Phospholipid fatty acid profiles at depositional and non-depositional sites in the North Sea

Abstract

The distribution of ester-linked phospholipid fatty acid (PLFA) in sediments of 12 sampling stations located in the German Bight, Skagerrak/northern Kattegat, Frisian Front, Oyster Ground, eastern North Sea and the Dogger Bank area was studied to compare the in situ microbial community structure of depositional and non-depositional sites. A total of 36 fatty acids in the range of C 12 to C 24 were determined. They consisted of saturated, branched, monounsaturated, polyunsaturated and hydroxy fatty acids, and variation was revealed in the relative proportions (mol %) of these fatty acids. The distribution of specific fatty acids was significantly different between depositional and non-depositional sites. Additionally, we could discriminate communities of sites which are intermediate in sedimentation regime. Highest total PLFA content was found at depositional sites. The PLFA profiles of all sites were dominated by bacteria, with highest bacterial contribution to the sedimentary PLFA pool at depositional sites. A high proportion of aerobic prokaryotes (up to 40%) at depositional sites indicated the occurrence of aerobic microniches in the corresponding anoxic sediments. Bacterial groups being a component of the degradation pathways of complex macromolecules (e.g. Cytophaga and Actinomycetes) were found in significant higher abundances at depositional sites compared to the other sites. At depositional sites, sulphate-reducing bacteria (SRB) (e.g. Desulfobacter spp.) were more abundant compared to the other stations. The relative contribution of microeukaryotes to the sedimentary PLFA pool was significantly higher at depositional sites. A nutritionally limited benthic system at non-depositional sites in the offshore is indicated by a microbial community exposed to higher physiological stress than those of the organically enriched sediments of the depositional sites.

Microbial diversity in waters, sediments and microbial mats evaluated using fatty acid-based methods

“…Similarly, the dominance of bacteria at both depositional and non-depositional sites in the North Sea was reported by Stoeck et al (2002). An analysis of PLFA profiles showed a high abundance of Cytophaga-Flavobacterium-Bacteroides and Actinomycetes, bacterial groups that are involved in the degradation of complex macromolecules, at depositional sites as compared to other sites.…”

Fatty acid signatures in plasma of captive herring gulls as indicators of demersal or pelagic fish diet

“…In addition to having low levels of the pelagic markers, the birds fed demersal fish also have a few features characteristic of benthic food webs in their FAS. Microbial lipids of North Sea sediments are rich in odd-and branched-chain saturated fatty acids, and the isomer distribution of their MUFA is different from that of the pelagic fatty acid sources and favours for example 18:1n-7 (Stoeck et al 2002). Consequently, the plasma FAS of the birds fed demersal fish contained relatively high percentages of iso-17:0, anteiso-17:0, 17:0 and 18:1n-7.…”

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

“…where I bacteria is the bacterial biomass or phyo C incorporation into bacterial biomass; I PLFA is the concentration of a bacteria-specific PLFA or its phyto C concentration; a is the PLFA concentration in bacteria within marine sediments (∼ 0.056 g of C PLFA per g of C biomass) (Brinch-Iversen and King, 1990); and b is the average contribution of bacterial PLFAs to the sediment PLFA pool (20 %) (calculated from Rajendran et al, 1993Rajendran et al, , 1994Boschker et al, 1998;Middelburg et al, 2000;Stoeck et al, 2002). Bacterial phyto C incorporation was then normalised to biomass to allow comparison between stations.…”