I am a Subject Coordinator and Lecturer in the School of Life Sciences, and the Manager of the Deep Green Biotech Hub.
The New South Wales Deep Green Biotech Hub (DGBH) located at the University of Technology Sydney, brings together researchers, SMEs, industry, start-ups, students and other stakeholders to bring NSW to the forefront of algae-based biotechnology innovation in Australia.
I completed my undergraduate degree in Environmental biology in 2011 at UTS. My honours project took me to Victoria in 2012, where I researched asexual long-distance dispersal mechanisms of Zostera nigricaulis.
I commenced my PhD at UTS in 2013, under the supervision of Dr. Peter Macreadie, Prof. Peter Ralph, and Dr. Daniel Nielsen – with the research project “The Role of Bioturbators in Blue Carbon Cycles”. The focus of my research is on vegetated coastal habitats – or “Blue Carbon” systems, encompassing seagrass, saltmarsh, and mangrove environments. These systems are critically important, not just as essential marine ecosystems, but also as global carbon sinks.My research aims to observe and experiment with Blue Carbon cycles, their biogeochemical and microbial drivers, and ecological factors affecting them. I have since been undertaking field and lab work, observing how macrofauna influence the cycling and quality of carbon in seagrass sediment.
Title: The role of bioturbators in Blue Carbon cycles (PhD Research)
Supervisors: Dr. Peter Macreadie, Prof. Peter Ralph and Dr. Daniel Nielsen
Background: Vegetated coastal habitats (salt marsh, mangrove and seagrass environments) are among the most efficient carbon storage systems worldwide. Given their capacity to cycle and store carbon, these habitats are known as “Blue Carbon” ecosystems. This ability to sequester and store carbon in both the short and long (> thousands of years) term makes Blue Carbon ecosystems an estimated 5 – 30 times more proficient than terrestrial habitats. This ability of global environments to sequester carbon is a key process in the overall cycle of atmospheric CO2, and therefore a contributing factor to the prevention of further climate change. While the extent of research into terrestrial C cycling is vast, many of the questions that have been addressed in those systems have yet to be investigated in the marine environment.
Benthic infauna can appear in Blue Carbon environments in a myriad of densities and community compositions. The actions of these animals have the potential to both positively and negatively impact both seagrass productivity, and Blue Carbon sequestration. It is generally accepted that the effects of these animals are a poorly studied component of Blue Carbon ecosystems. Their actions potentially have major impacts on Blue Carbon cycling and sequestration, given their influence on sediment, and relationship with sediment microbes.
UTS School of Life Sciences
• Career Management for Scientists – 2nd and 3rd Year Science Elective
• Ecology – 2nd Year Environmental Subject
• Biocomplexity – 1st Year Science Subject
Thomson, A, Trevathan-Tackett, S, Ralph, P, Macreadie, P & Maher, D 2019, 'Bioturbator-stimulated loss of seagrass sediment carbon stocks', Limnology and Oceanography.View/Download from: UTS OPUS or Publisher's site
Seagrass ecosystems are highly productive, and are sites of significant carbon sequestration. Sediment‐held carbon stocks can be many thousands of years old, and persist largely due to sediment anoxia and because microbial activity is decreasing with depth. However, the carbon sequestered in seagrass ecosystems may be susceptible to remineralization via the activity of bioturbating fauna. Microbial priming is a process whereby remineralization of sediment carbon (recalcitrant organic matter) is stimulated by disturbance, i.e., burial of a labile source of organic matter (seagrass). We investigated the hypothesis that bioturbation could mediate remineralization of sediment carbon stocks through burial of seagrass leaf detritus. We carried out a 2‐month laboratory study to compare the remineralization (measured as CO2 release) of buried seagrass leaves (Zostera muelleri) to the total rate of sediment organic matter remineralization in sediment with and without the common Australian bioturbating shrimp Trypaea australiensis (Decapoda: Axiidea). In control sediment containing seagrass but no bioturbators, we observed a negative microbial priming effect, whereby seagrass remineralization was favored over sediment remineralization (and thus preserving sediment stocks). Bioturbation treatments led to a two‐ to five‐fold increase in total CO2 release compared to controls. The estimated bioturbator‐stimulated microbial priming effect was equivalent to 15% of the total daily sediment‐derived CO2 releases. We propose that these results indicate that bioturbation is a potential mechanism that converts these sediments from carbon sinks to sources through stimulation of priming‐enhanced sediment carbon remineralization. We further hypothesized that significant changes to seagrass faunal communities may influence seagrass sediment carbon stocks.
