Hydrography
Hydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, coastal areas and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development and defence, scientific research, environmental protection. The origins of hydrography lay in the making of charts to aid navigation, by individual mariners as they navigated into new waters; these were the private property closely held secrets, of individuals who used them for commercial or military advantage. As transoceanic trade and exploration increased, hydrographic surveys started to be carried out as an exercise in their own right, the commissioning of surveys was done by governments and special hydrographic offices. National organizations navies, realized that the collection and distribution of this knowledge gave it great organizational and military advantages.
Thus were born dedicated national hydrographic organizations for the collection, organization and distribution of hydrography incorporated into charts and sailing directions. Prior to the establishment of the United Kingdom Hydrographic Office, Royal Navy captains were responsible for the provision of their own charts. In practice this meant that ships sailed with inadequate information for safe navigation, that when new areas were surveyed, the data reached all those who needed it; the Admiralty appointed Alexander Dalrymple as Hydrographer in 1795, with a remit to gather and distribute charts to HM Ships. Within a year existing charts from the previous two centuries had been collated, the first catalogue published; the first chart produced under the direction of the Admiralty, was a chart of Quiberon Bay in Brittany, it appeared in 1800. Under Captain Thomas Hurd the department received its first professional guidelines, the first catalogues were published and made available to the public and to other nations as well.
In 1829, Rear-Admiral Sir Francis Beaufort, as Hydrographer, developed the eponymous Scale, introduced the first official tide tables in 1833 and the first "Notices to Mariners" in 1834. The Hydrographic Office underwent steady expansion throughout the 19th century; the word hydrography comes from the Ancient Greek ὕδωρ, "water" and γράφω, "to write". Large-scale hydrography is undertaken by national or international organizations which sponsor data collection through precise surveys and publish charts and descriptive material for navigational purposes; the science of oceanography is, in part, an outgrowth of classical hydrography. In many respects the data are interchangeable, but marine hydrographic data will be directed toward marine navigation and safety of that navigation. Marine resource exploration and exploitation is a significant application of hydrography, principally focused on the search for hydrocarbons. Hydrographical measurements include the tidal and wave information of physical oceanography.
They include bottom measurements, with particular emphasis on those marine geographical features that pose a hazard to navigation such as rocks, shoals and other features that obstruct ship passage. Bottom measurements include collection of the nature of the bottom as it pertains to effective anchoring. Unlike oceanography, hydrography will include shore features and manmade, that aid in navigation. Therefore, a hydrographic survey may include the accurate positions and representations of hills and lights and towers that will aid in fixing a ship's position, as well as the physical aspects of the sea and seabed. Hydrography for reasons of safety, adopted a number of conventions that have affected its portrayal of the data on nautical charts. For example, hydrographic charts are designed to portray what is safe for navigation, therefore will tend to maintain least depths and de-emphasize the actual submarine topography that would be portrayed on bathymetric charts; the former are the mariner's tools to avoid accident.
The latter are best representations of the actual seabed, as in a topographic map, for scientific and other purposes. Trends in hydrographic practice since c. 2003–2005 have led to a narrowing of this difference, with many more hydrographic offices maintaining "best observed" databases, making navigationally "safe" products as required. This has been coupled with a preference for multi-use surveys, so that the same data collected for nautical charting purposes can be used for bathymetric portrayal. Though, in places, hydrographic survey data may be collected in sufficient detail to portray bottom topography in some areas, hydrographic charts only show depth information relevant for safe navigation and should not be considered as a product that portrays the actual shape of the bottom; the soundings selected from the raw source depth data for placement on the nautical chart are selected for safe navigation and are biased to show predominately the shallowest depths that relate to safe navigation.
