Toxicity of ten herbicides to the tropical marine microalgae Rhodomonas salina

Thomas, Marie C., Flores, Florita, Kaserzon, Sarit, Fisher, Rebecca, and Negri, Andrew P. (2020) Toxicity of ten herbicides to the tropical marine microalgae Rhodomonas salina. Scientific Reports, 10. 7610.

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Herbicide contamination of nearshore tropical marine ecosystems is widespread and persistent; however, risks posed by most 'alternative' herbicides to tropical marine microalgae remain poorly understood. Experimental exposures of the important but understudied microalgae Rhodomonas salina to seven individual Photosystem II (PSII) inhibitor herbicides (diuron, metribuzin, hexazinone, tebuthiuron, bromacil, simazine, propazine) led to inhibition of effective quantum yield (Delta F/F-m ') and subsequent reductions in specific growth rates (SGR). The concentrations which reduced Delta F/F-m ' by 50% (EC50) ranged from 1.71-59.2 mu gL(-1), while the EC(50)s for SGR were 4-times higher, ranging from 6.27-188 mu gL(-1). Inhibition of Delta F/F-m ' indicated reduced photosynthetic capacity, and this correlated linearly with reduced SGR (R-2=0.89), supporting the application of F/F-m' inhibition as a robust and sensitive indicator of sub-lethal toxicity of PSII inhibitors for this microalga. The three non-PSII inhibitor herbicides (imazapic, haloxyfop and 2,4-Dichlorophenoxyacetic acid (2,4-D)) caused low or no toxic responses to the function of the PSII or growth at the highest concentrations tested suggesting these herbicides pose little risk to R. salina. This study highlights the suitability of including R. salina in future species sensitivity distributions (SSDs) to support water quality guideline development for the management of herbicide contamination in tropical marine ecosystems.

Item ID: 63387
Item Type: Article (Research - C1)
ISSN: 2045-2322
Copyright Information: Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit
Funders: National Environmental Science Program (NESP), AIMS@JCU
Projects and Grants: NESP Tropical Water Quality Hub, Project 3.1.5
Date Deposited: 03 Jun 2020 07:35
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 100%
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