Blinded by the light: Increased chlorophyll fluorescence of herbicide-exposed periphyton masks unfavorable structural responses during exposure and recovery

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Blinded by the light: Increased chlorophyll fluorescence of herbicide-exposed periphyton masks unfavorable structural responses during exposure and recovery

Feckler, Alexander (author): Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för vatten och miljö,Department of Aquatic Sciences and Assessment

Rakovic, Jelena (author): Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för vatten och miljö,Institutionen för mark och miljö,Department of Aquatic Sciences and Assessment,Department of Soil and Environment

Kahlert, Maria (author): Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för vatten och miljö,Department of Aquatic Sciences and Assessment

Tröger, Rikard (author): Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för vatten och miljö,Department of Aquatic Sciences and Assessment

Bundschuh, Mirco (author): Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för vatten och miljö,Department of Aquatic Sciences and Assessment

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Elsevier BV, 2018
2018
English.
In: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 203, s. 187-193

Related links:: https://res.slu.se/i...; show more...; https://doi.org/10.1...; show less...

Journal article (peer-reviewed)

Abstract Subject headings

In surface waters within agricultural catchments, periphyton - i.e., biofilms containing algae, heterotrophs, and associated detritus - is subjected to multiple stressors including herbicides. Although herbicide effects on periphyton are frequently studied, the focus has been on photosynthesis-inhibiting herbicides while other modes of toxic action have received little attention. Against this background, a 21-days-lasting bioassay was conducted, during which mature periphytic communities were exposed to the carotenoid-biosynthesis-inhibiting herbicide diflufenican for 12 days (up to 10 mu g/L; n = 4), followed by a 9-days-lasting recovery phase in herbicide-free medium. Variables related to periphytic functioning (photosynthetic efficiency and non-photochemical quenching) and structure (pigment concentrations, biomass, and algal community structure) were quantified every third day during both experimental phases. Exposure to >= 0.2 mu g diflufenican/L resulted in 20-25% and 25-30% lowered carotenoid and chlorophyll a concentrations, respectively, likely explained by a reduced algal biovolume as well as diflufenican's mode of toxic action and thus a shift towards a higher heterotrophy of the communities. Despite these adverse effects on the photosynthetic apparatus, the photosynthetic efficiency increased by up to similar to 15% under diflufenican exposure judged on higher chlorophyll fluorescence. This may be explained by an up to similar to 60% reduced non-photochemical quenching as well as binding of diflufenican to the pigment-protein membrane complex of the photosystem II, two processes causing higher chlorophyll fluorescence. Additionally, phototrophs may have actively increased energy assimilation to cope with higher energy demands under chemical stress. Although periphyton showed some recovery potential following the exposure phase, observed as increasing chlorophyll a concentrations and non-photochemical quenching, periphyton may not be able to quickly recover from stress given the persistent increase in the photosynthetic efficiency. While the processes underlying the observed effects yet remain speculative, the results suggest a shift towards a higher degree of heterotrophy in periphytic communities ultimately increasing the importance of heterotrophic ecosystem functions at impacted sites over the long term.

Subject headings

NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)
NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)
NATURVETENSKAP -- Biologi -- Ekologi (hsv//swe)
NATURAL SCIENCES -- Biological Sciences -- Ecology (hsv//eng)

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By the author/editor: Feckler, Alexand ...; Rakovic, Jelena; Kahlert, Maria; Tröger, Rikard; Bundschuh, Mirco

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NATURAL SCIENCES: NATURAL SCIENCES; and Earth and Relate ...; and Environmental Sc ...

NATURAL SCIENCES: NATURAL SCIENCES; and Biological Scien ...; and Ecology

Articles in the publication: Aquatic Toxicolo ...

By the university: Swedish University of Agricultural Sciences

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