title: In situ impact of petrochemicals on the photosynthesis of the seagrass Zostera capricorni.
abstract: We used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of pulsed exposures of aged crude oil (Champion Crude), dispersant (VDC) and an oil+dispersant mixture on the seagrass Zostera capricorni Aschers in laboratory and field experiments, using custom-made chambers. Samples were exposed for 10 h to 0.25% and 0.1% concentrations of aged crude oil and dispersant as well as mixtures of 0.25% oil+0.05% dispersant and 0.1% oil+0.02% dispersant. During this time and for the subsequent four day recovery period, the maximum and effective quantum yields of photosystem II (Fv/Fm and DeltaF/Fm' respectively) were measured. In the laboratory experiments, both values declined in response to oil exposure and remained low during the recovery period. Dispersant exposure caused a decline in both values during the recovery period, while the mixture of aged crude oil+dispersant had little impact on both quantum yields. In situ samples were less sensitive than laboratory samples, showing no photosynthetic impact due to dispersant and oil+dispersant mixture. Despite an initial decline in DeltaF/Fm', in situ oil-exposed samples recovered by the end of the experiment. Chlorophyll pigment analysis showed only limited ongoing impact in both laboratory and field situations. This study suggests that laboratory experiments may overestimate the ongoing impact of petrochemicals on seagrass whilst the dispersant VDC can reduce the impact of oil on seagrass photosynthesis.
authors: Institute of Water and Environmental Resource Management, University of Technology, Sydney, Cnr Pacific Hwy, Westbourne Street, Gore Hill, NSW 2065, Australia. cate.macinnis@uts.edu.au
authors: Catriona M O
authors: CM
authors: Macinnis-Ng
authors: Peter J
authors: PJ
authors: Ralph
mesh_terms: D000704:Analysis of Variance; D001315:Australia; D002734:Chlorophyll; D000077194:Chlorophyll A; D004781:Environmental Exposure; D005453:Fluorescence; D010578:Petroleum / Q000032:analysis*; D010788:Photosynthesis / Q000502:physiology*; D013053:Spectrophotometry; D013501:Surface-Active Agents / Q000032:analysis*; D035962:Zosteraceae / Q000502:physiology*
chemical_list: D010578:Petroleum; D013501:Surface-Active Agents; D002734:Chlorophyll; D000077194:Chlorophyll A