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The Scientific Method ‣ Scientific knowledge is gained through a process called the scientific method. ‣ This process involves: " observing and measuring " hypothesizing and predicting " planning and executing investigations designed to test
formulated predictions Making Observations ‣ Many types of observation can be made on biological systems. They may involve: " observation of certain behaviors in wild populations " physiological measurements made during previous
experiments " ‘accidental’ results obtained when seeking answers to
completely unrelated questions ‣ The observations may lead to the formation of questions about the system being studied.
Forming a Hypothesis ‣ Generating a hypothesis is crucial to scientific investigation. A scientific hypothesis is a possible explanation for an observation, which is capable of being tested by experimentation. ‣ Features of a sound hypothesis are: " it offers an explanation for an observation. " it refers to only one independent variable. " it is written as a definite statement and not as a question. " it is testable by experimentation. " it is based on observations and prior knowledge of the
system. " it leads to predictions about the system.
Types of Hypotheses ‣ Hypotheses can involve: " Manipulation: where the biological effect of a variable is
investigated by manipulation of that variable, e.g. the influence of fertilizer concentration on plant growth rate.
" Species preference: where species preference is investigated, e.g. woodpeckers show a preference for tree
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" Species preference: where species preference is investigated, e.g. woodpeckers show a preference for tree type when nesting.
" Observation: where organisms are being studied in the field where conditions cannot be changed, e.g. fern abundance is influenced by the degree of canopy establishment.
The Null Hypothesis ‣ For every hypothesis, there is a corresponding null hypothesis; a hypothesis against the prediction, of no difference or no effect. " A hypothesis based on observations is used to generate the
null hypothesis (H0). Hypotheses are usually expressed in this form for the purposes of statistical testing.
" H0 may then be rejected in favor of accepting the alternative hypothesis (HA) that is supported by the predictions.
" Rejection of the hypothesis may lead to new, alternative explanations (hypotheses) for the observations.
‣ Scientific information is generated as scientists make discoveries through testing hypotheses.
Generating Predictions ‣ An observation may generate a number of plausible hypotheses, and each hypothesis will lead to one or more predictions, which can be further tested by further investigation and are usually reliable or accurate. For example: ‣ Observation 1: Some caterpillar species are brightly colored and appear to be conspicuous to predators such as insectivorous birds. " Despite their being
conspicuous, predators usually avoid these brightly colored species.
" Brightly colored caterpillars are often found in groups, rather than as solitary animals.
Generating Predictions ‣ Observation 2: Some caterpillar species are cryptic in appearance or behavior. Their camouflage is so convincing
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‣ Observation 2: Some caterpillar species are cryptic in appearance or behavior. Their camouflage is so convincing that, when alerted to danger, they are difficult to see against their background. Such caterpillars are usually found alone.
Generating Predictions ‣ There are several hypotheses and predictions that could be generated to account for the two previous observations: " Hypothesis 1: Bright colors signal to potential predators that
the caterpillars are distasteful. " Prediction 1: Inexperienced birds will learn from a distasteful experience with an unpalatable caterpillar species and will avoid them thereafter.
" Hypothesis 2: Inconspicuous caterpillars are palatable and their cryptic coloration reduces the chance that they will be discovered and eaten. " Prediction 2: Insectivorous birds will avoid preying on brightly colored caterpillars and they will prey readily on cryptically colored caterpillars if these are provided as food.
Assumptions ‣ In any experimental work, you will make certain assumptions about the biological system you are working with. ‣ Assumptions are features of the system (and your experiment) that you assume to be true but do not (or cannot) test. ‣ Possible assumptions for the previous hypotheses (and their predictions) include: " Birds and other predators
have color vision. " Birds and other predators
can learn about the palatability of their prey by tasting them.
Planning An Investigation ‣ Use a checklist or a template to construct a plan as outlined below:
Variables ‣ A variable is any characteristic or property able to take any one of a range of values. Investigations often look at the effect of changing one variable on another (the biological response
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changing one variable on another (the biological response variable). ‣ It is important to identify all variables in an investigation: independent, dependent, and controlled. Note that there may be nuisance factors of which you are unaware. ‣ In all fair tests, only one variable (the independent variable) is changed by the investigator.
