Pesticide residues in waters of the Great Barrier Reef region Jon Brodie A brief history……. • Superficial analysis in early 1990s suggested no pesticides still in common use are capable of reaching the reefs of the GBR. • Studies in Atherton Tablelands, Johnstone, lower Burdekin and Bundaberg catchments in 1990s onwards show common presence of herbicide residues of a number of compounds (Hunter, Ham, Armour and colleagues). • Presence of herbicide residues in coastal sediments, seagrasses and waters along much of the GBR coast (Haynes et al., 2000a; Duke et al., 2005 Bengston Nash et al., 2005; McMahon et al., 2005). • Experimental toxicity studies show the ‘effect concentration’ of the herbicides of concern to mangroves, seagrass, algae and corals (e.g. Haynes et al., 2000b; Seery et al., 2006; Jones, 2005; Jones et al., 2003; Negri et al., 2005; Bell and Duke, 2005). • Loads of herbicides being discharged to GBR estimated in Mackay Whitsunday and lower Burdekin regions (Mitchell et al., 2005; Lewis et al., 2007). • Use of passive samples in rivers and GBR lagoon to detect long-term contamination (e.g. Shaw and Muller, 2005). Monitoring of the Great Barrier Reef Catchment Area Recent catchment studies • Paddock and stream scale studies in Burnett (Stork et al) • Stream scale studies in Mackay Whitsunday (Rohde et al), Tully (Bainbridge et al), Burdekin (Davis et al) summarised in Lewis et al 2009 • Fitzroy river work (Packett et al 2009) • Paddock scale work lower Burdekin (Davis et al) • Passive samplers in rivers (GBRMPA MMP, Mueller et al) • Stream studies in Burnett (yet to be published) Herbicide runoff GBR waterways Lewis et al. (2009) Herbicide runoff linked to different land uses Land Use Herbicides detected Sugar cane Diuron, atrazine, ametryn, hexazinone Urban Diuron Grain crops Atrazine Grazing Tebuthiuron Horticulture Atrazine, hexazinone Plantation forestry Simazine EMC EMC Hexazin EMC Diuron Atrazine Site Year Flow (ML) (µg/ (µg/ one (µg/ (kg) (kg) L) L) (kg) L) 2005/06 138,200 46 0.33 80 0.58 2.7 0.02 West Barratta Creek 2006/07 150,500 79 0.52 116 0.77 2.2 0.01 2007/08 176,000 44 0.25 70 0.40 1.0 0.01 2005/06 254,600 63 0.25 72 0.28 + - Haughton River 2006/07 530,000 39 0.07 26 0.05 BDL - 2007/08 256,000 16 0.06 25 0.10 BDL - 2001/02a 126,000 470 3.73 75 0.60 28 0.22 Pioneer River 2004/05 207,000 310 1.50 95 0.46 45 0.22 2006/07 415,000 470 1.13 310 0.75 140 0.34 2002/03a 21,000 26 1.24 BDL - BDL - Sandy Creek 2004/05 67,000 180 2.69 40 0.60 36 0.54 2006/07 130,000 200 1.54 66 0.51 73 0.56 2004/05 65,000 17 0.26 3.7 0.06 2.5 0.04 O'Connell River 2005/06 61,000 30 0.49 6.6 0.11 4.9 0.08 2006/07 27,000 31 1.15 20 0.74 2.5 0.09 aMitchell et al. 2005; EMC: Event mean concentration Catchment summary Easily detectable residues of atrazine and diuron (+others including ametryn, hexazinone and metolachlor) are found in the waterways draining sugarcane land use Tebuthiuron found in waterways draining grazing land use ANZECC and ARMCANZ guidelines have been exceeded for atrazine and diuron in some freshwater samples Burdekin Mackay Whitsunday Flood plumes 28 January, 2005 Aqua Terra 9th February 2007 11th February 2007 Plume monitoring • Marine samples collected in river flood plumes adjacent to the Tully/Murray, Burdekin/Townsville, Fitzroy and Mackay Whitsunday Regions. • More than 100 samples collected in the marine waters from these areas over 5 years. • Data for diuron presented in contour plots based on latest GBRMPA 99% guideline (0.9 µg/L), lowest effect levels (0.1 µg/L) and detection limit (0.01 µg/L). Tully- Murray Basin Diuron Burdekin- Townsville Region Diuron Mackay Whitsunday Region Diuron Plume summary Diuron and atrazine (+ others) residues in all river water plumes which drain cane lands. Tebuthiuron residues in the plumes of the large dry tropics catchment draining grazing lands Residues found a long way offshore (>50 km) in easily detectable concentrations. Concentrations, at times, above known effect levels (reduced photosynthesis) for certain species of seagrass and coral zooxanthellae. Diuron and atrazine display conservative mixing behavior in river water plumes (which allows the herbicides to travel large distances offshore). Residues persist in the marine environment (chronic effects). Toxic effects to marine plants • Short-term effects (hours to days) of herbicide exposure show that certain species of mangroves, seagrass and corals more sensitive than others (Bell and Duke, 2005; Haynes et al., 2000; Jones, Negri and colleagues). • Certain herbicide products more toxic than others. • Exposure to diuron concentrations as low as 0.1 µg/L reduces photosynthesis in certain species of seagrass (Haynes et al. 2000) while 0.3 μg/L is the lowest effect concentration to corals (e.g. Acropora formosa) (Jones et al. 2003; Jones and Kerswell, 2003) – lowest effect level for atrazine in corals is 3 µg/L. Toxic effects to marine plants (continued) • Synergistic effects of diuron and sediments affects crustose coralline algae (Harrington et al. 2005). • Link between diuron and mangrove dieback in the Mackay Whitsunday area (Duke et al. 2005). • Most marine plants appear to be able to recover following short-term exposure to herbicides – laboratory studies may not account for complex range of environmental and chemical conditions in the marine environment (Macinnis-Ng and Ralph, 2003). Conclusions • Our study shows that herbicide residues in river water plumes in the Great Barrier Reef lagoon are at (additive) levels which cause reduced photosynthesis potential to marine plant communities. • The chronic effects of long-term persistence of herbicide residues in the Great Barrier Reef lagoon may not be evident for several years. • Possible effects of chronic exposure of herbicide residues may result in a change in the community structure of freshwater wetland, mangrove, seagrass and coral reef ecosystems.
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