Misplaced Pages

#915084

40-556: Earth's trade winds and Coriolis force cause the ocean currents in South Pacific Ocean to circulate counterclockwise. The currents act to isolate the center of the gyre from nutrient upwelling , and few nutrients are transported there by the wind ( eolian processes ) because there is relatively little land in the Southern Hemisphere to supply dust to the prevailing winds . The low levels of nutrients in

80-447: A course along which the winds can be expected to blow in the direction of travel. During the Age of Sail , the pattern of prevailing winds made various points of the globe easy or difficult to access, and therefore had a direct effect on European empire-building and thus on modern political geography. For example, Manila galleons could not sail into the wind at all. By the 18th century,

120-546: Is caused by descending air aloft from within the subtropical ridge . The weaker the trade winds become, the more rainfall can be expected in the neighboring landmasses. The trade winds also transport nitrate- and phosphate-rich Saharan dust to all Latin America , the Caribbean Sea , and to parts of southeastern and southwestern North America. Sahara dust is on occasion present in sunsets across Florida . When dust from

160-445: Is dependent on the quantities of radioactive isotopes present, sediment porosity, and grain size. These criteria indicate that certain sediment types, such as abyssal clays and siliceous oozes, may have higher radiolytic H 2 production relative to other seafloor strata. Also, radiolytic H 2 production has been measured in seawater intrusions into subseafloor basement basalts. The microbes best suited to utilize radiolytic H 2 are

200-700: Is known as a temperature inversion. When it occurs within a trade wind regime, it is known as a trade wind inversion. The surface air that flows from these subtropical high-pressure belts toward the Equator is deflected toward the west in both hemispheres by the Coriolis effect . These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere . Because winds are named for

240-522: Is warm, trade winds are stronger within the tropics. The cold phase of the AO leads to weaker trade winds. When the trade winds are weaker, more extensive areas of rain fall upon landmasses within the tropics, such as Central America . During mid-summer in the Northern Hemisphere (July), the westward-moving trade winds south of the northward-moving subtropical ridge expand northwestward from

280-653: The Atlantic Ocean and the Pacific Ocean . In meteorology , they act as the steering flow for tropical storms that form over the Atlantic, Pacific, and southern Indian oceans and cause rainfall in North America , Southeast Asia , and Madagascar and East Africa . Shallow cumulus clouds are seen within trade wind regimes and are capped from becoming taller by a trade wind inversion , which

320-451: The Caribbean Sea into southeastern North America (Florida and Gulf Coast). When dust from the Sahara moving around the southern periphery of the ridge travels over land, rainfall is suppressed and the sky changes from a blue to a white appearance which leads to an increase in red sunsets. Its presence negatively impacts air quality by adding to the count of airborne particulates. Although

360-419: The Sahara travels over land, rainfall is suppressed and the sky changes from a blue to a white appearance which leads to an increase in red sunsets. Its presence negatively impacts air quality by adding to the count of airborne particulates. The term originally derives from the early fourteenth century sense of trade (in late Middle English ) still often meaning "path" or "track". The Portuguese recognized

400-495: The seafloor of the region and could be the longest-living life forms ever found. Benthic microbes in organic-poor sediments in oligotrophic oceanic regions, such as the South Pacific Gyre, are hypothesized to metabolize radiolytic hydrogen (H 2 ) as a primary energy source. The oceanic regions within the South Pacific Gyre (SPG), and other subtropical gyres, are characterized by low primary productivity in

440-469: The weathering of parent material (bedrock) to form soil , as well as biogeochemical cycling of sulfur , potassium , and other elements. The existence of undiscovered strains of microbial lithoautotrophs is theorized based on some of these cycles, as they are needed to explain phenomena like the conversion of ammonium in iron-reducing environments. Lithoautotrophs may be present in the deep terrestrial subsurface (they have been found well over 3 km below

