Ecological impacts of time-variable exposure regimes to the fungicide azoxystrobin on freshwater communities in outdoor microcosms

Abstract

This paper evaluates the effects of different time-varying exposure patterns of the strobilurin fungicide azoxystrobin on freshwater microsocosm communities. These exposure patterns included two treatments with a similar peak but different time-weighted average (TWA) concentrations, and two treatments with similar TWA but different peak concentrations. The experiment was carried out in outdoor microcosms under four different exposure regimes; (1) a continuous application treatment of 10 μg/L (CAT10) for 42 days (2), a continuous application treatment of 33 μg/L (CAT33) for 42 days (3), a single application treatment of 33 μg/L (SAT33) and (4) a four application treatment of 16 μg/L (FAT16), with a time interval of 10 days. Mean measured 42-d TWA concentrations in the different treatments were 9.4 μg/L (CAT10), 32.8 μg/L (CAT33), 14.9 μg/L (SAT33) and 14.7 μg/L (FAT16). Multivariate analyses demonstrated significant changes in zooplankton community structure in all but the CAT10 treated microcosms relative to that of controls. The largest adverse effects were reported for zooplankton taxa belonging to Copepoda and Cladocera. By the end of the experimental period (day 42 after treatment), community effects were of similar magnitude for the pulsed treatment regimes, although the magnitude of the initial effect was larger in the SAT33 treatment. This indicates that for long-term effects the TWA is more important for most zooplankton species in the test system than the peak concentration. Azoxystrobin only slightly affected some species of the macroinvertebrate, phytoplankton and macrophyte assemblages. The overall no observed ecologically adverse effect concentrations (NOEAEC) in this study was 10 µg/L.

Resilience and recovery: The effect of triclosan exposure timing during development, on the structure and function of river biofilm communities

“…These characteristics make them highly-relevant and suitable for assessment of resistance-resilience phenomena in aquatic ecosystems (Lawrence et al, 2009;Proia et al, 2011Proia et al, , 2012Sabater et al, 2007). Previous resilience experiments used a variety of community cultivation approaches: artificial channels, mesocosms, as well as in situ cultivation and transplantation to create scenarios of exposure and recovery where return to reference composition and function is monitored using various parameters (Begon et al, 2006;Baho et al, 2012;Proia et al, 2011;Zafar et al, 2012). In the current study the experimental set up used rotating annular reactors (Lawrence et al, 2000) where there was continuous flow-through of river water with metered addition of TCS to achieve a controlled exposure.…”

“…Lawrence et al (2009) reported that TCS exposure at 10 g l −1 resulted in significant reductions in algal biomass, carbon utilization, changes in bacterial community composition and alteration of the community structure. Exposures to effluents, however, may occur intermittently, or in pulses (Ellis 2007), therefore, pulsed or time-variable exposures are also of considerable interest (Proia et al, 2011;Reinert et al, 2002;Zafar et al, 2012). Proia et al (2011) used an exposure recovery design to assess river biofilm community responses to TCS.…”

Azoxystrobin Causes Oxidative Stress and DNA Damage in the Aquatic Macrophyte Myriophyllum quitense

“…At 20°C, the solubility of AZX in water is 6.7 mg/L (pH 5.2 and 7.0) and it has a low vapor pressure of 1.1 9 10 -7 mPa (Rodrigues et al 2013). AZX dissition rates from water with half-life values of 18 days and 15-25 days were also determined by Zafar et al (2012); Gustafsson et al (2010), respectively. Analytical measurements of AZX were not carried out in the aqueous media of exposure used but the design of the present study was made taking into account the physicochemical characteristics of AZX detailed above.…”

Aquatic risk assessment of a novel strobilurin fungicide: A microcosm study compared with the species sensitivity distribution approach

“…However, fairly scarce eco-toxicology information is available on them (Balba, 2007). According to our knowledge, no SSD study is available for strobilurin fungicides, and no information other than that published in Gustafsson et al (2010), Zafar et al (2012) and Van Wijngaarden et al (2014) is available on the toxic effects of strobilurin fungicides in microcosms and/or mesocosm. Pyraoxystrobin is a strobilurin fungicide, and it has demonstrated an excellent antifungal effect.…”