| Gelidium | |
|---|---|
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| Gelidium amansii | |
Scientific classification  | |
| Clade: | Archaeplastida |
| Division: | Rhodophyta |
| Class: | Florideophyceae |
| Order: | Gelidiales |
| Family: | Gelidiaceae |
| Genus: | Gelidium J.V. Lamouroux, 1813 |
| Synonyms | |
AcanthopeltisOkamura, 1892 | |
Gelidium is a genus of thalloid red algae comprising 134 species. Its members are known by a number of common names. [note 1]
Specimens can reach around 2–40 cm (0.79–16 in) in size. Branching is irregular, or occurs in rows on either side of the main stem. Gelidium produces tetraspores. Many of the algae in this genus are used to make agar. [1] Agarocolloids are known to be extracted in algae belonging to the orders Gracilariales and Gelidiales with certain applications in the food and cosmetics. Gelling properties often differ among species, seasons, seaweed age, and substitutions between sulphate esters, among other compounds. Sulphate composition often dictates gel strength, while methyl esters determine gelling and elasticity. [2]
Gelidium is assumed to follow the Polysiphonia life cycle, with sexual and tetrasporangial generations. [3] Tetrasporangia formation is also known to be affected by temperature and other environmental factors including light, salinity and moisture, [4] although germination rates remain unaffected based on an earlier study. [5]
In 1993, Gelidium robustum in Santa Barbara, California was investigated for 16-months showing tetrasporangial abundance throughout the year, but may not have the ability to germinate despite maximum spore output. [3]
Gelidium are widely distributed globally, specifically in tropical to temperate regions, but lacking in polar regions. [6] In the ocean, Gelidium can be found inhabiting the intertidal to subtidal zone. [7] Species from the genus require further studies to distinguish boundaries among members, as recent molecular research have shown that there are cryptic, unidentified species assumed to be regionally endemic and isolated but may also be ubiquitous in nature. [7] Some species are common in the Atlantic and Pacific Ocean (G. crinale) while some are confined in North Atlantic waters (G. pussillum) [8] [9] [10] . Reports of G. pussillum occurrence outside of its specified range may be questionable and requires further verification. [7]
Gelidiales consists of many species that are economically important as they produce agar while some serve ecologically significant functions such as substrate cover. [6] The growth of Gelidium can primarily be affected by nutrient availability and light. In turn, these factors are also regulated by temperature and water movement, respectively. Santelices (1991) evaluated how eight factors may affect Gelidium productivity, all of which are important in understanding how different interactions correlate to production yield. Some of these factors include seasonality, phenotypic characters, age, reproductive state, and even the source of the algae. [6]
An important agarophyte, Gelidium has been cultured in Korea [11] and China [12] since the early 1990s, with some cultivation efforts noted in Europe, specifically in Spain [13] and Portugal. [11] [14] In South Africa, G. pristoides has been cultivated in the field while laboratory trials on G. crinale and Pterocladiella capillacea were tested in Israel. [15] [16] In Portugal, G. sesquipedale has commonly been harvested for agar since the 1960s. [17] Management strategies are yet to be implemented especially among big commercial companies that should be responsible in harvesting the resource, similar to South Africa where the decrease in annual Gelidium landings show how fisher folk shifted to collecting kelp for abalone feeds instead of Gelidium harvesting. [18]
Gelidium has been found to be over-exploited in Japan, depleting algal beds [19] which in part, affects agar production, pushing the need for even more efforts in cultivation, replacing the practice of harvesting wild Gelidium. [20] In 2017, global data have shown that Norway, China, and Chile are among the countries that lead the overharvesting of seaweeds, mostly kelp. [20] Advances in Gelidium cultivation have been put forth including the use of floaters at sea and marine ponds for free-float technology in cultivation. [21] At its core, environmental factors are needed to be controlled for favorable growth of Gelidium revealing how ponds may be the better option among the set-ups. [20]
Agar is primarily extracted from Gelidium especially among North African Atlantic and South European species based on specific gel properties with water. In Morocco, Gelidium sesquipidale is known to be harvested during summer time to extract agar used commercially, making the country among the top producers in the world. [2]
