Pollution is defined as the release of toxic or harmful substances into the environment (air, water and land) by their natural forces or man and other animals to an extent that cause biological damage to man and his resources. The harmful substances that cause pollution to the environment are called pollutants ( Eshagberi, 2014). There are six main types of pollution, these are; Air pollution, noise pollution, land pollution, water pollution, thermal pollution and nuclear pollution. AIR POLLUTION - This is defined as the presence in the atmosphere (indoor or outdoor) one or more air contaminants (dust, fumes, gases, mist, odour, smoke, noise, particles or vapour) in sufficient quantities, of characteristics and duration, as to be or threatened to be injurious to human, plant or animal life or to properties or which reasonably interfere with a comfortable enjoyment of life or property (World Bank, 2005). NOISE POLLUTION - This refers to any unwanted sound that affect our health. The unit of noise is decibel. Noise pollution encompasses roadway noise, aircraft noise, industrial noise, noise from generator, high pitched music e.t.c LAND POLLUTION - Is any process carried out by man that leads to an adverse change in terrestrial environment. There are a number of sources of land pollution. These include; refuse, sewage, metal scraps, pesticides or fertilizers, chemicals glass particles, crude oil spillage. THERMAL POLLUTION - This is a form of pollution that involves the raising or lowering of air or water temperature above or below normal seasonal ranges in streams, lakes or estuaries or oceans as the result of discharge of hot or cold effluents into such water or atmosphere. The main cause of thermal pollution is the use of water as a coolant especially in power plants. Water used as coolant is returned to the natural environment at a higher temperature. Increase in water temperature can alter aquatic organisms' lives by decreasing oxygen supply, kill juvenile fish which are vulnerable to small increase in temperature and also affect ecosystem composition. NUCLEAR POLLUTION - This refers to the release of radioactive materials into the environment. Major source of radioactive pollution include nuclear power plants, nuclear weapon, transportation, disposal of nuclear waste, uranium mining. WATER POLLUTION - This refers to the release of toxic materials, agents of pollution into water bodies. Until recently, water pollution has been a relatively local problem of the developed world. Eutrophication is the most common problem where inland waters and rivers are polluted with nitrogen and phosphorus run-off from fertilizers used in intensive agriculture and discharge of phosphate-rich sewage effluents. Such problems are increasingly occurring on a worldwide basis and now affect marine as well as freshwater ecosystem (Eshagberi, 2014). Sewage from coastal settlement discharges, sometimes untreated, into coastal waters where it generates a direct health hazard for recreational bathers as well as marine organisms. Land drainage from urban areas, industrial and waste disposal site is often contaminated with heavy metals or hydrocarbons. Biological concentration of heavy metals in marine food chains may give lethal doses, as occurred following the industrial discharge of mercury into coastal waters at Minimata in Japan. Here concentration in fish led to the death of many humans and other animal predators. At sub-lethal levels, heavy metals and contaminants such as pesticides and oil derivatives may lower resistance to disease. During the last decade, measures to control and eventually stop toxic waste dumping and incineration at the sea have been introduced by countries bordering North Sea in an attempt to reduce pollution and damage to this ecosystem. Other forms of water pollution include thermal pollution and crude oil pollution (Eshagberi, 2014). Crude oil is one of the poisonous chemicals in water bodies. Crude oil also known as petroleum is a dark brown liquid, mixed with gases and solids in oil wells. It is believed that it was formed by bacterial decomposition of animal and plant remains over a long period of time (Ogali, 2009). Crude oil pollution is the uncontrolled release of toxic chemicals caused by equipment failure, operation mishaps, human error or intentional damage to facilities. The extent of damage depends on what, when and how much has been spilled and how long it remains in the immediate and impacted environment. In the case of aquatic environment, the impacts are in the range of unquantifiable damages on fishes and other economically important aquatic organisms, as well as the direct and indirect negative effects on the socio-economic lives of human settlers whose survival has much to do with the products of aquatic ecosystem (SPDC, 1997). Apart from uncontrolled oil spills, production operations inevitably release effluent in form of produced waters, storm waters and flushing wastes into the aquatic environment and these are found to contain significant quantities of hydrocarbons and associated pollutants(SEEMS, 1997). Dissolved oxygen refers to the free, non-compound oxygen present in water. Oxygen enters water by direct absorption from the atmosphere which is enhanced by turbulence. Water also absorbs oxygen released by aquatic plants during photosynthesis. Dissolved oxygen is an important parameter in assessing water quality because of its influence on the organisms living within a body of water. A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality (Kemker, 2013). pH of a solution is simply the negative logarithm of hydrogen ion concentration. The pH of a solution describes the acidity of that solution. Acidic solutions are those with a pH of less than 7 and basic solutions have a pH greater than 7. The normal pH of pure water is 7 which is neutral. In aquatic ecosystem, the pH of water varies depending on the type of organism in a particular habitat. Living organisms in water are highly sensitive to pH changes. Too high or too low pH will affect the lives and activities of plants and animals in water. Plants and animals are adapted to special pH values. pH of freshwater is low while marine pH is high (Eshagberi, 2014). 1.2. STATEMENT OF PROBLEM The magnitude of crude oil pollution and damage occasioned by human activities is incredible. Crude oil or petroleum became a richly available commodity of essence about a century ago. The now widespread use of this black gold cannot be over emphasized. It is noteworthy that, the environment with its eventual hazards on both aquatic and terrestrial ecosystem contribute to an irreversible chain effect on both the biodiversity and human safety. Crude oil pollution has a wide range effect on aquatic organisms as to the whole aquatic ecosystem. The effect of crude oil pollution faced with aquatic ecosystem is fluctuations in pH and dissolved oxygen level which affect the survival rate of the aquatic organisms. 1.3 OBJECTIVES OF THE STUDY The following are the specific objectives designed to be strictly adhered to. I. To determine the effect of water extract of crude oil on the aquatic macrophyte Eicchornia crassipes. II. To determine the effect of water extract of crude oil on dissolved oxygen of aquatic ecosystem. III. To assess the effect of water extract of crude oil on pH of aquatic ecosystem. 1.4. SIGNIFICANCE OF THE STUDY The significance of this study is to provide an up-to-date knowledge of the effect of crude oil pollution on dissolved oxygen and pH in aquatic ecosystem. This study is therefore carried out to know the causes of crude oil pollution in aquatic ecosystem and the effect it has on dissolved oxygen and pH and if possible, provide solution to these effects. It is also hoped that the study will provide a sound knowledge about the standard value of dissolved oxygen and pH concentrations and how deviations from the standard value affect aquatic organisms and how the deviations can be controlled. 1.5. SCOPE OF THE STUDY This research is designed to cover the effect of crude oil pollution on dissolved oxygen and pH level in aquatic ecosystem and on the growth of Eicchornia crassipes. This research work will evaluate how the level of dissolved oxygen and pH affect Eicchornia crassipes and as well as suggest possible ways through which these effects can be rectified. 1.6. DEFINITION OF TERMS The following terms are used in this research work. For a clear understanding, the following definitions have been given. Toxic- A substance is said to be toxic when it contains poison. Pollutants- Pollutants can be defined as substance present in greater than normal concentration as a result of human activities that has a net detrimental effect upon the environment. Contaminants- Contaminants can be defined as substance present in the environment without any foreseeable harmful effect. Ecosystem- This can be defined as the community of plants and animals interacting with themselves and their external environment and forms a functional unit. Sewage- Sewage can be defined as liquid waste from domestic sources, industrial sources, and agricultural sources. Concentration- Concentration can be defined as weight of solute per weight of solvent or as number of moles of solute per number of moles of solvent.