River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts. River ecosystems are part of larger watershed networks or catchments, where smaller headwater streams drain into mid-size streams, which progressively drain into larger river networks.
River ecosystems are prime examples of lotic ecosystems. Lotic refers to flowing water, from the Latin lotus, meaning washed. Lotic waters range from springs only a few centimeters wide to major rivers kilometers in width. Much of this article applies to lotic ecosystems in general, including related lotic systems such as streams and springs. Lotic ecosystems can be contrasted with lentic ecosystems, which involve relatively still terrestrial waters such as lakes, ponds, and wetlands. Together, these two ecosystems form the more general study area of freshwater or aquatic ecology.
The following unifying characteristics make the ecology of running waters unique among aquatic habitats.
The non living components of an ecosystem are called abiotic components. E.g stone,air,soil,etc.
Unidirectional water flow is the key factor in lotic systems influencing their ecology. Stream flow can be continuous or intermittent, though. Stream flow is the result of the summative inputs from groundwater, precipitation, and overland flow. Water flow can vary between systems, ranging from torrential rapids to slow backwaters that almost seem like lentic systems. The speed or velocity of the water flow of the water column can also vary within a system and is subject to chaotic turbulence, though water velocity tends to be highest in the middle part of the stream channel (known as the thalveg). This turbulence results in divergences of flow from the mean downslope flow vector as typified by eddy currents. The mean flow rate vector is based on variability of friction with the bottom or sides of the channel, sinuosity, obstructions, and the incline gradient. In addition, the amount of water input into the system from direct precipitation, snowmelt, and/or groundwater can affect flow rate. The amount of water in a stream is measured as discharge (volume per unit time). As water flows downstream, streams and rivers most often gain water volume, so at base flow (i.e., no storm input), smaller headwater streams have very low discharge, while larger rivers have much higher discharge. The "flow regime" of a river or stream includes the general patterns of discharge over annual or decadal time scales, and may capture seasonal changes in flow.
While water flow is strongly determined by slope, flowing waters can alter the general shape or direction of the stream bed, a characteristic also known as geomorphology. The profile of the river water column is made up of three primary actions: erosion, transport, and deposition. Rivers have been described as "the gutters down which run the ruins of continents". Rivers are continuously eroding, transporting, and depositing substrate, sediment, and organic material. The continuous movement of water and entrained material creates a variety of habitats, including riffles, glides, and pools.
Light is important to lotic systems, because it provides the energy necessary to drive primary production via photosynthesis, and can also provide refuge for prey species in shadows it casts. The amount of light that a system receives can be related to a combination of internal and external stream variables. The area surrounding a small stream, for example, might be shaded by surrounding forests or by valley walls. Larger river systems tend to be wide so the influence of external variables is minimized, and the sun reaches the surface. These rivers also tend to be more turbulent, however, and particles in the water increasingly attenuate light as depth increases. Seasonal and diurnal factors might also play a role in light availability because the angle of incidence, the angle at which light strikes water can lead to light lost from reflection. Known as Beer's Law, the shallower the angle, the more light is reflected and the amount of solar radiation received declines logarithmically with depth. Additional influences on light availability include cloud cover, altitude, and geographic position.
Most lotic species are poikilotherms whose internal temperature varies with their environment, thus temperature is a key abiotic factor for them. Water can be heated or cooled through radiation at the surface and conduction to or from the air and surrounding substrate. Shallow streams are typically well mixed and maintain a relatively uniform temperature within an area. In deeper, slower moving water systems, however, a strong difference between the bottom and surface temperatures may develop. Spring fed systems have little variation as springs are typically from groundwater sources, which are often very close to ambient temperature. Many systems show strong diurnal fluctuations and seasonal variations are most extreme in arctic, desert and temperate systems. The amount of shading, climate and elevation can also influence the temperature of lotic systems.
Water chemistry in river ecosystems varies depending on which dissolved solutes and gases are present in the water column of the stream. Specifically river water can include, apart from the water itself,
Dissolved stream solutes can be considered either reactive or conservative. Reactive solutes are readily biologically assimilated by the autotrophic and heterotrophic biota of the stream; examples can include inorganic nitrogen species such as nitrate or ammonium, some forms of phosphorus (e.g., soluble reactive phosphorus), and silica. Other solutes can be considered conservative, which indicates that the solute is not taken up and used biologically; chloride is often considered a conservative solute. Conservative solutes are often used as hydrologic tracers for water movement and transport. Both reactive and conservative stream water chemistry is foremost determined by inputs from the geology of its watershed, or catchment area. Stream water chemistry can also be influenced by precipitation, and the addition of pollutants from human sources. Large differences in chemistry do not usually exist within small lotic systems due to a high rate of mixing. In larger river systems, however, the concentrations of most nutrients, dissolved salts, and pH decrease as distance increases from the river’s source.
