Effect of Sequential Isoproturon Pulse Exposure on Scenedesmus vacuolatus

Abstract

Aquatic organisms are typically exposed to fluctuating concentrations of herbicides in streams. To assess the effects on algae of repeated peak exposure to the herbicide isoproturon, we subjected the alga Scenedesmus vacuolatus to two sequential pulse exposure scenarios. Effects on growth and on the inhibition of the effective quantum yield of photosystem II (PSII) were measured. In the first scenario, algae were exposed to short, 5-h pulses at high isoproturon concentrations (400 and 1000 lg/l), each followed by a recovery period of 18 h, while the second scenario consisted of 22.5-h pulses at lower concentrations (60 and 120 lg/l), alternating with short recovery periods (1.5 h). In addition, any changes in the sensitivity of the algae to isoproturon following sequential pulses were examined by determining the growth rate-EC 50 prior to and following exposure. In both exposure scenarios, we found that algal growth and its effective quantum yield were systematically inhibited during the exposures and that these effects were reversible. Sequential pulses to isoproturon could be considered a sequence of independent events. Nevertheless, a consequence of inhibited growth during the repeated exposures is the cumulative decrease in biomass production. Furthermore, in the second scenario, when the sequence of long pulses began to approach a scenario of continuous exposure, a slight increase in the tolerance of the algae to isoproturon was observed. These findings indicated that sequential pulses do affect algae during each pulse exposure, even if algae recover between the exposures. These observations could support an improved risk assessment of fluctuating exposures to reversibly acting herbicides.

Sulfamethoxazole and isoproturon degradation and detoxification by a laccase-mediator system: Influence of treatment conditions and mechanistic aspects

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Isolation and characterization of an isoproturon mineralizing Sphingomonas sp. strain SH from a French agricultural soil

“…Although this compound has been banned in several countries or restricted to 1.2 kg ha -1 year -1 since 2003 in several countries including France, it is still extensively used worldwide. Several studies have indicated the harmful effects of IPU and its metabolites on aquatic invertebrates, freshwater algae and microbial communities (Mansour et al 1999;Widenfalk et al 2008;Vallotton et al 2009). IPU and its metabolites have also been suspected to be carcinogenic to human beings and animals (Behera and Bhunya 1990;Hoshiya et al 1993).…”

Addressing the environmental impacts of butachlor and the available remediation strategies: a systematic review

“…Eisenia fetida and Perionyx sansibaricus (Gobi and Gunasekaran 2010). The ecotoxicological studies suggest that butachlor may be harmful to aquatic invertebrates (Vallotton et al 2009), microbial communities (Widenfalk et al 2008) and also a possible carcinogen in animals and humans (Geng et al 2005a). It is reported as a neurotoxin (Rajyalakshmi et al 1996), genotoxin (Ateeq et al 2005;Geng et al 2005a) and carcinogen (Dwivedi et al 2012).…”