Too much algae produces algal blooms, which spreads toxins known as "brown tides" or "red tides". Both red tides and brown tides are responsible for killing seabirds, fish, marine mammals, and harm humans.
When these harmful blooms die, the bacteria consumes all of the oxygen and creates a dead zone and fish cannot live in this area. Another example of aquatic pollution is with acid rain, which is the result of certain chemicals. In particular, acid rain is the result of nitrogen oxides and sulfur dioxide forming to make mild acidic compounds. Acid rain is responsible for leaching the soils toxic aluminum.
At really low levels, acid rain can simply stress the fish in streams and lakes. However, at higher levels, acid rain can kill them. In addition, acid rain causes trees to become weaker and creates harmful air pollution to humans.
Detergents can be most simply understood as organic compounds widely used in both homes and industrial process. The main way detergents enter into water is through sewage. There are two different types of detergents and each has different characteristics.
Phosphate detergents are used in hard water to soften it and to assist in the suspension of dirt in water. These detergents are extremely caustic. Surfactant detergents are extremely toxic.
These types of detergents are used to bolster the foaming, wetting, emulsifying, and dispersing properties of detergents. They can end up in watercourses through sewage treatment works, surface water run-off, direct discharge or leachates from landfill sites.
One effect that has been observed on wildlife is the feminisation of male fish Jobling et al. Having said the above, there are also natural sources of endocrine disruptors.
For instance, Fusarium fungus infesting corn and other grains produces zearalenone, a potent oestrogenic chemical that causes cessation of lactation and hyperoestrogenisation in pigs Burkhardt-Holm, In terms of water supply, endocrine disruptors can be present if untreated groundwater is used for potable supplies, if the groundwater is contaminated with the suspect chemicals.
Bottled water can contain endocrine disruptors from plasticisers and detergents used in the production process. In addition, highly acidic waters can dissolve heavy metals, especially if the pH is below 3. This occurs in the case of mine wastewaters. The metals present tend to be brought into solution, especially iron, zinc, lead and molybdenum. To be able to predict the adverse effects of metal pollutants in water it is necessary to determine the physical form or chemical speciation of the metal present, since metals can exist in a wide range of forms.
The subject is too complicated to be covered fully here, but the following two theoretical examples are extreme cases of metal pollution to show the range of events that can occur. Various industries produce suspended material or particulates in their effluents, and this has several consequences. All solids tend to reduce light penetration, so the growth of plant life in watercourses is inhibited.
This will have secondary effects on food chains. Bottom-living animals and plants may be smothered as particles settle. If the particles settle on gravels, fish spawning can be seriously disrupted. Predators that hunt by day may be restricted in their activities: for example, in turbid water there may be an abundance of leeches as fish are no longer able to see and consume them as food.
One of the most important effects on animals is the damage to fish gills. Some effluents pollute because substances in them enter into a chemical reaction with salts already dissolved in the water. For example, iron hydroxide may be precipitated if water containing iron is discharged into a naturally alkaline river. This phenomenon typically arises from abandoned mines, where the clear water pumped out and discharged into a clear stream can produce a bright orange coloration that prevents penetration of light and hence inhibits plant life.
Some suspended solids can also cause harmful effects when soluble toxic components present in them are dissolved into the water by biological or chemical action. Immiscible liquids may be present as oils, greases or tarry substances, often in the form of an emulsion a colloidal suspension of one liquid in another, as in mayonnaise.
They may affect turbidity in the same way as suspended solids. However, emulsions are not likely to settle to the bed of the river. Frequently they float on the surface and adhere to vegetation at the waterline. Some immiscible liquids are decomposed slowly by aquatic microorganisms.
Many oils and tars are slightly soluble in water and thereby impart tastes and odours to it. Oil is generally less dense than water and will spread over the surface to form an extremely thin, often visible film; a small quantity of oil is therefore likely to pollute a large area.
It can also affect the life cycle of insects, since the larvae of some species float on the surface. Oil is one of the more serious pollution problems.
As an example, there are now around pollution incidents involving oil and fuels every year in England and Wales Environment Agency, Although some of these affect land, the vast majority affect the water environment. Industrial effluents are frequently discharged at temperatures different from those of the receiving river. Almost invariably the effluent is warmer than the river, since water is widely used for carrying away heat.