For instance, if there is a deep area that can not be reached because it is surrounded by shallow water, the deep area may not be shown. The color filled areas that show different ranges of shallow water are not the equivalent of contours on a topographic map since they are drawn seaward of the actual shallowest depth portrayed. A bathymetric chart does show marine topology accurately. Details covering the ab
Raceway (aquaculture)
A raceway known as a flow-through system, is an artificial channel used in aquaculture to culture aquatic organisms. Raceway systems are among the earliest methods used for inland aquaculture. A raceway consists of rectangular basins or canals constructed of concrete and equipped with an inlet and outlet. A continuous water flow-through is maintained to provide the required level of water quality, which allows animals to be cultured at higher densities within the raceway. Freshwater species such as trout and tilapia are cultured in raceways. Raceways are used for some marine species which need a constant water flow, such as juvenile salmon, brackish water sea bass and sea bream and marine invertebrates such as abalone; the most important factor to consider when selecting a site for a raceway farm is the water supply. Water sources for raceway aquaculture operations are streams, reservoirs or deep wells. Trout do best in spring water because it keeps a constant temperature, while catfish need a strong flow, about 80 litres per second for every 0.4 hectares of raceway.
A backup water supply should be positioned so, if the water supply or pump fails, it can flow by gravity into the start of the raceway. Most raceways are made of reinforced concrete, though some earthen raceways are built. Earthen raceways with plastic liners cost little and are easy to build, but cleaning and disinfecting them is difficult and plastic linings are fragile. Reinforced concrete is more expensive, but can be shaped in complex ways. Raceway tanks can be built from polyester resin; these tanks have smooth walls, are mobile and easy to service. However, their cost limits them under 5 cubic metres. A raceway is most a rectangular canal with a water current flowing from a supply end to an exit end; the length to width ratio is important in raceways. To prevent the fish stock from swimming in circular movements, which would cause debris to build up in the centre, a length to width ratio of at least six to one is recommended. If the width is too large this could result in a feeble current speed, not desirable.
The length of a raceway unit is constrained by the water quality or by how much stock a unit can hold for ease of management. The average depth of a raceway for fin fish, such as rainbow trout, is about one metre; this means each section in a raceway should be about 30 m long and 2.5–3 m wide. The landscape should sloped to one or two percent, so the flow through the system can be maintained by gravity; the raceway should not be curved, so the flow will be uniform. A raceway farm for freshwater fin fish has a dozen or more parallel raceway strips build alongside each other, with each strip consisting of 15 to 20 or more serial sections; the risk of unhygienic conditions increases towards the lower level sections, can be kept in check by ensuring there are not too many sections and the water flow is adequate. In order to isolate any diseased section and avoid transmitting the disease back to the upper raceways, each section should have its own drainage channel. Controls, such as weirs, are needed to ensure individual raceways can't accidentally overflow or empty.
The water flow rate in a raceway system needs to be sufficiently high to meet the respiratory requirements for the species concerned and to flush out metabolic wastes ammonia. In a well designed system, the existing water in the raceway is replaced by new water when the same volume of new water enters the raceway. Self-cleaning can sometimes be achieved if the fish stocks density is sufficiently high and the water level is sufficiently low. For example, if trout are stocked at 20 kilograms per cubic metre, they can keep the raceway unit clean by their swimming movements, preventing waste solids from settling to the raceway floor. However, in most cases it is necessary to clean raceways; the simplest way is to lower the water level in the raceway units, which increases the speed of the water current, herd the fish together till they flush the waste from the raceway. Solid wastes which accumulate at the raceway bottom can be removed by pumps. Oxygen levels in the water can be kept high if the raceway units are placed one after the other with intermediate drops over weirs, or by the use of aeration systems such as pumps and agitators.
The water should be replaced about every hour. This means. However, the optimum flow through rate depends on the species, because there are differences in the rates at which oxygen is consumed and metabolic wastes are produced. For example and juvenile salmon are less tolerant of degraded water quality and require a more rapid water turnover than catfish or tilapia; the flow rate necessary to maintain water quality can change through the year, as the temperature changes and the cultured species grow larger. For reason such as these, continuous monitoring of water quality is important, including measurements of water flow rates, pH levels and temperature, as well as the levels of dissolved oxygen, suspended and solid waste material; the maximum load of organisms that can be cultured in a raceway system depends on the species, on the size of the species. For trout, stocking rates of 30 to 50 kg/m3 are normal at the end of a rearing cycle, while for marine species, such as sea bass and sea bream, the achievable load is lower, between 15 and 20 kg/m3.
