Toxicity thresholds of nine herbicides to coral symbionts (Symbiodiniaceae)

Marzonie, Magena, Flores, Florita, Sadoun, Nora, Thomas, Marie C., Valada-Mennuni, Anais, Kaserzon, Sarit, Mueller, Jochen F., and Negri, Andrew P. (2021) Toxicity thresholds of nine herbicides to coral symbionts (Symbiodiniaceae). Scientific Reports, 11. 21636.

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Over 30 herbicides have been detected in catchments and waters of the Great Barrier Reef (GBR) and their toxicity to key tropical species, including the coral endosymbiotic algae Symbiodiniaceae, is not generally considered in current water quality guideline values (WQGVs). Mutualistic symbionts of the family Symbiodiniaceae are essential for the survival of scleractinian corals. We tested the effects of nine GBR-relevant herbicides on photosynthetic efficiency (Delta F/F-m ') and specific growth rate (SGR) over 14 days of cultured coral endosymbiont Cladocopium goreaui (formerly Symbiodinium clade C1). All seven Photosystem II (PSII) herbicides tested inhibited Delta F/F-m ' and SGR, with toxicity thresholds for SGR ranging between 2.75 and 320 mu g L-1 (no effect concentration) and 2.54-257 mu g L-1 (EC10). There was a strong correlation between EC(50)s for Delta F/F-m ' and SGR for all PSII herbicides indicating that inhibition of Delta F/F-m ' can be considered a biologically relevant toxicity endpoint for PSII herbicides to this species. The non-PSII herbicides haloxyfop and imazapic did not affect Delta F/F-m ' or SGR at the highest concentrations tested. The inclusion of this toxicity data for Symbiodiniaceae will contribute to improving WQGVs to adequately inform risk assessments and the management of herbicides in tropical marine ecosystems.

Item ID: 72202
Item Type: Article (Research - C1)
ISSN: 2045-2322
Keywords: Conservation biology, Ecology, Environmental impact, Marine biology, Ocean sciences
Copyright Information: © The Author(s) 2021. 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 licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence 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 licence, visit
Date Deposited: 09 Feb 2022 11:01
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