Identifying Variables ‣ All variables (independent, dependent, and controlled) must be identified in an investigation.
Dependent and Independent Variables ‣ How the dependent variable changes depends on the changes in the independent variable, i.e. the dependent variable is influenced by the independent variable ‣ When heating water, the temperature of the water rises over time. " Therefore the temperature of the water is dependent upon
the length of time it is left for. " Time is independent as it is not influenced by the
temperature of the water. Variables and Data ‣ Data are the collected values for monitored or measured variables. " Like their corresponding variables, data may be qualitative,
ranked, or quantitative (or numerical). Examples of Investigations ‣ Once all of the variables have been identified in an investigation, you need to determine how these variables will be set and measured. ‣ You need to be clear about how much data, and what type of data, you will collect. " Some examples of investigations are shown below:
Stages In An Investigation ‣ Investigations involve written stages (planning and reporting), at the start and end. The middle stage is the practical work when the data are collected (in this case by dataloggers as
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when the data are collected (in this case by dataloggers as shown below).
Field Studies ‣ A framework for a simple field study is outlined below: Sample Size ‣ When designing your field study, the size of your sampling unit and the sample size (n) should be major considerations. " A sampling unit might be (for example) an individual
organism or a quadrat. " The sample size might be the number of individuals or the
number of quadrats. ‣ For field studies, sample size is often determined by the resources and time available to collect and analyze your data. ‣ It is usually best to take as many samples as you can, as this helps to account for any natural variability present and will give you greater confidence in your data.
Replication ‣ Replication in experiments refers to the number of times you repeat your entire experimental design (including controls). Multiple experiments only improves the validity of a given experiment. " Increasing the sample size (n) is not the same as true
replication. In the replicated experiment below, n=6. Making Investigations ‣ An example of a basic experimental design aimed at investigating effect of pH on the growth of a bog adapted plant species follows: " Observation: A student noticed an
abundance of a common plant (species A) in a boggy area of land. The student tested the soil pH and found it to be quite low (between 4 and 5). Garden soil was about pH 7.
" Hypothesis: Species A is well adapted to grow at low pH and pH will influence the vigor with which this plant species grows.
" Prediction: Species A will grow more
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" Prediction: Species A will grow more vigorously (as measured by wet weight after 20 days) at pH 5 than at lower or a higher pH.
Making Investigations ‣ Experiment: An experiment was designed to test the prediction that the plants would grow best at low pH. The design is depicted graphically below and on the next slide. It is not intended to be a full methodology.
Making Investigations ‣ Note that in experiments with a large number of treatments and replication, it is important to randomize the arrangement of the treatments to account for any effects of location in the set-up. " In this case, n = 6, there are four different treatments and the
experiment has been replicated six times. Making Investigations 4 ‣ Control of variables: " Fixed variables include lighting and watering regime, soil type
and volume, age and history of plants, pot size and type. " The independent variable is the pH of the water provided to
the plants. " The dependent variable is plant growth rate
(g day-1) calculated from wet weight of entire plants (washed and blotted) after 20 days. " Other variables include genetic variation between plants and
temperature. ‣ Assumptions include: All plants are essentially no different to each other in their growth response at different pH levels; the soil mix, light quality and quantity, temperature, and water volume are all adequate for healthy continued growth.
Collection and Analysis ‣ Data collected by measuring or counting in the field or laboratory are called raw data. " As part of planning an investigation, a suitable results table
must be designed to record raw data. ‣ Once all the required data has been collected, they need to be analyzed and presented. " To do this, it may be necessary to transform or process the
data first.
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" To do this, it may be necessary to transform or process the data first.
