A harmful algal bloom (HAB) near California (USA) has caused thousands of sea lions to become ill and aggressive, with some attacking nearby humans. The culprit is Domoic acid, a neurotoxin released by the algae diatom Pseudo-nitzschia, which blooms explosively under certain conditions.
How Domoic Acid Affects Sea Lions
- Domoic acid enters the marine food chain via small fish that eat the algae.
- Sea lions, which feed on those fish, ingest the toxin in large amounts.
- The toxin overstimulates neurons, causing:
- Unbearable stress
- Aggression
- Muscle spasms
- Seizures
- Permanent brain damage
- This isn’t intentional aggression — it’s neurological distress.
What Are Harmful Algal Blooms (HABs)?
- HABs are explosive growths of algae that release toxins or deplete oxygen, harming:
- Fish and shellfish
- Marine mammals (like sea lions, whales, dolphins)
- Birds
- Humans (via seafood poisoning or beach exposure)
- They’re natural phenomena, but are becoming more frequent and severe due to human activity and climate change.
Causes of HABs?
- Upwelling: Brings nutrient-rich deep water to the surface — ideal for algae growth.
- Pollution: Runoff and effluents (especially agricultural fertilizers and chemical waste) feed algal blooms.
- Climate factors: Rising sea surface temperatures, sluggish water circulation, and extreme weather events like hurricanes and floods have all been linked to more frequent and intense HABs.
(Sources: DOE & NOAA)
