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Cladophora

(Redirected from Mekong weed)
For the other genus of algae called blanket weed, see Spirogyra.

Cladophora is a genus of reticulated filamentous green algae in the class Ulvophyceae. They may be referred to as reticulated algae, branching algae,[1] or blanket weed.[2] The genus has a worldwide distribution and is harvested for use as a food and medicine.

Cladophora
Cladophora
Cladophora
Scientific classification Edit this classification
Clade: Viridiplantae
Division: Chlorophyta
Class: UTC clade
Order: Cladophorales
Family: Cladophoraceae
Genus: Cladophora
Kütz., 1843
Kingdom: Plantae
Cladophora glomerata, showing branching filaments and cellular structures

Description and appearance

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Cladophora coloring is bright green which reflects the chlorophyll a, and chlorophyll b, which are similar to higher plant ratios and that also contains β-carotene and xanthophylls.[3] The thallus branches are smaller than the main axis, dichotomous, rough in texture, and have narrow tips.

Temperature, water currents and waves affect their metabolism and morphology, and branching patterns. At 15–20 °C branches appear alternate, they can also appear completely absent in temperatures below 25 °C.[3]

Cladophora form a branched filamentous chlorophyte structure with large cylindrical cells forming long, regularly branched growths. The filaments can be quite long and may form dense mats or tufts in aquatic environments. When Cladophora becomes detached from the rocky substrate that it grows upon, it can then build up on shorelines, making their reticular formations, (dense mats) visible to onlookers. When dense mats form, this can affect light penetration and oxygen levels in aquatic ecosystems. Mats may also serve as habitat and food for various aquatic organisms.[3]

Cellular structure

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The cells within Cladophora have multiple pyrenoids, are large and multiple nucleated and have many parietal round chloroplasts, which usually join into a net-like reticular formation.[citation needed] Thick walls called akinetes are made out of vegetative cells in times of short photoperiods, low temperatures or nutrient unavailability. The cell walls of Cladophora species often contain cellulose and pectin, providing strength and flexibility.[3] Thick walls and sheaths are mucilaginous.

Life cycle

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Asexual reproduction

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This plant is annual and can reproduce through both sexual and asexual mechanisms. Some species have isogametic capacities but little is known about this and it seems to be a rare occurrence present in few species. The few cases that have occurred were in apical and sub apical un-specialized cells. Cladophora generally reproduces asexually using 2 flagellated zoospores using mitotic division and distal cells of side branches.

Sexual reproduction

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This occurs when the male and female gametes fuse, usually in water. The fusion of gametes results in the formation of a diploid zygote. The diploid zygote undergoes mitotic divisions to form a diploid sporophyte. The sporophyte phase is often short-lived and less conspicuous. It produces haploid spores through meiosis. Haploid spores are released from the sporophyte and can be dispersed by water currents or other means. Haploid spores germinate to form new haploid gametophytes, completing the life cycle. Reproductive cells, often referred to as zoospores, are typically motile and possess flagella, allowing them to move in water.

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.

Habitat and distribution

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Cladophora exist in multiple ecosystems which include both tropical and moderate climates, freshwater, wastewater, and marine water ecosystems, and in multiple biomes which include lakes, ponds, dam reservoirs, large rivers and the coastal littoral zones as well as in areas of oceanic depth (which determines temperatures and light availability as well as oxygen availability, which can become a limiting factor). This taxon needs nitrates, and orthophosphates, as well as hard water conditions with pH levels between 7–10, high light intensity and nutrient densities that are rich in nature. Cladophora may attach to submerged surfaces like rocks or other aquatic substrates, enabling it to grow more rapidly through optimization of space availability, (another limiting factors and source of infraspecific, intraspecies and interspecies competition).

