INA8
8th International Nannoplankton Association Conference


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David U. Hernández-Becerril, Ernesto Bravo-Sierra:
High contributions of coccolithophorids to the phytoplankton abundances in Baja California, Mexico, during El Niño 1997-1998
(Poster)


The phytoplankton from waters off Baja California, Mexico, are relatively well-known: the best studied groups are diatoms and 'armoured' dinoflagellates. However, there have been few attempts to study the contributions of the different groups and/or fractions of phytoplankton to the biomass and productivity. During a cruise from March to April, 1998 - considered the fall of the El Niño (1997-1998) event - samples were taken to collect the 'preservable' fraction of the phytoplankton from three depths at six points in three different zones off Baja California: 4l of water were filtered and preserved with a buffered (pH7.5-8) solution. The analysis of the filters, by light and electron microscopy, revealed assemblages with low diversity, dominated by coccolithophorids, mainly the species, Emiliania huxleyi. Coccolithophores are a rather poorly-known group in Baja California. The abundances of phytoplankton ranged between 5.4x103 and 1.2x105, with the coccolithophorids contributing upto a maximum of 93% to the total abundance, and reaching to a ratio of 21:1 with regard to diatoms, traditionally the most important group in the study area. Diatoms were dominated by small (<20µm), solitary and lanceolate/centric species. The main thermocline was at about 50-60m, except in a shallow station. Discussion is made on the methodology used, as well as on the effects of the oceanographic changes caused by El Niño on the phytoplankton community.


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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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Tania Hildebrand-Habel (hiha@micropal.uni-bremen.de)