Whoops, sorry about the year! I changed it to 2011!
This exhibit is for alligators so I don't think they'll be eating too much of the duckweed. By cleaning up I meant to say that I'm pretty sure they dredged the exhibit and cleaned out some of the muck that had been building up.
I really like the use of props in this exhibit, the tire swing and the "no swimming" sign. The outhouse is cool too. These zoo designers have a good sense of humor that enhances the exhibits nicely.