Landoltia punctata is in the same family as Lemna disperma and superficially looks very similar to the latter. Landoltia punctata is distinguished by each thallus having several roots and at least 3 veins obvious on the upper surface. The thallus is purple on its underside, and has a purple edge from above. Lemna disperma was also present in the same area. Sorry the photo isn't particularly good, but it shows the keys features.