Less than two weeks after the birth of two polar bear cubs at Sea World on the Gold Coast, one has died.

The cubs were born on Wednesday April 26 weighing approximately 600 grams and had been expected to be on display to the public in September.

However, Sea World director of marine sciences Trevor Long said concerns about the smaller cub's health were raised on Thursday after it stopped growing at a healthy rate when mother Liya focused her attention on the other cub.

The situation improved on Friday but went downhill again on Saturday.