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An algal bloom near California’s coast has caused usually friendly sea lions to become aggressive and attack humans — a behaviour that has been reported to be unprecedented and ‘demonic’.
An adult male sea lion weighs up to 300 kilogrammes and when such an animal resorts to aggression towards humans, the results can be lethal. There have been dozens of isolated cases where surfers and beach goers have been bit by the sea lions but fortunately, no death has been reported so far.
What is really heartbreaking is that these animals aren’t attacking humans because they want to. Instead, a neurotoxin released by the algal bloom is altering their neural networks and causing them to experience unbearable stress, aggression, muscle spasms and permanent brain damage.
Domoic acid — which is secreted by the algae diatom Pseudo-nitzschia — is a known marine neurotoxin that enters the food chain and affects not just small fishes but also larger animals that feed on these fishes. Consequently, thousands of sick sea lions are found to be lying on the Californian beaches and are attacking humans in vicinity.
Kathi Lefebvre, a research biologist with America’s National Oceanic and Atmospheric Administration (NOAA) fisheries who has been studying domoic acid in marine mammals since 1998, told National Geographic that the domoic acid overstimulates the nerves in animals which causes them to exhibit aggression.
What is even more concerning is that the neurotoxin can eventually reach humans too and in high amounts, it is a lethal poison.
Prior observations across the world establish that algal blooms happen when the marine waters suddenly undergo an accumulation of nutrients that foster the growth of algae.
Upwelling, a marine phenomenon that causes nutrient-rich deep waters to rise to the surface, is a major contributor to the algal bloom. This upwelling is majorly caused by high speed winds which are on the rise due to global warming which causes turbulence in the waters. Additionally, releasing effluents into the oceans also contributes to such blooms as chemical waste contains the much needed nutrients which toxic algae thrive on.
“This is the fourth year in a row with an algae bloom affecting Southern California marine life. There is often little that responders can do to help dolphins, but they can bring some California sea lions into authorised rehabilitation facilities,” NOAA has mentioned in an article titled Early Bloom of Toxic Algae off Southern California Sickens Hundreds of Sea Lions and Dolphins.
Interestingly, another aspect of climate change, the recently extinguished Californian wildfires are also touted to have contributed to the crisis.
It is reported that researchers believe that runoff from wildfires in Los Angeles also disturbed the marine ecology along the California coast, triggering the bloom of toxic algae.