Within limits, a raised temperature increases the metabolic rates of all aquatic organisms. The overall effect on the oxygen balance of a particular heated effluent therefore depends to a certain extent on the oxygen balance in the river at the point of discharge.
A small increase in the temperature of a clean, fast-flowing stream may not affect the ecosystem adversely. Provided oxygen is plentiful, plant and animal populations may be altered slightly but remain in a balanced state.
Species indigenous to warmer climates may become established in a heated portion of a river. However, heated effluents are usually discharged to watercourses that are already polluted to some degree, so the polluting effects are compounded.
A heightened biochemical oxygen demand BOD on the river water due to a sewage discharge upstream may be exacerbated by raising the temperature. Any animals or plants that die as a result of the heat or greater oxygen deficit are decomposed by bacteria, which decreases the oxygen level even more. Variations in the flow of a river can result from excessive abstraction or from intermittent discharges of relatively large volumes of effluent, as when settling ponds which are used to remove particulates from effluents in the ceramic industry, for example are emptied.
There are, however, maximum limits that must be adhered to. Since the organisms that become established in a river will be those best suited to its conditions, sudden and repeated fluctuations in the rate of flow will mean that only those organisms that can withstand the changes will survive. Plants growing in silt deposits on the bed of a stream will be destroyed when the silt is washed away by a sudden increase in flow. When the flow falls, organisms that are dependent on a high dissolved oxygen concentration will die if the river reverts to a series of near-stagnant pools.
Very low concentrations of some chemical compounds will produce unpleasant tastes and odours, or will taint the flesh of fish living in water contaminated by them. Interaction between substances may produce tastes that are apparent at concentrations well below those at which either substance is individually detectable. Phenolic compounds can occur naturally in lowland rivers. Unpleasant tastes and smells, usually earthy or sulfurous in nature, can also occur naturally from decaying vegetation.
The ecological effect of colour will depend on its light-absorptive properties in relation to the spectral requirements of algae and plants i. Many rivers are naturally coloured e.
The ecological effects of colour are usually minimal compared with other factors. The flow rate of the river is a constant 20 m 3 per day. The effluent flow rate is m 3 per hour, which equates to 14 m 3 per day. The final temperature in the river will be:. The higher temperature will:. Biological pollutants are organisms that may be harmful to other forms of life, but they have to be ingested to have any effect.
The most usual form of transmission is the faecal—oral route, in which faecal matter from one human being finds its way into another. This can happen through the ingestion of faecally contaminated water or food. Alternatively, sometimes pathogenic organisms can be consumed through eating contaminated undercooked food, as in the case of certain strains of Escherichia coli.
The effects of the different organisms are varied, and can be more easily ascertained through sources such as the WHO or local health protection agencies.
However, in this subsection I will describe the characteristics of the main water-borne pollutants, namely:. As well as the bacteria that are found naturally in river water and that are essential for the natural cycle of nutrients, there may be other, less desirable bacteria. Pathogenic bacteria such as Salmonella typhi , Figure 7 can cause disease in a variety of organisms, including humans. Since the presence of pathogenic bacteria is generally due to the activities of humans, it constitutes a form of pollution.
Non-pathogenic bacteria, by definition, are harmless; indeed, as already mentioned, they can be beneficial and form an essential part of the aquatic ecosystem.
Coliforms are a large group of bacteria, often of intestinal origin. The coliform Escherichia coli Figure 8 is present in the intestines of humans and other mammals.
Its presence in water implies that human pathogens from faeces may also be present, and it is therefore a useful indicator organism of faecal contamination. The strain of E. However, there are other strains — such as E. These have been found in partially cooked meat and have led to deaths Rangel et al. Concentrations of E. The presence or absence of E. The faecal streptococci group of bacteria consists of the species Streptococcus faecalis Figure 9 , S.
They die fairly quickly outside their host, so their presence is indicative of recent pollution. It is a common cause of food poisoning. They can cause severe abdominal cramp and diarrhoea if present in water that is ingested. Endospores — or spores, as they are commonly referred to — are hardy structures that certain bacteria can form when their environment becomes unfavourable for growth.
