Abstract
There is little known about the ecology of microbial communities living in the water column over seamounts. Here, for the first time, the spatial distribution and abundance of virus-like particles (VLP) are described over a seamount. The association between VLP distribution, prokaryotic abundance, and environmental variables is also analyzed. Sampling was conducted in December 2004 on the Bajo O’Higgins 1 seamount (32°54’S, 73°53’W) located in the Humboldt Current System off Chile. A oxygen minimum layer (OMZ) was clearly present between 130 and 280 m in the water column over the seamount. Water samples were taken with Niskin bottles at 10 oceanographic stations over the seamount at depths of 5, 20, 50, 75, 100, and 150 m and at the benthic boundary layer (BBL; 5-12 m over the sediments). Temperature, salinity, oxygen, chlorophyll , and phaeopigments were measured at each station. Viral and prokaryotic abundances were determined with fluorochrome SYBR Green I. Viral abundance ranged from 1.53 x 10 9 VLP L -1 - 16.48 x 10 9 VLP L -1 , whereas prokaryotic abundance ranged from 1.78 x 10 8 cell L -1 - 14.91 x 10 8 cell L -1 . The virus-like particle/prokaryote ratio varied widely among the analyzed layers (i.e. surface, OMZ, and BBL), probably due to the presence of different prokaryotic and viral assemblages in each layer. Our results indicate that the environmental conditions, mainly the concentration of dissolved oxygen in the water column over Bajo O’Higgins 1 seamount, shape the association between viral and prokaryotic abundance.
Highlights
Viruses are the most abundant members of aquatic microbial communities (Winter et al, 2005) and their density can exceed bacterial abundance by between 5 and 25 times (Fuhrman, 1999)
Water samples were taken at 10 stations (bottom depth between 376 and FIG. 1. – Oceanographic stations on Bajo O’Higgins 1 seamount (32°54’S, 73°53’W)
This study describes, for the first time, the distribution and abundance of virus-like particles (VLP) on a seamount and the relationship of this distribution with prokaryotic abundance as well as with environmental factors
Summary
Viruses are the most abundant members of aquatic microbial communities (Winter et al, 2005) and their density can exceed bacterial abundance by between 5 and 25 times (Fuhrman, 1999). It has been shown that viral abundance increases significantly with system productivity (Weinbauer, 2004) and, in accordance with this, it has been proposed that the trophic state of a system is a controlling factor of viral spatial distribution (Corinaldesi et al, 2003). This general tendency, has not been contrasted in many marine environments such as seamounts, which influence local circulation and increase the area’s biological productivity No quantitative estimate of viral abundance on a seamount has ever been reported to date
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