John Burroughs School Biotic and Abiotic Stream Factors Manual · Diatoms are a major group of algae and are one of the most common phytoplankton. Diatoms are unicellular but can

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JBS: Biotic and Abiotic Stream Factors Manual Page 1 of 42

John Burroughs School

Biotic and Abiotic

Stream Factors Manual

Compiled by Margaret Bahe

Updated by Scott Deken

[NOTE: Most information used with permission from: Johnson, Robyn L., Scott Holman, Dan. D. Holmquist Water Quality with CBL, Portland

Oregon: Vernier Software, 1999.]

2009

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Table of Contents Algae & Phytoplankton ……............................................................................... 3 Alkalinity............................................................................................................... 5 Ammonium Nitrogen .......................................................................................... 7 Biological Oxygen Demand (B.O.D.)..................................................................... 9 Carbon dioxide......................................................................................................... 11 Coliform Bacteria Total and Fecal)........................................................................ 13 Dissolved Oxygen.................................................................................................... 15 Nomogram for Dissolved Oxygen Saturation …………………………………… 18 Hardness................................................................................................................. 19 Nitrate Nitrogen..........................................................................…….................... 21 pH.......................................................................................................................... 23 Phosphates.............................................................................................................. 25 Stream Flow ............................................................................................................ 27 Temperature............................................................................................................ 29 Total Dissolved Solids............................................................................................. 31 Total Solids............................................................................................................. 33 Turbidity and Color................................................................................................. 35 Bibliography........................................................................................................... 37 Water Quality Data Chart and Calculation Sheet................................................. 39 Taxonomy of Kingdom Animalia ……………………………………………………… 41 Appendix: Q-Value Graphs

Chart 1 – Water Temperature ………………………………………. A-1 Chart 2 – pH ………………………………………………………….. A-1 Chart 3 – Turbidity …………………………………………………… A-2 Chart 4 – Total Solids ……………………………………………….. A-2 Chart 5 – Dissolved Oxygen -- Percent Saturation ………………. A-3 Chart 6 – 5-Day BOD ……………………………………………….. A-3 Chart 7 – Total Phosphate ………………………………………… A-4 Chart 8 – Nitrates …………………………………………………… A-4 Chart 9 – Fecal Coliform …………………………………………... A-5 Table: Coliform MPN Index ………………………………………… A-6 Nomogram for Dissolved Oxygen Saturation ………………………. A-7 Quick Reference Guide to Common Parameters Tested …………… A-8

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Algae & Phytoplankton (The Producers)

Light has a significant impact on freshwater biomes: lakes and ponds (standing water), rivers and streams (running water), and a variety of wetlands. Because the producers make their own food they are limited to the depths of the freshwater biomes that allows light penetration (the photic zone). Plankton get their name from the Greek word planktos, meaning “to drift”. Plankton are defined based on their ecological niche rather than their genetic classification. Plankton fall into two groups: phytoplankton and zooplankton. Phytoplankton are those aquatic microorganisms capable of photosynthesis like plants and zooplankton are those aquatic microorganisms that receive their energy by feeding on others like animals. All phytoplankton are producers and include microscopic algae and cyanobacteria. Phytoplankton and multicellular algae produce food by photosynthesis and form the base of food chains in most aquatic ecosystems, like rivers, lakes, and oceans. Algae (another name that is not very useful for genetic classification) are modernly defined as eukaryotic, photosynthetic protists. Many of the phytoplankton described above can also be described as algae. Cyanobacteria is a an example of a phytoplankton that once belonged to the group algae but the more modern definitions of algae eliminate it as an algae since it is a prokaryote. Typical algae found in freshwater streams include euglena (some of which turn heterotrophic at night), filamentous spirogyra (dark green in color and move gently with the currents in the river), and abundant diatoms (unicellular with a glassy cell wall containing silica). Diatoms are a major group of algae and are one of the most common phytoplankton. Diatoms are unicellular but can live in colonies producing colonial filaments, fans, or ribbons. The organic molecules produced by diatoms are a key food source in all aquatic ecosystems and produce much of the earth’s oxygen. Diatoms are found near the surface of water in the sunlight. They accomplish their buoyancy by storing their food reserves as an oil which allows them to float in water. Some diatoms, however, live attached to plants, logs, rocks and bottom sediment. They often form a thick brown layer on the rocks in the bottom of a river or stream. Next to bacteria, there are probably more diatoms on earth than any other type of organism. They are particularly abundant in oligotrophic (clean) water. Cyanobacteria are the only prokaryotes capable of plant-like, oxygen generating photosynthesis. They are the base of many food chains in ponds and lakes and some can fix nitrogen, turning unusable atmospheric nitrogen into a form that other aquatic producers can use for their proteins and nucleic acids. Many cyanobacteria grow well in enriched (often polluted) eutrophic water. Such cyanobacteria often undergo a rapid increase in numbers, resulting in an algal bloom.

