Project 4.2 'The chronic effects of pesticides and their persistence in tropical waters'

Led by: Dr. Andrew Negri, Australian Institute of Marine Science

A key policy to minimising the effects of climate change on tropical marine organisms (e.g. coral bleaching and loss of seagrass cover) is to improve water quality, thereby reducing the potential for pollution to exacerbate the effects of thermal stress (Reef Plan, 2009). While pesticides are thought to contribute to stress on nearshore habitats, little is known of their chronic effects on tropical species or their persistence in tropical waters.

Pesticides, and particularly herbicides from agricultural sources, have been detected in nearshore sites of the Great Barrier Reef (GBR) all year round. The most commonly detected herbicides inhibit photosynthesis, thereby reducing primary productivity and calcification in key marine species. When plants and corals are stressed from increased sea surface temperatures (SSTs), additional stresses from reduced salinity and at high irradiance the impact of secondary chronic pollution such as herbicides exposure can become additive or synergistic. There is little data to explain to what extent chronic exposure to herbicides might interact with climate change to negatively affect sensitive tropical organisms such as corals and especially seagrass. Furthermore, little is known of the fate and persistence of agricultural herbicides that have been detected in the lagoon of the GBR. Understanding the half lives of these compounds and the toxicity of their breakdown products in the tropical marine environment is also a critical data-gap required to develop realistic ecological risk models for sensitive coastal organisms and communities of the GBR.

Project objectives at a glance

Identification of herbicide threshold concentrations for seagrass for use in risk assessment models.
Assessment of whether managing low-level, chronic herbicide exposures can protect seagrasses and corals from climate change pressures (e.g. thermal stress).
Determine whether chronic herbicide exposures may influence critical coral reef processes such as coral recruitment.
Identification of half lives of herbicides at multiple temperatures relevant to those in flood plumes for use in environmental risk models from catchment to coast.
Quantification of the contribution of herbicide breakdown products to potential toxicity.
A better understanding of how pesticides move through the water column (sediment bound or dissolved) and how this affects toxicity.

Specific objectives and intended outputs of this Project are detailed in the NERP TE Hub Multi-Year Research Plan.

Project Factsheet

Project Updates

See February 2012 Project Highlights here.