SECTION 10

#1732765417916

480-758: The 1970s. Every year, millions of tons of nutrient-rich Saharan dust cross the Atlantic Ocean, bringing vital phosphorus and other fertilizers to depleted Amazon soils. Lithoautotroph A lithoautotroph is an organism which derives energy from reactions of reduced compounds of mineral (inorganic) origin. Two types of lithoautotrophs are distinguished by their energy source; photolithoautotrophs derive their energy from light while chemolithoautotrophs (chemolithotrophs or chemoautotrophs) derive their energy from chemical reactions. Chemolithoautotrophs are exclusively microbes . Photolithoautotrophs include macroflora such as plants; these do not possess

520-608: The Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere , strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries. They enabled European colonization of the Americas , and trade routes to become established across

560-523: The SPG show rapid elimination of O 2 and nitrate at 1 meter below sea floor (mbsf) and 2.5 mbsf, respectively. This is evidence of much higher microbial activity, both aerobic and anaerobic. The production of radiolytic H 2 (electron donor) is stoichiometrically balanced with production of 0.5 O 2 (electron acceptor), therefore a measurable flux in O 2 is not expected in the substrate if both radiolysis of water and knallgas bacteria co-occur. So, despite

600-852: The Southeast US has some of the cleanest air in North America, much of the African dust that reaches the United States affects Florida. Since 1970, dust outbreaks have worsened due to periods of drought in Africa. There is a large variability in the dust transport to the Caribbean and Florida from year to year. Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida , primarily since

640-573: The ability to use mineral sources of reduced compounds for energy. Most chemolithoautotrophs belong to the domain Bacteria , while some belong to the domain Archaea . Lithoautotrophic bacteria can only use inorganic molecules as substrates in their energy-releasing reactions. The term "lithotroph" is from Greek lithos ( λίθος ) meaning "rock" and trōphos (τροφοσ) meaning "consumer"; literally, it may be read "eaters of rock". The "lithotroph" part of

680-510: The assumption that greener ocean water always contains more phytoplankton is not always true. Even though the South Pacific Gyre contains these patches of green water, it has very little organism growth. Instead, some studies hypothesize that these green patches are a result of the accumulated waste of marine life. The optical properties of the South Pacific Gyre remain largely unexplored. Trade winds The trade winds or easterlies are permanent east-to-west prevailing winds that flow in

720-549: The direction from which the wind is blowing, these winds are called the northeasterly trade winds in the Northern Hemisphere and the southeasterly trade winds in the Southern Hemisphere. The trade winds of both hemispheres meet at the Doldrums . As they blow across tropical regions, air masses heat up over lower latitudes due to more direct sunlight. Those that develop over land (continental) are drier and hotter than those that develop over oceans (maritime), and travel northward on

760-480: The diversity in using inorganic compounds that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecule to get its energy. A chemolithotrophic example are Anaerobic Ammonia Oxidizing Bacteria (ANAMMOX), which use ammonia and nitrite to produce N 2 . Additionally, in July 2020, researchers reported the discovery of chemolithoautotrophic bacterial cultures that feed on

800-417: The entire sediment column. Average cell abundances and net rates of respiration are a few orders of magnitude lower than in any other subseafloor biosphere previously studied. The South Pacific Gyre subseafloor community is also unusual because it contains oxygen throughout the entire sediment column. In other subseafloor biospheres, microbial respiration will break down organic material and consume all

840-514: The equator while the flow aloft is towards the poles . A low-pressure area of calm, light variable winds near the equator is known as the doldrums , near-equatorial trough, intertropical front, or the Intertropical Convergence Zone . When located within a monsoon region, this zone of low pressure and wind convergence is also known as the monsoon trough . Around 30° in both hemispheres, air begins to descend toward

