Characterization of microbial activity in the surface layers of a coastal subtropical sediment

Biochemical and traditional methods were used to determine the influence of Caflianassa trilobata on microbiological and meiofaunal communities within its large, hghly consolidated burrow. Sediment was collected from the lining of the shrimp's burrow, the burrow matrix, and ambient, subsurface sediment. The lining and matrix were composed of poorly sorted, fine-grained material compared to sandy ambient sediment. Meiofauna, predominantly nematodes, were most abundant in ambient sediment, not in the burrow as has been found for other species of macrofauna. Concentrations of chlorophyll a were very high in the lining, consistent with the suggestion that C. trilobata lines its burrow walls with seagrass. Analyses of lipids indicated that relative to the matrix and ambient sediment, the lining abounds with pro-and eukaryotic biomass. Thirty-four phospholipid, ester-linked fatty acids (PLFA) were identified and quantified. Fatty acids were assigned to functional groups of microorganisms to assess spatial variations in the absolute abundance and relative proportions of microbial populations. Dominance of prokaryotes was pronounced in all 3 areas, especially the matrix. The lining was the most aerobic location, but anaerobic microhabitats simultaneously allowed proliferation of sulfate-reducing bacteria, e. g. Desulfobacter. A radial trend was detected in the ratio of bacteria with terminally branched PLFA, typical of Gram-positive organisms, to those with unsaturated PLFA common to Gram-negative bacteria. The ratio increased from lining to matrix to ambient sediment. The ratios of tram to cls isomers of 16:lw7 indicated that prokaryotes in the matrix were starved. Through construction and maintenance of its burrow, C. trilobata determines not only the absolute and relative abundances of microbes in its sedimentary environment, but their physiologic state as well.

Section: Lipidssupporting

confidence: 81%

Callianassa trilobata (Crustacea: Thalassinidea) influences abundance of meiofauna and biomass, composition, and physiologic state of microbial communities within its burrow

Dobbs¹,

Guckert²

1988

“…At our sampling site, w e observed a n order of magnitude decrease in microbial biomass (as determined by total ATP) between the sediment-water interface and a sediment depth of 5cm. This depth distribution of ATP was coherent both in space and time (Novitsky & Karl 1986). The greatest change in microbial biomass was observed between interface layer and topmost sedi-ment sample.…”

Section: Introductionmentioning

confidence: 99%

“…In a previous paper (Novitsky & Karl 1986), we initially characterized the microbial populations in the surface sediment of Kahana Bay, Hawaii. At our sampling site, w e observed a n order of magnitude decrease in microbial biomass (as determined by total ATP) between the sediment-water interface and a sediment depth of 5cm.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of microbial growth in surface layers of a coastal marine sediment ecosystem

Karl¹,

Novitsky²

1988

Self Cite

ABSTRACT. Growth kinehcs of the microbial community of a coastal, sub-tropical sediment were studied by following uptake of 3~-a d e n i n e .3~-a d e n i n e was incorporated into RNA and DNA, thus providing a measure of both cell metabolism and growth. Extrapolation from measured values of isotope dilution of the ATP pool at isotopic equhbrium (i.e. SA,,, parameter) indicated that a large portion of the adenine required for community nucleic acid synthesis was derived from uptake of exogenous supplies. Microbial community doubling times, estimated from adenine nucleotide pool labeling kinetics, ranged from 26 h at the seawater-sediment interface to 47 to 92 h for samples beneath the interface. RNA synthesis rate consistently exceeded DNA synthesis rate by 1 to 2 orders of magnitude for all horizons examined, in spite of these relatively slow growth rates. The newly synthesized RNA was found to be stable with less than 10% being degraded during a period equivalent to the mean population doubling time. Our results indicate a sediment microbial community with growth rates and metabolism distinctly different from water-column communities. The results strongly suggest net, but unbalanced growth in these sediment communities.

“…However, sediments are far from homogeneous and some specific microenvironments are particularly conducive to microbial activities. Chemocline environments, such as those found at the sediment-water interface, are well known to be sites of enhanced microbial activities (Novitsky 1983, Novitsky & Karl 1986). The classic model of these interface environments places aerobic metabolism at the sediment surface, followed by various anaerobic processes in deeper sediment layers (e.g.…”

Section: Introductionmentioning

confidence: 99%

Distributions of total and active bacteria in biofilms lining tubes of the onuphid polychaete Diopatra cuprea

Phillips¹,

Lovell²

1999

Infaunal burrows and tubes support elevated levels of microbial biomass and activities relative to the surrounding bulk sediments. The impacts of these structures on sediment biogeochemistry have been intensively studled, but very little is known about the microbiota or their spatial organization within these microenvironments. Distributions of bacterial cells and microcolonies and of potentially active bacterial cells in tubes of the onuphid polychaete Diopatra cuprea were determined using confocal scanning laser microscopy. Distributions were examined among different tubes, at different locations within a tube, and at different depths in the biofilms lining these tubes. The average quantity of cells across all tubes examined was 5.61 X 1 0 ' cm-3 and there was no trend in the distribution of cells along the length of the tube or with increasing depth in the biofilm. Cell size across all tubes collected in February 1997 averaged 0.085 pm3 but varied seasonally. Mean cell size increased with increasing depth below the sediment surface of the tube site sampled, and decreased with increasing depth in the biofilm. Microcolonies were abundant and not confined to specific depths within the b i o f h or locations within the tube. Potentially active cells were observed at all depths within the biofilm and at least 46% (mean = 68%) of cells at any given site were potentially active. We hypothesize that the observed trends in cell distribution are responsive to tube irngation by the host polychaete