Aquatic Ecology Water: Importance, Availability and Renewal ‣ Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle: " Only about 0.02% of the earth’s water supply is available to
us as liquid freshwater. Water By The Numbers ‣ Water covers 71% of Earth’s surface. ‣ Oceans: 97%, Glaciers / polar ices caps: 1.8%, Groundwater: 0.9%, Other land surface water (rivers, lakes): 0.017% ‣ 20% of all surface freshwater is in Lake Baikal, Russia. ‣ The Ogallala Aquifer is the largest groundwater reserve. ‣ The Middle East has the lowest amount of naturally available freshwater and uses desalination for their water supply.
Fresh Water ‣ Accessible fresh water is extremely rare when considering the total volume of water on Earth. ‣ It is also unbalanced in its distribution. Some areas of land are continually wet, others have not seen permanent water in centuries.
Fresh Water Resources ‣ 71% of the Earth’s surface is covered with water. ‣ Most of this, more than 1.3 billion cubic kilometers, is contained in the oceans. Only 35 million cubic kilometers is fresh water. ‣ Only a tiny amount of the water on Earth is accessible and usable to humans because the ice caps and glaciers are the majority of freshwater and are not readily available for use.
Water Use: America
Fresh Water Use ‣ Intensive agriculture uses large amounts of water, 69% of the freshwater. " Improved irrigation techniques can reduce the amount
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freshwater. " Improved irrigation techniques can reduce the amount
required. " Every year huge quantities of water as transported to irrigate
crops. ‣ Industrial water use increases along with the human population using about 22%. " The cooling of power plants and the processing of almost all
commercial goods requires the use the water. ‣ Cities and residences use only 8% of the freshwater. Nearly half of the municipal water in the US is used to flush toilets or water lawns. " Another 20-35% is lost in water leaks. " Large savings can be made by improving the efficiency of
water use. " Treatment of waste water is a major issue.
Water Use in Industry ‣ Global rates of water withdrawal from surface and groundwater sources are projected to more than double in the next two decades as a result of increased population growth and economic development. ‣ Manufacturing and production processes are usually water intensive. Some everyday items use surprisingly large amounts of water in their production. ‣ This is termed virtual water usage as the water is not in the final product. Many energy saving practices can conserve water: " Turn off electric appliances when not in room " Turn off lights in daylight hours " Energy-efficient appliances and water heater " Set thermostat to high/lower temperatures
American Water Reserves Global Water Reserves Factors Affecting Aquatic Ecosystems ‣ Abiotic (physical) factors are the influences of the non-living parts of the ecosystem. " Examples include pH, salinity, temperature, turbidity, wind
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" Examples include pH, salinity, temperature, turbidity, wind speed and direction, humidity, precipitation, water pressure, and light intensity and quality.
‣ Biotic factors are the influences of the living parts of the ecosystem. Producers and consumers interact as competitors, parasites, pathogens, symbionts, and predators.
Organisms in Aquatic Zones ‣ Aquatic systems contain organisms that float, drift, swim, bottom-dwell, and decompose. These organisms are called:
" Plankton
" Nekton
" Benthos
" Decomposers Marine (Ocean) Ecosystems ‣ The ocean covers about 71% of Earth’s surface and contain
many organisms and habitats ‣ Oceans are so large that solar heat is distributed by ocean
currents & as ocean water evaporates. ‣ The oceans help regulate the earth’s climate by the distribution
of heat (regulate atmospheric temperature) & oceans are enormous reservoirs for carbon both sequestered and free as carbon dioxide.
Ocean Zones ‣ Coastal and Euphotic Zone: " Lots of light. From 0 - 200 meters. Photosynthesis takes
place here ‣ Bathyal Zone: " The dimly lit part of ocean. From 200 - 1500 meters.
‣ Abyssal Zone: " Completely dark. Extends to a depth of 4000 to 6000 meters
(2.5 to 3.7 miles). Water here is very cold & has little dissolved oxygen.
