs and its potential role in the fates of these proliferations. (2) Methods: Marine prokaryotic diversity was investigated using high-throughput sequencing of the 16S rRNA gene during the bloom declines of two dinoflagellates detected in the summer of 2019 along the northern and southern Tunisian coasts (South Mediterranean Sea). The species Gymnodinium impudicum (Carthage, Tunis Gulf) and Alexandrium minutum (Sfax, Gabes Gulf) were identified using microscopy and molecular methods and were related to physicochemical factors and prokaryotic compositions. (3) Results: The abundance of G. impudicum decreased over time with decreasing phosphate concentrations. During the G. impudicum bloom decay, prokaryotes were predominated by the archaeal MGII group (Thalassarchaeaceae), Pelagibacterales (SAR11), Rhodobacterales, and Flavobacteriales. At Sfax, the abundance of A. minutum declined with decreasing phosphate concentrations and increasing pH. At the A. minutum peak, prokaryotic communities were largely dominated by anoxygenic phototrophic sulfur-oxidizing Chromatiaceae (Gammaproteobacteria) before decreasing at the end of the survey. Both the ubiquitous archaeal MGII group and Pelagibacterales were found in low proportions during the A. minutum decay. Contrary to the photosynthetic Cyanobacteria, the photo-autotrophic and -heterotrophic Rhodobacterales and Flavobacteriales contents remained stable during the dinoflagellate bloom decays. (4) Conclusions: These results indicated changes in prokaryotic community diversity during dinoflagellate bloom decays, suggesting different bacterial adaptations to environmental conditions, with stable core populations that were potentially able to degrade HABs

Karenia selliformis bloom dynamics and growth rate estimation in the Sfax harbour (Tunisia), by using automated flow cytometry equipped with image in flow, during autumn 2019

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Caractérisation des flux de dépôt humides en HAP et métaux (hors Hg) pendant la campagne HIPPOCAMPE

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Hydrocarbures Aromatiques Polycycliques (HAPs) et éléments traces métalliques (ETMs) dans les dépôts atmosphériques le long d'un transect Nord-Sud en Méditerranée (campagne Hippocampe)

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Caractérisation des flux de dépôt humides en HAP et métaux (hors Hg) pendant la campagne HIPPOCAMPE

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Dinoflagellates encystment with emphasis on blooms in Boughrara Lagoon (South-Western Mediterranean): Combined effects of trace metal concentration and environmental context

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Contamination of planktonic food webs in the Mediterranean Sea: Setting the frame for the MERITE-HIPPOCAMPE oceanographic cruise (spring 2019)

International audienceThis paper looks at experiential feedback and the technical and scientific challenges tied to the MERITE-HIPPOCAMPE cruise that took place in the Mediterranean Sea in spring 2019. This cruise proposes an innovative approach to investigate the accumulation and transfer of inorganic and organic contaminants within the planktonic food webs. We present detailed information on how the cruise worked, including 1) the cruise track and sampling stations, 2) the overall strategy, based mainly on the collection of plankton, suspended particles and water at the deep chlorophyll maximum, and the separation of these particles and planktonic organisms into various size fractions, as well as the collection of atmospheric deposition, 3) the operations performed and material used at each station, and 4) the sequence of operations and main parameters analysed. The paper also provides the main environmental conditions that were prevailing during the campaign. Lastly, we present the types of articles produced based on work completed by the cruise that are part of this special issue