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76-549: Though individually distinct, each of the Rías Baixas share some common characteristics. They begin along the coastline of the Atlantic Ocean and jut inland, eventually meeting up with a river. Each ria has a basic funnel shape as well, being wider at the ocean and narrowing as it approaches land and the river. Geologists believe that the Rías Baixas formed as a result of tectonic action which sunk certain land areas near

152-553: A common and popular feature. The food in the Rías Baixas, taken locally from the ocean and rias, is claimed to be very high quality and also attracts tourists. Estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea . Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone . Estuaries are subject both to marine influences such as tides , waves , and

228-477: A diminishing quality of the soil and an increased risk of fire. The park is gradually replacing these species with arbutus , pine trees and birches , a process expected to take 20 years to completion. The Prestige oil spill in 2002 and the subsequent cleanup caused major environmental damage in the park. Although almost all traces of fuel have disappeared, two decades later the park's biodiversity has not yet recovered pre-spill levels. The population of lichens

304-573: A harsh environment for organisms. Sediment often settles in intertidal mudflats which are extremely difficult to colonize. No points of attachment exist for algae , so vegetation based habitat is not established. Sediment can also clog feeding and respiratory structures of species, and special adaptations exist within mudflat species to cope with this problem. Lastly, dissolved oxygen variation can cause problems for life forms. Nutrient-rich sediment from human-made sources can promote primary production life cycles, perhaps leading to eventual decay removing

380-529: A number of coastal water bodies such as coastal lagoons and brackish seas. A more comprehensive definition of an estuary is "a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible". This broad definition also includes fjords , lagoons , river mouths , and tidal creeks . An estuary

456-460: A sub-humid mediterranean climate of Atlantic tendency. Rain is less abundant than in the nearby coast due to the low altitude of the islands, which represents a minimal obstacle for passing clouds. The annual precipitation in Cíes is 1,000 mm/year, while Ons and Sálvora receive 1,500 mm/year. In the summer, precipitation becomes rare. Cortegada, due to its location in the inside of the estuary close to

532-408: A type of ecosystem in some estuaries that have been negatively impacted by eutrophication. Cordgrass vegetation dominates the salt marsh landscape. Excess nutrients allow the plants to grow at greater rates in above ground biomass, however less energy is allocated to the roots since nutrients is abundant. This leads to a lower biomass in the vegetation below ground which destabilizes the banks of

608-407: A variety of factors including soil erosion , deforestation , overgrazing , overfishing and the filling of wetlands. Eutrophication may lead to excessive nutrients from sewage and animal wastes; pollutants including heavy metals , polychlorinated biphenyls , radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion. The word "estuary"

684-563: A well-mixed water column and the disappearance of the vertical salinity gradient . The freshwater-seawater boundary is eliminated due to the intense turbulent mixing and eddy effects . The lower reaches of Delaware Bay and the Raritan River in New Jersey are examples of vertically homogeneous estuaries. Inverse estuaries occur in dry climates where evaporation greatly exceeds the inflow of freshwater. A salinity maximum zone

760-436: A wholly marine embayment to any of the other estuary types. The most important variable characteristics of estuary water are the concentration of dissolved oxygen, salinity and sediment load. There is extreme spatial variability in salinity, with a range of near-zero at the tidal limit of tributary rivers to 3.4% at the estuary mouth. At any one point, the salinity will vary considerably over time and seasons, making it

836-477: A wide effect on the surrounding water bodies.  In turn, this can decrease fishing industry sales in one area and across the country. Production in 2016 from recreational and commercial fishing contributes billions of dollars to the United States' gross domestic product (GDP). A decrease in production within this industry can affect any of the 1.7 million people the fishing industry employs yearly across

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912-516: Is Pontevedra . In the Ria de Pontevedra and the Ría Vigo there are a lot of different beaches. Furthermore, the cliffs just off shore offer extensive views. Naturally, many water and boating activities are also a central attraction for tourists visiting the Rías Baixas. The many towns located near the rias also offer added interest. Each town is distinctive, but churches, lighthouses, and manor houses are

