A miniature bioassay for testing the acute phytotoxicity of Photosystem II herbicides on seagrass

Wilkinson, Adam D., Collier, Catherine J., Flores, Florita, Mercurio, Phil, O'Brien, Jake, Ralph, Peter J., and Negri, Andrew P. (2015) A miniature bioassay for testing the acute phytotoxicity of Photosystem II herbicides on seagrass. PLoS ONE, 10 (2). e0117541. pp. 1-17.

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DOI: 10.1371/journal.pone.0117541

View at Publisher Website: http://dx.doi.org/10.1371/journal.pone.0...

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Abstract

Photosystem II (PSII) herbicides have been detected in nearshore tropical waters such as those of the Great Barrier Reef and may add to the pressure posed by runoff containing sediments and nutrients to threatened seagrass habitats. There is a growing number of studies into the potential effects of herbicides on seagrass, generally using large experimental setups with potted plants. Here we describe the successful development of an acute 12-well plate phytotoxicity assay for the PSII herbicide Diuron using isolated Halophila ovalis leaves. Fluorescence images demonstrated Diuron affected the entire leaf surface evenly and responses were not influenced by isolating leaves from the plant. The optimum exposure duration was 24 h, by which time the inhibition of effective quantum yield of PSII (∆F/Fm’) was highest and no deterioration of photosystems was evident in control leaves. The inhibition of ∆F/Fm’ by Diuron in isolated H. ovalis leaves was identical to both potted and hydroponically grown plants (with leaves remaining attached to rhizomes), indicating similar reductions in photosynthetic activity in these acute well-plate assays. The sensitivity of the assay was not influenced by irradiance (range tested 40 to 400 μmol photons m-2 s-1). High irradiance, however, caused photo-oxidative stress in H. ovalis and this generally impacted in an additive or sub-additive way with Diuron to damage PSII. The bioassay using isolated leaves is more rapid, uses far less biological material and does not rely on specialised aquarium facilities in comparison with assays using potted plants. The development and validation of this sensitive bioassay will be useful to reliably screen and monitor the phytotoxicity of existing and emerging PSII herbicides and contribute to risk assessments and water quality guideline development in the future.


Item ID:	37699
Item Type:	Article (Research - C1)
ISSN:	1932-6203
Additional Information:	© 2015 Wilkinson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funders:	National Environmental Research Program (NERP) Tropical Ecosystems Hub
Projects and Grants:	NERP Tropical Ecosystems Hub Project 4.2
Research Data:	http://eatlas.org.au/pydio/data/public/f3a2ac.php
Date Deposited:	31 Mar 2015 03:57
FoR Codes:	06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060701 Phycology (incl Marine Grasses) @ 50% 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 20% 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060705 Plant Physiology @ 30%
SEO Codes:	96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960502 Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments @ 30% 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 20% 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 50%
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