The Roles of Microbes in Stream Restorations

The goods and services provided by riverine systems are critical to humanity, and our reliance increases with our growing population and demands. As our activities expand, these systems continue to degrade throughout the world even as we try to restore them, and many efforts have not met expectations. One way to increase restoration effectiveness could be to explicitly design restorations to promote microbial communities, which are responsible for much of the organic matter breakdown, nutrient removal or transformation, pollutant removal, and biomass production in river ecosystems. In this paper, we discuss several design concepts that purposefully create conditions for these various microbial goods and services, and allow microbes to act as ecological restoration engineers. Focusing on microbial diversity and function could improve restoration effectiveness and overall ecosystem resilience to the stressors that caused the need for the restoration. Advances in next-generation sequencing now allow the use of microbial 'omics techniques (e.g., metagenomics, metatranscriptomics) to assess stream ecological conditions in similar fashion to fish and benthic macroinvertebrates. Using representative microbial communities from stream sediments, biofilms, and the water column may greatly advance assessment capabilities. Microbes can assess restorations and ecosystem function where animals may not currently be present, and thus may serve as diagnostics for the suitability of animal reintroductions. Emerging applications such as ecological metatranscriptomics may further advance our understanding of the roles of specific restoration designs towards ecological services as well as assess restoration effectiveness.

Native soil amendments combined with commercial arbuscular mycorrhizal fungi increase biomass of Panicum amarum

Coastal dune restorations often fail because of poorly performing plants. The addition of beneficial microbes can improve plant performance, though it is unclear if the source of microbes matters. Here, we tested how native soil amendments and commercially available arbuscular mycorrhizal (AM) fungi influenced performance of Panicum amarum, a dominant grass on Texas coastal dunes. In a greenhouse experiment, we manipulated the identity of native soil amendments (from P. amarum, Uniola paniculata, or unvegetated areas), the presence of soil microbes in the native soil amendments (live or sterile), and the presence of the commercial AM fungi (present or absent). Native soils from vegetated areas contained 149% more AM fungal spores than unvegetated areas. The commercial AM fungi, when combined with previously vegetated native soils, increased aboveground biomass of P. amarum by 26%. Effects on belowground biomass were weaker, although the addition of any microbes decreased the root:shoot ratio. The origin of native soil amendments can influence restoration outcomes. In this case soil from areas with vegetation outperformed soil from areas without vegetation. Combining native soils with commercial AM fungi may provide a strategy for increasing plant performance while also maintaining other ecosystem functions provided by native microbes.