988-455: Is a dynamic ecosystem having a connection to the open sea through which the sea water enters with the rhythm of the tides . The effects of tides on estuaries can show nonlinear effects on the movement of water which can have important impacts on the ecosystem and waterflow. The seawater entering the estuary is diluted by the fresh water flowing from rivers and streams. The pattern of dilution varies between different estuaries and depends on

1064-513: Is derived from the Latin word aestuarium meaning tidal inlet of the sea, which in itself is derived from the term aestus , meaning tide. There have been many definitions proposed to describe an estuary. The most widely accepted definition is: "a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which seawater is measurably diluted with freshwater derived from land drainage". However, this definition excludes

1140-412: Is equipped with an information center, and there are information points in Cíes, Ons and Cortegada. Due to successive fires and agricultural practice, the original forests of the islands eventually declined and reforestation attempts in the 70s and 80s of the 20th century were performed with foreign species, particularly Eucalyptus and Acacias . While successful at creating new forests, this resulted in

1216-411: Is formed, and both riverine and oceanic water flow close to the surface towards this zone. This water is pushed downward and spreads along the bottom in both the seaward and landward direction. Examples of an inverse estuary are Spencer Gulf , South Australia, Saloum River and Casamance River , Senegal. Estuary type varies dramatically depending on freshwater input, and is capable of changing from

1292-566: Is less restricted, and there is a slow but steady exchange of water between the estuary and the ocean. Fjord-type estuaries can be found along the coasts of Alaska , the Puget Sound region of western Washington state , British Columbia , eastern Canada, Greenland , Iceland , New Zealand, and Norway. These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting , volcanoes , and landslides . Inundation from eustatic sea-level rise during

1368-517: Is that of seafood and a large amount of that seafood comes from the Rías Baxias. Fishing and harvesting the abundant aquatic life that live in the rias is one way of supporting the industry. Another is using the area for aquaculture such as mussel farming. The port of Vigo is especially important in serving the fishing industry. In fact, it has become the leading fishing port in Europe. For many of

1444-553: Is the Colorado River Delta in Mexico, historically covered with marshlands and forests, but now essentially a salt flat. Atlantic Islands of Galicia National Park The Atlantic Islands of Galicia National Park ( Galician : Parque Nacional das Illas Atlánticas de Galicia , Spanish : Parque Nacional de las Islas Atlánticas de Galicia ) is the only national park located in the province of Pontevedra , in

1520-646: Is the whitefish species from the European Alps . Eutrophication reduced the oxygen levels in their habitats so greatly that whitefish eggs could not survive, causing local extinctions. However, some animals, such as carnivorous fish, tend to do well in nutrient-enriched environments and can benefit from eutrophication. This can be seen in populations of bass or pikes. Eutrophication can affect many marine habitats which can lead to economic consequences. The commercial fishing industry relies upon estuaries for approximately 68 percent of their catch by value because of

1596-748: The Holocene Epoch has also contributed to the formation of these estuaries. There are only a small number of tectonically produced estuaries; one example is the San Francisco Bay , which was formed by the crustal movements of the San Andreas Fault system causing the inundation of the lower reaches of the Sacramento and San Joaquin rivers . In this type of estuary, river output greatly exceeds marine input and tidal effects have minor importance. Freshwater floats on top of

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1672-688: The Leatherback Sea Turtle (Dermochelys coriacea) . In the amphibian family, the islands are home to smaller salamanders than in the nearby continent, with distinct reproduction and diurnal activity as an adaptation to insular conditions. Reptiles include Bedriaga's skinks (Chalcides bedriagai) and ocellated lizards (Timon lepidus) , and a notable insect is the rare Spanish festoon butterfly (Zerynthia rumina) . Mammals are scarce, although there are plenty of rabbits which practically have no predators. In recent years, otters have reappeared. There are traces of human occupation in