In Europe, only 15 known subtypes of Cladophora are freshwater. Cladophora exists in Africa, Asia, the Pacific Islands, Australia, Europe, the Atlantic Islands, North America, New Zealand, as well as the Caribbean. In some Asian countries, almost 5% of human diets are algae, and its consumption is popular in France, Thailand, as well as the Hawaiian Islands.[3]

Cladophora balls are formed from the filaments of the algae[4] 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.[5]

Ecological impact

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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.[citation needed]

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.[citation needed] Cladophora species can be an environmental nuisance, however, causing major alterations to benthic conditions linked particularly with increased phosphorus loading.[3]

Where Cladophora becomes a pest is generally where special circumstances cause such drastic overgrowth that algal blooms develop and form floating mats. Typical examples include where hypertrophication or high mortality of rival organisms produce high concentrations of dissolved phosphorus. Extensive floating mats prevent circulation that is necessary for the aeration of deeper water and, by blocking the light, they kill photosynthesising organisms growing beneath. The mats interfere with the fishing industry by clogging nets and preventing the use of lines. Where they wash ashore the masses of rotting material reduce shoreline property values along water bodies such as the Great Lakes in the United States.[6]

Quagga mussel populations have increased tremendously during the same time frame as the blooming of Cladophora, though their ecological relationships are not yet clear and may be complex.[7]

Phytoremediation and bioindication

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Some Cladophora species, including Cladophora fascicularis, have been investigated for their use in phytoremediation. Cladophora fascicularis may contribute to improving water quality in contaminated aquatic ecosystems. This algae is biologically active. Cladophora possesses unprecedented capacities to filter toxins from water such as heavy metals and pollutants and efficiently absorb nutrients, including nitrogen and phosphorus.[3]

Cladophora is known for its blooming activities which are seasonal, (early spring to summer) and indicate their eutrophic abilities as well as that pollution may be present in the environment that they are growing within.[3]

Uses

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Food

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Kháy phen served as an appetizer dish

Cladophora can be eaten as a food item either dried or fresh, however it loses some of its nutritional value with increased processing and with genetic modification. It is considered a carbohydrate when consumed.[3]

In Laos, Cladophora 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 similar to 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.[citation needed]

Biofuel

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Trans-esterification of Cladophora can be used to transform it into biodiesel. Alcohols and enzymes and Cladophora oils are used to form this reaction, but production is often highly dependent on oil content.[3]

Pharmacology

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Cladophora has pharmacological uses as medication. Cladophora is purported to have antimicrobial, antihistamine, antiviral, antioxidant, anti-sclerosis, anti-inflammatory and weight loss properties as well as secondary metabolites and bioactive components that have uses in diabetes, hypertension, cancer, and serves as a protection from parasites. However, as of December 2023, Cladophora has yet to be utilized commercially as a pharmacological agent.[3]

Other uses

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There is an additional demand for Cladophora for biomass productivity with utilization commercially as material for value added products. It can be used for cosmetic application and used as a fertilizer.[3] Marimo used to be classified in Cladophora, though is now called Aegagropila linnaei. Algae balls are significant in the hobby aquarium trade.[citation needed]

Taxonomy and selected species

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Cladophora is a green macroalgae alga classified within the Chlorophyta division. Cladophora has over 183 species within its genus 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.[8]

Some species include:

Aegagropila linnaei (marimo) was formerly placed here as Cladophora aegagropila.

References

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  1. ^ "Cladophora sp. Algae". Aquasabi. Retrieved 28 August 2024.
  2. ^ "The Ultimate Algae Guide". Green Aqua. Retrieved 28 August 2024.
  3. ^ a b c d e f g h i j k l Michalak, I., Messyasz, B. Concise review of Cladophora spp.: macroalgae of commercial interest. J Appl Phycol 33, 133–166 (2021). https://doi.org/10.1007/s10811-020-02211-3
  4. ^ Burrows, E.M.1991. Seaweeds of the British Isles Volume 2 Chlorophyta. Natural History Museum, London. ISBN 0-565-00981-8
  5. ^ Bryant, J. and Irvine, Linda. 2016. Marimo, Cladophora, Posidonia and Other Plant Balls. The Linnean. 32 (2) pp.11–14
  6. ^ "Great Lakes Science Center".
  7. ^ "The beach speaks for itself". June 29, 2008. Archived from the original on 3 March 2016.
  8. ^ Gestinari, L., et al. (2010). Distribution of Cladophora species (Cladophorales, Chlorophyta) along the Brazilian Coast. Phytotaxa 14 22.

Further reading

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