Filippini G1., Bugnot A2,3,4., Palmer J1., Erickson K3,5., Ferguson A., Coleman R6., Gribben P4,5., Siboni N., Varkey D1., Dafforn K1,4.
1Macquarie University, Sydney, Australia, 2Commonwealth Scientific and Industrial Research Organisation, Brisbane, Australia, 3University of Sydney, Sydney, Australia, 4Sydney Institute of Marine Science, Sydney, Australia, 5University of New South Wales, Sydney, Australia, 6University of Technology Sydney, Sydney, Australia
The increase of nitrogen inputs from anthropogenic activities into coastal waters stimulates algal productivity, which in excess can lead to eutrophication. Oyster reefs can play a crucial role in the removal of nitrogen from aquatic systems by enhancing microbial denitrification within oysters and in the surrounding sediments. Here, we investigated the potential of environmental DNA (eDNA) to provide more detailed information on the denitrification process occurring on and around six oyster reefs along the East coast of Australia with different environmental characteristics. At each site, quantitative PCR was used to measure abundance of 16S rRNA and denitrification genes (nirS, nirK, norB and nosZ) in sediments adjacent to oyster reefs and in oyster biofilm. Although results showed that sediments adjacent to oyster reefs presented a higher relative abundance of denitrification genes, they were mainly characterised by the nirK gene, which catalyses nitrite (NO2-) reduction to nitric oxide (NO). By contrast, oyster biofilm presented a greater proportion of the gene encoding nitrous oxide reductase (nosZ) – a key enzyme that produces dinitrogen gas (N2) from nitrous oxide (N2O). This result indicates that oyster biofilm not only makes a higher contribution to the removal of nitrogen, but also to the reduction of the most impactful greenhouse gas (N2O). Finally, when comparing sites, the relative abundance of the nosZ gene in oyster biofilm was found to be higher in the Northernmost sites, suggesting that both genetic and environmental factors (i.e. temperature) can be important modulators of the abundance of this gene.
Biography:
Since completing her degree in Marine Biology at the Polytechnic University of Marche, she has been awarded three scholarships and worked as Research Assistant at Macquarie University. During her time in this position, she investigated benthic biogeochemical processes and microbial diversity in four coastal lagoons in Sydney with different levels of urbanisation and human impact. She is currently working on her PhD, studying the role of shellfish reefs in ecosystem functions, with the final goal of delivering essential guidelines for using these organisms as bioremediation tools. Her research work will forge a novel link between direct measures of biogeochemical cycling and the microbial mechanisms driving these processes.