What’s driving thousands of South African seal deaths?

Over the past six months, thousands of Cape fur seals (Arctocephalus pusillus) have been turning up dead on South Africa’s Atlantic Coast. No one is sure why, but Tess Gridley, a scientist who ordinarily studies bioacoustics, is determined to find out.

“Seals are just gone from whole areas of coast, and no one has batted an eye,” Gridley told the Washington Post. “I’m filling a gap because it seems nobody else will.”

Gridley suspects the culprit is domoic acid, a substance released in algae blooms, which can spike due to warming waters and agricultural runoff. The acid is ingested by plankton and moves up through the food web. Similar die-offs have been seen among sea lions in California due to the chemical. California now tests ocean water and marine organism for the toxin.

Read more from the Washington Post.