Pond Boss Forums AQUATIC VEGETATION Identifying plants Film over the pond

Update on "Film Over The Pond". Here are results and comments to Bennie after examining water with film from his pond.

Most of the stuff based on biovolume in your last sample you sent was dead organics (detritus) - see attached No 1. During all my scans of the sample I did not see one recognizable pollen grain.

From no or low magnification, it mostly looks like brown 'dirt'. Usually the films that have a strong color are mostly composed of small celled algae either as single cells, colonies or filaments. Your sample was not the typical bloom-film conditions. On higher magnification there were numerous small algae present but they did not make up the majority of the sample. The dominant living cells in your sample were a type of single celled green algae (attached No 2). I was not able to identify specifically what they were because I am pretty sure they were in a resting stage (probably stressed) and not actively growing. Single celled flagellated green algae can often go into a resting stage and then they all look basically alike. I think they were a resting stage of Tetraselmis cordiformis (old name: Carteria) or maybe some species of Chlamydomonas sp. Both can form thin green surface films. Numerous other algae species can also form green films. I saw a few regular or normal celled Tetraselmis in the sample. The single celled alga contributed to most of the green color of the film.

I suppose it is not unusual to periodically have lots of dead organics on a pond surface esp when the pond is old and has a large input of decomposing organic materials such as leaves and organics from the watershed and those that have grown in the pond. Warm water(80+F), calm conditions or no wind trends to favor development of films and scums on pond surfaces. Low density dead organics can sometimes easily move into the water column and eventually float. Sometimes films are mostly dead stuff and sometimes mostly living stuff depending on conditions. If you would have collected the sample early in the development of the film the living stuff would have been 'fresher' and easier to identify or verify what was growing. The heavy rain and weather that occurred and broke up the film could have altered the condition of cells in the film/scum.

Let me know if you have any questions.