The Canary Current is a wind-driven surface current that is part of the

North Atlantic Gyre The North Atlantic Gyre of the Atlantic Ocean is one of five great oceanic gyres. It is a circular ocean current, with offshoot eddies and sub-gyres, across the North Atlantic from the Intertropical Convergence Zone (calms or doldrums) to the part ...

. This eastern

boundary current Boundary currents are ocean currents with dynamics determined by the presence of a coastline, and fall into two distinct categories: western boundary currents and eastern boundary currents. Eastern boundary currents Eastern boundary currents are ...

branches south from the

North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward. The NAC originates from wher ...

and flows southwest about as far as

Senegal Senegal,; Wolof: ''Senegaal''; Pulaar: 𞤅𞤫𞤲𞤫𞤺𞤢𞥄𞤤𞤭 (Senegaali); Arabic: السنغال ''As-Sinighal'') officially the Republic of Senegal,; Wolof: ''Réewum Senegaal''; Pulaar : 𞤈𞤫𞤲𞤣𞤢𞥄𞤲𞤣𞤭 � ...

where it turns west and later joins the Atlantic

North Equatorial Current The North Equatorial Current (NEC) is a westward wind-driven current mostly located near the equator, but the location varies from different oceans. The NEC in the Pacific and the Atlantic is about 5°-20°N, while the NEC in the Indian Ocean is v ...

. The current is named after the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

. The

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands. Examples of archipelagos include: the Indonesian Archi ...

partially blocks the flow of the Canary Current (Gyory, 2007). This wide and slow moving current is thought to have been exploited in the early

Phoenicia Phoenicia () was an ancient thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-states extended and shrank throughout their histor ...

n navigation and settlement along the coast of western

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

. The ancient Phoenicians not only exploited numerous fisheries within this current zone, but also established a factory at

Iles Purpuraires Iles Purpuraires are a set of small islands off the western coast of Morocco at the bay located at Essaouira, the largest of which is Mogador Island. These islands were settled in antiquity by the Phoenicians, chiefly to exploit certain marine re ...

off present day Essaouira for extracting a

Tyrian purple Tyrian purple ( grc, πορφύρα ''porphúra''; la, purpura), also known as Phoenician red, Phoenician purple, royal purple, imperial purple, or imperial dye, is a reddish-purple natural dye. The name Tyrian refers to Tyre, Lebanon. It i ...

dye from a marine gastropod

murex ''Murex'' is a genus of medium to large sized predatory tropical sea snails. These are carnivorous marine gastropod molluscs in the family Muricidae, commonly called "murexes" or "rock snails".Houart, R.; Gofas, S. (2010). Murex Linnaeus, 175 ...

species.

Upwelling

A prominent feature of Eastern Boundary Currents is the presence of

upwelling Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nut ...

. Ekman drift causes offshore transport of surface waters, which are then replaced with deep water from below. Deep waters are cold and

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

-rich and have a key role in stimulating

primary productivity In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...

. Upwelling has led to the enhancement of coastal fisheries in western

(Hance, 1975). Upwelling, with its consequent chilling on affected seas, also gives near-shore land areas a more temperate microclimate because any air of tropical origin which passes over the chilly water is cooled at its surface level. Major upwelling occurs between 23 and 25 degrees northern latitude (Canary Current, 2002). Upwelling occurs year-round at Cap Blanc (

Ras Nouadhibou Ras Nouadhibou ( ar, رأس نواذيبو) is a peninsula or headland divided by the border between Mauritania and Western Sahara on the African coast of the Atlantic Ocean. It is internationally known as ''Cabo Blanco'' in Spanish or ''Cap Bl ...

) and northward. South of Cap Blanc, upwelling is limited to winter and spring due to the northward migration of the

Azores High The Azores High also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda-Azores High, is a large subtropical semi-permanent centre of high atmospheric pressure typically found south of the Azores in the Atlantic Ocean, at the Ho ...

during summer, which is responsible for driving equatorward winds. Minas ''et al.'' (1982) showed that at the latitude of Cap Blanc, a front exists that separates North Atlantic Central Water (NACW) and South Atlantic Central Water (SACW). SACW, to the south of Cap Blanc, is richer in nutrients than NACW. A poleward subsurface counter-current is responsible for bringing SACW to the Cap Blanc region resulting in maximal primary production. Primary production to the north is limited by nutrient availability in NACW. Primary production to the south of Cap Blanc is limited by the occurrence of upwelling events.