1748-805: The Long-finned Pilot Whale (Globicephala melas) and the Short-beaked Common Dolphin (Delphinus delphis) . Additionally, the park sees a regular presence of marine turtles. Among them, the most frequent species is the Loggerhead Sea Turtle (Caretta caretta) , along with the Green Sea Turtle (Chelonia mydas) , Kemp's Ridley Sea Turtle (Lepidochelys kempii) , the Hawksbill Sea Turtle (Eretmochelys imbricata) or

1824-610: The Mandovi estuary in Goa during the monsoon period. As tidal forcing increases, river output becomes less than the marine input. Here, current induced turbulence causes mixing of the whole water column such that salinity varies more longitudinally rather than vertically, leading to a moderately stratified condition. Examples include the Chesapeake Bay and Narragansett Bay . Tidal mixing forces exceed river output, resulting in

1900-640: The Mid-Atlantic coast, and Galveston Bay and Tampa Bay along the Gulf Coast . Bar-built estuaries are found in a place where the deposition of sediment has kept pace with rising sea levels so that the estuaries are shallow and separated from the sea by sand spits or barrier islands. They are relatively common in tropical and subtropical locations. These estuaries are semi-isolated from ocean waters by barrier beaches ( barrier islands and barrier spits ). Formation of barrier beaches partially encloses

1976-734: The Severn Estuary in the United Kingdom and the Ems Dollard along the Dutch-German border. The width-to-depth ratio of these estuaries is typically large, appearing wedge-shaped (in cross-section) in the inner part and broadening and deepening seaward. Water depths rarely exceed 30 m (100 ft). Examples of this type of estuary in the U.S. are the Hudson River , Chesapeake Bay , and Delaware Bay along

2052-740: The Yellow-legged Gull (Larus cachinnans michahellis) is especially noteworthy; it is a migratory species, whose populational estimates in the Atlantic Islands of Galicia make up 7-15% of the population worldwide, and a third of the Spanish population; or the presence of the European Shag (Phalacrocorax aristotelis) , included in the category of Vulnerable in the Spanish Catalogue of Endangered Species and in

2128-484: The autonomous community of Galicia , Spain . It comprises the archipelagos of Cíes , Ons , Sálvora and Cortegada . The park covers a land area of 1,200 ha (3,000 acres) and a sea area of 7,200 ha (18,000 acres). It is the tenth most visited national park in Spain. It was the thirteenth national park to be established in Spain. Since 2021 it has been designated as a protected Ramsar site . The islands of

2204-478: The black-tailed godwit , rely on estuaries. Two of the main challenges of estuarine life are the variability in salinity and sedimentation . Many species of fish and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed osmoconformers and osmoregulators . Many animals also burrow to avoid predation and to live in a more stable sedimental environment. However, large numbers of bacteria are found within

2280-631: The Galician Catalogue of Endangered Species, which in this territory has 1-3% of its worldwide population and 78% of its Spanish population. Regarding the mammals that inhabit the marine environments, a noteworthy fact is the presence of up to 27 species of cetaceans and pinnipeds. The most frequent species are the Common Bottlenose Dolphin (Tursiops truncatus) , the Harbour Porpoise (Phocoena phocoena) ,

2356-570: The Galician summer tourist capital, which makes the Ria de Pontevedra the most touristic of the Rías Baixas. The estuary has numerous beaches on both shores such as Portocelo, Mogor, Aguete and Lapamán on the south shore and Cabeceira, Areas, Paxariñas, Canelas, Montalvo , Pragueira, Major and the famous La Lanzada on the north shore. The Ría de Vigo is the southernmost of the Rias Baixas. Within

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2432-676: The Grove Inlet. The largest river to join with the Ría de Arousa is the Ulla. The Ría de Arousa is especially important in the seafood industry as it accounts for over half of the mussel farming in the Rías Baixas. As is the case with the Ría de Muros e Noia, the Ría de Arousa has two lagoons, one with fresh water and the other with salt water. In the area there is also the Parque Natural de Dunas de Corrubedo where visitors can admire sand dunes-

