We Are Not ‘Finding Nemo’ in the Red Sea Anymore, as Warming Oceans Have Ruined Its Home

Unlike the delicate pink-white flowers that they appear in first glance, anemones are ferocious coral predators that can trap fish if they dare to come around close. However, when it comes to clownfish, anemones have developed a symbiotic relationship with them, a partnership built on mutual comfort and needs, something which has given the fish the nickname “anemonefish.” Lately, however, this iconic ocean duo, popularized in the Disney-Pixar movie Finding Nemo, is under threat. Pressures evoked by the increasing global warming are pushing the pair to extreme heat stress. As a result, the clownfish are headed towards a mass collapse. A study published in npj Biodiversity documents the effects of this heat stress across three reefs in the Red Sea.

The title “thermal refuge,” typically assigned to the Red Sea, doesn’t seem valid any longer. When scientist Morgan Bennett-Smith visited the Red Sea amidst the 2023 heat wave, he noticed that the otherwise softly swaying anemones had turned ghostly white. When he went on to catch a glimpse of clownfish, he became even more concerned. The fish seemed to have disappeared from the sea. The Red Sea is “not turning out to be the safe haven we thought it was,” he said in a press release.

According to Smith’s calculations, nearly 94 to 100 percent of the clownfish have disappeared, and nearly 66 to 94 percent of the anemones have died due to the lingering heat stress coupled with coral bleaching events. Sea anemones are not just soft corals or fish-trapping predators. They are also protective shelters that offer cozy shelters to young fish, especially the orange-and-white clownfish. Over the years, scientists have observed a peculiar, unusual romantic partnership unfolding between the two, linked by the intracellular microalgae, known as zooxanthellae. While the algae supply sugar and oxygen to the anemones, the anemones protect the clownfish and their egg clutches.

When the clownfish approaches the anemones for the first time, the anemones release a mucus-like substance that coats the body of the fish, offering them defense against predators and their own stinging tentacles. Also, anemones offer a range of services to the fish, including oxygenation and nutrients. Fitness of the anemone, therefore, is an important factor that can make or break the fate of clownfish. These days, the anemones’ fitness appears to be decreasing, triggered by heat stress and recurring bleaching events. A bleaching event is when the temperature becomes too high for the corals to tolerate. In anemones, particularly, the heat causes the anemones to lose their algal cells.

Without the essential algal cells, the anemones start to starve. Prolonged starvation leads to their death. And once the clownfish are gone, due to their decreasing protective power, they become even more vulnerable to predators like butterflyfish, who feed on anemones. “We always hope that anemones and clownfish groups survive bleaching events, as they have over and over again in the last 10 years, but it hit a point where it was too extreme,” Smith said in the press release. Smith decided to document this study, devastated by what he observed on his trip to the Saudi Arabian Red Sea reefs. He visited the reefs on three consecutive occasions between 2022 and 2024. With this research, he hopes that local experts will strengthen the conservation efforts.

Meanwhile, Theresa Rueger, Newcastle University, is joking that Pixar-Disney should bring a new chapter of Finding Nemo, inspired by this dramatic episode. "The movie told a really good story, but the next chapter of the story surely is, how does Nemo deal with ongoing environmental change?" she told BBC News.
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