In terms of dissolved gases, oxygen is likely the most important chemical constituent of lotic systems, as all aerobic organisms require it for survival. It enters the water mostly via diffusion at the water-air interface. Oxygen’s solubility in water decreases as water pH and temperature increases. Fast, turbulent streams expose more of the water’s surface area to the air and tend to have low temperatures and thus more oxygen than slow, backwaters. Oxygen is a byproduct of photosynthesis, so systems with a high abundance of aquatic algae and plants may also have high concentrations of oxygen during the day. These levels can decrease significantly during the night when primary producers switch to respiration. Oxygen can be limiting if circulation between the surface and deeper layers is poor, if the activity of lotic animals is very high, or if there is a large amount of organic decay occurring.
Rivers can also transport suspended inorganic and organic matter. These materials can include sediment or terrestrially-derived organic matter that falls into the stream channel. Often, organic matter is processed within the stream via mechanical fragmentation, consumption and grazing by invertebrates, and microbial decomposition. Leaves and woody debris recognizable coarse particulate organic matter (CPOM) into particulate organic matter (POM), down to fine particulate organic matter. Woody and non-woody plants have different instream breakdown rates, with leafy plants or plant parts (e.g., flower petals) breaking down faster than woody logs or branches.
The inorganic substrate of lotic systems is composed of the geologic material present in the catchment that is eroded, transported, sorted, and deposited by the current. Inorganic substrates are classified by size on the Wentworth scale, which ranges from boulders, to pebbles, to gravel, to sand, and to silt. Typically, substrate particle size decreases downstream with larger boulders and stones in more mountainous areas and sandy bottoms in lowland rivers. This is because the higher gradients of mountain streams facilitate a faster flow, moving smaller substrate materials further downstream for deposition. Substrate can also be organic and may include fine particles, autumn shed leaves, large woody debris such as submerged tree logs, moss, and semi-aquatic plants. Substrate deposition is not necessarily a permanent event, as it can be subject to large modifications during flooding events.
The living components of an ecosystem are called the biotic components. Streams have numerous types of biotic organisms that live in them, including bacteria, primary producers, insects and other invertebrates, as well as fish and other vertebrates.
Biofilm is the combination of algae, diatoms, fungi, bacteria, plankton, and other small microorganisms that exist in a film along the streambed or benthos. Biofilm assemblages themselves are complex, and add to the complexity of a streambed.
Bacteria are present in large numbers in lotic waters. Free-living forms are associated with decomposing organic material, biofilm on the surfaces of rocks and vegetation, in between particles that compose the substrate, and suspended in the water column. Other forms are also associated with the guts of lotic organisms as parasites or in commensal relationships. Bacteria play a large role in energy recycling (see below).
Algae, consisting of phytoplankton and periphyton, are the most significant sources of primary production in most streams and rivers. Phytoplankton float freely in the water column and thus are unable to maintain populations in fast flowing streams. They can, however, develop sizeable populations in slow moving rivers and backwaters. Periphyton are typically filamentous and tufted algae that can attach themselves to objects to avoid being washed away by fast currents. In places where flow rates are negligible or absent, periphyton may form a gelatinous, unanchored floating mat.
Plants exhibit limited adaptations to fast flow and are most successful in reduced currents. More primitive plants, such as mosses and liverworts attach themselves to solid objects. This typically occurs in colder headwaters where the mostly rocky substrate offers attachment sites. Some plants are free floating at the water’s surface in dense mats like duckweed or water hyacinth. Others are rooted and may be classified as submerged or emergent. Rooted plants usually occur in areas of slackened current where fine-grained soils are found. These rooted plants are flexible, with elongated leaves that offer minimal resistance to current.
Living in flowing water can be beneficial to plants and algae because the current is usually well aerated and it provides a continuous supply of nutrients. These organisms are limited by flow, light, water chemistry, substrate, and grazing pressure. Algae and plants are important to lotic systems as sources of energy, for forming microhabitats that shelter other fauna from predators and the current, and as a food resource.
Up to 90% of invertebrates in some lotic systems are insects. These species exhibit tremendous diversity and can be found occupying almost every available habitat, including the surfaces of stones, deep below the substratum in the hyporheic zone, adrift in the current, and in the surface film.