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Alkalinity INTRODUCTION The alkalinity of water is a measure of how much acid it can neutralize. If any changes are made to the water that could raise or lower the pH value, alkalinity acts as a buffer, protecting the water and its life forms from sudden shifts in pH. This ability to neutralize acid, or H+ ions, is particularly important in regions affected by acid rain.

In the diagram below, for example, the lake on the right has low alkalinity. When acid rain falls, it is not neutralized, so the pH of the water decreases. This drop in the pH level can harm or even kill some of the aquatic organisms in the lake. The lake on the left, however, has high alkalinity. When acid rain falls in this lake, the acid is partially neutralized and the pH of the water remains fairly constant. In this way, a high alkalinity level helps maintain the health of the water and the organisms that live there.

Alkalinity should not be confused with pH. The pH of a solution is a measure of the concentration of acid, or H+ ions, in the water. Alkalinity is a measure of the water’s capacity to neutralize an acid, or H+ ions, thereby keeping the pH at a fairly constant level.

Effects of Alkalinity Levels

• Buffers water against sudden changes in pH

• Protects aquatic organisms from sudden changes in pH

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The alkalinity of surface water is primarily due to the presence of hydroxide, OH–, carbonate, CO3

2–, and bicarbonate, HCO3–, ions. These ions react with H+ ions by means of the following

chemical reactions: OH– + H+ ! " ! H2O

CO32– + H+ ! " ! HCO3

–

HCO3– + H+ ! " ! CO2 + H2O

Most alkalinity in surface water comes from calcium carbonate, CaCO3, being leached from rocks and soil. This process is enhanced if the rocks and soil have been broken up for any reason, such as mining or urban development. Limestone contains especially high levels of calcium carbonate.

Alkalinity is significant in the treatment of wastewater and drinking water, because it will influence treatment processes such as anaerobic digestion. Water may also be unsuitable for use in irrigation if the alkalinity level in the water is higher than the natural level of alkalinity in the soil.

Expected Levels Alkalinity is reported in units of mg/L CaCO3, because the carbonate ion, CO3

2–, is its primary constituent. Alkalinity levels will vary across the country. Some sample data are shown in Table 1. In general, water in the eastern half of the United States will have a higher alkalinity than water in the west because of a higher occurrence of limestone. Areas in the extreme northeast that have had the limestone scoured away by glacial action will often have a lower alkalinity. If the pH is between 7 and 8 and the total alkalinity is at least 100-120 mg/liter, fish would most likely be protected from any sudden changes in the pH. In this case, the alkalinity is high enough to “absorb” pH change.

Sources of Alkalinity

• Leached from rock - limestone

• Leached from minerals - dolomite - calcite

• Leached from soil

Table 1: Alkalinity of Selected Rivers

Site Alkalinity (mg/L CaCO3)

Missouri River, St. Joseph, MO 224

Missouri River, Garrison Dam, ND 178

Cataloochee Creek, Cataloochee, NC 626

Columbia River, Northport, WA 49

Merrimack River, Lowell, MA 7

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Ammonium Nitrogen INTRODUCTION The ammonium ion, NH4

+, is an important member of the group of nitrogen-containing compounds that act as nutrients for aquatic plants and algae. In surface water, most of the ammonia, NH3, is found in the form of the ammonium ion, NH4

+. This fact allows us to approximate the concentration of all of the nitrogen in the form of ammonia and ammonium combined, commonly called ammonia nitrogen, by measuring only the concentration of the ammonium ions.

All plants and animals require nitrogen as a nutrient to synthesize amino acids and proteins. Most nitrogen on earth is found in the atmosphere in the form of N2, but plants and animals cannot utilize it in this form. The nitrogen must first be converted into a useable form, such as nitrate, NO3

–. These conversions among the various forms of nitrogen form a complex cycle called the nitrogen cycle, illustrated to the right.

