Abstract
Coastal wetlands may be subjected to numerous biotic and abiotic stressors from natural and anthropogenic forces in the landscape. The influx of nutrients, inorganic compounds and xenobiotics are suspected of degrading the belowground biomass of coastal macrophytes. Spartina patens acts as an ecosystem engineer for lower salinity coastal marshes and its biomechanical properties are vital to the stability and resilience of coastal wetlands. S.patens was exposed to one natural (flooding) and two anthropogenic stressors (atrazine and nutrient addition) in a greenhouse experiment to test the hypothesis that these three stressors reduce the tensile root strength of S. patens. A one-way Welch’s analysis of variance revealed that the tensile root strength S. patens significantly declined after exposure to two flood duration regimes, three levels of atrazine exposure, and two levels of nutrient addition that consisted of nitrogen-phosphorus combinations. A one-way ANOVA of tensile root strength with an atrazine-flood duration-nutrient addition combination treatment as the main effect resulted in a 52 to 63% loss in tensile strength, while the individual atrazine, flooding, and nutrient treatments produced 40, 39, and 37% losses in tensile root strength, respectively. These results indicate that the effects of multiple natural and/or anthropogenic stressors may degrade the tensile root strength of S. patens, which could facilitate coastal erosion and subsequent collapse of the wetland ecosystem.
Highlights
Coastal wetland ecosystems are uniquely threatened because of dense human populations in their midst. Crowell et al (2010) reported that 39% of the population of the United States lived in counties directly adjacent to the coast
There were no significant differences in tensile root strength between the High, Medium, and Low treatments
There was no significant difference in tensile root strength between the Bi-Weekly and the Monthly treatments
Summary
Coastal wetland ecosystems are uniquely threatened because of dense human populations in their midst. Crowell et al (2010) reported that 39% of the population of the United States lived in counties directly adjacent to the coast. Extensive anthropogenic habitat destruction and landscape alteration have modified natural hydrologic regimes (Mitsch and Gosselink 2000; Keddy 2010). Flood control efforts such as stream channelization, dams, levees, and river diversions have disrupted the natural hydropattern of wetlands and led to excessive inundation and extended floodwater residence time in wetlands (Mitsch and Gosselink 2000; Jackson 2006; Keddy 2010; Willey 2016). Flooding induces oxygen stress on wetland plants because inundated soils severely curtail gas transport and exchange between plants and the atmosphere. Floodinduced stress can inhibit photosynthesis and reduce carbon fixation within the plant (Justin and Armstrong 1987; Colmer and Voesenek 2009,)
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