Trevathan-Tackett, SM, Thomson, ACG, Ralph, PJ & Macreadie, PI 2018, 'Fresh carbon inputs to seagrass sediments induce variable microbial priming responses.', Science of the Total Environment, vol. 621, pp. 663-669.View/Download from: UTS OPUS or Publisher's site
Microbes are the 'gatekeepers' of the marine carbon cycle, yet the mechanisms for how microbial metabolism drives carbon sequestration in coastal ecosystems are still being defined. The proximity of coastal habitats to runoff and disturbance creates ideal conditions for microbial priming, i.e., the enhanced remineralisation of stored carbon in response to fresh substrate availability and oxygen introduction. Microbial priming, therefore, poses a risk for enhanced CO2 release in these carbon sequestration hotspots. Here we quantified the existence of priming in seagrass sediments and showed that the addition of fresh carbon stimulated a 1.7- to 2.7-fold increase in CO2 release from recent and accumulated carbon deposits. We propose that priming taking place at the sediment surface is a natural occurrence and can be minimised by the recalcitrant components of the fresh inputs (i.e., lignocellulose) and by reduced metabolism in low oxygen and high burial rate conditions. Conversely, priming of deep sediments after the reintroduction to the water column through physical disturbances (e.g., dredging, boat scars) would cause rapid remineralisation of previously preserved carbon. Microbial priming is identified as a process that weakens sediment carbon storage capacity and is a pathway to CO2 release in disturbed or degraded seagrass ecosystems; however, increased management and restoration practices can reduce these anthropogenic disturbances and enhance carbon sequestration capacity.
Macreadie, PI, Nielsen, DA, Kelleway, JJ, Atwood, TB, Seymour, JR, Petrou, K, Connolly, RM, Thomson, ACG, Trevathan-Tackett, SM & Ralph, PJ 2017, 'Can we manage coastal ecosystems to sequester more blue carbon?', Frontiers in Ecology and the Environment, vol. 15, no. 4, pp. 206-213.View/Download from: UTS OPUS or Publisher's site
© The Ecological Society of America To promote the sequestration of blue carbon, resource managers rely on best-management practices that have historically included protecting and restoring vegetated coastal habitats (seagrasses, tidal marshes, and mangroves), but are now beginning to incorporate catchment-level approaches. Drawing upon knowledge from a broad range of environmental variables that influence blue carbon sequestration, including warming, carbon dioxide levels, water depth, nutrients, runoff, bioturbation, physical disturbances, and tidal exchange, we discuss three potential management strategies that hold promise for optimizing coastal blue carbon sequestration: (1) reducing anthropogenic nutrient inputs, (2) reinstating top-down control of bioturbator populations, and (3) restoring hydrology. By means of case studies, we explore how these three strategies can minimize blue carbon losses and maximize gains. A key research priority is to more accurately quantify the impacts of these strategies on atmospheric greenhouse-gas emissions in different settings at landscape scales.
Thomson, AC, York, PH, Smith, TM, Sherman, CD, Booth, DJ, Keough, MJ, Ross, DJ & Macreadie, PI 2015, 'Seagrass Viviparous Propagules as a Potential Long-Distance Dispersal Mechanism', Estuaries and Coasts, vol. 38, no. 3, pp. 927-940.View/Download from: UTS OPUS or Publisher's site
Resilience of seagrass meadows relies on the ability of seagrass to successfully recolonise denuded areas or disperse to new areas. While seed germination and rhizome extension have been explored as modes of recovery and expansion, the contribution of seagrass viviparous propagules to meadow population dynamics has received little attention. Here, we investigated the potential of seagrass viviparous propagules to act as dispersal vectors. We performed a series of density surveys, and in situ and mesocosm-based experiments in Port Phillip Bay, VIC, Australia, using Zostera nigricaulis, a species known to produce viviparous propagules. Production of viviparous propagules was higher at sites with high wind and current exposure, compared to more sheltered environments. A number of propagules remained buoyant and healthy for more than 85 days, suggesting the capacity for relatively long-distance dispersal. Transplanted propagules were found to have improved survivorship within seagrass habitats compared to bare sediment over the short term (4 weeks); however, all propagules suffered longer-term (<100 days) mortality in field experiments. Conditions outside of meadows, including sediment scouring, reduced the likelihood of successful colonisation in bare sediment. Furthermore, sediment characteristics within meadows, such as a smaller grain size and high organic content, positively influenced propagule establishment. This research provides preliminary evidence that propagules have the potential to act as an important long-distance dispersal vector, a process that has previously gone unrecognised. Even though successful establishment of propagules may be rare, viviparous propagules show great potential for seagrass populations given they are facing global decline.
Thomson, ACG, York, PH, Smith, TM, Sherman, CDH, Booth, DJ, Keough, MJ, Ross, DJ & Macreadie, PI 2015, 'Response to "Comment on 'Seagrass Viviparous Propagules as a Potential Long-Distance Dispersal Mechanism' by A. C. G. Thomson et al"', ESTUARIES AND COASTS, vol. 39, no. 3, pp. 875-876.View/Download from: UTS OPUS or Publisher's site