Ecophysiological responses of Mediterranean pines to simulated sea aerosol polluted with an anionic surfactant: prospects for biomonitoring.

Sea aerosol may contain surfactants as pollutants. We examined ecophysiological mechanisms involved in the sensitivity of three Mediterranean pines to five spray treatments with sea water including an anionic surfactant, 5 to 500 mg/L dioctyl sodium sulphosuccinate. Despite the reduction of surfactant in sea aerosol over the past 20 years, Mediterranean pinewoods are still at risk for surfactant pollution, since concentrations in the field reach the visible injury threshold here recorded, i.e. 2 mg/L surfactant deposited on needles. The chloride toxicity threshold was 2 mg/g needle dw; values exceeded the threshold only when sea water was polluted by more than 30 mg/L surfactant. The surfactant altered epistomatal waxy microtubules and thus needle water potential. The phytotoxic effect increased with time, even in the absence of further exposures ("delayed-action" effect). Needle chloride content appeared better suited for biomonitoring surveys than structural damage to stomata, quantity of epicuticular waxes, drop contact angle, or midday water potential. All three species were sensitive to injury, according to the order: P. pinea > P. halepensis > P. pinaster.