The tensile root strength of Spartina patens declines with exposure to multiple stressors

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.