Responses of Selected U.S. Gulf Coast Marsh Macrophyte Species to Oiling and Commercial Cleaners

A shoreline cleaner was tested to determine its effectiveness in removing different types of oil from selected US Gulf coastal marsh macrophytes. Bulltongue (Sagittaria lancifolia L.), three cornered grass (Scirpus olneyi E. & G.) and broadleaf cattail (Typha latifolia L.) were subjected to oil application and cleaning in a greenhouse and the subsequent effects on plant functions were evaluated during the period immediately after treatment initiation. Plant stomatal functioning, photosynthesis, respiration, regeneration, growth and biomass were monitored. Two types of oil, South Louisiana Crude (SLC) or Arabian Medium Crude (AMC) were used. The treatments included: control (no oil or cleaner), cleaner only (COREXIT 9580 only, no oil), oiled with SLC or AMC only (no cleaner), and oiled using SLC or AMC and cleaned with COREXIT 9580 after two days. The existing leaves on the macrophytes at the time of treatment application directly subjected to oiling (but not cleaned) did not recover from the effects of oiling in all of the study species. However, leaves under oil+cleaner treatments or leaves developed during the post-oiling period (new leaves) showed a different pattern of response. For instance, in bulltongue plants, new leaves had stomatal conductances at or close to the values recorded for control plants. However, new leaves and leaves subjected to oil+cleaner treatment in cattail and three-cornered plants, had stomatal conductances significantly lower than their respective control plants. However, photosynthetic and respiration data indicated no overall significant differences within each species across treatments. Thus, the physiological functions of the study species had apparently recovered from the initial adverse effects of oiling within the experimental period. Based on photosynthetic and respiration data, the study species sensitivity ranking is similar. Furthermore, there were no significant differences in physiological responses of the study species to oil types. In addition, above-ground biomass was not affected significantly by the treatments in bulltongue or cattail but was reduced significantly in three-corner plants. Based on the overall physiological and biomass data, bulltongue was the least sensitive of the three species to SLC and AMC oil types than the other species while cattail appeared to be the most sensitive. Any beneficial effects of the cleaner may be more pronounced in plant species highly sensitive to specific oil types than the species studied.