Gelidium species have been collected, pressed and maintained in herbaria and personal collections from the 1850s onwards since seaweed collecting became a popular pastime for the middle classes as well as scientists in Europe and North America. [22] These numerous well-documented specimens can provide information beyond taxonomy. [23]
Sensitive measurement of stable nitrogen isotope ratios in Gelidium species collected in southern Monterey Bay between 1878 and 2018 showed a pattern of changes that matched with changes in the California current and provided support for a theory about the end of the local fishing industry. [24] Nitrogen isotope ratios are well established as a measure of nutrient productivity in aquatic ecosystems. The California current runs along coastal California and correlation with information on fish catches indicates that an increase in nutrient-rich cold water is important for fish productivity, notably sardines. [25] The California current has only been measured since 1946. The correlations with the Gelidium nitrogen ratios allowed the California current to be projected back into the nineteenth century and compared with historical records of fish catches. [24] The data matched, notably for the highest sardine catches through the 1930s and then the sudden decrease from 1945 to 1950 that ended the Monterey cannery industry. This information supports the theory that environmental changes as well as overfishing caused the collapse of the local fishery business. More broadly, this suggests that elemental analysis of historical samples of macroalgae can provide evidence of primary productivity processes. The species used included specimens of G. coulteri, G. robustum, G. purpurascens, G. pusillum and G. arborescens collected over a 140-year timespan from the 6 km coastline between Point Pinos, Pacific Grove and Cannery Row, Monterey in California, US. [24]
Gelidiaceae has 159 species, considered to be the largest family in Gelidiales with four major genera: Capreolia, Gelidium, Gelidiophycus, and Ptilophora. [26]
Gelidium was first described by Lamouroux in 1813 and is regarded to be one the genera with the most species. Species diversity has been established by previous studies, whereas, molecular analysis reveals biogeographic relations that concerns its current distribution pattern in oceans. [7]
Identification of species has been a challenge as sexual plants are somewhat difficult to find in nature, therefore, other physiological features are examined instead, such as branching patterns and vegetative traits, but subsequent studies revealed that these are also affected by its development and environmental factors [9] highlighting the need for genetic studies utilizing genetic markers. [7]
Chondrus crispus—commonly called Irish moss or carrageenan moss —is a species of red algae which grows abundantly along the rocky parts of the Atlantic coasts of Europe and North America. In its fresh condition it is soft and cartilaginous, varying in color from a greenish-yellow, through red, to a dark purple or purplish-brown. The principal constituent is a mucilaginous body, made of the polysaccharide carrageenan, which constitutes 55% of its dry weight. The organism also consists of nearly 10% dry weight protein and about 15% dry weight mineral matter, and is rich in iodine and sulfur. When softened in water it has a sea-like odour. Because of the abundant cell wall polysaccharides, it will form a jelly when boiled, containing from 20 to 100 times its weight of water.
Caulerpa is a genus of seaweeds in the family Caulerpaceae. They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world.
Ascophyllum nodosum is a large, common cold water seaweed or brown alga (Phaeophyceae) in the family Fucaceae. Its common names include knotted wrack, egg wrack, feamainn bhuí, rockweed, knotted kelp and Norwegian kelp. It grows only in the northern Atlantic Ocean, along the north-western coast of Europe including east Greenland and the north-eastern coast of North America. Its range further south of these latitudes is limited by warmer ocean waters. It dominates the intertidal zone. Ascophyllum nodosum has been used numerous times in scientific research and has even been found to benefit humans through consumption.
Callophyllis variegata, commonly known as carola, is a type of edible seaweed, a member of the genus Callophyllis. Callophyllis variegata occurs in Concepción de Chile and other parts of South America such as Peru, the Falkland Islands, Tierra del Fuego. But also in New Guinea, South Africa, Australia, New Zealand, Alaska, St. Paul Island, Antarctic and subantarctic islands such as the Graham Land, Kerguelen, Macquarie Island, South Georgia, and the South Orkney Islands.