Insects have developed several strategies for living in the diverse flows of lotic systems. Some avoid high current areas, inhabiting the substratum or the sheltered side of rocks. Others have flat bodies to reduce the drag forces they experience from living in running water. Some insects, like the giant water bug (Belostomatidae), avoid flood events by leaving the stream when they sense rainfall. In addition to these behaviors and body shapes, insects have different life history adaptations to cope with the naturally-occurring physical harshness of stream environments.. Some insects time their life events based on when floods and droughts occur. For example, some mayflies synchronize when they emerge as flying adults with when snowmelt flooding usually occurs in Colorado streams. Other insects do not have a flying stage and spend their entire life cycle in the river.
Like most of the primary consumers, lotic invertebrates often rely heavily on the current to bring them food and oxygen. Invertebrates are important as both consumers and prey items in lotic systems.
The common orders of insects that are found in river ecosystems include Ephemeroptera (also known as a mayfly), Trichoptera (also known as a caddisfly), Plecoptera (also known as a stonefly, Diptera (also known as a true fly), some types of Coleoptera (also known as a beetle), Odonata (the group that includes the dragonfly and the damselfly), and some types of Hemiptera (also known as true bugs).
Fish are probably the best-known inhabitants of lotic systems. The ability of a fish species to live in flowing waters depends upon the speed at which it can swim and the duration that its speed can be maintained. This ability can vary greatly between species and is tied to the habitat in which it can survive. Continuous swimming expends a tremendous amount of energy and, therefore, fishes spend only short periods in full current. Instead, individuals remain close to the bottom or the banks, behind obstacles, and sheltered from the current, swimming in the current only to feed or change locations. Some species have adapted to living only on the system bottom, never venturing into the open water flow. These fishes are dorso-ventrally flattened to reduce flow resistance and often have eyes on top of their heads to observe what is happening above them. Some also have sensory barrels positioned under the head to assist in the testing of substratum.
Lotic systems typically connect to each other, forming a path to the ocean (spring → stream → river → ocean), and many fishes have life cycles that require stages in both fresh and salt water. Salmon, for example, are anadromous species that are born in freshwater but spend most of their adult life in the ocean, returning to fresh water only to spawn. Eels are catadromous species that do the opposite, living in freshwater as adults but migrating to the ocean to spawn.
Other vertebrate taxa that inhabit lotic systems include amphibians, such as salamanders, reptiles (e.g. snakes, turtles, crocodiles and alligators) various bird species, and mammals (e.g., otters, beavers, hippos, and river dolphins). With the exception of a few species, these vertebrates are not tied to water as fishes are, and spend part of their time in terrestrial habitats. Many fish species are important as consumers and as prey species to the larger vertebrates mentioned above.
Invertebrates can be organized into many feeding guilds in lotic systems. Some species are shredders, which use large and powerful mouth parts to feed on non-woody CPOM and their associated microorganisms. Others are suspension feeders, which use their setae, filtering aparati, nets, or even secretions to collect FPOM and microbes from the water. These species may be passive collectors, utilizing the natural flow of the system, or they may generate their own current to draw water, and also, FPOM in Allan. Members of the gatherer-collector guild actively search for FPOM under rocks and in other places where the stream flow has slackened enough to allow deposition. Grazing invertebrates utilize scraping, rasping, and browsing adaptations to feed on periphyton and detritus. Finally, several families are predatory, capturing and consuming animal prey. Both the number of species and the abundance of individuals within each guild is largely dependent upon food availability. Thus, these values may vary across both seasons and systems.
Fish can also be placed into feeding guilds. Planktivores pick plankton out of the water column. Herbivore-detritivores are bottom-feeding species that ingest both periphyton and detritus indiscriminately. Surface and water column feeders capture surface prey (mainly terrestrial and emerging insects) and drift (benthic invertebrates floating downstream). Benthic invertebrate feeders prey primarily on immature insects, but will also consume other benthic invertebrates. Top predators consume fishes and/or large invertebrates. Omnivores ingest a wide range of prey. These can be floral, faunal, and/or detrital in nature. Finally, parasites live off of host species, typically other fishes. Fish are flexible in their feeding roles, capturing different prey with regard to seasonal availability and their own developmental stage. Thus, they may occupy multiple feeding guilds in their lifetime. The number of species in each guild can vary greatly between systems, with temperate warm water streams having the most benthic invertebrate feeders, and tropical systems having large numbers of detritus feeders due to high rates of allochthonous input.
Large rivers have comparatively more species than small streams. Many relate this pattern to the greater area and volume of larger systems, as well as an increase in habitat diversity. Some systems, however, show a poor fit between system size and species richness. In these cases, a combination of factors such as historical rates of speciation and extinction, type of substrate, microhabitat availability, water chemistry, temperature, and disturbance such as flooding seem to be important.