In the nitrogen cycle, bacteria convert atmospheric nitrogen into ammonium in a process called nitrogen fixation. This process often occurs in the roots of leguminous plants such as alfalfa, beans, and peas.

Bacteria can also convert the nitrogen in decaying plant and animal matter and waste products in the soil or water to ammonium in a process called ammonification. Other sources of organic matter for ammonification include industrial waste, agricultural runoff, and sewage treatment effluent.

Some trees and grasses are able to absorb ammonium ions directly, but most require their conversion to nitrate. This process, called nitrification, is usually accomplished by bacteria in the soil or water. In the first step of nitrification, ammonium ions are oxidized into nitrite. The nitrite is then converted into nitrate, which can subsequently be utilized by plants and algae.

Sources of Ammonia

• Decaying plants and animals

• Animal waste

• Industrial waste effluent

• Agricultural runoff

• Atmospheric nitrogen

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Animals require nitrogen as well. They obtain the nitrogen they need by eating plants or by eating other animals, which in turn have eaten plants.

If ammonium nitrogen levels in surface waters are too high, they can be toxic to some aquatic organisms. If the levels are only moderately high, plant and algal growth will usually increase due to the abundance of nitrogen available as a nutrient. This will have a ripple effect on other attributes of water quality, such as increasing biochemical oxygen demand and lowering dissolved oxygen levels. Dissolved oxygen levels can also be lowered when ammonium nitrogen is high due to the increased amount of nitrification occurring.

If enough nutrients are present, eutrophication may occur. Eutrophication occurs when there is such an abundance of nutrients available that there is a significant increase in plant and algal growth. As these organisms die, they will accumulate on the bottom and decompose, releasing more nutrients and compounding the problem. In some cases, this process of eutrophication can become so advanced that the body of water may become a marsh, and eventually fill in completely.

If too little ammonium nitrogen is present, it may be the limiting factor in the amount of plant and algal growth. Ammonium nitrogen can quickly be converted into nitrites or nitrates; therefore, a low level of ammonium-nitrogen does not necessarily indicate a low level of nitrogen in general.

Expected Levels Ammonium-nitrogen levels are usually quite low in moving surface waters. This is because there is little decaying organic matter collecting on the bottom. If there is a high level of ammonium nitrogen in a moving stream, it may be an indication of pollution of some kind entering the water. Ponds and swamps usually have a higher ammonium nitrogen level than fast-flowing water. While levels of ammonium nitrogen in drinking water should not exceed 0.5 mg/L, streams or ponds near heavily fertilized fields may have higher concentrations of this ion. Fertilizers containing ammonium sulfate, (NH4)2SO4, or ammonium nitrate, NH4NO3, may result in runoff from fields containing a high level of ammonium ions.

Effects of Ammonium Levels

• High levels - eutrophication - increased algal blooms - increased BOD - decreased DO - toxic to some organisms

• Low levels - limiting factor in plant and

algal growth

Table 1: Ammonium Levels of Selected Rivers Site Ammonium

(mg/L NH4+-N)

Mississippi River, Memphis, TN 0.07

Hudson River, Poughkeepsie, NY 0.08

Colorado River, Hoover Dam, AZ-NV 0.03

Willamette River, Portland, OR 0.09

Platte River, Louisville, NE 0.24

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Biochemical Oxygen Demand INTRODUCTION Oxygen available to aquatic organisms is found in the form of dissolved oxygen. Oxygen gas is dissolved in a stream through aeration, diffusion from the atmosphere, and photosynthesis of aquatic plants and algae. Plants and animals in the stream consume oxygen in order to produce energy through respiration. In a healthy stream, oxygen is replenished faster than it is used by aquatic organisms. In some streams, aerobic bacteria decompose such a large volume of organic material that oxygen is depleted from the stream faster than it can be replaced. The resulting decrease in dissolved oxygen is known as the Biochemical Oxygen Demand (BOD).

