By Melissa Marino
Two outstanding presentations based on the work of PhD students Tina Oldham and Jiadai Wu that could benefit aquaculture industries have won FRDC-sponsored awards at the Australian Marine Science Association (AMSA) annual conference.
The University of Tasmania’s Tina Oldham has addressed a key environmental challenge facing the Tasmanian Atlantic Salmon (Salmo salar) industry – hypoxia related to low levels of dissolved oxygen. In research assisted by Huon Aquaculture, she monitored levels of dissolved oxygen at five water depths in five commercial salmon cages throughout a summer season.
Her winning presentation, ‘Occurrence of hypoxia in Tasmanian Atlantic Salmon production cages – biological and environmental influences’, included findings that dissolved-oxygen saturation varies as much as 73 per cent from the surface to the bottom of a cage. She also found dissolved-oxygen levels are highly variable and can change dramatically within minutes.
Oxygen solubility reduces as water temperatures rise, and as Tasmania increasingly experiences warmer-than-average summer waters, salmon farmers are reporting more frequent problems with low dissolved-oxygen events. Impacts can range from decreased growth, reduced appetite and immune function to, in extreme cases, death.
Overall, Tina Oldham found dissolved-oxygen concentrations, which fluctuate naturally, were reduced in cages compared to reference sites. Optimal dissolved-oxygen concentrations were generally present only in the cage’s upper half.
She will examine more closely the reasons for reduced dissolved-oxygen levels in cages and the implications for fish health and mortality through the remainder of her PhD, co-supervised at the University of Melbourne.
Her findings will help the salmon industry plan future management and mitigation strategies to maximise fish welfare and production performance. These could include supplying additional oxygen or aeration, reducing stocking densities and farming at sites with greater water flow.
University of Sydney PhD student Jiadai Wu won the FRDC student poster award, which outlined her work sequencing a gene that helps Blacklip Abalone (Haliotis rubra) produce an antiviral protein.
This respiration protein – hemocyanin (HrH) – possesses antiviral activity against one of the most common human pathogens, herpes simplex virus type 1 (HSV-1), which is responsible for cold sores.
To investigate its potential as a novel antiviral drug, Jiadai Wu has cloned the entire gene that encodes for the HrH protein molecule, which is composed of nearly 7000 amino acids, and is detailed in her poster ‘The sequences of Blacklip Abalone hemocyanin’.
This data enabled her to predict the theoretical three-dimensional structure of HrH. She says this is a stepping stone to understanding how the antiviral mechanism works against HSV-1.
It opens the way for the development of therapeutic applications, such as a drug to treat HSV-1, which is the second-most-prevalent human virus in the world, after the common cold. HSV-1 infects 3.7 billion people globally, including 70 per cent of the Australian population.
Her findings could also benefit the abalone industry in Australia, which recently suffered an outbreak of an abalone herpes virus that killed 95 per cent of infected molluscs in 14 days.
Experimental models based on the HrH protein could provide new information and potential treatments for other herpes viruses.
The 2016 AMSA conference was held jointly with the New Zealand Marine Sciences Society in Wellington in July. Outstanding student presentations and posters are recognised each year with prizes, including the FRDC awards for research in the areas of environment and industry development.
The FRDC’s research projects manager Carolyn Stewardson, who chaired a conference session, says the FRDC is delighted to support students undertaking such high-calibre work. “These are students working hard and at the cutting edge of scientific research, and it’s great they have been recognised through these awards,” she says.