Friday, 10 July 2015


So it turns out (for whatever reason) that the Pipis just aren't keen on reproducing. The previous successful attempt at strip spawning them was accomplished in the Summer (around Christmas time), and so we have to wonder whether perhaps at this time of year, with the lower water temperatures, they just aren't prepared to reproduce? Whatever the reason, they refuse to fertilise, and this means moving on to a different species for our experiment..

Sydney Rock Oysters (SROs) (Saccostrea glomerata)

Sydney rock oysters are a native Australian oyster species which only occurs in estuaries along the New South Wales (NSW) and southeast Queensland coasts of Australia. The SRO aquaculture industry produced around 4500 metric tons of oysters in 2012 (worth about AUS$28.8 million - which is the same as about £13.8 million), which is about 40% of Australia's total oyster industry production value (NSW DPI 2011; ABARES 2013).  The SRO industry evolved in the 1790s and really became a high production industry in the late 1990s. However the SRO industry has been declining significantly since the late 1970s and it is uncertain what the future of the industry will look like. Major issues of the industry include disease, water quality decline in coastal areas, increasing competition from the Pacific oyster industry, and potential climate change impacts such as increasing sea levels, temperatures and acidity.

There has been quite a bit of research put into investigating the ideal conditions for culturing SROs, and so we already know a lot about the conditions that they grow best under. However, research into early stages of growth are still in relative infancy, and there is a lot of research still to conduct. Some examples of elements that we already have a good idea of:
- The development of embryos to larvae is affected by temperature and salinity, and the interaction of these together
- The growth rates of the different larval stages is affected by salinity & temperature
- Optimal temperature for growth of different larval stages
- Optimal salinity for greatest length increases in larvae
- Optimal combination of salinity and temperature for spat growth and survival
- Optimal temperature for fertilisation
- The effect of increased acidification on fertilisation, growth, and survival of larvae

As I mentioned earlier, coastal water quality decline is also a big worry for oyster farmers. As the coastal human population increases, there are often associated declines in water quality caused by organic contamination. On top of this, predicted increasing intense rain periods and flooding can could cause additional run-off of natural organic material from the land into coastal waters - and at the same time cause dramatic prolonged changes in salinity in these areas. High levels of organic matter in coastal waters can cause blooms of algae - and some of these blooms can be very harmful to fish, shellfish, or even humans (I think I have written a previous post regarding harmful algal blooms).

We would like to investigate the potential effect that one particular harmful algal Alexandrium species might have on the fertilisation and larval development of the Sydney rock oyster. 

Step 1: get hold of the algae we would like to investigate..

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