Marine heatwaves are getting longer and more frequent, impacting farmed shellfish. As ocean temperatures rise, juvenile shellfish in particular face increasing thermal stress at their most vulnerable life stages. For shellfish farmers, that translates directly to production losses and an uncertain future. 

Addressing that challenge requires some creative thinking. Researchers at New Zealand’s Cawthron Institute have been exploring whether plant-derived extracts could be used to prime shellfish physiology before heat stress hits and building resilience. They’re calling it “shellfish hydrotherapy”. 

A new study tested whether bathing juvenile green-lipped mussels (Perna canaliculus) in extracts from beetroot and prickly pear could improve their survival under acute heat stress.  

Beetroot and prickly pear might not be the first things that come to mind when you think about climate-proofing a mussel farm, but the results suggest they’re worth a closer look. 

Whilst the concept might sound unusual, the use of plant-derived extracts in aquaculture is not new. Naturally derived extracts have been explored across both fish and shellfish species to improve thermal tolerance, immune response, and resilience during transport.  

The mechanism behind it comes down to cellular stress biology. Beetroot and prickly pear are rich in bioactive compounds including betalains and phenolic compounds, which are thought to trigger a mild stress response at the cellular level. This prompts the production of heat shock proteins, which are molecular chaperones that stabilise and repair cellular damage when temperatures spike. The extract therefore primes the mussel’s stress machinery before the heat arrives. 

In this study, juvenile mussels were bathed in extract solutions for two hours, then exposed to an acute heat challenge. Survival was assessed 48 hours later. The juvenile mussels treated with beetroot extract showed a significant improvement when compared to untreated individuals.  

As marine heatwaves become a defining challenge for the Australian and New Zealand seafood sectors, approaches like shellfish hydrotherapy offer a glimpse of what climate adaptation might look like in practice: practical, low-input, and applicable at multiple stages of the production cycle. 

For more information, view the full article here.  

Image: Natalí Delorme