One by one, four California sea lions slipped out of their transport crates and glided into the cool Pacific waters, just off the Southern California coastline.

The SeaWorld San Diego rescue vessel floated nearby, its crew watching intently as the animals re-entered their natural habitat.

Almost immediately, one of the sea lions dove beneath the surface and resurfaced moments later with what looked like a squid dangling from his jaws — a promising sign of a successful return to foraging in the wild.

Jeni Smith, SeaWorld’s rescue and rehabilitation curator, stood on deck with a broad smile. “We had a pep talk before they went in,” she said, laughing.

“I told them, ‘No more of those toxic fish, alright? Go find the good ones!’” Her words, though lighthearted, reflected the serious reality behind the release.

Wednesday’s release marked a hopeful milestone in an ongoing struggle against a dangerous algae bloom that has swept along the California coast from San Luis Obispo to San Diego.

The bloom has poisoned the ocean food chain, sickening and killing hundreds of marine animals.

Three of the four sea lions set free that day had been rescued and treated for domoic acid poisoning — one of them had been found convulsing, an unmistakable and disturbing symptom of exposure to the powerful neurotoxin.

Since the toxic bloom began in late February, a wide variety of marine life — including seabirds, dolphins, sea lions, and even large whales — has been impacted.

The toll has been staggering. On one bleak Sunday, marine response teams recovered 16 dead dolphins from beaches around San Diego.

The situation grew so dire that the National Oceanic and Atmospheric Administration’s Marine Fisheries Science Center ran out of space to store carcasses and turned to SeaWorld for help.

The park stored eight deceased dolphins in its facilities so that necropsies could be performed.

Tissue and organ samples from these animals were shipped to a Seattle laboratory for toxicology testing.

Preliminary results from 14 tested dolphins revealed that 11 had dangerously high levels of domoic acid in their systems.

“In all my years here, I’ve never seen anything like this,” Smith said during an interview last week.

“We were heading up to Carlsbad to help a sea lion in distress, and on the way, we passed a pelican that had already died on the side of the road. It’s like the coastline is littered with the casualties.

We’re constantly fielding calls and reporting locations of deceased animals to Southwest Fisheries, but honestly, it’s overwhelming.”

The bloom behind this devastation is caused by a species of microscopic algae known as Pseudo-nitzschia, which has flourished along California’s coast for four consecutive years.

Under certain environmental conditions, Pseudo-nitzschia produces domoic acid, a potent neurotoxin that accumulates in filter-feeding fish such as anchovies and sardines.

These fish, in turn, become toxic to predators — especially marine mammals and seabirds — that rely on them for food.

The neurological effects of domoic acid are serious and, in some cases, fatal.

The toxin can cause disorientation, seizures, and cardiac problems in sea lions, often leading to erratic or aggressive behavior toward humans in the water.

The danger extends to even larger marine life: necropsy results confirmed high concentrations of domoic acid in a humpback whale that stranded in Huntington Beach in January, and in a minke whale that washed up dead in Long Beach Harbor in April.

While the release of the four sea lions is a small victory, it underscores the critical need for ongoing monitoring and environmental action as climate shifts and ocean conditions continue to fuel harmful algal blooms.

Every animal saved is a testament to the dedication of rescue teams — and a reminder of the fragility of life along the California coast.