When organisms die or when organic material is washed into streams and rivers bacteria and other microorganisms decompose it. In a healthy body of water, this process has only a slight impact on dissolved oxygen levels. It serves to release vital nutrients, such as nitrates and phosphates, which stimulate algae and aquatic plant growth. If the amount of decomposing organic material is too high, dissolved oxygen levels can be severely reduced. In a body of water with large amounts of decaying organic material the dissolved oxygen levels may drop by 90%—this would represent a high BOD. In a mountain stream with low levels of decaying organic material, the dissolved oxygen levels may drop by only 10% or 20%—a low BOD. Organic materials, such as leaves, fallen trees, fish carcasses, and animal waste, end up in the water naturally and are important in the recycling of nutrients throughout the ecosystem. Organic materials that enter the water as a result of human impact can be considered sources of pollution.

Aerobic decompose organisms, largely microorganisms like bacteria, are constantly at work in water breaking down organic compounds into carbon dioxide and water. Other bacteria convert ammonia and nitrites into nitrates. These processes, all of which require oxygen, are natural components of biogeochemical cycles and are essential to the functioning of an aquatic ecosystem. If a stream contains little organic matter, the aerobic bacteria can break the matter down without upsetting the oxygen balance in the water. Oxygen is replaced by natural means as fast as the aerobic decomposers use it up. If, however, massive quantities of organic matter are present in the water, the population of aerobic decomposer bacteria multiplies due to the additional food. This is usually

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followed by a serious oxygen depletion as the bacteria consume the organic matter. In nature this condition is frequently encountered in marshes, swamps and at the bottom of stagnant ponds and lakes. In these locations the concentration of organic matter is quite high due, in large part, to the presence of dead plants. The action of aerobic bacteria on this rich source of food often reduces the D.O. level to zero. When this happens, anaerobic decompose organisms take over as the main decomposers and putrefaction sets in. Where as aerobic bacteria produce odorless water and carbon dioxide, anaerobic bacteria produce gases like methane and hydrogen sulfide -- hence the stench.

When aquatic plants dies, aerobic bacteria feed them upon. Increased input of nutrients into a stream, such as nitrates and phosphates, stimulates plant growth. Eventually, more plant growth leads to more plant decay. Nutrients, then, can be a prime contributor to high B.O.D. in streams. Point sources of organic matter that increase B.O.D. include: pulp and paper mills, meat-packing plants, food processing industries and wastewater treatment plants. Non-point sources of organic matter are difficult to identify but include: urban runoff and melting snow that carries illegal sewer connections into storm drains, pet wastes from streets and sidewalks, nutrients from lawn fertilizers, grass clippings and golf courses; agricultural runoff that carries nutrients from fields; and runoff from animal feedlots that carries fecal material into rivers. In streams with high B.O.D. levels, much of the available dissolved oxygen is consumed by aerobic bacteria, robbing other aquatic organisms of oxygen they need to live. Organisms that are more tolerant of lower dissolved oxygen may appear and become numerous, such as carp, midge larvae and sewage worms. Organisms that are intolerant of low oxygen levels, such as caddisfly larvae, mayfly nymphs and stonefly nymphs, will not survive. As organic pollution increases, the ecologically stable and complex relationships present in waters containing a high diversity of organisms is replaced by a low diversity of pollution-tolerant organisms.

Expected Levels BOD levels are dependent on the body of water being tested. Shallow, slow-moving waters, such as ponds and wetlands, will often have large amounts of organic material in the water and high BOD levels. A water sample from a pond could have an initial dissolved oxygen reading of 9.5 mg/L. After the five-day incubation period, the dissolved oxygen could be down to 1 mg/L resulting in a high BOD level of 8.5 mg/L. In contrast, a water sample collected from a cold mountain stream with an initial dissolved oxygen reading of 11 mg/L may have decreased to 9 mg/L after incubation, resulting in a BOD of only 2 mg/L. Use Table 1 as a rough guide for the data you gather1.

1 Table 1 is from the Student Watershed Research Project manual, 3rd Edition 1996.

Table 1: Interpretation of BOD Levels

BOD Level (mg/L)

Status

1 – 2 mg/L Clean water with little organic waster. 3 – 5 mg/L Moderately clean water with some organic

waste. 6 – 9 mg/L Lots of organic material and many bacteria. >10 mg/L Very poor water quality. Large amounts of

organic material in the water.

