Kelly, 38, had been ill for several days and died last night.
Mrs Arnott said Marineland did not open for business today and the council, which owned the park, would hold a special consultation process with the community to decide whether it would continue without its trademark dolphins.
"For Napier and New Zealand it's the end of an era. For Marineland staff they are really grieving for a member of the family who has been there for 34 years."
Marineland nearly closed two years ago after the death of another dolphin, Shona.
"We were originally going to shut it after Shona died, but because Kelly was happy to carry on it remained open," Mrs Arnott said.
"(We were) thinking Kelly would be really lonely without Shona but she soldiered on. "So two 1/2 years after Shona died, Kelly -- at the great age of 38 -- has succumbed." Both dolphins had been at Marineland since 1974.
The Marineland website said the normal life expectancy for a common dolphin was 15 to 18 years.
