Marine biologists are investigating a mystery skin disease on whitetip reef sharks in Malaysia. Some early reports say that rising sea temperatures could be to blame.
Whitetip reef sharks usually rest around reefs during the day, and become active at night to hunt for small fish and other animals.
Pictures of one of the sharks with what appeared to be spots and wounds on its head went viral on social media in April. An underwater photographer took it off Sabah state on Borneo island.
Soon after, divers at Sipadan island began seeing the skin disease in every group of sharks they encountered.
Attempting to diagnose what could be causing the illness, researchers found the sea surface temperature at Sipadan had risen to 29.5 degrees Celsius in May, a degree higher than in 1985.
“We can almost certainly pin the warming ocean as having a role in what we are seeing with the sickly sharks in Sipadan,” said Davies Austin Spiji, a senior marine biologist with the conservation group Reef Guardian.
Sipadan is a marine protected area where fishing is strictly prohibited, and there are no settlements or industries nearby, so those could not be the cause, Spiji said.
“We cannot ignore that changes are happening there due to higher temperatures,” Mohamed Shariff Mohamed Din, a professor in aquatic veterinary studies with Universiti Putra Malaysia, said.
He added that the sightings of sharks with skin disease happened at the same time as reports of coral bleaching in the area. When water is too warm, corals will throw out the algae living in their tissues, causing the coral to turn completely white.
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