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Título

Microbial food web responses to light and nutrients beneath the coastal Arctic Ocean sea ice during the winter-spring transition

AutorTerrado, Ramon ; Lovejoy, Connie; Massana, Ramon ; Vincent, Warwick F.
Palabras claveProtists
Phytoplankton
Bacteria
Nutrients
Mixed layer
Sea ice
Light response
Fecha de publicación28-nov-2007
EditorElsevier
CitaciónJournal of Marine Systems 74: 964-977 (2008)
ResumenWe measured the abundance and biomass of phototrophic and heterotrophic microbes in the upper mixed layer of the water column in ice-covered Franklin Bay, Beaufort Sea, Canada, from December 2003 to May 2004, and evaluated the influence of light and nutrients on these communities by way of a shipboard enrichment experiment. Bacterial cell concentrations showed no consistent trends throughout the sampling period, averaging (± SD) 2.4 (0.9) × 108 cells L−1; integrated bacterial biomass for the upper mixed layer ranged from 1.33 mg C m−3 to 3.60 mg C m−3. Small cells numerically dominated the heterotrophic protist community in both winter and spring, but in terms of biomass, protists with a diameter > 10 µm generally dominated the standing stocks. Heterotrophic protist biomass integrated over the upper mixed layer ranged from 1.23 mg C m−3 to 6.56 mg C m−3. Phytoplankton biomass was low and variable, but persisted during the winter period. The standing stock of pigment-containing protists ranged from a minimum value of 0.38 mg C m−3 in winter to a maximal value of 6.09 mg C m−3 in spring and the most abundant taxa were Micromonas-like cells. These picoprasinophytes began to increase under the ice in February and their population size was positively correlated with surface irradiance. Despite the continuing presence of sea ice, phytoplankton biomass rose by more than an order of magnitude in the upper mixed layer by May. The shipboard experiment in April showed that this phototrophic increase in the community was not responsive to pulsed nutrient enrichment, with all treatments showing a strong growth response to improved irradiance conditions. Molecular (DGGE) and microscopic analyses indicated that most components of the eukaryotic community responded positively to the light treatment. These results show the persistence of a phototrophic inoculum throughout winter darkness, and the strong seasonal response by arctic microbial food webs to sub-ice irradiance in early spring.
Descripción14 pages, 4 tables, 5 figures.-- Printed version published Dec 2008.-- Issue title: "Sea ice and life in a river-influenced arctic shelf ecosystem".
Full-text version available Open Access at: http://www.icm.csic.es/bio/projects/icmicrobis/pdf/%20Terrado08.pdf
Versión del editorhttp://dx.doi.org/10.1016/j.jmarsys.2007.11.001
URIhttp://hdl.handle.net/10261/13994
DOI10.1016/j.jmarsys.2007.11.001
ISSN0924-7963
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