History
''Sargassum'' was named by the Portuguese sailors who found it in the Sargasso Sea. They called it after the wooly rock rose ('' Halimium lasianthum'') that grew in their water wells at home, and that was called ''sargaço'' in Portuguese ()Gómez de Silva, Guido 1988. ''Breve diccionario etimológico de la lengua española.'' Fondo de Cultura Económica, Mexico City, , p. 627. - from the Latin ''salicastrum''. The Florida Keys and mainland South Florida are well known for the high levels of ''Sargassum'' covering their shores. Sargassum or gulfweed was observed by Columbus. Although the seaweed acquired a legendary reputation for covering the entirety of the Sargasso Sea, making navigation impossible, it has since been found to occur only in drifts. ''Sargassum'' species are cultivated and cleaned for use as an herbal remedy. Many Chinese herbalists prescribe powdered ''Sargassum''—either the species ''S. pallidum'', or more rarely, hijiki, ''S. fusiforme''—in doses of 0.5 gram dissolved in warm water and drunk as a tea. It is called zh, c=海藻, p=hǎizǎo, labels=no in traditional Chinese medicine, where it is used to resolve "heat phlegm".Description
Species of this genus of algae may grow to a length of several metres. They are generally brown or dark green in color and consist of a holdfast, a stipe, and a frond.Ecology
Large, pelagic mats of ''Sargassum'' in the Sargasso Sea act as one of the only habitats available for ecosystem development; this is because the Sargasso Sea lacks any land boundaries. The Sargassum patches act as a refuge for many species in different parts of their development, but also as a permanent residence for endemic species that can only be found living on and within the ''Sargassum''.Laffoley, D.d’A., Roe, H.S.J., Angel, M.V., Ardron, J., Bates, N.R., Boyd, I.L., Brooke, S., Buck, K.N., Carlson, C.A., Causey, B., Conte, M.H., Christiansen, S., Cleary, J., Donnelly, J., Earle, S.A., Edwards, R., Gjerde, K.M., Giovannoni, S.J., Gulick, S., Gollock, M., Hallett, J., Halpin, P., Hanel, R., Hemphill, A., Johnson, R.J., Knap, A.H., Lomas, M.W., McKenna, S.A., Miller, M.J., Miller, P.I., Ming, F.W., Moffitt, R., Nelson, N.B., Parson, L., Peters, A.J., Pitt, J., Rouja, P., Roberts, J., Roberts, J., Seigel, D.A., Siuda, A.N.S., Steinberg, D.K., Stevenson, A., Sumaila, V.R., Swartz, W., Thorrold, S., Trott, T.M., and V. Vats. (2011). The protection and management of the Sargasso Sea: The golden floating rainforest of the Atlantic Ocean. Summary Science and Supporting Evidence Case. Sargasso Sea Alliance, 44 pp. These endemic organisms have specialized patterns and colorations that mimic the ''Sargassum'' and allow them to be impressively camouflaged in their environment. In total, these ''Sargassum'' mats are home to more than 11 phyla and over 100 different species. There is also a total of 81 fish species (36 families represented) that reside in the ''Sargassum'' or utilize it for parts of their life cycles. Other marine organisms, such as young sea turtles, will use the ''Sargassum'' as shelter and a resource for food until they reach a size at which they can survive elsewhere. This community is being affected by humans due to overfishing, trash and other types of pollution, and boat traffic, which could eventually lead to the demise of this diverse and unique habitat. Below is a list of organisms that are associated with the Sargassum in the Sargasso Sea. The Sargasso Sea plays a major role in the migration of catadromous eel species such as the European eel, theInundations
In limited amounts, washed-ashore ''Sargassum'' plays an important role in maintaining Atlantic and Caribbean coastal ecosystems. Once ashore, sargassum provides vital nutrients such as carbon, nitrogen, and phosphorus to coastal ecosystems which border the nutrient-poor waters of the western North Atlantic tropics and subtropics. Additionally, it decreasesBiological impacts
Unprecedented ''Sargassum'' inundation events cause a range of biological and ecological impacts in affected regions. The decomposition of large quantities of ''Sargassum'' along coastlines consumes oxygen, creating large oxygen-depleted zones resulting in fish kills. Decomposing sargassum additionally creates hydrogen sulfide gas, which causes a range of health impacts in humans. During the sargassum inundation event in 2018, 11,000 Acute Sargassum Toxicity cases were reported in an 8-month span on just the Caribbean islands of Guadalupe and Martinique. Massive amounts of floating ''sargassum'' present a physical barrier preventing corals and seagrasses from receiving sufficient light, fouling boat propellers, and entangling marine turtles and mammals. With every ''Sargassum'' inundation event, large amounts of nutrients are transported from the open ocean to coastal environments. This greatly increases nutrient transport, and its effect on marine and coastal ecosystems are still unknown. Understanding the causes and drivers of ''Sargassum'' inundations is critical as they become more commonplace.Nutrient factors