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Carbon Dioxide

Carbon dioxide, like oxygen, continually enters rivers and lakes from the air. However, air is only about 0.034% carbon dioxide by volume. Therefore, when air is the only source of carbon dioxide, very little carbon dioxide ends up in the water. Carbon dioxide, oxygen and other gases, are continually exchanged between the atmosphere and the stream water that is in contact with it. If the stream were calm, one would expect this exchange to occur only through the process of diffusion. This process is extremely slow under most conditions. Wave action at the surface helps the exchange of gases at the surface. Carbon dioxide also enters natural waters in rain water. As raindrops fall, they absorb carbon dioxide from the air. Normally the quantity absorbed does not exceed 0.6 mg/L. Once the carbon dioxide is dissolved in water, most of it does not remain in the form of molecules of carbon dioxide. Instead, it reacts with the water to form a weak acid called carbonic acid:

CO2 + H2O -> H2CO3

The carbonic acid, in turn, partially dissociates (separates) into hydrogen ions and bicarbonate ions:

H2CO3 -> H+ + HCO3-

The hydrogen ions from this last reaction are responsible for the acidic properties of a carbon dioxide solution. When rainwater falls on land rather than directly into water, it moves down through the sail, coming in contact with still more carbon dioxide, largely in the air spaces between soil particles. Finally, the rain water, now a fairly saturated concentrated solution of carbonic acid, comes in contact with calcium-bearing rocks like limestone. A reaction occurs which forms calcium bicarbonate:

CaCO3 + H2CO3 -> Ca(HCO3)2

Unless excess carbon dioxide is present, this calcium bicarbonate decomposes readily:

Ca(HCO3)2 -> CaCO3 + H2O + CO2

The calcium carbonate formed in this reaction precipitates out as limestone. If excess carbon dioxide is present, the calcium bicarbonate remains stable and eventually ends up in a stream as a result of runoff.

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The dissolved oxygen concentration in a stream is, in many ways, dependent upon the concentration of carbon dioxide in the water. Therefore, it is important to consider the factors that affect the concentration of carbon dioxide gas in water when air is in contact with water. The graph to the right illustrates the solubility of carbon dioxide in water at various temperatures. In summary much of the carbon dioxide that enters natural waters end up as carbonate or bicarbonate of calcium. If the soil contains magnesium-bearing rocks like dolomite, some of the carbon dioxide will end up as a carbonate or bicarbonate of magnesium. Most natural waters contain all of these compounds. Neither type of bicarbonate can exist for long, however, without free carbon dioxide in the water. Other factors that affect the carbon dioxide content of natural waters are photosynthesis and respiration. Photosynthesis consumes carbon dioxide. Surface water would have more photosynthesis than deeper water. Respiration by living organisms, plants and animals, releases carbon dioxide. During daylight, while photosynthesis is occurring, the carbon dioxide will be used up; it will tend to accumulate at night. Aerobic decomposition of organic residues at the bottoms of stream will consume oxygen and release carbon dioxide.

Expected Levels As a result of respiration, surface water usually contains up to 10 mg/L of free carbon dioxide. Water near bottom “ooze” has even more due to decomposers feeding on organic matter in the bottom ooze. Water that contains over 25 mg/L of free carbon dioxide can be harmful to many gill-breathers. It interferes with breathing. Concentrations of 50 mg/L or more will kill many species.

www.thepondprofessor.com

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Coliform Bacteria, Total and Fecal INTRODUCTION The concentration of fecal coliform bacteria in water is measured to determine the likelihood of contamination by microbiological organisms. While fecal coliform are not pathogenic (disease causing), they are commonly found alongside pathogenic organisms such as those responsible for dysentery, gastroenteritis, and hepatitis A. It is easier to test for fecal coliform than for pathogenic organisms; therefore, the presence of fecal coliform in a water sample is used to indicate potential contamination. A common source of coliforms and pathogenic bacteria is raw sewage. The fecal coliforms have a mutualistic relationship with their host animal. They are provided with a suitable environment in the large intestine and as they breakdown the waste products of digestion and they manufacture vitamin K for their human host.