The total volume required for a raceway is calculated by dividing the total amount of fish in kg by the desired stocking rate in kg per m3. In most raceway aquaculture food needs to be supplied; the composition of the food, the amount and time of feeding
Cosmetics
Cosmetics are substances or products used to enhance or alter the appearance of the face or fragrance and texture of the body. Many cosmetics are designed for use of applying to the face and body, they are mixtures of chemical compounds. Cosmetics applied to the face to enhance its appearance are called make-up or makeup. Common make-up items include: lipstick, eye shadow, foundation and contour. Whereas other common cosmetics can include skin cleansers, body lotions and conditioner, hairstyling products and cologne. In the U. S. the Food and Drug Administration, which regulates cosmetics, defines cosmetics as "intended to be applied to the human body for cleansing, promoting attractiveness, or altering the appearance without affecting the body's structure or functions". This broad definition includes any material intended for use as a component of a cosmetic product; the FDA excludes pure soap from this category. The word cosmetics derives from the Greek κοσμητικὴ τέχνη, meaning "technique of dress and ornament", from κοσμητικός, "skilled in ordering or arranging" and that from κόσμος, meaning amongst others "order" and "ornament".
Cosmetics have been in use for thousands of years. The absence of regulation of the manufacture and use of cosmetics has led to negative side effects, deformities and death through the ages. Examples are the prevalent use of ceruse, to cover the face during the Renaissance, blindness caused by the mascara Lash Lure during the early 20th century. Egyptian men and women used makeup to enhance their appearance, they were fond of eyeliner and eye-shadows in dark colors including blue and black. Ancient Sumerian men and women were the first to invent and wear lipstick, about 5,000 years ago, they crushed gemstones and used them to decorate their faces on the lips and around the eyes. Around 3000 BC to 1500 BC, women in the ancient Indus Valley Civilization applied red tinted lipstick to their lips for face decoration. Ancient Egyptians extracted red dye from fucus-algin, 0.01% iodine, some bromine mannite, but this dye resulted in serious illness. Lipsticks with shimmering effects were made using a pearlescent substance found in fish scales.
Six thousand year old relics of the hollowed out tombs of the Ancient Egyptian pharaohs are discovered. According to one source, early major developments include: Kohl used by ancient Egypt as a protectant of the eye. Castor oil used by ancient Egypt as a protective balm. Skin creams made of beeswax, olive oil, rose water, described by Romans. Vaseline and lanolin in the nineteenth century; the Ancient Greeks used cosmetics as the Ancient Romans did. Cosmetics are mentioned in the Old Testament, such as in 2 Kings 9:30, where Jezebel painted her eyelids—approximately 840 BC—and in the book of Esther, where beauty treatments are described. One of the most popular traditional Chinese medicines is the fungus Tremella fuciformis, used as a beauty product by women in China and Japan; the fungus increases moisture retention in the skin and prevents senile degradation of micro-blood vessels in the skin, reducing wrinkles and smoothing fine lines. Other anti-aging effects come from increasing the presence of superoxide dismutase in the brain and liver.
Tremella fuciformis is known in Chinese medicine for nourishing the lungs. In the Middle Ages, it seemed natural that the face should be whitened and the cheeks rouged. During the sixteenth century, the personal attributes of the women who used make-up created a demand for the product among the upper class. Cosmetic use was frowned upon at many points in Western history. For example, in the 19th century, Queen Victoria publicly declared make-up improper and acceptable only for use by actors. Many women in the 19th century liked to be thought of as fragile ladies, they emphasized their delicacy and femininity. They aimed always to look interesting. Sometimes ladies discreetly used a little rouge on the cheeks and used "belladonna" to dilate their eyes so it would make them stand out more. Make-up was frowned upon in general during the 1870s when social etiquette became more rigid. Teachers and clergywomen were forbidden from the use of cosmetic products. During the 19th century, there was a high number of incidences of lead-poisoning because of the fashion for red and white lead makeup and powder.
This led to swelling and inflammation of the eyes, weakened tooth enamel, caused the skin to blacken. Heavy use was known to lead to death. However, in the second part of the 19th century, great advances were made in chemistry from the chemical fragrances that enabled a much easier production of cosmetic products, it was acceptable for actresses in the 1800s to use makeup, famous beauties such as Sarah Bernhardt and Lillie Langtry could be powdered. Most cosmetic products available were still either chemically dubious or found in the kitchen amid food coloring and beetroot. By the middle of the 20th century, cosmetics were in widespread use by women in nearly all industrial societies around the world. In 1968 at the feminist Miss America protest, protestors symbolically threw a number of feminine products into a "Freedom Trash Can." This included cosmetics, which were among items the protestors called "instruments of female torture" and accouterments of what they perceived to be enforced femininity.
