SAN DIEGO — For the last two weeks, an algae bloom has dazzled crowds and lit up waves in Southern California. But now, scientists say it’s turning deadly for some fish, and they want to know why.

Scientists say there are a few possibilities that might explain the reason for a foul odor.

Clarissa Anderson from Scripps Institution of Oceanography says algal blooms, or red tides, are common and happen in spring and late summer. But she says this particular bloom, spanning from Los Angeles to Baja, is huge.

“This scale where it’s this extensive and this long is once every five or 10 years and this one might even be historic,” Anderson said.

It’s causing marine life as small as snails and as large as calico bass to die, most likely because the algae is sucking up the oxygen in the water, or because it could be producing hydrogen sulfide.

“Then there’s a third thing that we want to rule out, and that is that this algae that produced the bloom has been known to produce a toxin and even in California it did, at one point, kill off some invertebrates in a big event in 2011,” Anderson said.

While scientists try to figure it out, joggers are left waiting it out, hoping the smell will at least go away soon.