The pelicans like to do a few laps every morning. Seriously though, I think that those light-coloured lines are a reflection of the roof's overhang on the water.
California sea lions were the original inhabitants of this exhibit, which was built in the 1930's and is still standing today. The pinnipeds were moved into a brand-new exhibit in the "Northwest Passage" part of the zoo in 2006 and pelicans were placed in the 1930's pool.
