Impact of pesticide mixtures used in irrigation agriculture on freshwater ecosystems

Citation

Land & Water Australia. 2009. Impact of pesticide mixtures used in irrigation agriculture on freshwater ecosystems. [Online] (Updated June 23rd, 2009)
Available at: http://lwa.gov.au/node/3507 [Accessed Tuesday 26th of April 2011 05:06:16 AM ].

The principal aim of the research project is to assess the impacts of commonly used agricultural pesticides when present as mixtures on freshwater aquatic ecosystems.

More specifically, the research will help characterise the underlying chemical interactions (antagonistic, additive or synergistic) amongst different pesticide compounds and hence help explain the observed effects on aquatic biota and overall ecosystem health. The pesticide compounds that will be examined, for which there is limited toxicological data include terbufos and thiobencarb which are commonly used for corn and rice production respectively.

The toxicological assessment of pesticide degradates, terbufos sulfoxide and terbufos sulfone (metabolites of terbufos) will add to the novel nature of the current research project. Atrazine, which is also used in corn production and has been shown to act as a synergist with other organophosphorus pesticides will also be included in the assessment. Little is known of the toxicological effects associated with these degradates despite their similar toxicity to the parent compound.

Their greater persistence and mobility in the environment compared to the parent further justifies their inclusion in this study. The project will include laboratory experiments on a range of aquatic organisms occupying varying trophic levels – algae, zooplanton, macroinvertebrates and frog larvae followed by mesocosm/semi-field experimental ponds and caging experiments to assess the impacts of these pesticide mixtures under more environmentally realistic conditions.

The use of experimental mesocosms in the research also provides an opportunity to explore and document the behaviour and fate of terbufos sulfone and sulfoxide in lentic aquatic environments for which information is still lacking. The field assessment of macroinvertebrates and tadpole diversity in the Coleambally Irrigation Area, in southwestern NSW will function as a complementary third tier of the assessment that will help ascertain if effects observed in the laboratory and semi-field experiments are translated to effects in the environment.

Project Objectives

Assess the effects of commonly used pesticides, thiobencarb, atrazine, terbufos and its metabolites, terbufos sulfone and terbufos sulfoxide, on selected aquatic biota.
Determine interactive toxicological effects between the study pesticides when present as mixtures in laboratory tests.
Examine the effects of these chemical mixtures on various trophic levels (algae, zoo plankton, macroinvertebrates and tadpole larvae) in model ecosystems (mesocosms).
Document the fate and behaviour of terbufos sulfone and terbufos sulfoxide in the aquatic environment.
Undertake a field assessment of the macroinvertebrate and tadpole diversity in the Coleambally Irrigation Area.