The Effects of Oil and Dispersed Oil on Temperate Seagrasses

National Plan Research, Development & Technology

Background and progress to date, October 2005.

Seagrasses are a vital component of many near-shore areas of coastal Australia, providing habitat and food for a variety of marine, estuarine and beach-dwelling animal species, as well as being important in the nutrient cycle of near-shore and foreshore areas.

Oil spills may affect seagrasses either by direct smothering or by toxic effects of the water soluble fraction of oil.

Although Australian approved Oil Spill Dispersants rate predominantly as "slightly toxic" to "practically non-toxic" by the International Maritime Organization GESAMP classification system, there is limited knowledge on the specific effects on seagrasses exposed to dispersants. The use of dispersants may also increase the exposure of submerged seagrasses to oil as dispersed oil enters the water column.

To address the knowledge gap on the impact on seagrasses exposed to oil spills, AMSA has entered into a funding agreement on behalf of the National Plan with the University of Technology Sydney (UTS). The National Plan is also providing in-kind support and technical advice to the research team. UTS has contributed additional funding and has also been successful in securing an Australian Research Council Industry Linkage grant to expand the project.

The UTS researchers are using a combination of laboratory and field experiments to compare the toxicity of several oils and dispersant/oil mixtures on seagrasses, and to provide advice on the best approach to the use of dispersants on oil spills in the vicinity of seagrasses.

The project outcomes to date have been a literature review [ PDF: 187Kb] completed in late 2004, and a report on the proof-of-concept experimental work completed in June 2005. In this work, the toxic impact of oil and dispersants on the seagrass Zostera capricorni was measured at field sites (Pittwater, NSW) and in the laboratory using seagrass leaf sections, thylakoid membranes and migroalgal cells.

Whole plants, leaf sections, thylakoids and microalgae were exposed to the water soluble fraction of Gippsland Crude oil produced with and without the addition of Slickgone NS dispersant.

The main findings so far are that seagrasses are mostly unaffected by Gippsland Crude oil and mixtures of this oil and Slickgone NS dispersant. Furthermore, microalgae bioassays may provide a time- and cost-efficient way to test for concentrations of toxic petrochemicals in the field that might affect seagrasses.

Over the next three years, UTS will carry out further experiments with several more oil and oil/dispersant mixtures. The National Plan Environment Working Group will provide advice and assistance to UTS for the duration of the project.

For further information please contact Environment Protection

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last updated: November 2006