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4 results on '"Kefi-Daly Yahia O."'

1. Seasonal variability of picophytoplankton under contrasting environments in northern Tunisian coasts, southwestern Mediterranean Sea

Author

Salhi, N., Zmerli Triki, H., Molinero, Juan Carlos, Laabir, M., Sehli, E., Bellaaj-Zouari, A., Daly Yahia, N., Kefi-Daly Yahia, O., Salhi, N., Zmerli Triki, H., Molinero, Juan Carlos, Laabir, M., Sehli, E., Bellaaj-Zouari, A., Daly Yahia, N., and Kefi-Daly Yahia, O.

Abstract

Highlights: • Picophytoplankton was able to grow under a wide range of environmental conditions varying seasonally. • Picophytoplankton variability was more marked in the bay than in the lagoon. • Picophytoplankton decreased in the lagoon under enhanced anthropogenic stress. • Synechococcus, the most abundant group of the community, was frequently present in both ecosystems during the monitoring. We investigated at the single cell level during 16months (June 2012 to September 2013) the temporal distribution of picophytoplankton (picoeukaryotes, Synechococcus and Prochlorococcus) communities in two contrasted ecosystems: the Bay of Bizerte characterised by an oligotrophic regime typical of the Mediterranean Sea and the Bizerte Lagoon that exhibits a mesotrophic/eutrophic state. We aimed at depicting seasonal variations and quantifying the relationships between the environmental factors and the structure and abundance of picophytoplankton communities. Results showed that picophytoplankton groups were able to grow under a wide range of environmental conditions varying seasonally, although their abundances and contributions to the total chlorophyll biomass significantly varied and showed importance in the Bay of Bizerte. Synechococcus was the most abundant group reaching 225*103 cells·cm-3 in the Bay and 278*103 cells·cm-3 in the lagoon. This group was present all over the year in both ecosystems. Structural equation model results pointed out a different configuration regarding the picophytoplankton environmental drivers. The complexity of the configuration, i.e. number of significant links within the system, decreased under enhanced eutrophication conditions. The less exposure to anthropogenic stress, i.e. in the Bay of Bizerte, highlight a larger role of nutrient and hydrological conditions on the seasonal variations of picophytoplankton, whereas a negative effect of eutrophication on picophytoplankton communities was unveiled in the Bizerte Lagoon. We stress that suc

Published
2018
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3. Jellyfish blooms perception in Mediterranean finfish aquaculture

Author

Verónica Fuentes, Ons Kéfi-Daly Yahia, Stefano Piraino, Alan Deidun, Kristian Pulis, Giacomo Milisenda, Ernesto Azzurro, Anton Micallef, Mar Bosch-Belmar, Bosch Belmar, Mar, Azzurro, Ernesto, Pulis, Kristian, Milisenda, Giacomo, Fuentes, Verónica, Kéfi Daly Yahia, On, Micallef, Anton, Deidun, Alan, Piraino, Stefano, Bosch-Belmar Mar, Azzurro E., Pulis K., Milisenda G., Fuentes V., Kefi-Daly Yahia O., Micallef A., Deidun A., Piraino S., and European Commission

Subjects
0106 biological sciences, Mediterranean climate, Settore BIO/07 - Ecologia, Economics and Econometrics, Jellyfish, Gelatinous zooplankton, Fish farming, Aquaculture, Management, Monitoring, Policy and Law, Aquatic Science, 01 natural sciences, Central and western Mediterranean, Mediterranean sea, Central and Western Mediterranean, biology.animal, 14. Life underwater, General Environmental Science, biology, business.industry, 010604 marine biology & hydrobiology, 04 agricultural and veterinary sciences, Fish farmers' perception, biology.organism_classification, Fishery, Geography, 13. Climate action, Agriculture, Gelatinous zooplankton, Fish farmers' perception, Aquaculture, Central and Western Mediterranean, 040102 fisheries, 0401 agriculture, forestry, and fisheries, business, Tuna, Law
Abstract