Although many alternate theories have been postulated for the ability of guild-mates to coexist (see Morin 1999), resource partitioning has been well documented in lotic systems as a means of reducing competition. The three main types of resource partitioning include habitat, dietary, and temporal segregation.
Habitat segregation was found to be the most common type of resource partitioning in natural systems (Schoener, 1974). In lotic systems, microhabitats provide a level of physical complexity that can support a diverse array of organisms (Vincin and Hawknis, 1998). The separation of species by substrate preferences has been well documented for invertebrates. Ward (1992) was able to divide substrate dwellers into six broad assemblages, including those that live in: coarse substrate, gravel, sand, mud, woody debris, and those associated with plants, showing one layer of segregation. On a smaller scale, further habitat partitioning can occur on or around a single substrate, such as a piece of gravel. Some invertebrates prefer the high flow areas on the exposed top of the gravel, while others reside in the crevices between one piece of gravel and the next, while still others live on the bottom of this gravel piece.
Dietary segregation is the second-most common type of resource partitioning. High degrees of morphological specializations or behavioral differences allow organisms to use specific resources. The size of nets built by some species of invertebrate suspension feeders, for example, can filter varying particle size of FPOM from the water (Edington et al. 1984). Similarly, members in the grazing guild can specialize in the harvesting of algae or detritus depending upon the morphology of their scraping apparatus. In addition, certain species seem to show a preference for specific algal species.
Temporal segregation is a less common form of resource partitioning, but it is nonetheless an observed phenomenon. Typically, it accounts for coexistence by relating it to differences in life history patterns and the timing of maximum growth among guild mates. Tropical fishes in Borneo, for example, have shifted to shorter life spans in response to the ecological niche reduction felt with increasing levels of species richness in their ecosystem (Watson and Balon 1984).
Over long time scales, there is a tendency for species composition in pristine systems to remain in a stable state. This has been found for both invertebrate and fish species. On shorter time scales, however, flow variability and unusual precipitation patterns decrease habitat stability and can all lead to declines in persistence levels. The ability to maintain this persistence over long time scales is related to the ability of lotic systems to return to the original community configuration relatively quickly after a disturbance (Townsend et al. 1987). This is one example of temporal succession, a site-specific change in a community involving changes in species composition over time. Another form of temporal succession might occur when a new habitat is opened up for colonization. In these cases, an entirely new community that is well adapted to the conditions found in this new area can establish itself.
The River continuum concept (RCC) was an attempt to construct a single framework to describe the function of temperate lotic ecosystems from the headwaters to larger rivers and relate key characteristics to changes in the biotic community (Vannote et al. 1980). The physical basis for RCC is size and location along the gradient from a small stream eventually linked to a large river. Stream order (see characteristics of streams) is used as the physical measure of the position along the RCC.
According to the RCC, low ordered sites are small shaded streams where allochthonous inputs of CPOM are a necessary resource for consumers. As the river widens at mid-ordered sites, energy inputs should change. Ample sunlight should reach the bottom in these systems to support significant periphyton production. Additionally, the biological processing of CPOM (Coarse Particulate Organic Matter - larger than 1 mm) inputs at upstream sites is expected to result in the transport of large amounts of FPOM (Fine Particulate Organic Matter - smaller than 1 mm) to these downstream ecosystems. Plants should become more abundant at edges of the river with increasing river size, especially in lowland rivers where finer sediments have been deposited and facilitate rooting. The main channels likely have too much current and turbidity and a lack of substrate to support plants or periphyton. Phytoplankton should produce the only autochthonous inputs here, but photosynthetic rates will be limited due to turbidity and mixing. Thus, allochthonous inputs are expected to be the primary energy source for large rivers. This FPOM will come from both upstream sites via the decomposition process and through lateral inputs from floodplains.
Biota should change with this change in energy from the headwaters to the mouth of these systems. Namely, shredders should prosper in low-ordered systems and grazers in mid-ordered sites. Microbial decomposition should play the largest role in energy production for low-ordered sites and large rivers, while photosynthesis, in addition to degraded allochthonous inputs from upstream will be essential in mid-ordered systems. As mid-ordered sites will theoretically receive the largest variety of energy inputs, they might be expected to host the most biological diversity (Vannote et al. 1980).
