Detritus Processing and Microbial Dynamics of an Aquatic Macrophyte and Terrestrial Leaf in a Thermally Constant, Spring-Fed Stream

Abstract

Past studies of organic matter processing in stream ecosystems have focused on the fate of allochthonous terrestrial leaf detritus. In streams with a reduced canopy, submerged macrophytes may provide a significant source of organic matter to the microbial community and higher trophic levels. We compared mass loss patterns and microbial dynamics between a submerged macrophyte, Sagittaria platyphylla, and a deciduous leaf, Populus deltoides. Mass loss rates were higher for the submerged macrophyte, though exponential decay values indicated that both are "fast" decomposers. Bacterial abundance was not significantly different between plant types, but bacterial productivity was significantly higher in Sagittaria. Although fungal biomass was higher overall for Populus, it was not significantly different from that of Sagittaria until day 30. Relative to fungi, bacteria made up 4% and 7% of the peak microbial biomass on Populus and Sagittaria, respectively. Aquatic hyphomycete sporulation was detected only on Populus. These results suggest that in systems where submerged macrophytes are abundant, they can provide a carbon source quantitatively comparable to that of riparian leaf detritus, but that qualitative differences in leaf structural composition cause a shift toward a more significant role for bacterial decomposers.

Regulators of coastal wetland methane production and responses to simulated global change

“…For example, West et al (2012) found that adding algal carbon significantly enhanced CH 4 production relative to terrestrial carbon. Although aquatic macrophyte carbon may be of lower quality than that of algae, aquatic macrophytes are generally more labile than terrestrial plants (Schlickeisen et al, 2003). For example, Tiegs et al (2013) found that terrestrial plants decomposed more slowly than aquatic macrophytes in CRD wetlands.…”

Beyond the water column: aquatic hyphomycetes outside their preferred habitat

“…The typical substrata of aquatic hyphomycetes, i.e., litter from trees and ligneous terrestrial vegetation, however, are progressively less abundant as rivers become larger (Vannote et al, 1980). In such environments, primary production (algae, aquatic and semi-aquatic plants) is mostly autochthonous, and aquatic hyphomycetes are not good colonizers of macrophytes, even though rare studies have reported their occurrence on macrophyte detritus (Kirby et al, 1990;Schlickeisen et al, 2003). Riparian forests may, however, provide substantial amounts of leaf litter and wood even in estuarine habitats.…”

Sulfate-Reducing Bacteria in Floating Macrophyte Rhizospheres from an Amazonian Floodplain Lake in Bolivia and Their Association with Hg Methylation

“…Organic matter in the rhizosphere comes mainly from dead leaves, root exudates (25,38), and photosynthetic periphyton. These carbon sources plus anatomical and physiological variations relevant to periphyton growth may explain the observed differences in MeHg production between macrophytes (29).…”