Plant-Microbial Symbioses in Coastal Systems: Their Ecological Importance and Role in Coastal Restoration

Abstract

Coastal systems are immensely valuable to humans. They contain unique ecosystems that are biodiversity reservoirs and provide key ecosystem services as well as a wealth of cultural heritage. Despite their importance to humans, many coastal systems are experiencing degradation that threatens their integrity and provisioning of services. While much is known about the plant communities and associated wildlife in coastal areas, the importance of microorganisms represents a large knowledge gap. Here we review the ecology of plant-microbial symbioses in coastal systems, including mycorrhizae, nitrogen fixers, endophytes, rhizosphere microbes, and pathogens. We focus on four common coastal communities: sand dunes, marshes, mangroves, and forests/shrublands. We also assess recent research and the potential for using microbes in coastal restoration efforts to mitigate anthropogenic impacts. We find that microbial symbionts are largely responsible for the health of plants constituting the foundation of coastal communities by affecting plant establishment, growth, competitive ability, and stress tolerance, as well as modulating biogeochemical cycling in these stressful coastal systems. Current use of microbial symbionts to augment restoration of stressful and degraded coastal systems is still very much in its infancy; however, it holds great promise for increasing restoration success on the coast. Much research is still needed to test and develop microbial inocula for facilitating restoration of different coastal systems. This is an excellent opportunity for collaboration between restoration practitioners and microbial ecologists to work toward a common goal of enhancing resilience of our coastal ecosystems at a time when these systems are vulnerable to an increasing number of threats.

Can biodiversity of preexisting and created salt marshes match across scales? An assessment from microbes to predators

“…Moreover, LHA also had a higher elevation compared with the other marshes, which would contribute to a drier and potentially less productive marsh environment. Microbial assemblage differences between created and reference marshes may alter basic ecosystem functions because microbes serve as food sources for higher trophic levels within the marsh food web, as well as play essential roles in biogeochemical processing and ecosystem development, including (but not limited to) organic carbon decomposition and recycling, nitrogen fixation, gas transport, sediment cohesion, establishing and maintaining redox conditions, and forming symbiotic associations with plants and other fauna (e.g., Abbott et al, 2022; Bodelier & Dedysh, 2013; Farrer et al, 2022). Similarly, macroinfauna are also an important element of marsh food webs because they regulate nutrient recycling, sedimentary processes via bioturbation, and serve as a source of energy to larger animals, among other processes (Adam, 1990; Fleeger et al, 2020).…”

“…Additionally, generalist species are expected to occupy created areas initially, followed by specialists and species that rely on the presence of others (e.g., top predators, parasites, and obligate mutualists; Massol et al, 2017). Belowground soil microbial communities, which would be inherited from dredged material used for marsh creation, may respond to new environmental conditions on different timescales (e.g., due to ecological carryover effects; O'Connor et al, 2014) that could slow or accelerate plant and infauna growth (e.g., Farrer et al, 2022). As such, comparisons across assemblages may clarify whether the entire system has been restored or whether only specific ecosystem compartments have returned (Noreika et al, 2020; Pärtel et al, 2013).…”

Aiding coastal wetland restoration via the belowground soil microbiome: an overview

“…Restoration projects in mangroves and saltmarshes have been predominantly focused on measuring aboveground plant responses (Bayraktarov et al 2016), neglecting the assessment of the belowground soil health and compatibility with plants. However, plants are highly reliant on soil microbial communities to withstand stressful environments because of high salinity, flooding, drought, or low nutrient concentrations (Farrer et al 2022). The potential of plant–microbial interactions in improving the success of restoration in mangroves and saltmarshes has been rarely explored (see Farrer et al 2022 and Srivastava et al 2017 for reviews of plant–microbe interactions in coastal and aquatic systems).…”

“…However, plants are highly reliant on soil microbial communities to withstand stressful environments because of high salinity, flooding, drought, or low nutrient concentrations (Farrer et al 2022). The potential of plant–microbial interactions in improving the success of restoration in mangroves and saltmarshes has been rarely explored (see Farrer et al 2022 and Srivastava et al 2017 for reviews of plant–microbe interactions in coastal and aquatic systems).…”

“…anoxic, hypersaline, potentially polluted from previous land use) coastal conditions. A recent review by Farrer et al (2022) provided a comprehensive overview of several plant–microbe symbioses (i.e. mycorrhizae, nitrogen fixers, endophytes, rhizosphere microbes, and pathogens) in coastal ecosystems and their importance in coastal restoration.…”