SEASONAL RESPONSE OF SPARTINA ALTERNIFLORA TO OIL

ABSTRACT Salt marsh plots located in Galveston Bay, Texas, were treated with oil during November and May, the respective periods of declining and increasing growth for Spartina alterniflora. Four oils (Arabian crude, Libyan crude, No. 6 fuel, and No. 2 fuel) were applied to plots in four ways: no oil (control), 1 liter (L) on sediment, 1.5 L on sediment and lower portions of S. alterniflora, and 2 L on sediment and entire S. alterniflora surfaces. Live plant biomass and residual oil in sediment were determined periodically after oil treatment. Season did not influence S. alterniflora response to oil when applied to sediment and lower plant portions. In these cases, plant response was similar after November and May applications, with a reduction in live plant biomass observed only for No. 2 fuel oil. Season did influence S. alterniflora response to oil when applied to entire plant surfaces. Completely covering the plant typically caused a longer reduction in live plant biomass after the May application. Again, No. 2 fuel oil caused the greatest decrease in live plant biomass. Long-term effects on live plant biomass were observed through 12 months for No. 2 fuel oil and for complete plant coverage in May, but results of these observations were not related to high concentrations of residual oil in sediment. We believe that long-term effects were the result of initial adverse effects on roots, which slowed plant recovery.