Effects of an invasive cattail species (Typha×glauca) on sediment nitrogen and microbial community composition in a freshwater wetland

Abstract

Sediments from Cheboygan Marsh, a coastal freshwater wetland on Lake Huron that has been invaded by an emergent exotic plant, Typhaxglauca, were examined to assess the effects of invasion on wetland nutrient levels and sediment microbial communities. Comparison of invaded and uninvaded zones of the marsh indicated that the invaded zone showed significantly lower plant diversity, as well as significantly higher aboveground plant biomass and soil organic matter. The sediments in the invaded zone also showed dramatically higher concentrations of soluble nutrients, including greater than 10-fold higher soluble ammonium, nitrate, and phosphate, which suggests that Typhaxglauca invasion may be impacting the wetland's ability to remove nutrients. Terminal restriction fragment length polymorphism analyses revealed significant differences in the composition of total bacterial communities (based on 16S-rRNA genes) and denitrifier communities (based on nirS genes) between invaded and uninvaded zones. This shift in denitrifiers in the sediments may be ecologically significant due to the critical role that denitrifying bacteria play in removal of nitrogen by wetlands.

Interlake variation and environmental controls of denitrification across different geographical scales

“…Lehee and Suolijärvi, with low Dn, low concentrations of nitrate in the water overlying the sediment and in the sediment porewater and high contents of organic matter in the sediment, had very similar nirK communities, whereas the communities were different in Pääjärvi and Ormajärvi. Our results, thus, suggest that the structure of the nirK community is regulated by the availability of nitrate and sediment characteristics, which is consistent with earlier studies (Angeloni et al 2006, Wallenstein et al 2006, Kjellin et al 2007, Magalhães et al 2008, Wu et al 2008. Thus, although availability of nitrate may immediately affect denitrification, it also acts more slowly through changes in community composition of denitrifiers (Wallenstein et al 2006).…”

Environmental and anthropogenic controls over bacterial communities in wetland soils

“…However, little is known about the taxonomic composition of uncultured soil bacteria in freshwater wetlands relative to other ecosystems, despite the disproportionate influence of wetlands in controlling biogeochemical cycling at landscape scales (3). With a single exception in a Sphagnum bog (4), existing knowledge of bacterial communities in freshwater wetlands has been obtained using DNA fingerprinting (5,6), group specific probes (7-9), or culture-based methods (8), which either have not identified bacterial taxonomic groups or do not adequately represent the vast diversity of uncultured soil bacteria (10). Furthermore, the environmental and anthropogenic factors controlling the distribution and abundance of bacterial groups in freshwater wetland soils are unknown.…”

Site History and Edaphic Features Override the Influence of Plant Species on Microbial Communities in Restored Tidal Freshwater Wetlands

“…Microbial biomass and oxygen (O 2 )-dependent metabolism are stimulated in the plant rhizosphere, where O 2 and C compounds are increased compared to levels in the surrounding soil (18)(19)(20). It has been observed that exotic plant species can significantly alter microbe-mediated function (21,22). For example, soils under the Eurasian lineage of Phragmites australis had nitrification rates three times greater than that of the native Spartina patens in a brackish marsh (23,24), and Lythrum salicaria tissue was observed to have a slower decomposition rate than the native Typha latifolia, leading to decreased nutrient pools (25,26).…”