Just how well the RCC actually reflects patterns in natural systems is uncertain and its generality can be a handicap when applied to diverse and specific situations. The most noted criticisms of the RCC are: 1. It focuses mostly on macroinvertebrates, disregarding that plankton and fish diversity is highest in high orders; 2. It relies heavily on the fact that low ordered sites have high CPOM inputs, even though many streams lack riparian habitats; 3. It is based on pristine systems, which rarely exist today; and 4. It is centered around the functioning of temperate streams. Despite its shortcomings, the RCC remains a useful idea for describing how the patterns of ecological functions in a lotic system can vary from the source to the mouth.
Disturbances such as congestion by dams or natural events such as shore flooding are not included in the RCC model. Various researchers have since expanded the model to account for such irregularities. For example, J.V. Ward and J.A. Stanford came up with the Serial Discontinuity Concept in 1983, which addresses the impact of geomorphologic disorders such as congestion and integrated inflows. The same authors presented the Hyporheic Corridor concept in 1993, in which the vertical (in depth) and lateral (from shore to shore) structural complexity of the river were connected. The flood pulse concept, developed by W.J. Junk in 1989, further modified by P.B. Bayley in 1990 and K. Tockner in 2000, takes into account the large amount of nutrients and organic material that makes its way into a river from the sediment of surrounding flooded land.
River pollution can include but is not limited to: increasing sediment export, excess nutrients from fertilizer or urban runoff, sewage and septic inputs, plastic pollution, nano-particles, pharmaceuticals and personal care products, synthetic chemicals, road salt, inorganic contaminants (e.g., heavy metals), and even heat via thermal pollutions. The effects of pollution often depend on the context and material, but can reduce ecosystem functioning, limit ecosystem services, reduce stream biodiversity, and impact human health.
Pollutant sources of lotic systems are hard to control because they can derive, often in small amounts, over a very wide area and enter the system at many locations along its length. While direct pollution of lotic systems has been greatly reduced in the United States under the government’s Clean Water Act, contaminants from diffuse non-point sources remain a large problem. Agricultural fields often deliver large quantities of sediments, nutrients, and chemicals to nearby streams and rivers. Urban and residential areas can also add to this pollution when contaminants are accumulated on impervious surfaces such as roads and parking lots that then drain into the system. Elevated nutrient concentrations, especially nitrogen and phosphorus which are key components of fertilizers, can increase periphyton growth, which can be particularly dangerous in slow-moving streams. Another pollutant, acid rain, forms from sulfur dioxide and nitrous oxide emitted from factories and power stations. These substances readily dissolve in atmospheric moisture and enter lotic systems through precipitation. This can lower the pH of these sites, affecting all trophic levels from algae to vertebrates. Mean species richness and total species numbers within a system decrease with decreasing pH.
Dams alter the flow, temperature, and sediment regime of lotic systems. Additionally, many rivers are dammed at multiple locations, amplifying the impact. Dams can cause enhanced clarity and reduced variability in stream flow, which in turn cause an increase in periphyton abundance. \Invertebrates immediately below a dam can show reductions in species richness due to an overall reduction in habitat heterogeneity. Also, thermal changes can affect insect development, with abnormally warm winter temperatures obscuring cues to break egg diapause and overly cool summer temperatures leaving too few acceptable days to complete growth. Finally, dams fragment river systems, isolating previously continuous populations, and preventing the migrations of anadromous and catadromous species.
Invasive species have been introduced to lotic systems through both purposeful events (e.g. stocking game and food species) as well as unintentional events (e.g. hitchhikers on boats or fishing waders). These organisms can affect natives via competition for prey or habitat, predation, habitat alteration, hybridization, or the introduction of harmful diseases and parasites. Once established, these species can be difficult to control or eradicate, particularly because of the connectivity of lotic systems. Invasive species can be especially harmful in areas that have endangered biota, such as mussels in the Southeast United States, or those that have localized endemic species, like lotic systems west of the Rocky Mountains, where many species evolved in isolation.
