Circulating on Facebook today is a photo (above) of 530-kg Inuka, a polar bear at the Singapore Zoo covered in algae.

Commenters were quick to register their unhappiness that the polar bear looks listless and is in the wrong colour.

Others were quick to defend the existence of green polar bears in a tropical zoo.

For the record, green polar bears are not new.

A BBC report from 10 years ago had already mentioned this phenomenon of green polar bears in Singapore.

The two polar bears in the zoo at that time, 13-year-old Inuka and his mother Sheba, were subjected to bleaching with a hydrogen-peroxide solution to remove the algae.

In fact, polar bear fur turning green as a result of algae growth in warm climates has been documented and explained before.

So, it is highly possible that the recent warm temperatures in Singapore could be contributing to the green-ness of the Singapore Zoo's only polar bear.

Inuka is currently 23 years old. He is Singapore's most well-known polar bear -- touted as the world’s first polar bear born in the tropics -- and serves as the Singapore Zoo's mascot.

Other Facebook users have since showcased their own photos of a green Inuka:

Source: Kaoru Nazuki Tsutomu

Source: Huiqi Bunny Zheng

A routine medical examination on Nov. 4, 2013, has found that Inuka is suffering from mild arthritis on his ankle and right wrist joints of his lower limbs and some harmless warty growths on the underside of his tongue.

Other than that he seems healthy.

But Inuka's existence in Singapore Zoo is not without controversy.

Local group Acres (Animal Concerns Research and Education Society) had been advocating since 2010 for polar bears to be phased out from tropical zoos as the climate here is not suitable.

But it does not appear to be happening any time soon as the Singapore Zoo has recently opened its Frozen Tundra exhibit.

Top photo from Lynn Lam Facebook