‣ Benthic Zone (Ocean Floor):
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‣ Benthic Zone (Ocean Floor): " Bacteria are common & can survive down to 500 meters
below ocean floor. Reefs, Sea Grass, and Kelp ‣ Reefs: " Reefs are Marine Protected Areas like national parks and
wildlife refuges and have significant economic value because of tourism. " They are composed of calcium carbonate living systems in
warm shallow water where light penetrates. ‣ Kelp (Seaweed): " Brown algae groups that provide habitats and food for many
organisms. " Kelp is being considered as a renewable resource because it
is fast growing and yields large amounts of methane. ‣ Seagrass: " Seagrass is highly adaptable and serves as a producer for
many marine ecosystems. Seagrass can reduce surface erosion
Phytoplankton & Zooplankton ‣ Phytoplankton are an autotrophic group of weakly swimming, free-floating biota that are producers that support most aquatic food chains. These organisms provide much of the oxygen in the Earth’s atmosphere and include: " Phytoplankton (plant-like organisms and cyanobacteria
Nekton and Benthos ‣ Nekton are larger, actively swimming consumers usually the top consumers in the aquatic ecosystems and include: " Fish, whales and turtles
‣ Benthos are bottom-dwelling creatures that may be primary consumers or decomposers. These highly diverse organisms may live in tide pools, shelves or the abyss and include: " Barnacles, oysters, lobsters and sea anemones
Freshwater Aquatic Zones ‣ Freshwater life zones include: " Standing (lentic) water such as lakes, ponds, and inland
wetlands. The size of lentic systems varies from standing water ponds to deep water lakes like Lake Baikal. The characteristics of the standing water are divided into different
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water ponds to deep water lakes like Lake Baikal. The characteristics of the standing water are divided into different varying depths of the water. " Flowing (lotic) systems include streams and rivers. The flow
of water is unidirectional with a constant state of physical change. Variability is high and biota are specialized to live in flow conditions.
Freshwater Streams and Rivers ‣ Water flowing from mountains to the sea creates different aquatic conditions and zones. Some precipitation infiltrates the ground and is stored in soil and rock the storage of the water that infiltrates is called groundwater. ‣ Water that does not sink into the ground or evaporate into the air runs off as surface runoff into bodies of water. The land from which the surface water drains into a body of water is called its watershed or drainage basin. ‣ The watersheds and basins are floodplain areas that often contain nutrient rich soils that are fertile for agricultural production.
Groundwater ‣ Groundwater or aquifers are water recharge areas that are located beneath the ground surface in soil pore spaces and fractures in the Earth’s formations. Natural discharge occurs from springs and wetlands. " The water table measures the level of Earth’s land crust to
which the aquifer is filled. " Renewability rates of aquifers differ depending on the surrounding conditions of the land and the water cycle. The circulation rate of most aquifers is usually slow (300 to 4,600 years) compared to the rate they are being depleted.
Stream (Lotic) Characteristics ‣ A fast moving stream or river is a lotic water system that narrow zone of cold, clear water that rushes over waterfalls and rapids. Large amounts of oxygen are present because of aeration. Fish and other aquatic organisms are are also present because of the high amount of oxygen. " Deposits nutrients and salt.
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present because of the high amount of oxygen. " Deposits nutrients and salt.
‣ Slower-moving lotic water systems contain less oxygen, has warmer temperatures, and contains a large amount of algae and cyanobacteria. " Provides different habitats and helps purify water.
Lakes (Lentic) Characteristics ‣ Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of:
" The littoral zone is near the shore and contains the shallow rooted plants.
" The limnetic zone is the open offshore area that is sunlit and contains organisms that do photosynthesis.
" The profundal zone is the deep open water that is too dark for photosynthesis and goes through periods of temperature and nutrient change.
" The benthic zone is the bottom of the lake and contains decomposers that are nourished by dead
organisms. Lake (Lentic) Characteristics Lake (Lentic) Characteristics ‣ Temperature, access to sunlight for photosynthesis, dissolved
oxygen content, nutrient availability changes with depth. Upwelling: Spring and Fall ‣ During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. The overturn exchanges nutrients and temperatures and this exchange is called upwelling or turnover. " The equalizing temperature occurs at all depths so that there
is a distribution of the photic and euphotic zones. " During the nutrient exchange, oxygen is brought from the
surface (limentic) of the lake to the bottom (profundal) and cold nutrient-rich water from the bottom will rise to the surface.