Florideophyceae is a class of exclusively multicellular red algae. They were once thought to be the only algae to bear pit connections, but these have since been found in the filamentous stage of the Bangiaceae. They were also thought only to exhibit apical growth, but there are genera known to grow by intercalary growth. Most, but not all, genera have three phases to the life cycle. In the subclass Nemaliophycidae there are three orders, Balbianiales, Batrachospermales, and Thoreales, which lives exclusively in freshwater.
A raceway pond is a shallow artificial pond used in the cultivation of algae.
Codium is a genus of edible green macroalgae under the order Bryopsidales. The genus name is derived from a Greek word that pertains to the soft texture of its thallus. One of the foremost experts on Codium taxonomy was Paul Claude Silva at the University of California, Berkeley. P.C. Silva was able to describe 36 species for the genus and in honor of his work on Codium, the species C. silvae was named after the late professor.
Gelidiella is a genus of red algae. Worldwide there are 22 species of Gelidiella, mostly tropical and subtropical. Gelidiella and Gelidium are now both united into one order Gelidiales.
The Gelidiaceae is a small family of red algae containing eight genera. Many species of this algae are used to make agar.
Red algae, or Rhodophyta, make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest phyla of algae, containing over 7,000 recognized species within over 900 genera amidst ongoing taxonomic revisions. The majority of species (6,793) are Florideophyceae, and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, no terrestrial species exist, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity.
Ice-ice is a disease condition of seaweed. Ice-ice is caused when changes in salinity, ocean temperature and light intensity cause stress to seaweeds, making them produce a "moist organic substance" that attracts bacteria in the water and induces the characteristic "whitening" and hardening of the seaweed's tissues. Bacteria involved include those in the Vibrio-Aeromonas and Cytophaga-Flavobacteria complexes. The bacteria lyse epidermal cells and chloroplasts, turning the seaweed tissue white. The disease is known from seaweeds including Kappaphycus alvarezii and Eucheuma denticulatum, economically important sources of carrageenan. In countries where seaweed is harvested as a crop, ice-ice can wreak havoc on yields. Zamboanga, Philippines, had an outbreak of ice-ice in 2004, and Bali, Indonesia, experienced an outbreak in 2009. A rise in surface sea temperatures of 2–3 degrees Celsius can trigger ice-ice outbreaks.
Seaweed farming or kelp farming is the practice of cultivating and harvesting seaweed. In its simplest form farmers gather from natural beds, while at the other extreme farmers fully control the crop's life cycle.
Kappaphycus is a genus of red algae. Species are distributed in the waters of East Africa, Indonesia, Malaysia, Hainan Island, the Philippines, and Micronesia.
Hildenbrandia is a genus of thalloid red alga comprising about 26 species. The slow-growing, non-mineralized thalli take a crustose form. Hildenbrandia reproduces by means of conceptacles and produces tetraspores.
Aquaculture of giant kelp, Macrocystis pyrifera, is the cultivation of kelp for uses such as food, dietary supplements or potash. Giant kelp contains iodine, potassium, other minerals vitamins and carbohydrates.
Hypnea is a genus of red algae, and a well known carrageenophyte.
The Gelidiellaceae is a small family of red algae containing 5 genera of agarophytes.
The Pterocladiaceae is a small family of red algae containing 2 genera of agarophytes.
The Gracilariaceae is a small family of red algae, containing several genera of agarophytes. It has a cosmopolitan distribution, in which 24 species are found in China, six in Great Britain and Ireland, and some in Australia and Chile.
Kathleen "Kay" Margaret Cole was a Canadian phycologist, known as one of the world's leading experts in the cytology of marine algae. In 1998 the Canadian Botanical Society awarded her the George Lawson Medal for lifetime achievement.
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