The Clavey River is a tributary of the Tuolumne River in the Sierra Nevada, located in the Stanislaus National Forest and Tuolumne County, California. The river is 31.3 miles (50.4 km) long, and is one of the few undammed rivers on the western slope of the Sierra. Via the Tuolumne River, the Clavey is part of the San Joaquin River watershed.Concord River
The Concord River is a 16.3-mile-long (26.2 km) tributary of the Merrimack River in eastern Massachusetts in the United States. The river drains a small rural and suburban region northwest of Boston. One of the most famous small rivers in U.S. history, it was the scene of an important early battle of the American Revolutionary War and was the subject of a famous 19th-century book by Henry David Thoreau.Coon Creek (Kishwaukee River tributary)
Coon Creek is a 28.1-mile-long (45.2 km) tributary of the Kishwaukee River in northern Illinois.Detroit River International Wildlife Refuge
The Detroit River International Wildlife Refuge is the only international wildlife refuge in North America. It was established in 2001 and is managed jointly by the United States Fish and Wildlife Service and the Canadian Wildlife Service. It is situated in the heart of a major metropolitan area. Detroit River International Wildlife Refuge is one of over 540 National Wildlife Refuges managed by the U.S. Fish and Wildlife Service within the Department of the Interior. It occupies 7.88 square miles (20.42 km2) of scattered property but has drawn boundaries for further expansion.The Detroit River International Wildlife Refuge consists primarily of coastal wetlands, several islands in the Detroit River, and waterfront parks. The Refuge includes islands, marshes, shoals, and waterfront lands along 48 miles (77 km) of the Detroit River and Western Lake Erie shoreline. It encompasses Humbug Marsh, a wetland in Gibraltar and Trenton in southeastern Wayne County, which is classified as a wetland of international importance.Elwha Dam
The Elwha Dam was a 108-ft (33 m) high dam located in the United States, in the state of Washington, on the Elwha River approximately 4.9 miles (7.9 km) upstream from the mouth of the river on the Strait of Juan de Fuca.
The Elwha River Ecosystem and Fisheries Restoration Act of 1992 authorized the US Federal Government to acquire the Elwha Dam and Glines Canyon Dam hydroelectric power projects for decommissioning and demolition for habitat restoration. Removal of the Elwha Dam began in September 2011 and was fully complete by March 2012, allowing the Elwha River to flow freely through the site.Elwha Ecosystem Restoration
The Elwha Ecosystem Restoration Project is a 21st-century project of the U.S. National Park Service to remove two dams on the Elwha River on the Olympic Peninsula in Washington state, and restore the river to a natural state. It is the largest dam removal project in history and the second largest ecosystem restoration project in the history of the National Park Service, after the Restoration of the Everglades. The controversial project, costing about $351.4 million, has been contested and periodically blocked for decades. It has been supported by a major collaboration among the Lower Elwha Klallam Tribe, and federal and state agencies.
The removal of the first of the two dams, the Elwha Dam, began in September 2011 and was completed ahead of schedule in March 2012. Removal of the second dam, the Glines Canyon Dam, was completed on August 26, 2014.Enteromius baudoni
Enteromius baudoni is a species of tropical cyprinid freshwater fish from Central and Western Africa. It is found in western Africa, in the river basins of the Chad Basin, the Volta basin, the Niger River basin, the Gambia River basin, the Senegal River basin, the Sassandra River basin, and the Bandama River basin. In central Africa, it is found in the Ubangui River ecosystem. It typically inhabits tropical freshwater ecosystems between 24 and 26 °C (75 and 79 °F). It was originally described by Belgian-British zoologist George Albert Boulenger as Barbus baudoni in 1918, and the holotype, collected from Bangui, Central African Republic, is stored at the Muséum national d’Histoire naturelle in Paris. The species was originally classified in the Barbus genus, but was reclassified as belonging to the Enteromius genus in 2015 after examining extensive taxon, geographical, and genomic sampling of the species in the family Cyprinidae.The fish grows to 3.3 cm (1.3 in) standard length and many specimens contain 3 small spots that are aligned on the middle of the sides of the fish. These spots are frequently linked with a distinct longitudinal band. The caudal fin is forked and the fish has two pairs of barbels.Enteromius baudoni are benthopelagic, potamodromous fish that are harvested for human consumption. Threats to the species include deforestation, which leads to additions of silt in their ecosystem. The species was evaluated in 2009, and found to be of Least Concern by the International Union for Conservation of Nature and Natural Resources.Gangamoola
Gangamoola is a hill in the Chikkamagaluru district of the state of Karnataka, India. Also known as Varaha Parvata, it is one of the hills in the Western Ghats range and is known for being the source of three rivers, Tunga, Bhadra and Netravathi.Glines Canyon Dam
Glines Canyon Dam, also known as Upper Elwha Dam, built in 1927, was a 210-foot (64 m) high concrete arch dam built on the Elwha River within Olympic National Park, Clallam County, Washington.
