Cladophora

Cladophora is a genus of reticulated filamentous Ulvophyceae (green algae). The genus Cladophora contains many species that are very hard to tell apart and classify, mainly because of the great variation in their appearances, which is affected by habitat, age and environmental conditions.^[1] Unlike Spirogyra the filaments of Cladophora branch and do not undergo conjugation. There are two multicellular stages in its life cycle – a haploid gametophyte and a diploid sporophyte – which look highly similar. The only way to tell the two stages apart is to either count their chromosomes, or examine their offspring. The haploid gametophyte produces haploid gametes by mitosis and the diploid sporophyte produces haploid spores by meiosis. The only visible difference between the gametes and spores of Cladophora is that the gametes have two flagella and the spores have four. The Cladophora species can be a major nuisance causing major alteration to benthic conditions linked particularly with increased phosphorus loading.

Cladophora balls are formed from the filaments of the alga^[2] which are photosynthetic. Large numbers of these balls were thrown ashore in Devon, England. They had an average diameter of 2.5 cm and several million balls were found forming a layer.^[3]

This is not to be confused with marimo, though formerly part of Cladophora, is now called Aegagropila linnaei.

In Laos, Cladophora spp. (ໄຄ [kʰáj] "river weed" or more precisely ໄຄຫີນ [kʰáj hǐːn] "rock river weed") are commonly eaten as a delicacy and usually known in English under the name "Mekong weed". The algae grow on underwater rocks and thrive in clear spots of water in the Mekong river basin. They are harvested 1 to 5 months a year and most often eaten in dry sheets (ໄຄແຜ່ນ [kʰáj pʰɛ̄ːn] kaipen -kháy sheets-), similar to Crispy Chinese Seaweed or Japanese nori, though much cruder in their format. Luang Prabang's speciality is dry khai with sesame (kaipen), while Vang Vieng is famous for its roasted kháy sheets. They can be eaten in strips as an appetizer, with a meal or as a snack with Beer Lao. Luang Prabang kháy sheets kaipen are the most readily available form of Mekong weed and are famous throughout the country and in the neighbouring Isaan, though difficult to find beyond Vientiane. Mekong weed can also be eaten raw, in soups, or cooked in steamed curries (Lao: ຫມົກໄຄ, [mók kʰáj]).

The genus Cladophora is cosmopolitan and accordingly infestations cannot often be regarded logically as being invasive. Where they occur they may at various times be seen as beneficial, as a nuisance, or an outright pest.

Modest growth of Cladophora is generally harmless; the growth is an important food for many fish and other aquatic animals, as a buffer for the sequestration of nutrients in the water body and for protection of some aquatic organisms from solar ultraviolet radiation.

Cladophora glomerata, showing branching filaments and cellular structures

Kháy phen served as an appetizer dish.