Spatial and temporal variation in denitrification and in the denitrifier community in a boreal lake

Aj Rissanen,A Ojala,M Tiirola

doi:10.3354/ame01506

Abstract

We investigated the spatial and temporal variation in denitrification rates (isotopepairing technique, IPT) and in the denitrifier community (examination of gene nirK by denaturinggradient gel electrophoresis [DGGE] of microbial DNA) in the sediments of a boreal, clear-water, eutrophic lake using samples collected from shallow littoral, deep littoral and shallow profundal sediments during early summer, mid-summer, autumn and winter. The measured denitrification rates (44 to 613 μmol N m−2 d−1) are among the lowest ever reported from lacustrine sediments. Denitri fi cation rates varied both spatially and temporally, being highest in the profundal zone during midsummer and in the littoral zones during winter. Correlation analyses indicated that these variations were due to variations in the concentrations of nitrate and oxygen in the water overlying the sediment. The structure of the denitrifier community was temporally extremely stable and differed only slightly between the sites. Distance-based linear model (DISTLM) analysis indicated that the observed variation was probably due mainly to variations in the content of organic matter, and in the porosity, of the sediment. The structure of the denitrifier community and the denitrifying activities were uncoupled.

Highlights

Aquat Microb Ecol 64: 27–40, 2011nirK and nirS (Wallenstein et al 2006)
We investigated the spatial and temporal variation in denitrification rates and in the denitrifier community in the sediments of a boreal, clear-water, eutrophic lake using samples collected from shallow littoral, deep littoral and shallow profundal sediments during early summer, mid-summer, autumn and winter
(44 to 613 μmol N m−2 d−1) are among the lowest ever reported from lacustrine sediments

Summary

INTRODUCTION

NirK and nirS (Wallenstein et al 2006). Approaches to microbial community fingerprinting, i.e. denaturing-gradient gel electrophoresis (DGGE) (Muyzer et al 1993, Throbäck et al 2004) and terminal restriction fragment length polymorphism (TRFLP) (Liu et al 1997, Rich et al 2003), provide cost-effective but sensitive methods for performing a statistically sufficient number of replicate analyses of community structure variations (Prosser 2010). For ral variation in denitrification rates, and in the denitrifuture local and global nitrogen modelling, more inforfier community, in the sediments of a boreal clearmation is needed about the mechanisms of nitrogen water lake. Because previous studies have indicated retention, and especially about denitrification, in these that shallow areas in lakes act as ‘hotspots’ of denitrifilakes. It will be important to assess both the spatial and cation (Ahlgren et al 1994, Saunders & Kalff 2001b), temporal variation in denitrification rates and to recogthe present study focused on littoral and nize the factors, e.g. temperature, O2 concentration shallow profundal sites. Denitrifier community can affect process rates (e.g. Rich et al 2003, Magalhães et al 2008), but this has never been assessed in denitrification studies of lake

MATERIALS AND METHODS

27 Feb 07

RESULTS

DISCUSSION