Effects of oil on growth and decomposition of Spartina alterniflora

Four oils (Arabian crude oil, Libyan crude oil, No. 6 fuel oil, and No, 2 fuel oil) were applied to one-square-meter salt marsh plots in Galveston Bay, Texas. Oils were applied at four levels: no oil, 1 liter on sediment, 1.5 liters on sediment and lower portions of Spartina alterniflora, and 2 liters on sediment and entire S. alterniflora surfaces. Within one week of oil application, nylon bags containing cut stems of S. alterniflora were staked in the center of all unoiled and 1.5 liter oil plots. Oil caused mortality of S. alterniflora within three weeks; the degree of mortality varied with oil type and the extent of plant coverage. Plant mortality was highest in plots with No. 2 fuel oil and those where oil was applied to entire plant surfaces. After five months, growth of plants in No. 2 fuel oil plots still was significantly below control levels. However, initial recovery was apparent in No. 2 fuel oil plots receiving 2 liters. Live biomass in Arabian crude oil, Libyan crude oil, and No. 6 fuel oil plots after five months was comparable to that of controls. Plots clipped three weeks after oil application were recolonized after five months by growth of new stems and seedlings. However, Arabian crude oil and No. 2 fuel oil significantly reduced the emergence of new stems while increasing the germination of seedlings. The decomposition of S. alterniflora was not affected significantly through the first eight months after oil application.