The results of coliform bacteria tests are generally used to monitor recreational areas, stormwater outflows, and drinking water supplies. Water is commonly tested for three types of coliform bacteria: total coliforms, fecal coliforms, and E. coli. As shown in the figure to the right, total coliforms includes fecal coliforms and E. coli, while fecal coliforms includes E. coli. E. coli bacteria are a group of bacteria found in the intestines of animals and humans. The presence of E. coli is the best evidence of fecal contamination. The standards for drinking water are generally based on total coliforms. The accepted standard for drinking water is that there should be no coliforms present after the water is filtered or treated. Natural waters will nearly always contain some form of bacteria. That is why you should never drink untreated water from a river or lake. Currently, the most common measurement for surface waters is fecal coliform.

Total coliforms include fecal coliforms and non-fecal species frequently found in soil and in plants. The coliforms are grouped together because of their similar biochemical reactions. Of greatest concern to environmental scientists are those bacteria that inhabit human sewage. Human excreta in the effluents from sewage treatment plants are the greatest source of pathogenic bacteria in our water. Fecal coliform bacteria are derived from the feces of humans and other warm-blooded animals. These bacteria can enter streams through direct discharge from mammals and birds; from agricultural and storm runoff carrying mammal and bird wastes; and from sewage discharged into the water. Pathogenic organisms include bacteria, viruses and parasites that cause diseases and illnesses. One might assume that pathogenic bacteria can be detected easily by analyzing water samples. This, however, is not the case. Pathogens are relatively scarce in water, which makes them tedious and time-consuming to monitor directly. Instead, fecal coliform levels are monitored, because of their greater abundance in waters and direct association with possible pathogenic organisms.

Sources of Raw Sewage

• Urban stormwater runoff containing domestic animal waste

• Agricultural sources such as dairies and cattle

• Sewage treatment overflow

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Each day billions of coliform bacteria leave the body of each human in feces. About 80-95% of these are E.coli. Since the feces of a diseased person could contain pathogens, the presence of E. coli indicates the possible presence of pathogens. Coliforms live much longer outside the body than do most pathogens. This fact increases their usefulness as indicators of infected water. If coliforms are not detectable in the water, it is likely free of pathogens, and therefore, fit to drink.

EXPECTED LEVELS Standards for fecal coliform differ from state to state. For specific requirements, it is best to contact your state or regional health department. Standards for fecal coliform are considerably stricter if the water is used for total body contact such as swimming, rather than used only for boating with minimal direct contact. Fecal coliform bacteria by themselves are NOT pathogenic; that is, they do not cause illness or disease. These bacteria naturally occur in the human digestive tract. In infected individuals, fecal coliform bacteria occur along with the pathogenic organisms. If fecal coliform counts are high (over 200 colonies/100 ml water sample) in the stream, there is a greater probability that pathogenic organisms are present. A person swimming in such water might swallow some pathogenic organisms or these organisms might enter the body through the nose and ears or through a cut in the skin. Diseases and illnesses such as typhoid fever, hepatitis, gastroenteritis, dysentery, and ear infections can be contracted in waters with high fecal coliform counts.

When interpreting data from fecal coliform tests, it is important to remember that there can be a high degree of randomness of distribution within a sample. A large number of data points are necessary to obtain statistically significant data. Fecal coliform is measured in colony forming units per 100 mL, CFU/100 mL, of water tested. [CFU/100 ml is equivalent to # of bacterial colonies per 100 mL of water tested.]

Table 12

Water use Desired level (CFU/100mL)

Permissible level (CFU/100mL)

drinking <1 <1

swimming <200 <1,000

boating or fishing <1,000 <5,000

2 CFU values in this chart were obtained from the LaMotte Company’s “The Monitor Handbook.” These values are

meant to be used as guidelines. Consult your local or state health department or your regional USEPA or USGS office for specific values for your region.

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Dissolved Oxygen INTRODUCTION Oxygen gas dissolved in water is vital to the existence of most aquatic organisms. Oxygen is a key component in cellular respiration for both aquatic and terrestrial life. The concentration of dissolved oxygen, DO, in an aquatic environment is an important indicator of the environment’s water quality.

Oxygen gas is dissolved in water by a variety of processes—diffusion between the atmosphere and water at its surface, aeration as water flows over rocks and other debris, churning of water by waves and wind, and photosynthesis of aquatic plants and algae. There are many factors that affect the concentration of dissolved oxygen in an aquatic environment. These factors include: temperature, stream flow, air pressure, aquatic plants, decaying organic matter, and human activities.

