Miss Giulia Filippini1, Dr Ana Bugnot2,4, Dr Angus Ferguson3, Professor Ross Coleman2, Professor Paul Gribben4,5, Dr Deepa Varkey1, Dr Katherine Dafforn1,4
1Macquarie University, , Australia, 2University of Sydney, , Australia, 3NSW Department of Planning, Industry and Environment, , Australia, 4Sydney Institute of Marine Science, , Australia, 5University of New South Wales, , Australia
The increase of nitrogen (N) 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 N from aquatic systems by enhancing microbial denitrification within oysters and in the surrounding sediments. However, the rates of microbial denitrification are likely to depend on site-specific characteristics. In this study, we investigated benthic metabolism and denitrification occurring on and around six Australian oyster reefs with different environmental characteristics. At each site, in situ incubation chambers were used to measure oxygen demand and N2 fluxes in sediments adjacent to oyster reefs, oysters alone, and oysters over sediments; and quantitative PCR was used to measure abundance of denitrification genes (nirS, nirK, norB and nosZ) in sediments and in oyster biofilm. Overall, we found that oxygen demand and N2 fluxes were substantially higher in the oysters alone. However, when comparing sediment types, oysters were found to enhance denitrification only in sites characterised by a higher percentage of sediment fines. While sediment adjacent to oyster reefs presented a higher relative abundance of denitrification genes, oyster biofilm had greater proportion of the nosZ gene (a key enzyme that catalyses N2O reduction to N2), but its abundance was unrelated to sediment fines. Findings demonstrate that oysters can be used as bioremediation tools as they remove significant N from estuarine systems. However, more studies are needed to better understand which environmental factors have the most effect on denitrification in oyster reefs.
Presentation Slides – Giulia Filippini
Biography:
Since completing her degree in Marine Biology at the Polytechnic University of Marche, Giulia 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