7 pages, 5 figures, 3 tables, supplemental material https://doi.org/10.1016/j.marpol.2016.11.005, In recent years, negative impacts of jellyfish blooms (JB) on marine human activities have been increasingly reported. Aquaculture has been affected by jellyfish outbreaks, mostly documented through repeated episodes of farmed salmon mortalities in Northern Europe; however, the valuation of JB consequences on the aquaculture sector still remains poorly quantified. This study aims to provide the first quantitative evaluation effects of JB on finfish aquaculture in the Mediterranean Sea and to investigate the general awareness of JB impacts among Mediterranean aquaculture professional workers. The aquaculture workers' perception about JB was assessed through a structured interview-based survey administered across 21 aquaculture facilities in central and western Mediterranean. The workers' awareness about JB impacts on aquaculture differed among countries. Italian and Spanish fish farmers were better informed about jellyfish proliferations and, together with Tunisian farmers, they all recognized the wide potential consequences of JB on sea bream and sea bass aquaculture. On the contrary, the majority of Maltese respondents considered JB as a non-significant threat to their activity, mostly based on off-shore tuna farming. This study for the first time shows that JB may negatively affect different Mediterranean aquaculture facilities from Tunisia (Sicily Channel) and Spain (Alboran Sea), by increasing farmed fish gill disorders and mortality, clogging net cages, or inflicting painful stings to field operators, with severe economic consequences. Available knowledge calls for the development of coordinated preventive plans, adaptation policies, and mitigation countermeasures across European countries in order to address the JB phenomenon and its impacts on coastal water activities, This work has received funding from the European Union's projects MED-JELLYRISK (grant n. I-A/1.3/098 - ENPI CBCMED programme), VECTORS (Vectors of Change in Oceans and Seas Marine Life, Impact on Economic Sectors, grant n. 266445, FP7th programme), and CERES (Climate Change and European Aquatic Resources, grant n. 678193, Horizon 2020 programme)

Published
2017

4. Effects of copper and butyltin compounds on the growth, photosynthetic activity and toxin production of two HAB dinoflagellates: The planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata.

Author

Couet D, Pringault O, Bancon-Montigny C, Briant N, Elbaz Poulichet F, Delpoux S, Kefi-Daly Yahia O, Hela B, Charaf M, Hervé F, Rovillon G, Amzil Z, and Laabir M

Subjects
Biomass, Dinoflagellida growth & development, Dinoflagellida metabolism, Marine Toxins metabolism, Microalgae drug effects, Microalgae metabolism, Plankton drug effects, Plankton metabolism, Water Pollutants, Chemical chemistry, Copper toxicity, Dinoflagellida drug effects, Organotin Compounds toxicity, Photosynthesis drug effects, Water Pollutants, Chemical toxicity
Abstract

Controlled laboratory experiments were conducted to test the effects of copper (Cu 2+ ) and butyltins (BuT) on the growth, photosynthetic activity and toxin content of two HABs (Harmful Algal Blooms) dinoflagellates, the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata. Microalgae were exposed to increasing concentrations of Cu 2+ (10 -4 to 31 nM) or BuT (0.084 to 84 nM) for seven days. When considering the growth, EC 50 values were 0.16 (±0.09) nM and 0.03 (±0.02) nM of Cu 2+ for A. catenella and O. cf. ovata, respectively. Regarding BuT, EC 50 was 14.2 (±6) nM for O. cf. ovata, while A. catenella growth inhibition appeared at BuT concentrations ≥27 nM. Photosynthetic activity of the studied dinoflagellates decreased with increasing Cu and BuT concentrations. For O. cf. ovata, the response of this physiological parameter to contamination was less sensitive than the biomass. Cu exposure induced the formation of temporary cysts in both organisms that could resist adverse conditions. The ovatoxin-a and -b concentrations in O. cf. ovata cells increased significantly in the presence of Cu. Altogether, the results suggest a better tolerance of the planktonic A. catenella to Cu and BuT. This could result in a differentiated selection pressure exerted by these metals on phytoplankton species in highly polluted waters. The over-production of toxins in response to Cu stress could pose supplementary health and socio-economic threats in the contaminated marine ecosystems where HABs develop., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Published
2018
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