title: Elevated water temperature reduces the acute toxicity of the widely used herbicide diuron to a green alga, Pseudokirchneriella subcapitata.
abstract: In the actual environment, temperatures fluctuate drastically through season or global warming and are thought to affects risk of pollutants for aquatic biota; however, there is no report about the effect of water temperature on toxicity of widely used herbicide diuron to fresh water microalgae. The present research investigated inhibitory effect of diuron on growth and photosynthetic activity of a green alga Pseudokirchneriella subcapitata at five different temperatures (10, 15, 20, 25, and 30 °C) for 144 h of exposure. As a result, effective diuron concentrations at which a 50% decrease in algal growth occurred was increased with increasing water temperature ranging from 9.2 to 20.1 μg L(-1) for 72 h and 9.4-28.5 μg L(-1) for 144 h. The photochemical efficiency of photosystem II (F v/F m ratio) was significantly reduced at all temperatures by diuron exposure at 32 μg L(-1) after 72 h. Inhibition rates was significantly increased with decreased water temperature (P < 0.01). Intracellular H2O2 levels as an indicator of oxidative stress were also decreased with increasing temperature in both control and diuron treatment groups and were about 2.5 times higher in diuron treatment groups than that of controls (P < 0.01). Our results suggest water temperatures may affect the toxicokinetics of diuron in freshwater and should therefore be considered in environmental risk assessment.
authors.affiliation: Laboratory of Marine Environmental Science, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581, Japan.
authors.forename: Rumana
authors.initials: R
authors.lastname: Tasmin
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shimasaki
authors.forename: Michito
authors.initials: M
authors.lastname: Tsuyama
authors.forename: Xuchun
authors.initials: X
authors.lastname: Qiu
authors.forename: Fatma
authors.initials: F
authors.lastname: Khalil
authors.forename: Nozomu
authors.initials: N
authors.lastname: Okino
authors.forename: Naotaka
authors.initials: N
authors.lastname: Yamada
authors.forename: Shinji
authors.initials: S
authors.lastname: Fukuda
authors.forename: Ik-Joon
authors.initials: IJ
authors.lastname: Kang
authors.forename: Yuji
authors.initials: Y
authors.lastname: Oshima
mesh_terms: D000460:Chlorophyta / Q000187:drug effects*; D004237:Diuron / Q000737:chemistry / Q000633:toxicity*; D005618:Fresh Water / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000032:analysis; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000502:physiology; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000633:toxicity*
chemical_list: D006540:Herbicides; D045332:Photosystem II Protein Complex; D014874:Water Pollutants, Chemical; D004237:Diuron; D006861:Hydrogen Peroxide