It was located 13 miles (21 km) upstream from the mouth of the Elwha River at the Strait of Juan de Fuca, and about 8 miles upriver from the Elwha Dam. It impounded Lake Mills reservoir. The dam was demolished in 2014 as part of the Elwha River ecosystem restoration project; as of 2015 it is the tallest dam ever to be intentionally breached.Grand Calumet River
The Grand Calumet River is a 13.0-mile-long (20.9 km) river that flows primarily into Lake Michigan. Originating in Miller Beach in Gary, it flows through the cities of Gary, East Chicago and Hammond, as well as Calumet City and Burnham on the Illinois side. The majority of the river's flow drains into Lake Michigan via the Indiana Harbor and Ship Canal, sending about 1,500 cubic feet (42 m3) per second of water into the lake. A smaller part of the flow, at the river's western end, enters the Calumet River and ultimately drains into the Illinois and ultimately the Mississippi River.
Today, a large portion of the river's flow originates as municipal and industrial effluent, cooling and process water and storm water overflows. Although discharges have been reduced, a number of contaminants continue to impair the area. The river is among the country's most severely polluted, and as of 2015 was in the late stages of a major dredging project to remove thousands of tons of contaminated sediment and rehabilitate the river ecosystem.Hyporheic zone
The hyporheic zone is the region of sediment and porous space beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water. The flow dynamics and behavior in this zone (termed hyporheic flow or underflow) is recognized to be important for surface water/groundwater interactions, as well as fish spawning, among other processes. As an innovative urban water management practice, the hyporheic zone can be designed by engineers and actively managed for improvements in both water quality and riparian habitat.The assemblage of organisms which inhabits this zone are called hyporheos.
The term hyporheic was originally coined by Traian Orghidan in 1959 by combining two Greek words: hypo (below) and rheos (flow).Ijen
The Ijen volcano complex is a group of composite volcanoes located on the border between Banyuwangi Regency and Bondowoso Regency of East Java, Indonesia.
It is inside a larger caldera Ijen, which is about 20 kilometres wide. The Gunung Merapi stratovolcano is the highest point of that complex. The name "Gunung Merapi" means "mountain of fire" in the Indonesian language (api being "fire"); Mount Merapi in central Java and Marapi in Sumatra have the same etymology.
West of Gunung Merapi is the Ijen volcano, which has a one-kilometre-wide turquoise-coloured acidic crater lake. The lake is the site of a labour-intensive sulfur mining operation, in which sulfur-laden baskets are carried by hand from the crater floor. The work is paid well considering the cost of living in the area, but is very onerous. Workers earn around Rp 50,000–75,000 ($5.50–$8.30) per day and once out of the crater, still need to carry their loads of sulfur chunks about three kilometers to the nearby Paltuding Valley to get paid.Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones run east-west across the southern side of the caldera. The active crater at Kawah Ijen has a diameter of 722 metres (2,369 ft) and a surface area of 0.41 square kilometres (0.16 sq mi). It is 200 metres (660 ft) deep and has a volume of 36 cubic hectometres (29,000 acre⋅ft).
The lake is recognised as the largest highly acidic crater lake in the world. It is also a source for the river Banyupahit, resulting in highly acidic and metal-enriched river water which has a significant detrimental effect on the downstream river ecosystem. On July 14–15, 2008, explorer George Kourounis took a small rubber boat out onto the acid lake to measure its acidity. The pH of the water in the lake's edges was measured to be 0.5 and in the middle of the lake 0.13 due to high sulfuric acid concentration.La Moine River
La Moine River is a 125-mile-long (201 km) tributary of the Illinois River in western Illinois in the United States. Its watershed covers approximately 2,000 square miles (5,000 km2), and it is the sixth-largest tributary to the Illinois River. It is part of the watershed of the Mississippi River.Lagoa de Óbidos
The Lagoa de Óbidos is a lagoon that extends between the municipalities of Óbidos and Caldas da Rainha, in the Oeste subregion of Portugal.
It is situated in a shallow depression, defined by unstable irregular contours close to the sea; it is a natural barrier that separate the Atlantic Ocean and marine biome from the river ecosystem of Foz do Arelho formed by lateral dunes. Its connection to the sea is made across an intermittent channel, whose transitional zone that requires timely interventions to maintain its access.Morley Nelson Snake River Birds of Prey National Conservation Area
The Morley Nelson Snake River Birds of Prey National Conservation Area has one of the densest populations of nesting raptors. The National Conservation Area (NCA) is located 35 miles (56 km) south of Boise, Idaho along 81 miles (130 km) of the Snake River, and is managed by the Bureau of Land Management. The NCA covers 484,873 acres (1,962.21 km2). In descending order of land area it is located in Ada, Elmore, Owyhee, and Canyon counties.