The purpose of the endospore is survival; it is very resistant to heat and desiccation, and may survive for many years at normal temperatures. When environmental conditions are favourable for growth, the endospore reactivates to form a normal, single cell. This ability leads to C. Thus its presence in the absence of E. Viruses are tiny 5—30 nanometres in size infective agents that can grow only in living cells. The virus that causes smallpox, declared eradicated from the world in , is illustrated in Figure Most viruses are able to remain viable in water at low temperatures, provided there is some organic matter present.
Once excreted, the number of viruses cannot increase since they only multiply within living susceptible cells. The main threat to water quality comes from human enteric intestinal viruses that are produced by infected persons and excreted faecally. Depending on local circumstances, this may contaminate river water directly or, if treated, via sewage effluent that may be discharged into a river. If the river water is abstracted and treated for drinking purposes, the viruses may not be completely removed.
It is possible for a person to be susceptible to only one viral particle. The presence of any enteric virus can be taken as an indication of the possible presence of other harmful viruses. In temperate climates, enteric viruses occur at peak levels in sewage during late summer and early autumn.
The exception is the hepatitis virus, which increases in the colder months. There have been several outbreaks of protozoal infections from water in several countries. For instance, each year in the UK there are — confirmed cases of cryptosporidiosis, caused by the protozoa Cryptosporidium ; the largest outbreak was in Torbay, Devon in , when people were taken ill Hunter et al.
The most common symptom of cryptosporidiosis is watery diarrhoea. Other symptoms include stomach pain, nausea, vomiting, fever and weight loss Centers for Disease Control and Prevention, In addition, some people can act as carriers of Cryptosporidium. Another, similar condition is giardiasis, caused by the protozoa Giardia.
Giardiasis outbreaks are not common in the UK, but one occurred in Bristol in , when cases were diagnosed Jephcott et al. Techniques for sampling and analysis of Cryptosporidium are complicated and time-consuming, requiring the filtration of large volumes of water — litres , followed by several stages of elution, isolation and concentration of the oocysts, and then identification and enumeration by immunofluorescent microscopy.
Initial testing does not provide information on whether the oocysts are viable and therefore capable of causing disease — this requires further testing. As a result, there is no specific standard for the organism in EU or UK regulations. There is, however, a general requirement that drinking water should not contain any microorganism or parasite at a concentration that would constitute a potential danger to human health Water UK, Cryptosporidium and Giardia can be trapped by membrane filtration or slow sand filters.
Other types of filters, such as wound fibre filters, are also employed. Chlorination and UV radiation at normal doses are ineffective against these organisms. Helminths Figure 12 are parasitic worms that can cause ill health in humans. They range from a millimetre long to more than a metre Baron, Helminths can cause morbidity, and sometimes death, by compromising the nutritional status of the infected person.
They can also affect cognitive processes, induce tissue reactions and provoke intestinal obstruction or rectal prolapse WHO, Infection occurs through ingestion of helminth eggs that are present in food. For example, helminth eggs may be present in the meat of cattle grazing on land that is contaminated by poorly treated sewage effluent or sludge. Many other forms of pollution mentioned previously could be considered as biological pollutants, e.
Examples that are more clearly of this type of pollution are the many species of blue-green algae, which produce substances that are toxic to terrestrial organisms and can impart tastes and odours to water. Identify which of the following statements are true. Continuously flowing organic pollutants such as domestic sewage cannot cause long-term damage to a watercourse in the way that toxic pollutants can.
Effluents from fish farms can be badly polluted. Concern has arisen about these effluents mainly because they contain unconsumed food and faecal matter from fish.
Pesticide pollution of watercourses is due solely to large-scale use of these compounds by farmers. Metals that are water soluble are able to bioaccumulate by diffusing across the biological membranes of organisms. Statement e is true. Statement c is also true, though concern has also arisen because fish farm effluents contain antibiotics see Section 2. Statement a is false: heavy organic loads on a watercourse can cause long-term damage to the water in the vicinity of the effluent outfall.
However, recovery is more likely if pollution ceases than would be the case for toxic chemicals. Statement b is false: the BOD will increase, as the metabolic rates of the microorganisms will be higher at a higher temperature.
Statement d is false: householders use a large quantity of pesticides in the form of herbicides and insecticides, and these can also contribute to water pollution. The toxicities of individual chemicals in a mixture can be summed up to give an overall toxicity figure. This is simpler than testing a complex mixture. In toxicity tests for a proposed discharge, the most sensitive species in the receiving watercourse should be used as the test organism.