The Sargasso Sea, a known source area for ''Sargassum'' blooms, is classified as an oligotrophic region. With warm, oxygen-poor waters and low nutrient contents, biomass production is limited by what little nutrients are present. Historically, low nutrient levels in the Sargasso Sea have limited ''sargassum'' production; however, new influxes of nitrogen and phosphorus are driving factors in increased biomass production. Recent studies have found three likely drivers of nutrient influx linked to increasing ''Sargassum'' biomass: an increase in nutrient output from the Amazon River, increased nutrients in the Gulf of Mexico, and coastal upwelling off the West African Coast which transfers deep nutrient-rich waters to the upper water column where sargassum resides. Nutrient output from the Amazon River has been shown to have a direct, yet delayed, effect on large Sargassum inundation events, with events occurring one to two years following years of high nutrient output. Phosphates and iron transported via the trade winds from North Africa have been reported to have a fertilizing effect on sargassum growth; however, further data is required to understand its role in causing inundating ''Sargassum'' blooms. Researchers globally agree that continued research is required to quantify the effect of marine chemical changes and other environmental factors in the recent increase in Sargassum biomass and inundation events.Currents and winds
The physical drivers behind ''Sargassum'' inundation events are prevailing winds and ocean surface currents. The Caribbean is located in a region heavily affected by trade winds. Trade winds are strong, consistent northeasterly winds which blow dust-filled dry air from the Sahara across the Atlantic. Trade winds additionally play a critical role in the annual hurricane season in the Western Atlantic. The Caribbean Current and Antilles branch of the Atlantic North Equatorial Current are the major current transporters of ''Sargassum'' in the region. Researchers have recently begun using Moderate Resolution Imaging Spectroradiometer satellite imagery and ocean current data to track and forecast inundation events with a high level of accuracy.Human impact
The effects of deforestation, waste-water runoff, and commercial agriculture fertilizer on facilitating the excess accumulation of nutrients in aquatic and marine environments have been well studied and shown to be driving factors in eutrophication. Since detrimental ''Sargassum'' inundation events did not begin until 2011, it is likely that an unknown nutrient threshold was reached and surpassed. Given current agricultural policies and practices, it is unlikely these inundation events will disappear on their own without human intervention. Sargassum (F. Sargassaceae) is an important seaweed excessively distributed in tropical and subtropical regions. Different species of Sargassum have folk applications in human nutrition and are considered a rich source of vitamins, carotenoids, proteins, and minerals. Many bioactive compounds chemically classified as terpenoids, sterols, sulfated polysaccharides, polyphenols, sargaquinoic acids, sargachromenol, and pheophytin were isolated from different Sargassum species. These isolated compounds and/or extracts exhibit diverse biological activities, including analgesic, anti-inflammatory, antioxidant, neuroprotective, anti-microbial, anti-tumor, fibrinolytic, immune-modulatory, anticoagulant, hepatoprotective, and anti-viral activities.Climate change
Variations in sea level, salinity, water temperature, chemical composition, rainfall patterns and water acidity all play roles in regulating algae blooms. As anthropogenic forces increase the variability of these factors, the frequency, duration, severity and geographic range of harmful algae blooms have increased, causing millions of dollars of lost revenue as well as damaging fragile coastal and coral ecosystems.References
Further reading
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