Section 2301 of the Omnibus Public Lands Management Act of 2009, section 2301 renamed the area as the Nelson Snake River Birds of Prey National Conservation Area in recognition of the contributions of Morley Nelson, a raptor expert and advocate and a leading proponent of the original creation of the National Conservation Area.About 14,000 years ago, as glaciers receded from the last ice age, the 20,000-square-mile (52,000 km2) Lake Bonneville crested at Red Rock Pass, Idaho, creating what is known as the Bonneville Flood. As soft soils eroded at the pass, the lake poured into the volcanic plain of the Snake River and its canyons. Today, visitors to the Snake River area can explore the house-size boulders, box canyons, and other evidence left behind by the tremendous flood. At Swan Falls (now Swan Falls Dam), peak discharge of the flood was an astounding 33 million cubic feet/second.
In the Snake River ecosystem, a unique combination of climate geology, soils, and vegetation supports extraordinary numbers of predators and prey. More than 700 pairs of raptors, representing 15 different species, nest on the high canyon walls. Nine additional raptor species use the Snake River area as seasonal hunting grounds during migrations or as wintering areas. Birds of Prey NCA is particularly important for prairie falcons, North America's only indigenous falcon. The area is home to a significant portion of the species' known population.
Unusually high numbers of small burrowing mammals, which make their home on a plateau rich in vegetative cover and ideal soil, support a high density of raptors. Paiute ground squirrels, the main prey of the prairie falcon, are the most abundant of the burrowing creatures (in fact, according to the BLM, portions of the Birds of Prey NCA support the densest ground squirrel populations ever recorded). Nesting success for prairie falcons is linked very closely to the squirrel abundance. Similarly, the success of golden eagles and other raptors is tied to the great quantity of black-tailed jackrabbits. Additionally, abundant prey and deep soil support one of the densest populations of badgers in the world (up to 11 badgers per square mile).
Recurring wildfires and military training exercises at Snake River have altered the prey base for the raptor population that the NCA was established to protect. As a result, the raptor population is at currently risk. A Bureau of Land Management (BLM) study documents that nesting prairie falcons in the NCA have declined from a historical 230 pairs to an estimated 110 pairs today.
Crater Rings are adjacent, symmetrical volcanic pit craters and a National Natural Landmark located in the Nelson Snake River Birds of Prey National Conservation Area.Mount Apo
Mount Apo (Cebuano: Bukid Apo; Tagalog: Bundok Apo) is a large solfataric, potentially active stratovolcano on the island of Mindanao, Philippines. With an elevation of 2,954 meters (9,692 ft) above sea level, it is the highest mountain in the Philippine Archipelago and is located between Davao City and Davao del Sur province in Region XI and Cotabato in Region XII. The peak overlooks Davao City 45 kilometers (28 mi) to the northeast, Digos 25 kilometers (16 mi) to the southeast, and Kidapawan 20 kilometers (12 mi) to the west.
The first two attempts to reach Mt. Apo's summit ended in failure: that of Jose Oyanguren (1852) and Señor Real (1870). The first recorded successful expedition was led by Don Joaquin Rajal in October 10, 1880. Prior to the climb, Rajal had to secure the permission of the Bagobo chieftain, Datu Manig. It is said that the Datu demanded that human sacrifice be made to please the god Mandarangan. But the datu agreed to waive this demand, and the climb commenced on October 6, 1880, succeeding five days later. Since then, numerous expeditions followed. These and more are described in colorful narrations by Fr. Miguel Bernad, S.J.
On May 9, 1936, Mount Apo was declared as a national park by President Manuel L. Quezon.Mt. Apo is said to be named after a nobleman named Apong, who was killed while mediating the battle between two suitors of his daughter Saribu. Apo in various local languages mean "grandfather", "master", "grandson", and "wise elder".Nelma
Stenodus nelma, known alternatively as the nelma, sheefish, inconnu or connie, is a commercial species of freshwater whitefish in the family Salmonidae. It is widespread in the Arctic rivers from the Kola Peninsula (White Sea basin) eastward across Siberia to the Anadyr River and also in the North American basins of the Yukon River and Mackenzie River.Owens Creek (Kishwaukee River tributary)
Owens Creek is a 15.0-mile-long (24.1 km) stream in the Kishwaukee River watershed in northern Illinois. It is a tributary of the South Branch Kishwaukee River.Salt River (California)
The Salt River is a formerly navigable hanging channel of the Eel River which flowed about 9 miles (14 km) from near Fortuna and Waddington, California, to the estuary at the Pacific Ocean, until siltation from logging and agricultural practices essentially closed the channel. It was historically an important navigation route until the early 20th century. It presently intercepts and drains tributaries from the Wildcat Hills along the south side of the Eel River floodplain. Efforts to restore the river began in 1987, permits and construction began in 2012, and water first flowed in the restored channel in October 2013.
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