As of 2016, the world's
Flinders Bay
Flinders Bay is a bay and locality, south of the townsite of Augusta, close to the mouth of the Blackwood River. The locality and bay lies to the north east of Cape Leeuwin, the most south-westerly mainland point of the Australian Continent, in the state of Western Australia. On Matthew Flinders Terra Australis Sheet 1 1801–1803 the area was known as Dangerous Bight; the bay runs from Point Matthew 1.5 kilometres East North East of Cape Leeuwin to Ledge Point some 8 kilometres east. It was named by either James Stirling or Septimus Roe in 1829 or 1830. Matthew Flinders was first in the Bay on 7 December 1801; the name of the locality of Flinders Bay is tied to the small settlement, a whaling and fishing location, as well as the terminus of the Busselton to Flinders Bay Branch Railway railway line. The name is tied to the Flinders Bay jetties; the settlement was in the earlier days considered to be separate from Augusta but now is more or less the southern portion of the larger community. The need for safe and efficient transfer of whale watchers and a safe mooring location in the Bay for fishermen has seen a proposal for a marina in 2004 which had included plans for the marina close to the old settlement of Flinders Bay.
The 2005 revised proposal has moved to a bay further around towards Cape Leeuwin. The Flat Rock site is complete and has been called "Augusta Boat Harbour" by the department of Transport; the landing area adjacent to the old railway station yard was known as "The Whaling". It was the area where boats would work from in early twentieth century. Up until the early 1970s sheds and ramps were still present. In the late 20th century the area had whale rescue operations occurring close to the area. Businesses involved in whale watching have more used the bay; the St Alouarn Islands stretch out south of Point Matthew, are effective barriers along with reefs for the outer reaches of the bay to the south. Like the majority of the southwestern coastal regions of Western Australia, Flinders Bay experiences a cool-summer Mediterranean climate with cool to warm summers and mild, wet winters. After trials in 2012, a world-first commercial "sea ranch" was set up in the Bay; the ranch is based on an artificial reef made up of 5000 separate concrete units called abitats.
The 900-kilogram abitats can host 400 abalone each. The reef is seeded with young abalone from an onshore hatchery; the abalone feed on seaweed that has grown on the abitats. The ecosystem enrichment of the bay results in growing numbers of dhufish, pink snapper, samson fish and other species. Brad Adams, from the company, has emphasised the similarity to wild abalone and the difference from shore based aquaculture. "We're not aquaculture, we're ranching, because once they're in the water they look after themselves." Fornasiero, Jean. Encountering Terra Australis: the Australian voyages of Nicholas Baudin and Matthew Flinders, Kent Town, South Australia,Wakefield Press,2004. ISBN 1-86254-625-8DLI Geographic names cards
Bigeye tuna
Bigeye tuna, Thunnus obesus, is a species of true tuna of the genus Thunnus, belonging to the wider mackerel family Scombridae. In Hawaiian, it is one of two species known as ʻahi. Bigeye tuna are found in the open waters of all tropical and temperate oceans, but not the Mediterranean Sea. Bigeye tuna can grow up in length. Maximum weight of individuals exceeds 180 kg, with the all-tackle angling record standing at 178 kg, they are deep-bodied, streamlined fish with large heads and eyes. The pectoral fins are long, reaching back beyond the start of the second dorsal fin in juveniles and the space between the first and second dorsal fin in adults, they have 14 dorsal spines. Bigeye tuna have a unique physiology which allows them to forage in deeper colder waters and tolerate oxygen-poor waters. Bigeye tuna are reported to tolerate ambient oxygen levels of 1.0 ml/L and reach depths where ambient oxygen content is below 1.5 ml/L due to the presence of blood with a high oxygen affinity. Vascular counter-current heat exchangers maintain body temperatures above ambient water temperature.
