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Effects of hydrocarbons on the physiology and growth of Ulva sp. (Chlorophyta)

Abstract:

Laboratory experiments were performed to investigate the physiological responses of an Ulva species to oil pollution. Ulva thalli were exposed at 16 °C for up to 12 days to emulsions in sea-water of one of four standard petroleum fractions (P1, d 0.7, bp 80-110 °C; P2, d 0.73, bp 100-140 °C; P3, d 0.76, bp 140-160 °C; P4, d 0.76, bp 180-220 °C), in each case at a concentration of 500, 1 000, 2 000, 4 000 or 8 000 ppm (v/v). The physiological variables determined were: photosynthesis rate, respiration rate, photochemical efficiency (Fv/Fmax), non-photochemical quenching (qN), chlorophyll a concentration, and growth rate. A probit analysis was used to determine 50 %-inhibition time and concentrations of the physiological responses. Our results showed that the best indicator of stress due to exposure to petroleum hydrocarbons was photosynthesis rate. The fraction P1 (low density, low boiling point) was the most toxic, with the 72-hour IC50 for rate of photosynthesis being 871 ppm.