Im Roten Meer verschwinden Clownfische, wenn Anemonen bleichen. Eine Meereshitzewelle im zentralen Roten Meer im Jahr 2023 führte dazu, dass 100 % der überwachten Seeanemonen ausbleichten, gefolgt vom Tod von 94–100 % der Clownfische und 66–94 % der Anemonen an drei untersuchten Riffen.

When Morgan Bennett-Smith descended to a familiar reef in the central Red Sea in September 2023, he expected to find the same tagged anemones and resident clownfish he had been monitoring for months. Instead, he found a ghostly landscape: every anemone had turned white, and most of the bright-orange fish that had been sheltering in protective tentacles just weeks earlier were gone.

By the following spring, the reef looked even worse. Of the 168 clownfish Bennett-Smith and his colleagues had counted in December 2022, only seven remained.

A new study, published in npj Biodiversity, documents the effects of a marine heat wave across three reefs in the Red Sea. First, all the anemones bleached. Then, 94-100% of the clownfish disappeared. Finally, 66-94% of the anemones died. The events represent the near-total local collapse of a mutualism that had endured for millions of years.

Between 2022 and 2024, researchers tracked 168 Red Sea clownfish (Amphiprion bicinctus) and 143 host magnificent sea anemones (Radianthus magnifica) through a 2023 marine heat wave that peaked at approximately 22 degree heating weeks, a measure of accumulated heat stress.

The findings challenge a long-held belief that the Red Sea might be a thermal refuge, or safe haven, from the impacts of climate change. Scientists thought that because Red Sea organisms already live in naturally hot water, they would handle rising temperatures better than marine life in cooler regions.

“The thinking is that, because those temperatures are naturally already higher, that the species in this body of water are adapted to higher temperature,” Bennett-Smith, a Ph.D. candidate at Boston University in the U.S., who led the research, told Mongabay. “Unfortunately, what we found is just like everywhere else, that already higher temperatures in the Red Sea are also increasing.”

https://www.nature.com/articles/s44185-025-00107-4

Well this is depressing. Coextinctions drive ecological collapse. It’s never just 1 species.