2508-503: The Rías Baixas shares its name with a major inland city. In the case of the Muros e Noia, it is two separate cities. The Ría de Arousa gets its name from the longer Vilagarcía de Arousa. The Ría de Muros e Noia is the smallest of the Rías Baixas as well as the most northern. The part of the ria known as Muros is in the area closest to the mouth (outer zone), while the Noia portion is farther in

2584-400: The United States. Estuaries are incredibly dynamic systems, where temperature, salinity, turbidity, depth and flow all change daily in response to the tides. This dynamism makes estuaries highly productive habitats, but also make it difficult for many species to survive year-round. As a result, estuaries large and small experience strong seasonal variation in their fish communities. In winter,

2660-581: The Vigo port. Access to Salvora and Cortegada is more restricted, requiring organized visits. There are no waste bins on the islands. Visitors are required to take their litter back to the mainland. In 2017, the number of visitors to the park totaled 327,149. The Cíes archipelago received by far the most tourists (216,975), followed by Ons (88,306), Sálvora (7,261) and Cortegada (6,500). The park has two visitor centers, one in Vigo and one in Ons. Additionally, Cíes

2736-437: The area. On the islands, many types of seabirds make their homes. Visitors to the park can participate in taking walks, bird and wildlife watching, and occasionally camping. However, the designation of the park as a protected area prevents too many people from being on the islands at once Special permission is needed for certain activities, such as scuba diving, snorkeling, or sailing. An especially important industry to Galicia

2812-613: The bird species, those that are particularly significant due to their threat level are the European Storm Petrel (Hydrobates pelagicus) , whose nesting colony could make up 1% of the Spanish Atlantic population, or the overwintering Balearic Shearwater (Puffinus mauretanicus) and the Eurasian curlew (Numenius arquata) included in the Spanish Catalogue of Endangered Species as Endangered. The presence of

2888-452: The bottom where they are harmless. Historically the oysters filtered the estuary's entire water volume of excess nutrients every three or four days. Today that process takes almost a year, and sediment, nutrients, and algae can cause problems in local waters. Some major rivers that run through deserts historically had vast, expansive estuaries that have been reduced to a fraction of their former size, because of dams and diversions. One example

2964-403: The coast and along river valleys. These areas were subsequently flooded by water from the ocean and adjoining rivers. Over time, erosion also helped shape each inlet. Water from the ocean flows into the ria and is eventually joined by inland rivers. This creates an estuary (a body of water where salt and fresh water mix). Geologists break each ria into two basic zones based on the composition of

3040-521: The coast, presents an oceanic climate, with a rainfall of 2000 mm/year. The average annual temperature oscillates in a range of 13-15 °C with little seasonal variability, with dominant winds from the North in the summer months and from the Southwest in winter. This sea-land ecosystem has a laurel forest and over 200 species of seaweed . It also stands out for its shellfish, corals and anemones. Among

3116-409: The dissolved oxygen from the water; thus hypoxic or anoxic zones can develop. Nitrogen is often the lead cause of eutrophication in estuaries in temperate zones. During a eutrophication event, biogeochemical feedback decreases the amount of available silica . These feedbacks also increase the supply of nitrogen and phosphorus, creating conditions where harmful algal blooms can persist. Given

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3192-401: The effects of modifying the estuarine circulation. Fjord -type estuaries are formed in deeply eroded valleys formed by glaciers . These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement. The estuary is shallowest at its mouth, where terminal glacial moraines or rock bars form sills that restrict water flow. In the upper reaches of

3268-601: The estuary impacted by human activities, and over time may shift the basic composition of the ecosystem, and the reversible or irreversible changes in the abiotic and biotic parts of the systems from the bottom up. For example, Chinese and Russian industrial pollution, such as phenols and heavy metals, has devastated fish stocks in the Amur River and damaged its estuary soil. Estuaries tend to be naturally eutrophic because land runoff discharges nutrients into estuaries. With human activities, land run-off also now includes

