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

Abstract

The effects of herbicide diuron on photosynthesis and vertical migration of intertidal microphytobenthos (MPB) assemblages were investigated using chlorophyll fluorometry. The results shown diuron ≤ 60 μgꞏL -1 had no obvious effect on MPB vertical migration during 24 h indicated by consistent rhythm. Low concentration of 10 μgꞏL -1 diuron had no significant influence on MPB photosynthesis throughout, however, high concentrations of 40, 50, and 60 μgꞏL -1 had significant impacts exhibited by decreased parameters of maximum relative electron transport rate (rETRmax), maximal PS II quantum yield (Fv/Fm) and non-photochemical quenching (NPQ). For middle concentrations of 20 and 30 μgꞏL -1 , above decreased 3 parameters recovered sooner or later after 2 h or 16.5 h. Comparatively, rETRmax, Fv/Fm and NPQ are concentration dependent and more sensitive than other parameters in assessing diuron toxicity. This study revealed the potential of using MPB assemblages and chlorophyll fluorometry for rapid assessing diuron toxicity in coastal sediments.

Fluctuating fortunes: Stressor synchronicity and fluctuating intensity influence biological impacts

“…However, photosynthetic impacts increase at higher stressor intensities (e.g. Du et al, 2021 ; King et al, 2022 ), and in this study, critical thresholds might have been surpassed and mechanisms for physiological compensation overwhelmed, resulting in no differences across variable intensities and synchronicities. Additionally, differences in effects could be masked due to impacts on physiological endpoints not measured here that can affect photosynthetic capacity (e.g.…”