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cold nutrient-rich water from the bottom will rise to the surface.
The Grand Banks ‣ The Grand Banks of Newfoundland consists of a series of underwater plateaux at the edge of the North American continental shelf. " The plateaux range from 36 m to
185 m deep. " The shape of the deep sea-floor causes nutrient rich water to
well up to the surface and the relatively shallow plateaux allow a huge range of fishes to proliferate.
‣ The Grand Banks have been fished since the fifteenth century but continual over fishing has devastated many fish stocks.
Estuaries ‣ Estuaries are a partially enclosed area of coastal water where sea water mixes with freshwater and are constantly changing. ‣ Salinity fluctuates with tidal cycles, the time of year, and precipitation. The organisms that live here must be able to tolerate these conditions. ‣ The high nutrients lend themselves to a breeding ground for many ocean species and thus highly productive. ‣ Estuaries serve as filters for pollutants and absorb water recharging groundwater stores to control flooding.
Wetlands ‣ Inland wetlands are defined by their water quality, soil type,
and species composition. ‣ Wetlands act like natural sponges that absorb and store
excess water from storms and provide a variety of wildlife habitats. They also filter and degrade pollutants. ‣ Wetlands replenish stream flows during dry periods and
recharge ground aquifers. If ground water is being depleted then saltwater intrusion may occur. " They also reduce flooding and erosion by absorbing slowly and releasing overflow water and provide economic resources and recreation
Ocean Margin Plants
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Ocean Margin Plants ‣ Ocean margin plants, e.g. intertidal seaweeds and mangroves, must cope with high salt content in the water and changing tidal conditions.
Adaptations of Halophytes ‣ Mangroves are halophytes, adapted to grow in saline, intertidal environments, where they form some of the most complex and productive ecosystems on Earth. ‣ Mangrove adaptations include: " Ability to secrete salt or accumulate it in older leaves. " Specialized tissue that allows water, but not salt, to enter the
roots. " Tissue tolerance for high salt levels. " Extensive root systems give support in soft substrates;
oxygen enters the roots through pneumatophores. Human Effects on Aquatic Systems ‣ Most water used by humans comes from: " rivers " lakes " aquifers
‣ Irrigation and diversions for drinking water displace vast amounts of the water for these resource stores. ‣ Damming rivers for electricity affects water flow downstream as seen in the James Bay project in Quebec. ‣ These actions can have dramatic effects on the environment and wildlife.
Rivers as Highways ‣ The major rivers of the worlds provide water for irrigation and drinking and enable the transport of large amounts of freight. ‣ Huge barges moved by tugboats are used on many rivers and lakes of developed countries. ‣ However there are many negative environmental effects. ‣ Some rivers such as the Yangtze are so polluted and congested with ships that little can live in them. " The Yangtze River Dolphin was last seen in 2002 and has
since been declared functionally extinct. It is the first cetacean extinction directly attributable to human interference.
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interference. Colorado River System ‣ The Colorado River flows for 2,330 km through the southwestern United States and into Mexico. ‣ The river’s catchment area is 629,000 km2. ‣ Average flow is around 600m3s-1, although flows vary considerably. ‣ There are more than 20 dams in its catchment system.
‣ The Colorado River’s location makes it subject to much controversy.
‣ It flows through seven states and two countries, with much of its course through desert.
‣ Large quantities of water are removed from it every year to reservoirs in other parts of the country.
‣ Many endangered species live in or along the course of the river.
‣ Advantages of the river’s use are: " provides water for more than
24 million people " irrigates 2 million acres of land " provides major tourist attractions " provides 4,000 MW of electricity
‣ Disadvantages of the river’s use are: " lowered water quality " river delta affected by low water flows " loss of habitat for many animals " major construction and diversion issues
‣ The dams along the Colorado River provide for: " flood control " water storage for irrigation and domestic supply " hydroelectric power generation
‣ Much of the river’s flow is diverted for irrigation and domestic use.
