Distribution and activity of bacteria in the headwaters of the Rhode River Estuary, Maryland, USA

Biology Department Whitman College 99362 Walla Walla WA USA; Marine Biological Laboratory Ecosystems Center 02543 Woods Hole MA USA
Microbial Ecology (Impact Factor: 3.28). 08/1984; 10(3):243-255. DOI: 10.1007/BF02010938

ABSTRACT A transect along the axis of the headwaters of a tidal estuary was sampled for microbial, nutrient, and physical parameters. Chlorophylla averaged 42g 1–1 and phytoplankton comprised an estimated 80% of the total microbial biomass as determined by adenosine triphosphate (ATP). Bacterial concentrations ranged from 0.3–53.9106 cells ml–1 and comprised about 4% of the total living microbial biomass. Bacterial production, determined by3H-methyl-thymidine incorporation was about 0.05–2.09 109 cells 1–1 h–1, with specific growth rates of 0.26–1.69 d–1. Most bacterial production was retained on 0.2m pore size filters, but passed through 1.0m filters. Significant positive correlations were found between all biomass measures and most nutrient measures with the exception of dissolved inorganic nitrogen nutrients where correlations were negative. Seasonal variability was evident in all parameters and variability among the stations was evident in most. The results suggest that bacterial production requires a significant carbon input, likely derived from autotrophic production, and that microbial trophic interactions are important.

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    ABSTRACT: The temporal variability of the abundance and the incorporation of 3H-thymidine and 14C-glucose by attached and free-living bacteria, as well as their relation with environmental factors, were analyzed in a coastal marine ecosystem during a year. Both communities were quantitatively very different. Attached bacteria represented only 6.8% of the total bacterial abundance, whereas free-living bacteria represented 93.2%. The environmental factors most closely linked to the abundance and activity of free-living bacteria were temperature and the concentration of dissolved nutrients. Moreover, the free-living community showed similar temporal variations in abundance and in activity, with lower values in the cold months (from October to May). The attached community did not present the same pattern of variation as the free-living one. The abundance of the attached bacteria was mainly correlated to the concentration of particulate material, whereas their activity was correlated to temperature. We did not find a significant correlation between the abundance and the activity of the attached community. On the other hand, the activity per cell of the two communities did not present a clear temporal variation. Attached bacteria were more active than free-living ones in the incorporation of radiolabeled substrates on a per cell basis (five times more in the case of glucose incorporation and twice as active in thymidine incorporation). However, both communities showed similar specific growth rates. The results suggest that the two aquatic bacterial communities must not be considered as being independent of each other. There appears to be a dynamic equilibrium between the two communities, regulated by the concentrations of particulate matter and nutrients and by other environmental factors.
    Microbial Ecology 12/1991; 23(1):27-39. · 3.28 Impact Factor
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    ABSTRACT: Vertical profiles of bacterial biomass (AODC method), production of biomass (Thymidine method) and total ETS (Electron Transport System) activity were recorded on 14 dates during the destratification process in the monomitic eutrophic Biétri Bay (Ebrié lagoon, Ivory Coast). Bacterial biomass and production were both very high, indicating the importance of heterotrophic processes in this system. Interpretation of ETS data suggests that bacteria or "bacteria-associated organisms" are responsible for most of the oxygen consumed in the water column. Integrated bacterial production of biomass represented ca 80% of carbon produced by primary producers, thus showing that autotrophic production does not meet heterotrophic requirements of bacteria. Destratification appears to be of less importance than suggested by the physical and chemical characteristics, resulting in decrease of bacterial biomass and production by a factor of 2 in the epilimnion. (D'après résumé d'auteur)
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    ABSTRACT: Samples were collected at stations located in the mesohaline, oligohaline, and tidal fresh regions of the Potomac River, Maryland, between April 1998 and December 1999 to evaluate the seasonal distribution of bacterioplankton and microbially labile organic carbon (MLOC) in relation to hydrodynamic parameters (dissolved oxygen, salinity, and temperature). Bacterioplankton abundance (BA) averaged 13 × 106 cells ml−1 at all stations, a value that is higher than the average observed in many other temperate estuaries around the world, and were almost exclusively free-living. During the summer of 1998, BA often exceeded 30 × 106 cells ml−1 in the mesohaline region during periods of anoxia in subpycnocline waters. Dissolved MLOC typically accounted for 40% of total MLOC and on some occasions during summer and autumn accounted for 80%. A significant positive relationship between dissolved MLOC and BA was evident in the mesohaline Potomac River, the region where anoxia occurs each summer, but the regressions of particulate MLOC and chla on BA were not significant at this location. In the mesohaline Potomac River, BA regressed negatively and significantly on dissolved oxygen (r2=0.50, p<0.001). BA may be an important indicator of ecosystem health in this and other eutrophied estuaries, because of the relationships between BA, dissolved MLOC, and dissolved oxygen in the salinity stratified Potomac River and because free-living BA was elevated along the length of the river.
    Estuaries and Coasts 29(1):40-53. · 2.56 Impact Factor

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