SECTION 20

#1732765417916

880-537: The genus Nitrospira . Several environmental hazards, such as ammonium (NH 4 ), hydrogen sulfide (H 2 S), and the greenhouse gas methane (CH 4 ), may be converted by chemolithoautotrophs into forms that are less environmentally harmful, such as N 2 , SO 4 , and CO 2 . Although it was long believed that these organisms require oxygen to make these conversions, recent literature suggests that anaerobic oxidation also exists for these systems. Lithoautotrophic microbial consortia are responsible for

920-624: The importance of the trade winds (then the volta do mar , meaning in Portuguese "turn of the sea" but also "return from the sea") in navigation in both the north and south Atlantic Ocean as early as the 15th century. From West Africa, the Portuguese had to sail away from continental Africa, that is, to west and northwest. They could then turn northeast, to the area around the Azores islands, and finally east to mainland Europe. They also learned that to reach South Africa, they needed to go far out in

960-464: The importance of the trade winds to England's merchant fleet for crossing the Atlantic Ocean had led both the general public and etymologists to identify the name with a later meaning of "trade": "(foreign) commerce". Between 1847 and 1849, Matthew Fontaine Maury collected enough information to create wind and current charts for the world's oceans. As part of the Hadley cell , surface air flows toward

1000-504: The knallgas bacteria, lithoautotrophes , that obtain energy by oxidizing molecular hydrogen via the knallgas reaction : In the surface layer of sediment cores from oligotrophic regions of the SPG, O 2 is the primary electron acceptor used in microbial metabolisms. The O 2 concentrations decline slightly in surface sediment (initial few decimeters) and are unchanged to depth. Meanwhile, nitrate concentrations slightly increase downward or remain constant in sediment column at approximately

1040-460: The known occurrence of radiolytic H 2 production, molecular hydrogen is below the detectable limit in the SPG cores, leading to the hypothesis that H 2 is the primary energy source in low-organic seafloor sediments below the surface layer. Satellite data images show that some areas in the gyre are greener than the surrounding clear blue water, which is frequently interpreted as areas with higher concentrations of living phytoplankton . However,

1080-643: The metal manganese after performing unrelated experiments and named its bacterial species Candidatus Manganitrophus noduliformans and Ramlibacter lithotrophicus . Some chemolithotrophs use redox half-reactions with low reduction potentials for their metabolisms, meaning that they do not harvest a lot of energy compared to organisms that use organotrophic pathways. This leads some chemolithotrophs, such as Nitrosomonas , to be unable to reduce NAD directly; therefore, these organisms rely on reverse electron transport to reduce NAD and form NADH and H . Lithoautotrophs participate in many geological processes, such as

1120-422: The name refers to the fact that these organisms use inorganic elements/compounds as their electron source, while the "autotroph" part of the name refers to their carbon source being CO 2 . Many lithoautotrophs are extremophiles , but this is not universally so, and some can be found to be the cause of acid mine drainage . Lithoautotrophs are extremely specific in their source of reduced compounds. Thus, despite

1160-521: The ocean, head for Brazil, and around 30°S go east again. (This is because following the African coast southbound means sailing upwind in the Southern hemisphere.) In the Pacific Ocean, the full wind circulation, which included both the trade wind easterlies and higher-latitude westerlies , was unknown to Europeans until Andres de Urdaneta 's voyage in 1565. The captain of a sailing ship seeks

1200-857: The organic carbon exported from surface waters. In oligotrophic regions where sediments are poor in organic material, subsurface benthic life exploits other primary energy sources, such as molecular hydrogen (H 2 ). Radioactive decay of naturally occurring uranium ( U and U ), thorium (Th), and potassium ( K ) in seafloor sediments collectively bombard the interstitial water with α , β , and γ radiation. The irradiation ionizes and breaks apart water molecules, eventually yielding H 2 . The products of this reaction are aqueous electrons (e aq ), hydrogen radicals (H·), protons (H), and hydroxyl radicals (OH·). The radicals are highly reactive, therefore short-lived, and recombine to produce hydrogen peroxide (H 2 O 2 ), and molecular hydrogen (H 2 ). The amount of radiolytic H 2 production in seafloor sediments

