NDLI: Vitamine B12 et phytoplancton au niveau de la thermocline en Méditerranée nord-occidentale

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Vitamine B12 et phytoplancton au niveau de la thermocline en Méditerranée nord-occidentale

Content Provider	Semantic Scholar
Author	Fiala, Marco
Copyright Year	1982
Abstract	M. Fiala Laboratoire Arago, 66650 Banyuls-sur-Mer, France. Recu le 23/11/81, revise le 1/3/82, accepte le 18/3/82. La distribution de la vitamine B12 et des communautes phytoplanctoniques a ete suivie durant l'ete pres des cotes de Banyuls (Mediterranee nord-occidentale). La vitamine B12 a ete determinee par dosage biologique selon le protocole preconise par Droop auquel quelques ameliorations ont ete apportees. C'est au tiers inferieur de la thermocline que l'on observe des floraisons de diatomees dans les eaux riches en reserves nutritives et en vitamine B12. Cette richesse est due a une remontee inhabituelle d'eau «profonde »jusqu'au niveau de cette thermocline. On note, a trois periodes, l'apparition concomitante de fortes concentrations en B12 et de floraisons de diatomees. Les especes dominantes appartiennent essentiellement au groupe des Pseudonitzschia. Cinq diatomees (Nitzschia cuspidata, N. subpaciftca, N . . sp., Leptocylindrus danicus et Cylindrotheca closterium) caracteristiques de ces floraisons estivales, ont ete isolees puis testees, afm de determiner leurs besoins en vitamines. Seule la vitamine B12 s'avere etre indispensable a la croissance de ces 5 algues. Ceci met en evidence le role de cette vitamine dans la determination de la specificite des communautes phytoplanctoniques estivales dans cette region. Oceanol. Acta, 1982, 5, 3, 339-347 Vitamin B12 and phytoplankton at the thermocline level in the North-West Mediterranean The distribution of vitamin B12 and phytoplankton communities was studied over the summer period close to the coast at Banyuls (North-West Mediterranean). Vitamin B12 was measured in a biossay according to an improved procedure adapted from Droop's method. In the lower third of the thermocline, diatom blooms were observed in water rich in nutrients and vitamin B12. This enrichment is due to an exceptional upwelling of "deep" water to the thermocline level. At three different times, high B12 concentrations occur concomitantly with the diatom blooms. Dominant species belong chiefly to the Pseudonitzschia group. 5 diatoms (Nitzschia cuspidata, N. subpaciftca, N. sp., Leptocylindrus danicus and Cylindrotheca closterium) typical of these summer blooms were isolated and tested for their vitamin requirements. Only vitamin B12 was found to be indispensable for the growth of these algal species. The results demonstrate the role of vitamin B12 in determining the speciftcity of summer phytoplankton communities in this area. Oceanol. Acta, 1982, 5, 3, 339-347 0399-1784/1982/339/$ 5. 00/® Gauthier-Villars 339
Starting Page	339
Ending Page	347
Page Count	9
File Format	PDF HTM / HTML
Volume Number	5
Alternate Webpage(s)	https://archimer.ifremer.fr/doc/00120/23172/21017.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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