Sporobolus alterniflorus
Background
Plant life in salt marshes is crucial to ecosystem regulation and plays key roles in ecological services like carbon sequestration, soil enrichment, and flood protection. As these services have become increasingly important as carbon emissions increase and sea levels continue to rise, our study aimed to better understand adaptive mechanisms utilized by species that are critical to conservation efforts in urban estuaries. Urbanization exposes plants to a variety of stressors, including increased salinity and oil exposure. As sessile organisms, plants respond to these stressors by altering their gene expression. Epigenetic modifications, such as DNA methylation, change levels of gene expression in an organism and represent an important way that plants can quickly respond to a changing, often stressful environment. To better understand how prolonged urban stressors affect estuarine plants, we measured their global DNA methylation levels, a well-documented indicator of environmental stress in plants.
Experiment
In the lab, we exposed the Sporobolus alterniflorus from the Bronx River and Greenwich Cove to urban stressors. In 2018, our study documented epigenetic changes in the marsh grass in response to increased concentrations of a single stressor, motor oil. In 2019, in addition to motor oil, we investigated the plants’ epigenetic response to increased levels of salinity, and the synergistic effects of both salinity and motor oil. We stressed the plants for four days and then proceeded to extract their DNA and measure the global methylation levels.
Model Organism
We chose a halophytic grass, Sporobolus alterniflorus, as our model organism. This species has a high salinity tolerance and is a dominant foundational species in urban estuaries. It provides numerous ecosystem services, such as acting as a natural barrier to floods, filtering water, and providing nutrient-rich soil.
Sites
We collected Sporobolus alterniflorus for our experiment from two sites, the Bronx River (NY), an urban estuary, and Greenwich Cove (CT), a less impacted suburban site.
Conclusions
Our data from 2018 and 2019 show that Greenwich Cove plants exhibit greater changes in methylation than the Bronx River plants when exposed to each form of urban stress. In addition, in 2018 global methylations increased for the Bronx River plants and Greenwich Cove plants when exposed to the stressors. In 2019 we observed a decrease in methylation levels when plants were exposed to the stressors. The difference in the direction of methylation change indicate that the native urban conditions of a plant's environment influence the epigenetic responses. In the future, we would like to perform various time course studies to elucidate the fluctuations in the direction of global methylation change. In addition, we hope to measure the epigenetic responses of plants to other prevalent pollutants and stressors, such as drought and diesel fuel.