These heat exchangers are engaged to conserve heat in deeper colder waters and are disengaged to allow rapid warming as the tuna ascend from cold water into warmer surface waters, providing short-latency, physiological thermoregulation. The eyes of bigeye tuna are well developed and with a large spherical lens allowing their vision to function well in low light conditions. Conventional tagging data and counts of growth increments in otoliths of bigeye tuna have recorded a maximum age of 16 years. Recorded lengths at which sexual maturity is attained varies geographically with a length at which 50% of fishes sampled are mature of 135 cm in the eastern Pacific Ocean and 102–105 cm in the western Pacific Ocean; this translates to an age of maturity of 2 – 4 years. Differences in methods of studies may contribute to this variability. Spawning takes place across most months of the year in tropical regions of the Pacific Ocean, becoming seasonal at higher latitudes when sea surface temperatures are above 24 °C.
In the northwestern tropical Atlantic spawning occurs in June and July, in January and February in the Gulf of Guinea, the only known Atlantic nursery area. Bigeye tuna undertake a distinct diel shift in vertical behaviour descending at dawn to deeper, cooler waters and returning to shallower, warmer waters at dusk. During the day they can undertake vertical movements into waters of 300–500 m depth that can be as low as 20 °C than surface temperatures. Individuals undertake thermoregulatory behaviour whilst at depth, periodically returning from deeper, cooler waters to shallower, warmer waters to re-warm. Across the Pacific Ocean the depths at which bigeye tuna spend the majority of their time during the day vary: in the eastern Pacific the majority of time is spent at 200–350 m; these suggest that bigeye tuna are tracking an optimum temperature, shallower in the eastern Pacific Ocean than in the western Pacific Ocean. The diel shift in the vertical behaviour of bigeye tuna has been suggested to be associated with the diel migration of their prey.
This is supported by the identification of a number of diurnally migrating species from the stomachs of bigeye tuna and observations of close associations between bigeye tuna and the sound scattering layer both during the day and at night. Typical vertical behaviour of bigeye tuna shifts when fish associate with seamounts and fish aggregating devices, with individuals remaining in surface waters. Association with objects has been observed to occur over periods of 10–30 days; this associative behaviour of bigeye tuna is taken advantage of by fisheries with 27% of all catches of tunas by purse seine vessels in the western and central Pacific Ocean derived from fish aggregating devices. Results from tagging studies show that bigeye tuna are capable of traversing ocean basins, but can show a high degree of site fidelity to some regions. One study suggested an annual migration influenced by water temperature that near the surface. Central Pacific bigeye migrate from subtropical waters in September to tropical waters in March.
The fish briefly travel outside these thermal ranges. Other data indicate similar Pacific-wide variations. Bigeye tuna feed on epipelagic and mesopelagic fish and cephalopods. Globally 450,500 metric tonnes of bigeye tuna were caught by commercial vessels in 2012. Commercial fisheries for bigeye tuna are regionally managed within the Pacific Ocean by the Western and Central Pacific Fisheries Commission and the Inter-American Tropical Tuna Commission. In the Indian Ocean catches are managed by the Indian Ocean Tuna Commission and in the Atlantic Ocean by the International Commission for the Conservation of Atlantic Tunas. Regular stock assessments are carried out for bigeye tuna by each of the regional fisheries management organisations with bigeye tuna regarded as overfished in the western and central Pacific Ocean and eastern Pacific Ocean, close to or being overfished in the Atlantic Ocean and not overfished in the Indian Ocean; the majority of commercial catches across the Pacific Ocean is by purse seine fleets, while catches are dominated by longline fleets in the Indian and Atlantic Oceans.
Various conservation measures have been introduced by the regional fisheries management organisations which apply to particular sized vessels and fleets and include
Faroe Islands
The Faroe Islands, or the Faeroe Islands—a North Atlantic archipelago located 200 miles north-northwest of the United Kingdom and about halfway between Norway and Iceland—are an autonomous country of the Kingdom of Denmark. Total area is about 1,400 square kilometres with a population of 50,322 in October 2017; the terrain is rugged. Temperatures average above freezing throughout the year because of the Gulf Stream. Between 1035 and 1814, the Faroes were part of the Hereditary Kingdom of Norway. In 1814, the Treaty of Kiel granted Denmark control over the islands, along with two other Norwegian island possessions: Greenland and Iceland; the Faroe Islands have been a self-governing country within the Kingdom of Denmark since 1948. The Faroese have control of most of their domestic affairs; those that are the responsibility of Denmark include military defence and the justice department and foreign affairs. However, as they are not part of the same customs area as Denmark, the Faroe Islands have an independent trade policy and can establish trade agreements with other states.
