Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon.

Virginia Rich,Olga Pantos,Gene W Tyson,Hemerson Tonin,Florent E Angly,David G Bourne,Andrew P Negri,Philip Mercurio,Thomas C Morgan

doi:10.7717/peerj.1758

Virginia Rich, Olga Pantos + Show 7 more

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https://doi.org/10.7717/peerj.1758

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Abstract

Diuron is a herbicide commonly used in agricultural areas where excess application causes it to leach into rivers, reach sensitive marine environments like the Great Barrier Reef (GBR) lagoon and pose risks to marine life. To investigate the impact of diuron on whole prokaryotic communities that underpin the marine food web and are integral to coral reef health, GBR lagoon water was incubated with diuron at environmentally-relevant concentration (8 µg/L), and sequenced at specific time points over the following year. 16S rRNA gene amplicon profiling revealed no significant short- or long-term effect of diuron on microbiome structure. The relative abundance of prokaryotic phototrophs was not significantly altered by diuron, which suggests that they were largely tolerant at this concentration. Assembly of a metagenome derived from waters sampled at a similar location in the GBR lagoon did not reveal the presence of mutations in the cyanobacterial photosystem that could explain diuron tolerance. However, resident phages displayed several variants of this gene and could potentially play a role in tolerance acquisition. Slow biodegradation of diuron was reported in the incubation flasks, but no correlation with the relative abundance of heterotrophs was evident. Analysis of metagenomic reads supports the hypothesis that previously uncharacterized hydrolases carried by low-abundance species may mediate herbicide degradation in the GBR lagoon. Overall, this study offers evidence that pelagic phototrophs of the GBR lagoon may be more tolerant of diuron than other tropical organisms, and that heterotrophs in the microbial seed bank may have the potential to degrade diuron and alleviate local anthropogenic stresses to inshore GBR ecosystems.

Highlights

Coral reefs are very rich and diverse ecosystems, though due to both local and global anthropogenic disturbances, they are in a state of gradual decline (Pandolfi et al, 2003).How to cite this article Angly et al (2016), Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon
At the end of the incubation experiment, Oceanospirillales were very abundant in the control flasks exposed to light, while Thiotrichales dominated the samples incubated in the dark
This study used amplicon and metagenomic sequencing to evaluate the effects of a photosystem II (PSII) herbicide on the composition of entire prokaryotic communities, rather than selected species

Summary

Introduction

Coral reefs are very rich and diverse ecosystems, though due to both local and global anthropogenic disturbances, they are in a state of gradual decline (Pandolfi et al, 2003).How to cite this article Angly et al (2016), Diuron tolerance and potential degradation by pelagic microbiomes in the Great Barrier Reef lagoon. Coral reefs are very rich and diverse ecosystems, though due to both local and global anthropogenic disturbances, they are in a state of gradual decline (Pandolfi et al, 2003). Local impacts such as coastal pollution (Brodie et al, 2012) and overfishing (De’ath et al, 2012) affect both the reef macrobiota (Fabricius, 2005; Sandin et al, 2008) and the microorganisms in their associated microbiomes (Dinsdale et al, 2008; Thurber et al, 2009; Webster et al, 2011). Changes to microbiome structure and function can compromise the health of coral reefs and their ability to recover from stresses (Ainsworth, Thurber & Gates, 2010; Hughes et al, 2010)

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