‣ This has reduced the amount of water flowing through the lower part of river and the river delta.
Colorado River Profile
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lower part of river and the river delta. Colorado River Profile ‣ A number of large hydroelectric dams are located along the Colorado River as well as dams used for irrigation or diverting water flows.
Aswan High Dam ‣ Two dams straddle the Nile River at Aswan, Egypt. The Aswan High Dam was completed in 1970 and formed Lake Nasser. which is 550 km long and capable of holding two years of the Nile's annual flow. ‣ The main objectives of the project were: " energy generation in a renewable form. " flood control in downstream locations. " provision of water for agriculture and domestic use.
‣ A serious detrimental effect is the loss of the annual floods downstream. These used to replenish the nutrients of the flood plain and flush out accumulated salts.
Aswan High Dam Three Gorges Dam ‣ The Three Gorges Dam spans the Yangtze River at Sandouping, China, and is the largest hydroelectric dam in the world, capable of producing 22,500MW of electricity. ‣ Major construction began in 1994 and is expected to be fully completed by 2011.
Filling the Dam ‣ The reservoir behind the Three Gorges Dam extends 600km upstream. The dam itself is over 2km wide and 186m high.
Filling the Dam Filling the Dam
Three Gorges Dam Issues ‣ Before construction of the Three Gorges Dam, major flooding downstream cost many lives and billions of dollars in damage. ‣ Continual but regulated discharge of water from the dam allows management of drought prone areas during the dry season. ‣ Silting could eventually lower the efficiency of the dam. ‣ The dam has been linked to the disappearance of the Yangtze river dolphin and has greatly affected stocks of the Yangtze
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‣ The dam has been linked to the disappearance of the Yangtze river dolphin and has greatly affected stocks of the Yangtze sturgeon.
Three Gorges Dam Issues ‣ Advantages of construction: " reduction of coal use in coal fired power stations " flood control downstream " drought relief " better navigation of the river by ships
‣ Disadvantages of construction: " submergence of wetlands and agricultural lands " loss of endangered plant and animal habitats " archaeological sites flooded upstream " towns and cities flooded and 1.2 million people displaced
The Aral Sea ‣ The Aral Sea has been greatly affected by water diversion projects for irrigation and this has caused lake water levels to drop. ‣ Some of the effects of the dropping sea level dropping 22 meters since 1961 include: " The sea’s salinity has tripled " 20 of the 24 native fish species have gone extinct.
Detecting Water Pollution ‣ The extent of water pollution can be determined in many ways: " The nutrient loading can be assessed by measuring the BOD
(the Biochemical (or Biological) Oxygen Demand). " Electronic probes and chemical tests can
identify the absolute levels of various inorganic pollutants (nitrates, phosphates, and heavy metals).
Indicator Species ‣ The presence (or absence) of indicator species can give a biological indication of the pollution status of the waterway. ‣ Different species have different tolerance levels to varying levels of pollution. Clean water communities are typically diverse, dominated by species with high oxygen requirements. ‣ Communities in polluted or turbid streams are much less diverse and are dominated by species that are tolerant of low oxygen levels and sluggish water flows.
Monitoring Water Quality
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oxygen levels and sluggish water flows. Monitoring Water Quality ‣ The quality of water in a stream, river, or lake is defined in terms of its various chemical, physical, and biological characteristics. " Some measures of water quality cannot be made in the field;
water samples must be transported to a laboratory for analysis.
" Telemetry stations transmit continuous measurements of the water level to a central control office.
Measuring Water Quality ‣ The following measurements are routinely made by agencies involved in water quality monitoring: " Dissolved oxygen and temperature (in the field) " Clarity (in the field or the laboratory) " Conductivity, pH, color, nutrients (nitrogen and phosphorus),
major ions (magnesium, calcium, sodium, potassium, chloride, bicarbonate, and sulfate), organic carbon, and fecal bacteria (coliforms).