3344-555: The estuary near the head (inner zone). Out of all five Rias Baixas, this is the only one not to have islands near the mouth. The principal river to join the Ría de Muros e Noia is the Tambre. Important natural features in the area are the mountain and lagoon of Louro as well as the Corrubedo wetlands. The Ría de Arousa is the largest of the Rías Baixas. In addition to the main ria, there is a smaller branch inlet further inland known as

3420-424: The estuary, the depth can exceed 300 m (1,000 ft). The width-to-depth ratio is generally small. In estuaries with very shallow sills, tidal oscillations only affect the water down to the depth of the sill, and the waters deeper than that may remain stagnant for a very long time, so there is only an occasional exchange of the deep water of the estuary with the ocean. If the sill depth is deep, water circulation

3496-776: The estuary, with only narrow inlets allowing contact with the ocean waters. Bar-built estuaries typically develop on gently sloping plains located along tectonically stable edges of continents and marginal sea coasts. They are extensive along the Atlantic and Gulf coasts of the U.S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 m (13 ft). The barrier beaches that enclose bar-built estuaries have been developed in several ways: Fjords were formed where Pleistocene glaciers deepened and widened existing river valleys so that they become U-shaped in cross-sections. At their mouths there are typically rocks, bars or sills of glacial deposits , which have

3572-455: The first two the predominant parent rock is two-mica gneiss-granite, while in Sálvora the predominant material is coarse-grained amphibole-biotite late granodiorite . Cortegada, meanwhile, presents a composition that is predominantly of metamorphic rock shale and paragneiss , with migmatic granite . Although located in a region of oceanic climate , most of the islands of the park present

3648-609: The fish community is dominated by hardy marine residents, and in summer a variety of marine and anadromous fishes move into and out of estuaries, capitalizing on their high productivity. Estuaries provide a critical habitat to a variety of species that rely on estuaries for life-cycle completion. Pacific Herring ( Clupea pallasii ) are known to lay their eggs in estuaries and bays, surfperch give birth in estuaries, juvenile flatfish and rockfish migrate to estuaries to rear, and anadromous salmonids and lampreys use estuaries as migration corridors. Also, migratory bird populations, such as

3724-400: The great biodiversity of this ecosystem. During an algal bloom , fishermen have noticed a significant increase in the quantity of fish. A sudden increase in primary productivity causes spikes in fish populations which leads to more oxygen being utilized. It is the continued deoxygenation of the water that then causes a decline in fish populations. These effects can begin in estuaries and have

3800-420: The impacts do not end there. Plant death alters the entire food web structure which can result in the death of animals within the afflicted biome . Estuaries are hotspots for biodiversity , containing a majority of commercial fish catch, making the impacts of eutrophication that much greater within estuaries. Some specific estuarine animals feel the effects of eutrophication more strongly than others. One example

3876-476: The influx of saline water , and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment , making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when

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3952-572: The islands . Ons Island is still home to a small permanent population of 63 people. In 1980 the Cíes Islands were declared a natural park. They are also a Special Protection Area for birds. On June 13, 2002 was declared a national park. However, 6 months later, the oil spill caused by the Prestige oil tanker came on its shores, except on the island of Cortegada . The islands of Lobeiras and Sisargas were initially discussed to be part of

4028-520: The islands Monteagudo, Montefaro and San Martiño. The 8,480 ha of the national park are distributed as follows: The geological history of the islands dates back to the Palaeozoic era , when the geological materials which currently form the land and marine areas of the park were formed. The geological composition of the Archipelagos of Cíes, Ons and Sálvora is of granitic nature, although in

4104-579: The islands since the Iron Age. Ceramics have also been found since Roman times. The islands were occupied by various monastic orders during the Middle Ages, were owned by the Church, gauged by nobles of the time and attacked by invaders who used them as a base for raids on the coast. More recently, the Cíes Islands were inhabited until the eighteenth century, but by pirates' action, people had to abandon

4180-638: The largest in Galicia. The Ria de Pontevedra is the second southernmost of the Rías Baixas. Similar to the Ría de Arousa, the Ría de Pontevedra also has a smaller, distinct, inlet known as the Ría de Aldan. The Lérez River is the principal river to flow into the Ría de Pontevedra and at the mouth are islands known as Ons Island and Onza Island. Unique to the Pontevedra area are a series of rock engravings. The Ria de Pontevedra has numerous marinas such as Pontevedra , Combarro, Aguete (Marín) and Sanxenxo ,

