Azolla commonly known by various names such as Red Azolla, duckweed fern, fairy moss, and water fern with about six or seven species; some placing it in its own family Azollaceae others put it in a related family Salviniaceae.  Azolla resembles duck weeds locally called Mangolae, but is differs from it in structure, size and in morphology. The plant that has infested our crystal clear waters is identified as Azolla filiculoids.  Occurance of A. pinnata in our water bodies has already been refuted.  Azolla species are difficult to identify because of the mess created by the systematists, in merging and separating them and creating sub species. This has led to many misidentifications, confusion and thus uncertainty over correct identification. Three species Azolla microphylla,  A. mexicana，A. caroliniana are regarded as synonyms of A. cristata. Similarly.  A. caroliniana and A. microphylla are synonyms of the previously described A. filiculoides. The taxonomy of the New World species of Azolla has been the subject of much debate and remains unsatisfactory.
A. Filiculoids is mostly temperate or subtropical water fern compared to A cristata which is mostly tropical, less suitable for our temperate conditions. A. cristata is restricted in distribution compared to A. filiculoids which is cosmopolitan, easily infests new regions when carried by agents like water fowls and other migratory birds. The only ultramicroscopic difference between the two is that in A. filiculoids the hair like projection with the hooked tip (glochdia) arising from the mucilaginous extension (massulae) surrounding micro and megaspores and helping in buoyancy is up to 2 septa, while in A. cristata it is sometimes above two septa. It can be an ecological variation and is of less importance. Similarly its change of colouration is an ecological  variation, so cannot be distinguished even into subspecies etc. Our main goal is the eradication or to keep this alien invasive under control so that it will not further add stress to our water bodies which are already debilitated.
Azolla, is an invasive alien noxious water weed that has recently invaded all our wetlands and water bodies with prolific growth and has formed thick deep green or red mats in every nook and corner of all valley lakes. This year it was also reported in Manasbal lake for the first time and from Kondabal side it is in thick mats. Its early stages are green, but gradually turn red when continuously exposed to sunlight and reaches to maturation stage producing sporocarps.
Azolla though noxious and a health hazard is not harmful in many parts of the world but has been made beneficial to the aquatic environment in many ways. It was used as green fertilizer since times immemorial in Asia particularly in China from 540 AD (Chinese book of Agricultural techniques). Cynobacterium (Anbeana azollae) living as a symbiotic within thallus of Azolla helps to fix atmospheric nitrogen, converting it to ammonia and then nitrates, so it was used in paddy fields in European and African countries to increase rice yield. It is a beneficial biofertiliser and has many advantages over chemical nitrogenous fertilizers, being cheap, natural, safe and sustainable. Besides it also supplies additional nutrients to the crop and also improves soil structure. There is no run off to harm environment unlike chemical fertilizers.  It is much helpful to remove nitrogenous compounds and being capable of absorbing heavy metals like lead and zinc from waste waters as well as from the environment. There are many other uses of Azolla such as it is the best livestock feed, supplement for cattle, chicken and ducks. When its thick layer covers the surface of water, it prevents mosquitoes to lay eggs and their larvae to breathe, hence also called mosquito fern. It is also considered as aesthetic plant and is cultivated in park pools because of its seasonal green or red colourations. It is also food source to various water fowls, insects, worms, snails and various crustaceans, besides providing them shelter. Thick mats of it also restrict exotic aquatic weeds to flourish. But why is it detrimental in our water bodies and is of no use is a question to ponder.

Lastupdate on : Mon, 24 Sep 2012 21:30:00 Makkah time
Lastupdate on : Mon, 24 Sep 2012 18:30:00 GMT
Lastupdate on : Tue, 25 Sep 2012 00:00:00 IST