Experimental oil exposure of Ascophyllum nodosum (L.) Le Jolis

The effect of weathered, crude oil on Ascophyllum nodosum was tested in an outdoor experiment and in a laboratory experiment. Adult A. nodosum plants which were exposed to oil in an outdoor basin for 3 days showed reduced growth for a certain period of time, after which growth recovered. Also, some necrotic damage was observed. Three-week-old and 1-year-old germlings placed under the adult plants showed no significant reduction in number compared to control plants. In the laboratory experiment some of the 1-month-old germlings were initially exposed to oil for 6 min, some for 1 h, some for 3 h and some for 5 h. After 3 weeks in running, filtered water oil-exposed germlings had reached the same length as those in the control groups, and no effect of exposing the germlings to oil for different lengths of time at the start of the experiment was found. The results indicate that a limited oil pollution of weathered, crude oil may reduce growth and biomass of adult plants for a certain period of time. However, this need not be detrimental to a population with good recruitment from germlings or vegetative shoots growing under a dense canopy layer.