Animal rights activists and SeaWorld supporters faced off at a California Coastal Commission meeting which decided to allow SeaWorld San Diego to expand its killer whale tanks. The commission approved the $100m (£65.07m) expansion of the tanks on 8 October, but it banned breeding of the captive orcas that would live in them.

The People for the Ethical Treatment of Animals (Peta) demonstration was led by actress Pamela Anderson, an avid animal rights activist. "SeaWorld is just trying to make money, trying to make money off of vulnerable animals and it's pathetic," said Anderson.

Executives at the theme park wanted to build two orca pools, one filled with 5.2m gallons of water and the other with a capacity of 450,000 gallons, to replace the current 1.7m gallon tank. Animal rights groups that have been trying for years to get the orcas released into the wild argue that the whales might have larger tanks under the SeaWorld plan but would still be captive.

"The orcas at SeaWorld are suffering," said Peta's director of animal law, Jared Goodman. "They are kept in woefully inadequate conditions that prohibit them from engaging in any of their natural behaviours. They can't swim meaningful distances, they can't dive and this drives them crazy. They break their teeth biting on the sides of the tanks, they attack each other and kill trainers, something that never happens in the wild, and this is because they're driven crazy by captivity."

However, SeaWorld San Diego veterinarian Dr Hendrik Nollens disputed Peta's accusations, saying the whales at the park are not only safe, but have healthier lives than those in the wild. Nollens said: "The animals at SeaWorld don't face many of the factors that cause stress in the wild, and in fact, when scientists study stress, they use samples from animals at aquariums as baseline non-stress samples.

"Killer whales naturally develop worn teeth regardless of whether they're in the wild or at SeaWorld. They explore and manipulate their environment with their mouth which leads to dental wear. Many wild whales have been found stranded, dead, with worn, infected and abscessed teeth. Unlike wild killer whales, we provide comprehensive medical care, comprehensive dental care which is primarily based in prevention."