Man Xiao (Mandy)

Australian Rivers Institute/Griffith School of Environment

Room 2.02A, Building N13 (Environment 2), 

Griffith University, Nathan Campus,

170 Kessels Road, Nathan
Brisbane, QLD 4111,
Australia

Tel: + 61 7 373 57711+ 61 7 373 57711

Email: man.xiao@griffithuni.edu.au

PhD research outline

I am a PhD candidate within the Australian Rivers Institute. My supervisor is Prof.  Michele Burford and co-supervised by Dr Anusuya Willis and Dr Kate O’Brien (University of Queensland). My research work focuses on how physical factors, i.e., temperature, light attenuation, turbulent mixing and their interactions affect the competition between Cylindrospermopsis raciborskii and Microcystis aeruginosa.

C. raciborskii and M. aeruginosa are two of the most notorious cyanobacterial species as they both spread throughout the world and produce toxins that present great risks to living creatures. They both possess a range of unique eco-physiology traits to highly adapt to environmental changes, but vary with each other. C. raciborskii, due to its filamentous shape, it requires low light attenuation for growth but has less morality in turbulent mixing layers. It can tolerate a wide range of water temperature but prefers higher temperatures and more stratified waters. Compared to C. raciborskii, M. aeruginosa needs high light intensity for growth and prefers lower temperatures. It can regulate vertical distributions and overcome turbulent mixing to some extent due to its colonial morphology and gas-vesicle production. In addition, there is evidence that C. raciborskii is replacing M. aeruginosa or becoming co-dominant in some tropical lakes. Hence, the competition strategy between them should be considered, thus approaches for bloom control needed to be figure out as basis.

Master research brief

My master’s research focused on Microcystis blooms in Lake Taihu, the 3 rd biggest fresh lake in China. On the one hand, I emphasized on the ecology and morphology of different Microcystis strains that dominant in Lake Taihu, i.e., M. aeruginosa, Microcystis wesenbergii, Microcystis ichthyoblabe and Microcystis flos-aquae. The main results are as follows. 1) Microcystis blooms are not the result of fast growth of single cells but the floatation and accumulation on water surface of colonies in a short time, in contrast, blooms disappearance are the result of colonies disaggregate from water surface and uniformly distribute along the water depth. 2) The in-situ growth rate of Microcystis in Lake Taihu can be calculated form RNA/DNA ratio of colonies, which is a simpler method to know the cell density of Microcystis

On the other hand, how hydrodynamics affects the spatial and temporal distribution of Microcystis colonies with varying size along water depth. A vertical turbulent simulator was designed by me to study the relationship between turbulent mixing and Microcystis colony distribution. The main results are as follows. 1) Microcystis blooms formation and disappearance can be better described by vertical turbulent kinetic energy rather than threshold wind velocity. 2) When the average vertical turbulent kinetic energy exceeded in water column 55 cm 2/s 2, surface blooms disappeared and there were no differences in Microcystis size distribution vertically. 3) When the average vertical turbulent kinetic energy reached 60 cm 2/s 2, only colonies with 600-μm diameter or more can overcome the turbulence and float up for a short time.

Qualifications

MSc Environmental Science and Engineering, School of Environment, Hohai University, Nanjing, Jiangsu Province, China. 2014.

BSc Environmental Engineering, School of Environment, Hohai University, Nanjing, Jiangsu Province, China. 2011.

Awards & Scholarships

PhD Scholarship, Griffith University, 2014.

National Scholarship awarded by the Ministry of Education of the People's Republic of China (5%), 2013.

Excellent Graduation Thesis for Bachelor's Degree honored by Hohai University (5%), 2011.

Spiritual Civilization Scholarship and Excellent Student honored by Hohai University (10%), 2008 & 2011.

Outstanding Academic Scholarship honored by Hohai University (10%), 2008-2011.

Publications

Man Xiao, Wei Zhu, Ming Li, et al. 2013. The influence of water oscillation on the vertical distribution of Microcystis colonies of different sizes. Fresenius Environmental Bulletin, 22 (12): 3511-3518.

Ming Li, Man Xiao. 2014. In situ growth rate of Microcystis in a hypertrophic lake: RNA/DNA ratio as an indicator. Fresenius Environmental Bulletin, 23(4): 1100-1106.