Spatial and Temporal Variability in Pesticide Exposure Downstream of a Heavily Irrigated Cropping Area: Application of Different Monitoring Techniques

Abstract

23Pesticide exposure threatens many freshwater and estuarine ecosystems around the world. 24This study examined the temporal and spatial trends of pesticide concentrations in a 25 waterway within an agriculturally developed dry-tropics catchment using a combination of 26 grab and passive sampling methods over a continuous two year monitoring program. A total 27 of 43 pesticide residues were detected with seven pesticides exceeding ecologically relevant 28 water quality guidelines/trigger values during the study period and four (ametryn, atrazine, 29 diuron and metolachlor) of these exceeding guidelines for several months. The presence and 30 concentration of the pesticides in the stream coincided with seasonal variability in rainfall, 31 harvest timing/cropping cycle and management changes. Our sampling approach 32demonstrates that the application of these complementary sampling techniques (both grab 33 and passive sampling) were effective to establish pesticide usage patterns in upstream 34 locations where application data are unavailable. 35

Toxicity of the herbicides diuron, propazine, tebuthiuron, and haloxyfop to the diatom Chaetoceros muelleri

“…Regular monitoring of pesticides in the GBR has found that exceedances of WQGVs by individual herbicides in the GBR marine waters occur only occasionally 15,16,24 ; however, approximately 80% of the water samples collected in the GBR catchment area between 2011 and 2015 contained mixtures of up to 20 pesticides with two to four modes of action 29 . Consequently, there is a strong likelihood of additivity or synergistic interactions between multiple herbicides, and the total toxicity of herbicide mixtures should be considered in monitoring programs and for risk assessments 14,[30][31][32] .…”

Polyps of the Jellyfish Aurelia aurita Are Unaffected by Chronic Exposure to a Combination of Pesticides

“…Other effects in nontarget species exposed to chlorpyrifos include reduced settlement and metamorphosis of coral larvae (Markey et al 2007), as well as decreased hatching success (Mhadhbi and Beiras 2012) and muscle cholinesterase activity in fish (Botte et al 2012). Considering the intense use of atrazine and chlorpyrifos in agriculture and the fact that they often co‐occur in aquatic environments (Shaw et al 2010; Smith et al 2012; O'Brien et al 2016), research on potential interactive effects of these pesticides in marine species is warranted.…”

Peer Review #1 of "Toxicity thresholds of three insecticides and two fungicides to larvae of the coral Acropora tenuis (v0.1)"

“…Successive Australian government programs have aimed to reduce the loads of pesticides entering waters of the GBR and its catchments (Brodie et al 2017;RWQIP 2018). At the same time, there have been changes in regulations and registration for pesticide application in coastal agriculture (Davis et al 2014), leading to shifts in usage patterns and to at least 44 "alternative" pesticides being detected in the GBR catchments and lagoon (King et al 2013;O'Brien et al 2016). For example, the insecticides chlorothalonil, fipronil and propiconazole have been detected in the catchments while imidacloprid and diazinon have been found in both the catchments and GBR lagoon (Devlin et al 2015;O'Brien et al 2014).…”