Temporal effects of oiling and plant type on rates of nitrogen cycling: A mesocosm study in April/September 2016

Mesocosms were established with a variety of marsh vegetation types to examine the impact to oil exposure and plant type on denitrification and nitrogen fixation. Replicated mesocosms were set up at Dauphin Island Sea Lab and contained buckets planted with combination of plants: the black mangrove, Avicennia germinans, black mangroves with either a monoculture or polyculture of the smooth cord grass, Spartina alterniflora, and monoculture and polyculture of the smooth cord grass. Buckets were oiled in October of 2015 with emulsified weathered oil. Sediments were collected from control and oil amended mesocosms 6 months (April, 2016) and 11 months (September 2016) from oiled (October 2015) and control treatments for rate determination. In April 2016 potential denitrification, nitrogen fixation as well as benthic fluxes of oxygen, nitrate, nitrite, phosphate, and ammonium were measured. In September 2016 potential denitrification, nitrogen fixation, and denitrification with the isotope pairing technique as well as total petroleum hydrocarbons were measured.