The unique and fascinating symbiotic relationship that is formed between anemonefish and their host sea anemones is now recognised throughout the world, thanks largely to the Disney film “Finding Nemo”. There are over 1,000 species of sea anemone in the world, of these only ten are known to provide essential habitat for 28 species anemonefish. Australian waters are home to all ten species of host anemone and 13 species of anemonefish. There has been a significant decline in anemonefish in some areas, primarily due to the demands for private aquaria. But there may also be another factor at play - that of climate change...

What most people don’t realise is that these anemones also form a lesser known symbiosis with algae (zooxanthellae). These algae live within the cells of the anemone and provide the colouration we see in the tentacles and also provide food for the anemone by converting sunlight to nutrients through photosynthesis.

Photographers sometimes show beautifully coloured anemonefish against a background of bright white tentacles, not knowing they are displaying stressed anemones and a breakdown of the algae/animal symbiosis, which is called ‘bleaching’. If temperatures remain above the optimal range for a long period, the loss of symbiotic algae will deprive the anemone of an essential food source and can ultimately lead to their death.

Although the adverse effects of bleaching on corals has received increasing research and media attention over the past decade, the effects of bleaching on host sea anemones have gone relatively unnoticed. Climate change is expected to lead to increased ocean temperatures and this will have wide spread impacts on marine ecosystems. We need to be able to understand how vulnerable these anemones are to the elevated temperatures associated with different climate change scenarios. The outcomes of our research will reveal how close anemones are living to their upper thermal threshold. It is expected that small increases in sea temperature (only 1-2°C above summer averages) will be enough to induce a bleaching response.

Dr Anna Scott from Southern Cross University, Lismore and Dr Ross Hill from the University of Technology, Sydney will answer this question with the help of the Sydney Aquarium Conservation Fund, by investigating the impact of warmer seawater conditions on the bulb-tipped anemone (Entacmaea quadricolor). Ensuring the survival of host sea anemone populations is important not only for the anemones, but also for their resident fish, which cannot survive in the wild without their anemone homes.