In: Proceedings of the conference on pesticide pollution detection and management at the University of Agriculture, Abeokuta, Nigeria Google Scholar.
Dubaish F, Liebezeit G Suspended microplastics and black carbon particles in the jade system, southern North Sea. DWA Wastewater limit values applicable to the discharge of wastewater into a river resource. FAO b The state of world fisheries and aquaculture, contributing to food security and nutrition for all. FAO c The state of world fisheries and aquaculture, contributing to food security and nutrition for all.
Focardi S, Corsi I, Franchi E Safety issues and sustainable development of European aquaculture: new tools for environmentally sound aquaculture. Francis G Poisonous Australian lake. Nature —12 CrossRef Google Scholar. In: Proceedings of the GESAMP international workshop on micro-plastic particles as a vector in transporting persistent, bio-accumulating and toxic substances in the oceans Google Scholar.
Gibbs RJ Mechanisms of trace metal transport in rivers. Gregory MR Environmental implications of plastic debris in marine settings: entanglement, ingestion, smothering, hangers-on, hitch-hiking and alien invasions.
Gyllenhammer A, Hakanson L Environmental consequence analyses of fish farm emissions related o different scales and exemplified by data from the Baltic—a review. Ecosphere 6 10 :1—43 CrossRef Google Scholar. Igbinosa EO, Okoh AI The impact of discharge wastewater effluents on the physiochemical qualities of a receiving watershed in a typical rural community. Hydrobiologia — CrossRef Google Scholar. Jin L Environmental bionomy, 1st edn. Larsson DGJ Pollution from drug manufacturing: review and perspectives.
Lawson TB Aquaculture in open systems. In: Fundamentals of aquacultural engineering. H2O 14 15 —47 Google Scholar. Lorenz JJ A review of the effects of altered hydrology and salinity on vertebrate fauna and their habitats in northeastern Florida bay. Wetlands — CrossRef Google Scholar. Major DN, Wang H How public health impact is addressed: a retrospective view on three different oil spills.
Mancuso M Fish welfare in aquaculture-editorial. Margesin R, Schinnur F Efficiency of endogenous and inoculated cold-adapted soil microorganisms for biodegradation of diesel oil in alpine soils.
Martinez-Cordova LR, Enriquez-Ocana F Study of the benthic fauna in a discharge lagoon of the shrimp faro with special emphasis on polychaeta. J Biol Sci —17 Google Scholar. Environ Monit Assess Environ Water SA Google Scholar. Morris JG Harmful algal blooms: an emerging public health problem with possible links to human stress on the environment. In: Environmental contamination and remediation. Bioscience 55 5 — CrossRef Google Scholar. New and emerging water pollutants arising from agriculture, prepared by Alistair B.
Boxall, Paris Google Scholar. Paerl HW Nuisance phytoplankton blooms in coastal, estuarine and inland waters. Limnol Oceanogr — Google Scholar. Paerl HW, Huisman J Climate change: a catalyst for global expansion of harmful cyanobacterial blooms.
Paez-Osuna F The environmental impact of shrimp aquaculture: causes, effects and mitigating alternatives. Paez-Osuna F Restos y perspectivas de la camaroniculturaen la zona costera. Revistalatinoamericana de Recursosnaturales —31 Google Scholar.
Perkins S Nearly every seabird may be eating plastic by Perkol-Finkel S, Benayahu Y Differential recruitment of benthic communities on neighboring artificial and natural reefs. Porter KG The plant-animal interface in freshwater ecosystems. Am Sci — Google Scholar. Purvis A Ten largest oil spills in history. Environ Monit Assess 2 Rochman CM Plastics and priority pollutants: a multiple stressor in aquatic habitats. Schindler DW Eutrophication and recovery in experimental lakes: implications for lake management.
Science — CrossRef Google Scholar. Schindler DW Recent advances in the understanding and management of eutrophication. Schreinemachers P, Tipraqsa P Agricultural pesticides and land use intensification in high, middle and low income countries.
Sharma YC A guide to the economic removal of metals from aqueous solutions. Thompson RC Mircoplastics in the marine environment: sources, consequences and solutions. Chem Class J —30 Google Scholar. Turner AM, Chislock MF Blinded by the stink: nutrient enrichment impairs the perception of predation risk by freshwater snails. UNEP Water quality for ecosystem and human health.
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