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Microbial spatial variability: an example from the Celtic Sea

Microbial spatial variability: an example from the Celtic Sea
Microbial spatial variability: an example from the Celtic Sea
In July 2004, dominant populations of microbial ultraplankton (<5 ?m), in the surface of the Celtic Sea (between UK and Eire), were repeatedly mapped using flow cytometry, at 1.5 km resolution over a region of diameter 100 km. The numerically dominant representatives of all basic functional types were enumerated including one group of phototrophic bacteria (Syn), two groups of phytoplankton (PP, NP), three groups of heterotrophic bacterioplankton (HB) and the regionally dominant group of heterotrophic protists (HP).
The distributions of all organisms showed strong spatial variability with little relation to variability in physical fields such as salinity and temperature. Furthermore, there was little agreement between distributions of different organisms. The only linear correlation consistently explaining more than 50% of the variance between any pairing of the organism groups enumerated is between two different groups of HB. Specifically, no linear, or non-linear, relationship is found between any pairings of SYB, PP or HB groups with their protist predators HP. Looking for multiple dependencies, factor analysis reveals three groupings: Syn, PP and low nucleic acid content HB (LNA); high nucleic acid content HB (HNA); HP and NP. Even the manner in which the spatial variability of Syn, PP and HB abundance varies as a function of lengthscale (represented by a semivariogram) differs significantly from that for HP. In summary, although all microbial planktonic groups enumerated are present and numerically dominant throughout the region studied, at face value the relationships between them seem weak.
Nevertheless, the behaviour of a simple, illustrative ecological model, with strongly interacting phototrophs and heterotrophs, with stochastic forcing, is shown to be consistent with the observed poor correlations and differences in how spatial variability varies with lengthscale. Thus, our study suggests that a comparison of microbial abundances alone may not discern strong underlying trophic interactions. Specific knowledge of these processes, in particular grazing, will be required to explain the causes of the observed microbial spatial variability and its resulting consequences for the functioning of the ecosystem.
Ecology, Plankton, Predator–prey interactions, Spatial variations, Celtic Sea
1744-9561
443-465
Martin, A.P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Fasham, M.J.
2f7a0f41-c77e-4468-99fa-84ec0ec2b7f0
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557
Holland, R.J.
4fa388a7-6f5d-4c05-ae3a-bbf254c04483
Martin, A.P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Fasham, M.J.
2f7a0f41-c77e-4468-99fa-84ec0ec2b7f0
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557
Holland, R.J.
4fa388a7-6f5d-4c05-ae3a-bbf254c04483

Martin, A.P., Zubkov, M.V., Fasham, M.J., Burkill, P.H. and Holland, R.J. (2008) Microbial spatial variability: an example from the Celtic Sea. Biology Letters, 76 (4), 443-465. (doi:10.1016/j.pocean.2008.01.004).

Record type: Article

Abstract

In July 2004, dominant populations of microbial ultraplankton (<5 ?m), in the surface of the Celtic Sea (between UK and Eire), were repeatedly mapped using flow cytometry, at 1.5 km resolution over a region of diameter 100 km. The numerically dominant representatives of all basic functional types were enumerated including one group of phototrophic bacteria (Syn), two groups of phytoplankton (PP, NP), three groups of heterotrophic bacterioplankton (HB) and the regionally dominant group of heterotrophic protists (HP).
The distributions of all organisms showed strong spatial variability with little relation to variability in physical fields such as salinity and temperature. Furthermore, there was little agreement between distributions of different organisms. The only linear correlation consistently explaining more than 50% of the variance between any pairing of the organism groups enumerated is between two different groups of HB. Specifically, no linear, or non-linear, relationship is found between any pairings of SYB, PP or HB groups with their protist predators HP. Looking for multiple dependencies, factor analysis reveals three groupings: Syn, PP and low nucleic acid content HB (LNA); high nucleic acid content HB (HNA); HP and NP. Even the manner in which the spatial variability of Syn, PP and HB abundance varies as a function of lengthscale (represented by a semivariogram) differs significantly from that for HP. In summary, although all microbial planktonic groups enumerated are present and numerically dominant throughout the region studied, at face value the relationships between them seem weak.
Nevertheless, the behaviour of a simple, illustrative ecological model, with strongly interacting phototrophs and heterotrophs, with stochastic forcing, is shown to be consistent with the observed poor correlations and differences in how spatial variability varies with lengthscale. Thus, our study suggests that a comparison of microbial abundances alone may not discern strong underlying trophic interactions. Specific knowledge of these processes, in particular grazing, will be required to explain the causes of the observed microbial spatial variability and its resulting consequences for the functioning of the ecosystem.

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More information

Published date: March 2008
Keywords: Ecology, Plankton, Predator–prey interactions, Spatial variations, Celtic Sea

Identifiers

Local EPrints ID: 50833
URI: http://eprints.soton.ac.uk/id/eprint/50833
ISSN: 1744-9561
PURE UUID: 88b7b038-1447-40ae-ae65-231294484944

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Date deposited: 03 Apr 2008
Last modified: 15 Mar 2024 10:12

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Contributors

Author: A.P. Martin
Author: M.V. Zubkov
Author: M.J. Fasham
Author: P.H. Burkill
Author: R.J. Holland

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