Upwelling and primary production

Huntsman and Barber (1977) hypothesized that high productivity results from alternating upwelling events and relatively calm periods. Upwelling is necessary to bring the nutrients to the surface but if the event is sustained for a long period of time, it is tough for

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

to remain in the

euphotic zone The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...

. Calm periods allow for stratification to develop, which means that phytoplankton can grow and multiply while held in the shallow

mixed layer The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, surface heat fluxes, or processes such as evaporat ...

. In other words, there is a miniature

spring bloom The spring bloom is a strong increase in phytoplankton abundance (i.e. stock) that typically occurs in the early spring and lasts until late spring or early summer. This seasonal event is characteristic of temperate North Atlantic, sub-polar, and ...

during each calm period (Mann & Lazier, 1996).

Upwelling and zooplankton

Upwelling and primary production follow the onset of a strong wind within a few days (Mann & Lazier, 1996).

Zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

, such as

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s, take longer to respond to the abundance of food available because they have life cycles of weeks rather than days. Zooplankton in the Canary Current reach their peak density in autumn when upwelling intensity decreases. The decrease in upwelling allows the zooplankton to stay over the shelf where their food supply exists. Due to the rapid response of phytoplankton to upwelled nutrients, zooplankton are seldom food-limited.

Upwelling and fish

Four types of fish comprise 75% of total catch in the Cap Blanc region (Mann & Lazier, 1996).

Clupeid Clupeidae is a family of ray-finned fishes, comprising, for instance, the herrings, shads, sardines, hilsa, and menhadens. The clupeoids include many of the most important food fishes in the world, and are also commonly caught for production of ...

s (''Sardina pilchardus'', the

sardine "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the It ...

, and ''Sardinella aurita'') were the most abundant. ''S. pilchards'' dominate in the cooler northern waters while ''S. aurita'' are prevalent in warmer southern waters. Next most abundant were

Jack mackerel Jack mackerels or saurels are marine fish in the genus ''Trachurus'' of the family Carangidae. The name of the genus derives from the Greek words ''trachys'' ("rough") and ''oura'' ("tail"). Some species, such as ''T. murphyi'', are harvested in ...

(''Trachurus'' spp.) and Redfish (Sparidae). Ansa-Emmin (1982) found that in 1974, the total fish landings reached 2.68 million tons. Nearly 1 million tons were Clupeidae with .67 million tons being sardines.

Nutrient recycling

Phytoplankton over the shelf area either sink to the bottom or are consumed by zooplankton. If they settle to the bottom, phytoplankton release

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

during their

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

, which returns nitrogen to the waters. Consequently, the phytoplankton remains could be consumed by

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

dwellers, which also excrete ammonia. If consumed by zooplankton, nitrogen from the phytoplankton will be returned to the environment via excreted ammonia or fecal pellets, which settle to the bottom. Regardless of the mechanism, a high proportion of phytoplankton nitrogen ends up being released in the shoreward-moving lower layer of the water column (Mann & Lazier, 1996). This water will later be upwelled and can stimulate further primary production. Barber and Smith (1981) estimated that on the shelf off Cap Blanc, regenerated nitrogen accounted for 72% of total nitrogen.

References

* Ansa-Emmin, M. (1982) Fisheries in the CINECA region. ''Rapp. P.-v. Reun. Cons. Int. Explor. Mer.'' 180: 405-422. * Barber, R.T. and Smith R.L. (1981) Coastal upwelling ecosystems. pp 31–68. In: A.R. Longhurst (Ed) ''Analysis of Marine Ecosystems''. Academic Press, New York. 741 pp. * C.Michael Hogan, ''Mogador: Promontory Fort'', The Megalithic Portal, ed. Andy Burnham, November 2, 200

Canary Current (2002)
* Huntsman, S.A. and Barber, R.T. (1977) Primary production off northwest Africa: the relationship to wind and nutrient conditions. ''Deep-Sea Research''. 24: 25-33.

* Mann, K. H., and J. R. N. Lazier. Dynamics of Marine Ecosystems: Biological-physical Interactions in the Oceans. Boston: Blackwell Science, 1996. Print. * Minas, H.J., Codispoti, L.A. and Dugdale, R.C. (1982) Nutrients and primary production in the upwelling region off northwest Africa.'' Rapp. P.-v. Reún. Cons. Int. Explor. Mer.'' 180: 148-183. * William Adams Hance (1975) ''The Geography of Modern Africa'', Columbia University Press,

External links

Encyclopedia of Earth: Canary Current

Canary Current Large Marine Ecosystem (CCLME) project
{{Ocean Marine ecoregions Currents of the Atlantic Ocean