The islands have representation in the Nordic Council as members of the Danish delegation. The Faroe Islands have their own national teams competing in certain sports. In Faroese, the name appears as Føroyar. Oyar represents the plural of oy, older Faroese for "island". Due to sound changes, the modern Faroese word for island is oyggj; the first element, før, may reflect an Old Norse word fær, although this analysis is sometimes disputed because Faroese now uses the word seyður to mean "sheep". Another possibility is that the Irish monks, who settled the island around 625, had given the islands a name related to the Gaelic word fearrann, meaning "land" or "estate"; this name could have been passed on to the Norwegian settlers, who added oyar. The name thus translates as either "Islands of Sheep" or "Islands of Fearrann". In Danish, the name Færøerne contains the same elements, though øerne is the definite plural of ø. In English, it may be seen as redundant to say the Faroe Islands, since the oe comes from an element meaning "island".
Most notably in the BBC Shipping Forecast, where the waters around the islands are called Faeroes. The name is sometimes spelled "Faeroe". Archaeological evidence shows settlers living on the Faroe Islands in two successive periods before the Norse arrived, the first between 300 and 600 AD and the second between 600 and 800 AD. Scientists from the University of Aberdeen have found early cereal pollen from domesticated plants, which further suggests people may have lived on the islands before the Vikings arrived. Archaeologist Mike Church noted, he suggested that the people living there might have been from Ireland, Scotland, or Scandinavia with groups from all three areas settling there. A Latin account of a voyage made by Brendan, an Irish monastic saint who lived around 484–578, includes a description of insulae resembling the Faroe Islands; this association, however, is far from conclusive in its description. Dicuil, an Irish monk of the early 9th century, wrote a more definite account. In his geographical work De mensura orbis terrae he claimed he had reliable information of heremitae ex nostra Scotia who had lived on the northerly islands of Britain for a hundred years until the arrival of Norse pirates.
Norsemen settled the islands c. 800, bringing Old West Norse, which evolved into the modern Faroese language. According to Icelandic sagas such as Færeyjar Saga, one of the best known men in the island was Tróndur í Gøtu, a descendant of Scandinavian chiefs who had settled in Dublin, Ireland. Tróndur led the battle against the Norwegian monarchy and the Norwegian church; the Norse and Norse–Gael settlers did not come directly from Scandinavia, but rather from Norse communities surrounding the Irish Sea, Northern Isles and Outer Hebrides of Scotland, including the Shetland and Orkney islands. A traditional name for the islands in Irish, Na Scigirí refers to the Skeggjar "Beards", a nickname given to island dwellers. According to the Færeyinga saga, more emigrants left Norway who did not approve of the monarchy of Harald Fairhair; these people settled the Faroes around the end of the 9th century. Early in the 11th century, Sigmundur Brestisson – whose clan had flourished in the southern islands before invaders from the northern islands exterminated it – escaped to Norway.
He was sent back to take possession of the islands for Olaf Tryggvason, King of Norway from 995 to 1000. Sigmundur introduced Christianity, forcing Tróndur í Gøtu to convert or face beheading and, though Sigmundur was subsequently murdered, Norwegian taxation was upheld. Norwegian control of the Faroes continued until 1814, when the Kingdom of Norway entered the Kalmar Union with Denmark, it resulted in Danish control of the islands; the Reformation with Protestant Evangelical Lutheranism and Reformed reached the Faroes in 1538. When the union between Denmark and Norway dissolved as a result of the Treaty of Kiel in 1814, Denmark retained possession of the Faroe Islands. Following the turmoil caused by the Napoleonic Wars in 1816, the Faroe Islands became a county in the Danish Kingdom; as part of Mercantilism, Denmark maintained a monopoly over trade with the Faroe Islands and forbade their inhabitants trading
Organisms involved in water purification
Most organisms involved in water purification originate from the waste, wastewater or water stream itself or arrive as resting spore of some form from the atmosphere. In a few cases associated with constructed wetlands, specific organisms are planted to maximise the efficiency of the process. Biota are an essential component of most sewage treatment processes and many water purification systems. Most of the organisms involved are derived from the waste, wastewater or water stream itself or from the atmosphere or soil water; however some processes those involved in removing low concentrations of contaminants, may use engineered eco-systems created by the introduction of specific plants and sometimes animals. Some full scale sewage treatment plants use constructed wetlands to provide treatment Parasites and viruses may be injurious to the health of people or livestock ingesting the polluted water; these pathogens may have originated from domestic or wild bird or mammal feces. Pathogens may be killed by ingestion by larger organisms, infection by phages or irradiation by ultraviolet sunlight unless that sunlight is blocked by plants or suspended solids.