4256-525: The many chemicals used as fertilizers in agriculture as well as waste from livestock and humans. Excess oxygen-depleting chemicals in the water can lead to hypoxia and the creation of dead zones . This can result in reductions in water quality, fish, and other animal populations. Overfishing also occurs. Chesapeake Bay once had a flourishing oyster population that has been almost wiped out by overfishing. Oysters filter these pollutants, and either eat them or shape them into small packets that are deposited on

4332-422: The marine environment, such as plastics , pesticides , furans , dioxins , phenols and heavy metals . Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation . They also accumulate in benthic environments, such as estuaries and bay muds : a geological record of human activities of the last century. The elemental composition of biofilm reflect areas of

4408-575: The marsh causing increased rates of erosion . A similar phenomenon occurs in mangrove swamps , which are another potential ecosystem in estuaries. An increase in nitrogen causes an increase in shoot growth and a decrease in root growth. Weaker root systems cause a mangrove tree to be less resilient in seasons of drought, which can lead to the death of the mangrove. This shift in above ground and below ground biomass caused by eutrophication could hindered plant success in these ecosystems. Across all biomes, eutrophication often results in plant death but

4484-589: The more northern Rías Altas ("Upper Rias") in location and other characteristics. As compared to the Rías Altas, the waters of the Rías Baixas are calmer and smoother. The coast that contains the Rías Altas is sometimes known as the Costa da Morte (in Galician : Coast of Death), due to a high number of shipwrecks, a fact that only underlines the turbulent nature of the waters. Most of the Rías Baixas have islands in

4560-502: The national park and could be added to the park in the future. During the summer, daily boats link Cíes with the ports of Vigo , Baiona and Cangas , and Ons with Portonovo , Sanxenxo , Bueu , Marín and Pontevedra . Daily affluence is limited and all visitors are required to previously book an authorization request from the Galician Government. In Cíes there is a camping area but permissions have to be reserved at

4636-440: The now off-balance nitrogen cycle , estuaries can be driven to phosphorus limitation instead of nitrogen limitation. Estuaries can be severely impacted by an unbalanced phosphorus cycle, as phosphorus interacts with nitrogen and silica availability. With an abundance of nutrients in the ecosystem, plants and algae overgrow and eventually decompose, which produce a significant amount of carbon dioxide. While releasing CO 2 into

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4712-463: The ocean near the mouth, which help to create the calm waters. Due to the proximity to the ocean, the climate of the area is mild and moist. This creates the green landscape for which the area is known. The land around the Rías Baixas is also known for abundant pine and eucalyptus forests. Neither pine nor eucalyptus is indigenous to the area, but were introduced and have taken hold. Naturally occurring vegetation includes oak and chestnut trees. Each of

4788-653: The overall ria there are two separate areas: the San Simón Inlet and the Ria of Bayona. The main river to join with the Ría de Vigo is the Verdugo. Out to sea, the Cies Islands are associated with the ría. Their location in the ocean near the mouth allow for the protection necessary to have a safe port. In addition to the port, the Ría de Vigo contains many marinas. The coastline within the Ría de Vigo has two distinct parts. The upper and inner areas are calm, while

4864-576: The park are located in the continental platform of the Galician Rías Baixas . The archipelagos of Cortegada and Sálvora are located in the inner and outer areas of the Ría de Arousa , respectively. The Ons archipelago, formed mainly by the Ons and Onza islands, are located at the entrance of the Ría de Pontevedra . Similarly, the Cíes Islands surround the entrance of the Ría de Vigo and comprise

4940-430: The park, which takes up a total of around 8,333 hectares. The designation of the area as a national park is still fairly recent, occurring on July 1, 2002. In addition to attracting visitors, the park serves as an important refuge for a variety of marine and island life. Populations of algae and shellfish are present in the water around the islands. Even large mammals such as dolphins, seals, and whales occasionally appear in

