Emerging diseases in Australian oysters and the challenges of climate change and uncertain futures

Oysters are a valuable and iconic seafood, deeply rooted in Australian culture. However, oysters have always been vulnerable to disease, with disease outbreaks leading to mass mortality events that regularly cost the oyster aquaculture industry millions of dollars and affect livelihoods. Notably, there is evidence that climate change is rapidly causing the emergence of new diseases alongside the amplification of impacts of existing diseases. This is because warming, acidification and freshening of coastal and estuarine habitats is affecting the three axes of disease; the host, the external environment and the pathogens. Here we explore how climate change is likely to impact all three axes of disease in Australian oyster aquaculture. Climate change is affecting oyster physiology, leading to weaker immune defences that allow for increased susceptibility to viral and bacterial infections. For example, there is evidence that recent heavy rain events precede oyster disease in estuaries. In addition, climate change is increasing the abundance and virulence of bacterial and viral pathogens, potentially resulting in the introduction of novel disease into new habitats. In order to remain viable, we suggest that the Australian oyster industry needs to enhance selective breeding programs currently underway with a diversification of products and research on emerging diseases to ensure resilience in the sector.