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Biogeosciences Discussions 1, 1 (2004) 413-428

Quantifying the structure of the mesopelagic microbial loop from observed depth profiles of bacteria and protozoa

T. Tanaka 1, F. Rassoulzadegan 2, T. F. Thingstad 1

(2004-08-19)

t is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the structure of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that a similar amount of bacterial production is allocated to viruses and heterotrophic nanoflagellates, and that heterotrophic nanoflagellates are the important remineralizers.

1:	Department of Biology
	University of Bergen
2:	Laboratoire d'océanographie de Villefranche (LOV)
	CNRS : UMR7093 – INSU – Université Pierre et Marie Curie - Paris VI

Subject

:

Physics/Astrophysics Sciences of the Universe/Astrophysics Sciences of the Universe/Continental interfaces, environment Sciences of the Universe/Ocean, Atmosphere Sciences of the Universe/Earth Sciences

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From: Publication EGU <>

Submitted on: Thursday, 19 August 2004 08:00:00

Updated on: Tuesday, 14 October 2008 10:10:50