5016-409: The people who live in Galicia, the ocean and rías have provided their livelihood. Approximately 400,000 people make their living from fishing or performing services that help the industry. Most of the population of the region is still located near the coast and Vigo is the city with the largest population of the working class in Galicia. However, even though the fishing industry remains strong, changes in

5092-435: The sea level began to rise about 10,000–12,000 years ago. Estuaries are typically classified according to their geomorphological features or to water-circulation patterns. They can have many different names, such as bays , harbors , lagoons , inlets , or sounds , although some of these water bodies do not strictly meet the above definition of an estuary and could be fully saline. Many estuaries suffer degeneration from

5168-427: The seawater in a layer that gradually thins as it moves seaward. The denser seawater moves landward along the bottom of the estuary, forming a wedge-shaped layer that is thinner as it approaches land. As a velocity difference develops between the two layers, shear forces generate internal waves at the interface, mixing the seawater upward with the freshwater. An examples of a salt wedge estuary is Mississippi River and

5244-411: The sediment which has a very high oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions, which can be further exacerbated by limited water flow. Phytoplankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with the tides . Their productivity is largely dependent upon the turbidity of

5320-435: The southern coastline contains more turbulent waters. Galicia's only national park is Parque Nacional Marítimo-Terrestre das Illas Atlánticas de Galicia ( Galician for "Galician Atlantic Islands Maritime-Terrestrial National Park"). This park is made up of the Ons, Salvora, Cortegada and Cíes Islands , each located at the mouth of one of the Rías Baixas. Both the islands as well as surrounding oceanic areas are included in

5396-456: The volume of freshwater, the tidal range, and the extent of evaporation of the water in the estuary. Drowned river valleys are also known as coastal plain estuaries. In places where the sea level is rising relative to the land, sea water progressively penetrates into river valleys and the topography of the estuary remains similar to that of a river valley. This is the most common type of estuary in temperate climates. Well-studied estuaries include

5472-453: The water and atmosphere, these organisms are also intaking all or nearly all of the available oxygen creating a hypoxic environment and unbalanced oxygen cycle . The excess carbon in the form of CO 2 can lead to low pH levels and ocean acidification , which is more harmful for vulnerable coastal regions like estuaries. Eutrophication has been seen to negatively impact many plant communities in estuarine ecosystems . Salt marshes are

5548-408: The water and sediments: the outer zone and the inner zone. The outer zone is that which joins with the Atlantic Ocean. The inner zone is inland where rivers join with the ria. Another way to refer to these two zones is with the terms "mouth" and "head". The mouth of the ria is the part closest to the ocean and the "head" joins with the river. The four rias that make up the Rías Baixas are distinct from

5624-835: The water. The main phytoplankton present are diatoms and dinoflagellates which are abundant in the sediment. A primary source of food for many organisms on estuaries, including bacteria , is detritus from the settlement of the sedimentation. Of the thirty-two largest cities in the world in the early 1990s, twenty-two were located on estuaries. As ecosystems, estuaries are under threat from human activities such as pollution and overfishing . They are also threatened by sewage, coastal settlement, land clearance and much more. Estuaries are affected by events far upstream, and concentrate materials such as pollutants and sediments. Land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into estuaries. Contaminants can be introduced which do not disintegrate rapidly in

5700-463: The wine produced there. This wine is especially successful in the area because the grapes that are the main ingredient are able to withstand and even thrive in the moist, coastal, climate. The Rías Baixas are an important source of tourism within Galicia, even more so than the Rías Altas. A large draw for tourists is the expansive coastline that results from the nature of the rias. This coastline also leads to many beaches. The most important historic city

5776-420: The world's oceans, such as less available fish, as well as competition with other countries have caused many young people to leave the industry and even the country. Wine making is another industry that is important to the Rías Baixas and surrounding land. There are approximately 20,000 different vineyards in the area. A specific type of white wine, Albariño , originated in the Rías Baixas and now takes up 90% of

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