A comparison of sediment microbial communities associated with<Emphasis Type="Italic">Phragmites australis</Emphasis> and<Emphasis Type="Italic">Spartina alterniflora</Emphasis> in two brackish wetlands of New Jersey |
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| Authors: | Email author" target="_blank">Beth?RavitEmail author Joan?G?Ehrenfeld Max?M?Haggblom |
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| Institution: | 1.Graduate Program in Environmental Sciences, Cook College,Rutgers University,New Brunswick;2.Department of Ecology, Evolution, and Natural Resources, Cook College,Rutgers University,New Brunswick;3.Department of Biochemistry and Microbiology, Cook College,Rutgers University,New Brunswick |
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| Abstract: | The extensive spread ofPhragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration
decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important
in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment
microbial communities inPhragmites marshes. Microbial populations associated with invasivePhragmites vegetation and with native salt marsh cordgrass,Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose
organic substrates (community biogeochemical function). This study compares sediment microbial communities associated withPhragmites andSpartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically
affected Hackensack meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymataic activity to profile sediment
microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter,
and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting
greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase,
acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as
measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns
of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments,
macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical
site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially,
microbial biogeochemical functions. |
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