1240-497: The oxygen near the seafloor leaving the deeper portions of the sediment column anoxic. However, in the South Pacific Gyre the low levels of organic material, the low rates of respiration, and the thin sediments allow the porewater to be oxygenated throughout the entire sediment column. In July 2020, marine biologists reported that aerobic microorganisms (mainly), in "quasi- suspended animation ", were found in organically poor sediments , up to 101.5 million years old, 250 feet below

South Pacific Gyre - Misplaced Pages Continue

1280-469: The phenomenon known as acid mine drainage , whereby pyrite present in mine tailing heaps and in exposed rock faces is metabolized, using oxygen , to produce sulfites , which form potentially corrosive sulfuric acid when dissolved in water and exposed to aerial oxygen . Acid mine drainage drastically alters the acidity and chemistry of groundwater and streams , and may endanger plant and animal populations. Activity similar to acid mine drainage, but on

1320-463: The region result in extremely low primary productivity in the ocean surface and subsequently very low flux of organic material settling to the ocean floor as marine snow . The low levels of biogenic and eolian deposition cause sediments to accumulate on the ocean floor very slowly. In the center of the South Pacific Gyre, the sedimentation rate is 0.1 to 1 m (0.3 to 3.3 ft) per million years. The sediment thickness (from basement basalts to

1360-408: The same concentrations as the deep water above the seafloor. Measured negative fluxes of O 2 in the surface layer demonstrate that a relatively low abundance of aerobic microbes that are oxidizing the minimally deposited organic matter from the ocean above. Extremely low cell counts corroborate that microbes exist in small quantities in these surface sediments. In contrast, a sediment cores outside of

1400-473: The seafloor) ranges from 1 to 70m, with thinner sediments occurring closer to the center of the Gyre. The low flux of particles to the South Pacific Gyre causes the water there to be the clearest seawater in the world. Beneath the seafloor, the marine sediments and surrounding porewaters contain an unusual subseafloor biosphere . Despite extremely low amounts of buried organic material, microbes live throughout

1440-433: The surface in subtropical high-pressure belts known as subtropical ridges . The subsident (sinking) air is relatively dry because as it descends, the temperature increases, but the moisture content remains constant, which lowers the relative humidity of the air mass. This warm, dry air is known as a superior air mass and normally resides above a maritime tropical (warm and moist) air mass. An increase of temperature with height

1480-494: The surface ocean; i.e. they are oligotrophic. The center of the SPG is the furthest oceanic province from a continent and contains the clearest ocean water on Earth with ≥ 0.14 mg chlorophyll per m. Carbon exported to the underlying deep ocean sediments via the biological pump is limited in the SPG, resulting in sedimentation rates that are orders of magnitude lower than in productive zones, e.g. continental margins. Typically, deep-ocean benthic microbial life utilizes

1520-481: The surface of the planet), in soils , and in endolith communities. As they are responsible for the liberation of many crucial nutrients, and participate in the formation of soil , lithoautotrophs play a crucial role in the maintenance of life on Earth. For example, the Nitrogen cycle is influenced by the activity of ammonium-oxidizing archaea, ANAMMOX bacteria, and Complete Ammonium-Oxidizing (COMAMMOX) bacteria of

1560-605: The trade wind inversion. Trade winds originate more from the direction of the poles (northeast in the Northern Hemisphere, southeast in the Southern Hemisphere) during the cold season, and are stronger in the winter than the summer. As an example, the windy season in the Guianas , which lie at low latitudes in South America , occurs between January and April. When the phase of the Arctic oscillation (AO)

1600-416: The western periphery of the subtropical ridge. Maritime tropical air masses are sometimes referred to as trade air masses. All tropical oceans except the northern Indian Ocean have extensive areas of trade winds. Clouds which form above regions within trade wind regimes are typically composed of cumulus which extend no more than 4 kilometres (13,000 ft) in height, and are capped from being taller by

#915084