Sea urchins can tolerate hot, acidic ocean water

Black sea urchins in the Mediterranean Sea can withstand hot, acidic water that is high in carbon dioxide, according to a new study from the University of Sydney. The urchins have been living off the coast of Ischia – a volcanic island in the Gulf of Naples – for at least three decades.

The experts are studying this resilient population of sea creatures to predict how animals may or may not survive the future oceanic conditions associated with climate change, pollution, and global warming.

The researchers have discovered that the urchins can tolerate unprecedentedly warm sea temperatures, which means that they will likely expand their range as the ocean continues to heat up. The experts noted that the Mediterranean Sea is warming 20 percent faster than the global average, and is expected to warm up by 5.8°C this century.

“Given their ability to withstand a large temperature range, these sea urchins are likely to continue spreading throughout the Mediterranean Sea, with serious consequences for coastal habitats,” said lead researcher and marine biologist Dr.  Shawna Foo.

Sea urchins are fast-spreading and can be very destructive. They are known to ravage underwater kelp forests, leaving behind a barren seafloor that can no longer support other marine species that rely on kelp for food or shelter

Along the southeast coast of Australia, the long-spined sea urchin has multiplied and has expanded from New South Wales to Tasmania, destroying kelp forests along the way. In this region, the negative impacts threaten abalone and lobster farms.

The study was focused on populations of urchins living in and outside CO2 vents. The team exposed lab-fertilized embryos to a wide range of temperatures from 16 to 34 degrees Celsius. Off the coast of Ischia, the water is typically 24 degrees Celsius.

The results showed that 24-hour-old embryos from the low pH-acclimated urchins (from the vents) could withstand a greater temperature range than those living in normal pH levels. 

“We didn’t know if acclimating to one stress – high CO2 levels – would mean the urchins would be more susceptible to other stressors, such as warming,” said Dr. Foo. “You could compare it to humans not performing as well at work when they’re really stressed out. Yet our results show that living in a low pH environment didn’t create any trade-offs.”

On the bright side, Dr. Foo said the vent urchins’ superpower survival abilities may offer insights into adaptations other animals might need to survive as the oceans warm and become more acidic, for example, by determining the genes responsible for their high stress tolerance.

“We’re lucky to have the opportunity to work in such a unique system with low pH-acclimated animals. They give us a glimpse into the state of organisms and ecosystems in a future ocean.”

The study is published in the journal Biology Letters.

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By Chrissy Sexton, Earth.com Staff Writer