Biodegradable vegetable-derived lubricants (VDL) might be less toxic to marine organisms than mineral-derived oils (MDL) due
to the absence of high molecular weight aromatics, but this remains largely untested. In this laboratory study, adult corals and coral
gametes were exposed to various concentrations of a two-stroke VDL-1A and a corresponding MDL to determine which lubricant
type was more toxic to each life stage. In the fertilization experiment, gametes from the scleractinian coral Acropora microphthalma
were exposed to water-accommodated fractions (WAF) of VDL-1A and MDL for four hours. The MDL and VDL-1A WAFs
inhibited normal fertilization of the corals at 200 mg l1 total hydrocarbon content (THC) and 150 mg l1 THC respectively. Disturbance
of a stable coral-dinoflagellate symbiosis is regarded as a valid measure of sub-lethal stress in adult corals. The state of the
symbiosis in branchlets of adult colonies of Acropora formosa was monitored using indicators such as dinoflagellate expulsion and
dark-adapted photosystem II yields of dinoflagellate (using pulse amplitude modulation fluorescence). An effect on symbiosis was
measurable following 48 h exposure to the lubricants at concentrations of 190 mg l1 and 37 mg l1 THC for the MDL and VDL-1A
respectively. GC/MS revealed that the main constituent of the VDL-1A WAF was the compound coumarin, added by the manufacturer
to improve odour. The fragrance containing coumarin was removed from the lubricant formulation and the toxicity
towards adult corals re-examined. The coumarin-free VDL-2 exhibited significantly less toxicity towards the adult corals than all of the
other oil types tested, with the only measurable effect being a slight but significant drop in photosynthetic efficiency at 280 mg l1.
Crown Copyright # 2004 Published by Elsevier Ltd. All rights reserved.