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“Sea lions must swim farther and deeper for Dr. Mike Adkesson performed an
food, which is especially difficult for endoscopic exam on Carolyn California
weaned yearlings like Carolyn and Sabiena.” Sea Lion shortly after she arrived at the
Also, sea lions must leave their rookeries for zoo’s hospital. He removed pieces of
longer periods of time to find food, causing plastic and three more rocks from her
their pups to starve. stomach (left). Swallowing rocks is a sign
of starvation.
Ocean warming may be contributing
to another hazard. “Domoic acid toxicosis BROOKFIELD ZOO | SPRING 2020 17
is a significant problem in the California
marine ecosystem,” said Dr. Michael
Adkesson, vice president of clinical medi-
cine at CZS. Domoic acid is a neurotoxin
that primarily attacks an animal’s brain
causing disorientation, lethargy, seizures,
and death, if not treated. The toxin is pro-
duced by several species of algae that thrive
in water that is warmer than normal or
contaminated by nutrient and sewage run-
off. It accumulates in the bodies of fish and
shellfish that are eaten by marine mammals.

Harmful algal blooms, or “red tides,”
have grown larger and more frequent, said
Stacey. Domoic acid is also toxic to fish,
seals, dolphins, whales, marine birds, and
humans. Ingesting contaminated shellfish
can cause amnesiac shellfish poisoning, a
life-threatening condition. Human lives
have been saved because public health offi-
cials were quickly notified when sea lions
poisoned by domoic acid were discovered.

Ocean Debris

Each year millions of tons of debris enter
the ocean—including more than 8 million
tons of plastic—according to the Ocean
Conservancy. This includes single-use
plastic bags, bottles, cups, cutlery; cigarette
butts; soda cans; and fishing gear.

“Plastic in our ocean is a growing and
significant problem for all marine wildlife,”
said Dr. Adkesson. When swallowed,
“it can cause digestive obstructions and
trauma to the stomach and intestines.”

Also, animals that become entangled
in ocean debris are often injured, maimed,
or drowned. Lost or discarded fishing
gear—line, pots, traps, nets, and hooks—is
especially dangerous. Sabiena had multiple
fish hooks in her body, including one in an
eye that caused so much damage the eye
needed to be removed.