USA Waterways ‣ In the USA, the Clean Water Act (CWA) legislation, administered by the EPA, is used in the protection and management of waterways. ‣ The CWA provides for the maintaining and restoring of the physical, chemical and biological integrity of waterways. ‣ The Great Lakes Water Quality Agreement between the US and Canada focuses on the water quality of the Great Lakes.
Environmental Effects Eutrophication ‣ Eutrophication is a term describing the enrichment of waters with nutrients especially phosphorous and nitrogen. It often results in excessive growth of weed and algae. (Nitrogen and phosphorous are often limiting factors for freshwater ecosystems. (Oligotrophic describes waters with high water clarity and low nutrients.) ‣ Microorganisms decompose the organic matter in the polluted water and their activity increases the uptake of dissolved oxygen.
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oxygen. " This reduces the amount of dissolved oxygen available to
other aquatic organisms and may subsequently cause their death.
Organic Pollutants ‣ Most organic water pollutants are synthetic chemicals created for human activities. These include pesticides, solvents, industrial chemicals, and plastics. " Some organic compounds enter water sources directly or
through seepage from landfills, through agrichemical runoff, or by leaching into groundwater.
Inorganic Pollutants ‣ Inorganic chemical pollutants include mercury, lead, road salt, and acid drainage. Most are toxic to aquatic organisms and their presence may make water unsuitable for drinking and other uses. " Inorganic chemicals enter water courses from industrial
plants, mines, irrigation runoff, oil drilling, and municipal storm drainage.
Sediment Pollution ‣ Sediment pollution comes from agricultural land, forest soils exposed by logging, overgrazed rangelands, strip mining, and construction. " Suspended sediments increase turbidity and reduce light
penetration. When they settle out, they smother aquatic organisms and reduce available habitat.
" Increased sediment loads may choke waterways and cause sediment buildup behind dams and in reservoirs. Downstream from artificial levees and embankments however, the sediment load will be increased.
Sewage Pollution ‣ Raw or partially treated sewage is a common water pollutant. " Sewage pollution results from the disposal of household and
industrial wastes into rivers, lakes, and seas. Most communities apply some treatment to raw sewage prior to discharge from point sources, but even treated sewage can be high in nutrients. " Sewage is a source of pathogens (disease-causing agents).
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" Sewage is a source of pathogens (disease-causing agents). During floods, human waste may mix with drinking water and increase the risk of water-borne diseases such as cholera.
Irrigation Types ‣ Irrigation is the artificial application of water to the soil. Generally irrigation is used to assist the growth of agricultural crops but can also be used for landscaping and revegetation. The most common types of irrigation include: " Gravity flow which comes from an aqueduct or nearby river
and uses gravity for application. " Center pivot uses underground pumps and mobile sprinklers
to provide water to plants. " Drip irrigation uses above or below ground pipes to deliver
water to individual plant roots. Desalinization ‣ Desalinization is the process of removing salt from salt water to provide accessible freshwater. ‣ The process of desalinization is one of high energy and results in leftover salt, an inorganic substance sometimes sold as table salt. ‣ The process is used heavily in Middle Eastern countries to provide freshwater.
Marine Water ‣ Oceans and seas have been fished for centuries, providing a vital food source and income for many people. ‣ Today oceans are used in many ways from fish farming to mineral production. Now, this once seemingly infinite resource is beginning to show signs of reaching its limits.
Marine Water Use ‣ Water from marine sources (seawater) is used mainly by the fishing industry. " Seawater is used preferentially during seafood processing
because its osmolarity is the same as the fish, keeping the fish fresh and stopping osmotic shock.
" Seawater is also used to clean fish processing factories, as it is readily available.
‣ Most of the world’s salt supplies come from evaporated seawater.
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seawater. ‣ The use of seawater is not feasible in most industries because it causes rapid corrosion.
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