You are here:
Responses of Spartina alterniflora to Multiple Stressors: Changing Precipitation Patterns, Accelerated Sea Level Rise, and Nutrient Enrichment
Citation:
Hanson, Alana, R. Johnson, C. Wigand, A. Oczkowski, E. Davey, AND E. Markham. Responses of Spartina alterniflora to Multiple Stressors: Changing Precipitation Patterns, Accelerated Sea Level Rise, and Nutrient Enrichment. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, 39(5):1376-1385, (2016).
Impact/Purpose:
The goal was to analyze the effects of multiple stressors on Spartina alterniflora plants in a controlled greenhouse setting. Climate change predictions for the northeast predict longer periods of drought with less frequent, but heavier storms. These climate change effects by precipitation, in addition to accelerated sea level rise and eutrophication of systems, would have a serious impact on salt marshes in the northeast. The greenhouse setting allowed us to control for the effects of precipitation changes, nutrient enrichment, and accelerated sea level rise, and analyze the response of salt marshes to these stressors.
Description:
Coastal wetlands, well recognized for their ecosystem services, have faced many threats throughout the United States and elsewhere. Managers require good information on responses of wetlands to the combined stressors that these habitats experience, or may in the future as a result of climate change, and few studies have explored the effect of multiple stressors on wetlands. We conducted a 4-month mesocosm study to analyze the multiple stressor effects of precipitation changes, sea level rise, and eutrophication on the salt marsh plant Spartina alterniflora. Pots containing plants in a soil matrix were positioned in tanks and received Narragansett Bay (RI) water. The mesocosms simulated three precipitation levels (ambient daily rain, biweekly storm, and drought); three elevation levels, low (15 cm below mean high water (MHW)), middle (MHW), and high (15 cm above MHW); and two nutrient enrichment levels (unenriched and nutrient-enriched bay water). Our results demonstrate storm and drought stressors led to significantly less above- and belowground biomass than those in ambient rain conditions. Plants that were flooded at the low elevation had less belowground biomass, fine roots, and S. alterniflora shoots. Nutrients had no detectable effect on total above- and belowground biomass, but the enriched pots had higher stem counts and more fine roots than unenriched pots, in addition to greater CO2 emission rates. However, the unenriched pots had significantly more coarse roots and rhizomes, which help to build peat in organogenic marshes. These results suggest that multiple stressors of altered precipitation, sea level rise, and nutrient enrichment combine to cause a decrease in belowground plant productivity and organic matter accumulation which both contribute to peat growth and marsh sustainability.
