The plant microbiome, composed of diverse interacting microorganisms, plays key functional roles for hosts. Pervasive environmental perturbations such as oil pollution have been shown to alter the diversity and composition of these plant microbiomes, yet these impacts may be site dependent, contingent on the local abiotic and biotic factors. In addition, they can vary between aboveground and belowground microbial communities within the same host plant. We examined the effects of oil history six years after the Deepwater Horizon accident on aboveground leaf and belowground endophytic root and rhizosphere fungal communities of Spartina alterniflora using amplicon sequencing of the fungal "barcode" internal transcribed spacer (ITS1). We compared Spartina-associated fungal communities in oiled areas relative to reference non-oiled areas (i.e. oil spill history) within two sites in southeastern Louisiana.
Results/Conclusions
Oil spill history showed strong influences on aboveground fungal communities by causing compositional turnover with consequent loss in diversity for leaf fungal endophytes of plants in oiled areas, although the strength of influence varied between sites. On the other hand, belowground communities showed different responses. Root endophytic communities did not differ with oil history, but rhizosphere soil communities showed shifts in community composition with oil spill history. Oiling did not lead to increased or decreased similarities among communities of each plant compartment within a host, indicating that the host plant exerts stronger control than external (to host) factors in shaping their own microbiome. Taken together, these results show that fungal community responses were variable within compartments of the same host plant, and that differences in the local environment or, alternatively, differences in the residual oil between each site can constrain the magnitude of fungal responses to perturbation. Such comprehensive understanding is important in assessing the ecological impacts of environmental perturbations like oil pollution, including consequences on S. alterniflora physiology, and ultimately, on ecosystem function.