Taken March 21, 2007 looking down into the water from the round overlook that extends into the swamp, shown first row center and last row far-right.

The swamp at The Phoenix Zoo is very large, and it used to be the old alligator habitat. In the words of my Aunt Margaret in a recent message: "Uncle Bill and Bill Mangino designed the old alligator enclosure as one of many architects who donated their time and design to the zoo. There were bronze plaques with names at each place and Uncle Bill's and Bill Mangino's names were at the old alligator pit." I became aware of the duckweed in Fall 2003. Since that time, the zoo has made several attempts to remove it from the swamp. It eventually reached the water in the Ant-eater exhibit nearby, also, the pond in Monkey Village. Each time a group of flying fowl has made the swamp their home, they have been relocated. The ducks shown in the first few rows of images were relocated because one duck turned up without a foot, causing concern that there was a snapping turtle living in the waters of the swamp, hidden by the duckweed. Much later residents, the swans were relocated to a different zoo prior to another removal campaign. Over time, the duckweed invasions and control have become a saga that is still unfolding as of September 2007. March 21, 2007 Update: aquatic ecologist Matt Dodson emailed me with a possible solution for eliminating the duckweed. Pertinent content of Matt's email can be seen verbatim at the bottom of this page. I have also passed his information along to the zoo. September 30, 2007 Update: Visited the Phoenix Zoo today and noticed that the duckweed has again become thick in the swamp. I was curious if the above-referenced treatment had ever been tried, so I called their lead horticulturist Scott Frische. He said they haven't tried the treatment yet, but are considering it as well as another possibility of using carp to eat the duckweed. The big lake at the zoo is already saturated with one breed of carp, koi, that might be used. They are very colorful and children love to look for them swimming around in the water, the paying public might welcome this addition to the swamp (my thoughts). The duckweed will have to be a little thinner to try the koi as a solution, though, because with complete coverage the water will be oxygen-depleted and the fish might suffocate at night. Unless I am mistaken, koi are present in the Monkey Village pond, perhaps they have played a role in preventing the duckweed from taking over in that location...? If the zoo is unable to implement this natural solution, they plan to try Matt Dodson's environmentally friendly suggestion. For now, the duckweed is every bit as thick as shown in the first few rows of pictures taken in 2003 when the ducks were in residence.

The timetime for the initial sets of pictures (the row above and seven below) is between November 2003 and January 2004, before the first big campaign to rid the swamp of the duckweed. The image on the far right reveals a clear spot behind the palms where there was more circulation in the water (duckweed cannot thrive where water is circulating) at a location about halfway up the bridge and to the right.

In the pictures above, a horticulturist from the Phoenix Zoo reached into the swamp to gather some Duckweed on his hands for up-close pictures. It looks like a small clover. It sits on top of the water. There is very little branching off the root, since there is no need to hunt for water

Some of the pictures show the quiet of the area nicely. It is overall very peaceful, with moments of unrest. The middle image shows what appears to be two ducks facing off after a flurry of preceding activity. Only a small group of ducks has chosen this area of the zoo to live in.

This is the only page on my site with no mathematical models in the pictures. I have included it because of the fractal boundary patterns the duckweed makes in the water: duckweed fractal coastlines, if you will. Fractal properties (parts that are similar to the whole) are visible in almost all nature photographs, simple to identify once one knows what to look for.

These images show a nearly complete invasion of the water and banks of the swamp by the Duckweed. I like the way it is a tattletale. Even after it closes back in on itself, it leaves a visible seam where it was breached.

Although an extraordinarily clean plant with no toxic by-products, during the night when no photosynthesis is taking place, it depletes the water of needed oxygen, causing some water life including fish to suffocate. Notice the clumping of the Duckweed on broken tree branches sticking out of the water. This is what initially attracted me to it. I can't say for sure, but this is likely an instance of a fractal property called diffusion limited aggregation, or DLA.

The middle and right images were taken at the same spot shown in the first row, far-right image, where the swamp has good water circulation.

This ends the images taken between November 2003 and January 2004. What follows are images all taken the same day in April 2005 after the duckweed was again in full swing. A group of swans had taken up residence, pictures of them follow, along with many turtles. I had unfortunately stopped visiting the exhibit and was very lucky to revisit the area in time to take pictures of these swans. About a week later they were relocated to a different zoo during the second major attempt (that I am aware of) to rid the swamp of the duckweed.

Notice in the pictures shown above, that the duckweed is plentiful but there are also areas where it is barely present. It was heavy before the impending removal, but not as heavy as it has been in times past. The pictures below were taken on September 29, 2006, and as you can see, the duckweed has absolutely taken over again! There is not a breath of water visible in the swamp. There is a new group of birds in residence, athough, they don't appear to land on the duckweed. They stick their narrow beaks into it, but this may be to get to the water below. There are a few turtles that I observed living in the swamp. The turtles in these pictures are located in the same spot as the turtles in the previous set of pictures. They are sitting on the same log. The enclosure surrounding the swamp is the Capybaras and Pelican exhibit, although I have yet to see either of them in the swamp or near its edges.

This ends the representative images I have to date of the changing states of the duckweed in the swamp at the Phoenix Zoo. The conversation is not over, I wonder if the zoo isn't stuck with it for the duration, with the best they can do being to (try to) control it. See updates at top of page, a synopsis of this saga precedes the images.

Here is to the ducks and swans of recent years past, to the alligators way back when, and finally, to my late Uncle Bill Scarbro and his partner, Bill Mangino, for designing the old 'alligator' exhibit. The bridge approaching the overlook is shown in the first row of pictures. The circular overlook actually extends out into the swamp and is shown in the picture above-right.

Duckweed solution proposed by Matt Dodson, in his words:

"I found your webpage on the Phoenix Zoo duckweed problem when I was doing a Google Image search for duckweed pictures, and I wanted to share a solution to their problem. I am an aquatic ecologist who specializes in environmentally responsible aquatic weed control and in my line of work we deal with infestations of this nature regularly.

"The duckweed (Lemma spp.) and water fern (Azolla spp.) which was also pictured could easily be brought under control with a low level application of the systemic herbicide SONAR, which contains the active ingredient Fluridone. This product blocks the biosynthesis of carotenoid accessory pigments that protect the chlorophyll in the plants. With this protection gone, the chlorophyll quickly photodegrades rendering the plant unable to produce food via photosynthesis. The real beauty of this product is the extremely low concentration at which it is effective. SONAR is effective at the parts per BILLION range. Duckweed can be controlled by maintaining a concentration of only 50 ppb for a period of 45 days. The SePRO Corporation which manufactures SONAR offers a service known as Fastest where you send in a water sample and they tell you the fluridone concentration so that you can supplement your application accordingly to maintain the desired concentration.

"SONAR would provide the ideal solution to the Zoo’s problem for a number of reasons. At the ppb concentrations the product would pose no threat to the resident animals. The systemic nature of fluridone’s action makes for a longer term control and more complete extirpation of the target population. The gradual death of the target population prevents the sudden drop in dissolved oxygen that could result in a fish kill.

"Please forward this information to your contacts at the Zoo. If they need to obtain the necessary product they can contact me or a local SePRO aquatic application specialist. We can sell them the product to apply themselves if they have appropriately licensed employees, or they may need to contract a for hire aquatics applicator to handle the job for them.

Regards,
Matt Dodson
Aquatic Ecologist
Virginia Lake Management Company