Particles of soil or organic matter may be suspended in the water. Such materials may give the water a turbid appearance; the anoxic decomposition of some organic materials may give rise to obnoxious or unpleasant smells as sulphur containing compounds are released. Compounds containing nitrogen, potassium or phosphorus may encourage growth of aquatic plants and thus increase the available energy in the local food-web; this can lead to increased concentrations of suspended organic material. In some cases specific micro-nutrients may be required to allow the available nutrients to be utilised by living organisms. In other cases, the presence of specific chemical species may produce toxic effects limiting growth and abundance of living matter. Many dissolved or suspended metal salts exert harmful effects in the environment sometimes at low concentrations; some aquatic plants are able to remove low metal concentrations, with the metals ending up bound to clay or other mineral particles. Saprophytic bacteria and fungi can convert organic matter into living cell mass, carbon dioxide, water and a range of metabolic by-products.
These saprophytic organisms may be predated upon by protozoa, rotifers and, in cleaner waters, Bryozoa which consume suspended organic particles including viruses and pathogenic bacteria. Clarity of the water may begin to improve as the protozoa are subsequently consumed by rotifers and cladocera. Purifying bacteria and rotifers must either be mixed throughout the water or have the water circulated past them to be effective. Sewage treatment plants mix these organisms as activated sludge or circulate water past organisms living on trickling filters or rotating biological contactors. Aquatic vegetation may provide similar surface habitat for purifying bacteria and rotifers in a pond or marsh setting. Plants and algae have the additional advantage of removing nutrients from the water; because of the complex chemistry of Phosphorus much of this element is in an unavailable form unless decomposition creates anoxic conditions which render the phosphorus available for re-uptake. Plants provide shade, a refuge for fish, oxygen for aerobic bacteria.
In addition, fish can limit pests such as mosquitoes. Fish and waterfowl feces return waste to the water, their feeding habits may increase turbidity. Cyanobacteria have the disadvantageous ability to add nutrients from the air to the water being purified and to generate toxins in some cases; the choice of organism depends on other factors. Indigenous species tend to be better adapted to the local environment; the choice of plants in engineered wet-lands or managed lagoons is dependent on the purification requirements of the system and this may involve plantings of varying plant species at a range of depths to achieve the required goal. Plants purify water by consuming excess nutrients and by providing surfaces upon which a wide range of other purifying organisms can live, they are effective oxygenators in sunlight. They have the ability to translocate chemicals between their submerged foliage and their root systems and this is of significance in engineered wet-lands designed to de-toxify waste waters.
Plants that have been used in temperate climates include Nymphea alba,Phragmites australis, Sparganium erectum, Iris pseudacorus, Schoenoplectus lacustris and Carex acutiformis. Where oxygenation is a critical requirement Stratiotes aloides, Hydrocharis morsus-ranae, Acorus calamus, Myriophyllum species and Elodea have been used. Hydrocharis morsus-ranae and Nuphar lutea have been used where shade and cover are required Fish are the top level predators in a managed treatment eco-system and in some case may be a mono-culture of herbivorous species. Management of multi-species fisheries requires careful management and may involve a range of fish species including bottom-feeders and predatory species to limit population growth of the herbivorous fish Rotifers are microscopic complex organisms and are filter feeders removing fine particulate matter from water, they occur in aerobic lagoons, activated sludge processes, in trickling filters and in final settlement tanks and are a significant factor in removing suspended bacterial cells and algae from the water column.
Annelid worms are essential to the effective operation of trickling filters helping to remove excess bio-mass and enhanci
