Resilience and bioresponse of two marine algae to petroleum fuel pollution

Abstract

ABSTRACT Petroleum pollution can upset the ecological stability and health of a marine ecosystem. The physiological, biochemical and morphological responses of Nannochloropsis oculata and Porphyridium cruentum to three different petroleum fuels, kerosene, diesel and gasoline were examined. The effect of water soluble fractions (WSFs) of the three petroleum fuels was investigated at 0%, 25%, 50% and 100%. The growth response of both species was monitored optically every two days for 14 days using a 721 visible spectrophotometer. Chlorophyll a, morphology and antioxidant enzyme activity of the algae were examined using prescribed methods. In both algae, minimum growth was obtained with 100% WSF of the petroleum fuels. In N. oculata, there was growth stimulation and the maximum growth was obtained at different concentrations (25% and 50%) depending on the test fuels. The maximum growth of P. cruentum was obtained at 10% WSF in all the fuels. ANOVA (p < 0.05) showed significant differences in algal growth with changes in concentration of the test fuels. Unpaired t-tests showed that in all the fuels, there was a significant difference (p < 0.05) between the growth of N. oculata and P. cruentum. N. oculata showed more tolerance to petroleum fuel pollution than P. cruentum. Morphological studies showed that petroleum fuel pollution altered the size of N. oculata and caused severe cell clumping in P. cruentum. Antioxidant concentration assessment showed that whereas N. oculata produced high levels of superoxide dismutase, catalase and peroxidase, P. cruentum produced high levels of superoxide dismutase but was less efficient in catalase and peroxidase production. Clumping and inefficiency in antioxidant production affect the physiological and biochemical response of algae. This study showed that the severity of petroleum fuel pollution is reflected in physiological, morphological, and biochemical responses of the test algae. This research provides baseline information that can be used for the evaluation of the effect of petroleum fuel pollution in marine environment and policy making.