Effect of Redox Conditions on Bacterial Community Structure in Baltic Sea Sediments with Contrasting Phosphorus Fluxes

Abstract

Phosphorus release from sediments can exacerbate the effect of eutrophication in coastal marine ecosystems. The flux of phosphorus from marine sediments to the overlying water is highly dependent on the redox conditions at the sediment-water interface. Bacteria are key players in the biological processes that release or retain phosphorus in marine sediments. To gain more insight in the role of bacteria in phosphorus release from sediments, we assessed the effect of redox conditions on the structure of bacterial communities. To do so, we incubated surface sediments from four sampling sites in the Baltic Sea under oxic and anoxic conditions and analyzed the fingerprints of the bacterial community structures in these incubations and the original sediments. This paper describes the effects of redox conditions, sampling station, and sample type (DNA, RNA, or whole-cell sample) on bacterial community structure in sediments. Redox conditions explained only 5% of the variance in community structure, and bacterial communities from contrasting redox conditions showed considerable overlap. We conclude that benthic bacterial communities cannot be classified as being typical for oxic or anoxic conditions based on community structure fingerprints. Our results suggest that the overall structure of the benthic bacterial community has only a limited impact on benthic phosphate fluxes in the Baltic Sea.

Carbon and Phosphorus Cycling in Arabian Sea Sediments across the Oxygen Minimum Zone

“…As these particular samples are surficial, the preferential loss of P org must be occurring either in the water column or during residence in surficial sediments. We explore these issues later in a discussion of depth trends, but several recent studies have indicated that the transformation process of P org is rapid and can even begin significantly in the water column [15,43,44]. Overall, the mean C org :P org ratios found here show a modest elevation within the OMZ compared to above and below that ( Figure 3) The values above the OMZ nearer the shoreline are slightly higher than those below the OMZ on the continental slope and rise, perhaps due to the influence of terrestrial organic matter with higher C org :P org ratios than marine organic matter [6].…”

Do Water Matrix and Particulate Buffering Capacity Affect the Rate and Extent of P Release?

“…The key factors are temperature [5] [6] [7] pH [8] [9], dissolved oxygen [10], redox conditions (Eh) [11] [12], microbes [13] [14], SPM size distribution [15] [16] and SPM texture [17], the organic matter content of the sediment and salinity [18].…”

Phylogenetic Characterization of Phosphatase-Expressing Bacterial Communities in Baltic Sea Sediments

“…We used a PCR-DGGE (PCR-Denaturing Gradient Gel Electrophoresis) analysis targeting bacterial 16S rRNA genes to determine the phylogenetic affiliation of the sorted cells. The results from this study were then compared to the non-sorted whole-cell bacterial community composition of the incubations (which will be referred to as “non-sorted whole-cell fraction”) determined in a previous study, which focused on the impact of redox conditions on the bacterial community structure of Baltic Sea sediments ( 18 ). The present study presents a phylogenetic characterization of phosphatase-expressing bacteria in Baltic Sea sediments.…”

“…ELF-labeled cells were sorted from the whole-cell fraction with a modular flow cytometer/cell sorter. DNA was extracted from the sorted cells by three cycles of snap-freezing in liquid nitrogen and subsequent thawing, as described in Steenbergh et al ( 18 ). The extracts were dialyzed using membrane filters (Millipore MF 0.025 μm VSWP; Millipore, Darmstadt, Germany) to lower the salt content of the samples.…”

“…The extracts were dialyzed using membrane filters (Millipore MF 0.025 μm VSWP; Millipore, Darmstadt, Germany) to lower the salt content of the samples. PCR targeting 16S rRNA genes, DGGE, sequencing, and a phylogenetic analysis were performed as described in ( 18 ). A full description of these methods is given in the supplemental material .…”