Growth Recovery of Lemna gibba and Lemna minor Following a 7-Day Exposure to the Herbicide Diuron

Abstract

In agricultural catchments, aquatic ecosystems can experience a pulse exposure to pesticides. Following such exposure, non-target organisms that are not extirpated may recover. This paper investigates the potential of two duckweed species (Lemna minor and Lemna gibba) to recover from a 7-day exposure to different concentrations (0.4-208 µg L(-1)) of the herbicide diuron. There was significant inhibition in the growth and biomass after the initial 7-day exposure (e.g. frond number EC50=59.2 and 52.2 µg L(-1) for L. minor and L. gibba, respectively). Following transfer to clean media, recovery (the highest concentration yielding no significant difference in the effect endpoint from the control) was observed for all effects endpoints at concentrations ranging 60-111 µg L(-1) for L. minor and 60-208 µg L(-1) for L. gibba. These results suggest that recovery is possible for primary producers at environmentally relevant concentrations considered significant in ecological risk assessment.

Growth inhibition and recovery patterns of common duckweed Lemna minor L. after repeated exposure to isoproturon

“…L. minor accumulates isoproturon (Böttcher and Schroll 2007;Dosnon-Olette et al 2011) but duckweed plants are considered not capable to metabolise the aromatic ring of the isoproturon molecule (Böttcher and Schroll 2007). Recovery of growth indicates that the effects of isoproturon on photosynthesis are not permanent possible due to non-covalent binding of phenylurea herbicides to D1 protein and fast elimination from the affected cells (Burns et al 2015) and the effective repair mechanisms of oxidative damage to PS II (Cedergreen et al 2005). Restoration Fig.…”

“…Therefore, the present study aimed to investigate the effects of repeated exposures to isoproturon on growth, as a standard endpoint, and recovery potential of common duckweed, Lemna minor L. Tests were performed as a modified standard growth inhibition test in three repeated treatment cycles with isoproturon in a concentration range below reported 7-day effective concentration (EC 50 ) causing 50% inhibition of frond number growth rate (Knežević et al (2016): EC 50 = 220 µg L −1 ; Tunić et al (2015): EC 50 = 230 µg L −1 ). L. minor, a standard photosynthetic nontargeted aquatic organism has been chosen for this study due to favorable traits that enable population-level studies in laboratory conditions and a high potential for recovery from a single exposure to isoproturon (Varga et al 2019) and other types of herbicides (Wilson and Koch 2013;Burns et al 2015;Tunić et al 2015). The specific study objectives were (1) to compare the effects of repeated isoproturon exposure on the growth of L. minor in two time-variable exposure scenarios with the effects observed in a standard growth inhibition test with continuous exposure (to enable direct comparison of effects from different time-variable exposure scenarios TWA approach was used), (2) to assess the overall effects of multiple exposures and expected carry-over effect on plant biomass production and (3) to discuss comparability of standard toxicity endpoints in modified laboratory test simulating repeated exposures with the recovery phase.…”

Diuron effects on photosynthesis and vertical migration of microphytobenthos: Potential rapid bioassessment of herbicide toxicity in coastal sediments

“…recovery was observed after 2 h exposure for rETRmax, while it needed the overnight period for NPQ and Fv/Fm. Such recovery was also observed in other aquatic photosynthetic organisms and very much species-dependent (Negri et al, 2005;Magnusson et al, 2012;Burns et al, 2015;Esteves et al, 2017). Among them, diatoms are often considered as more resistant to and more rapidly recoverable from diuron toxicity (Juneau et al, 2007;Magnusson et al, 2012;Stachowski-Haberkorn, et al, 2013), which possibly most thanks to the capability of diatom frustules (porous silica cell-wall) to sort and filter nutrients from harmful agents (De Tomassi et al, 2017).…”

High‐Frequency Sampling of Small Streams in the Agroecosystems of Southwestern Ontario, Canada, to Characterize Pesticide Exposure and Associated Risk to Aquatic Life

“…The effect of pulsed exposure and capacity to recover will also vary across species. Many aquatic primary producers (i.e., algae and macrophytes) have the capacity to recover from pulsed exposure to herbicides (Vallotton et al 2008; Prosser et al 2013; Burns et al 2015). In the study by Mohr et al (2012), indoor stream mesocosms were exposed to weekly 12‐h pulses of imidacloprid 3 times (12 µg/L) in the spring and 3 times in the summer (12 µg/L).…”