AME 45:129-145 (2006)  -  doi:10.3354/ame045129

Linking bacterioplankton community structures to environmental state variables and phytoplankton assemblages in two South Carolina salt marsh estuaries

Wes Johnson1,*, Alan J. Lewitus2,3, Madilyn Fletcher1,2

1Marine Science Progam, EWS Rm 603, University of South Carolina, Columbia, 29208 South Carolina, USA
2Belle W. Baruch Institute for Marine and Coastal Sciences, EWS Rm 604, University of South Carolina, Columbia, 29208 South Carolina, USA
3Present address: NOAA Center for Sponsored Coastal Ocean Research, 1501 East West Highway, Silver Spring, 20910 Maryland, USA

ABSTRACT: Microorganisms are among the most important organisms to the ecology of salt marsh estuaries; however, fundamental questions regarding their distribution, environmental controls, and interactions with phytoplankton remain unanswered. We used denaturing gradient gel electrophoresis (DGGE) of bacterial rRNA genes and high performance liquid chromatography (HPLC) of phytoplankton photopigments to characterize planktonic communities from the Ashepoo, Combahee, and Edisto (ACE) Basin and North Inlet (NI) estuaries on the South Carolina coast, USA. Multivariate comparisons of the planktonic community profiles revealed that the 2 estuaries supported distinct bacterial communities. Furthermore, bacterial communities in both systems were partitioned into separate particle-associated (PA) and free-living (FL) components. Differences in bacterial populations were also observed along the salinity gradient within each system. Comparisons of water physicochemistry with bacterial profiles indicated significant correlation of PA bacterial community structures with temperature, salinity, organic carbon, total phosphorus, and ammonium, whereas FL communities were affected by nitrate, ammonium, total phosphorus and orthophosphate. PA bacterioplankton community structures were also associated with diatoms, dinoflagellates, haptophytes and cryptophytes, while FL assemblages corresponded to prasinophytes, chlorophytes, and cyanobacteria. Comparisons between estuaries further demonstrated that ACE Basin communities were mostly associated with the same pigments as PA samples, and that NI assemblages correlated with FL-associated phytoplankton, suggesting different trophodynamics of particles in the 2 systems.

KEY WORDS: Bacteria · Phytoplankton · Community structure · HPLC · DGGE · Salt marsh estuary

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