Deck fountain PVC pipe green algae

[waterbear]

So we recently purchased this house with a pool and there is a PVC pipe directed straight up uncovered towards the sky.

Any idea why? Can you post a pic? Most deck jets are not just plain PVC and are buired in the deck in a box. Sounds like itwas a place where there was some type of water feature that was removed or possibly a hookup for a slide.