The California sea lion can be seen diving and frolicking in coastal waters, barking and jostling with each other on beaches, and lounging on sunny piers. Humans have a lot more in common with sea lions than meets the eye. We're both mammals, we give birth to live young, we're highly social, and we also eat some of the same kinds of fish. That's important to many scientists, because when sea lions get sick from their diet it may have the same effect on humans. And sea lions have been getting sick - very sick. Each year, the number of sea lions that strand on California beaches has increased dramatically. Frances Gulland, Veterinary Director of the Marine Mammal Center and a NOAA partner, has been on the forefront of understanding these strandings. The Center rescues and rehabilitates sick sea lions and has traced one of the causes to harmful algal bloom-related illnesses. All sea water contains microscopic algae. Algae are normally beneficial because they form the base of all marine food chains. But just like plants on land, some algae produce toxins, which build up in fish or shellfish. In the past, only a few regions of the U.S. were affected by harmful algal blooms, but now most coastal states have reported major outbreaks. One of these algae, known as pseudo-nitzchia, can produce a potent neurotoxin called domoic acid, which is invisible to the naked eye. Fish eat the toxic algae and sea lions eat the fish. The domoic acid enters the sea lion's bloodstream and damages it's brain, causing tremors, seizures, and disorientation. By studying sea lions, scientists can better understand how this toxin may affect other mammals, including humans. Domoic acid can also build up in shellfish. While rare, people who eat toxic shellfish can develop what is called amnesic shellfish poisoning. This may result in permanent short-term memory loss, brain damage, and in severe cases, death. NOAA and its partners have developed new tools to improve monitoring and prediction of harmful algal toxins. This allows state managers to close shellfish beds before and during an outbreak, and prevent people from consuming toxic shellfish. By studying how domoic acid affects sea lions, we can gain a better understanding of how it affects humans and how to treat exposure to toxic seafood.
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Sick Sea Lions Signal Susceptible Humans

Credit: NOAA