As a result of plant activity, DO levels may fluctuate during the day, rising throughout the morning and reaching a peak in the afternoon. At night photosynthesis ceases, but plants and animals continue to respire, causing a decrease in DO levels. Because large daily fluctuations are possible, DO tests should be performed at the same time each day. Large fluctuations in dissolved oxygen levels over a short period of time may be the result of an algal bloom. While the algae population is growing at a fast rate, dissolved oxygen levels increase. Soon the algae begin to die and are decomposed by aerobic bacteria, which use up the oxygen. As a greater number of algae die, the oxygen requirement of the aerobic decomposers increases, resulting in a sharp drop in dissolved oxygen levels. Following an algal bloom, oxygen levels can be so low that fish and other aquatic organisms suffocate and die.

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Temperature is important to the ability of oxygen to dissolve, because oxygen, like all gases, has different solubilities at different temperatures. Cooler waters have a greater capacity for dissolved oxygen than warmer waters. Human activities, such as the removal of foliage along a stream or the release of warm water used in industrial processes, can cause an increase in water temperature along a given stretch of the stream. This results in a lower dissolved oxygen capacity for the stream. See the graph to the right.

Factors that affect DO levels • Temperature • Aquatic plant populations

• Decaying organic material in water

• Stream flow

• Altitude/atmospheric pressure

• Human activities

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Expected Levels The unit mg/L3 is the quantity of oxygen gas dissolved in one liter of water. When relating DO measurements to minimum levels required by aquatic organisms, mg/L is used. The procedure described in this chapter covers the use of a Dissolved Oxygen Probe to measure the concentration of DO in mg/L. Dissolved oxygen concentrations can range from 0 to 15 mg/L. Cold mountain streams will likely have DO readings from 7 to 15 mg/L, depending on the water temperature and air pressure. In their lower reaches, rivers and streams can have DO readings between 2 and 11 mg/L.

Some organisms, such as salmon, mayflies, and trout, require high concentrations of dissolved oxygen. Other organisms, such as catfish, mosquito larvae, and carp, can survive in environments with lower concentrations of dissolved oxygen. The diversity of organisms is greatest at higher DO concentrations. Table 1 lists the minimum dissolved oxygen concentrations necessary to sustain selected animals.

When discussing water quality of a stream or river, it can be helpful to use a different unit than mg/L. The term percent saturation is often used for water quality comparisons. Percent saturation is the dissolved oxygen reading in mg/L divided by the 100% dissolved oxygen value for water (at the same temperature and air pressure). The manner in which percent saturation relates to water quality is displayed in Table 2. In some cases, water can exceed 100% saturation and become supersaturated for short periods of time.

3 The unit of mg/L is numerically equal to parts per million, or ppm. 4 Supersaturation can be harmful to aquatic organisms. It can result in a disease known as Gas Bubble Disease.

Table 1: Minimum DO Requirements

Organism Minimum

dissolved oxygen (mg/L)

Trout 6.5

Smallmouth bass 6.5

Caddisfly larvae 4.0

Mayfly larvae 4.0

Catfish 2.5

Carp 2.0

Mosquito larvae 1.0

Table 2

DO Level Percent Saturation of DO

Supersaturation4 ≥ 100% for an extended amount of time

Excellent 90 – >100%

Adequate 80 – 89%

Acceptable 60 – 79%

Poor < 60%

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Hardness, Total INTRODUCTION When water passes through or over deposits such as limestone, the levels of Ca2+, Mg2+, and HCO3

– ions present in the water can greatly increase and cause the water to be classified as hard water. This term results from the fact that calcium and magnesium ions in water combine with soap molecules, making it “hard” to get suds. In Test 13, Calcium and Water Hardness, an Ion-Selective Electrode was used to determine calcium hardness, in mg/L as CaCO3. In this test, total hardness will be determined. Total hardness is defined as the sum of calcium and magnesium hardness5, in mg/L as CaCO3. In addition to total

hardness, the test described here will allow you to determine the concentration of Mg2+, in mg/L.

High levels of hard-water ions such as Ca2+ and Mg2+ can cause scaly deposits in plumbing, appliances, and boilers. These two ions also combine chemically with soap molecules, resulting in decreased cleansing action. In fact the term “hard” results from the fact that calcium and magnesium ions in water combine with soap molecules, forming a sticky scum that interferes with soap action and makes it “hard” to get suds. The American Water Works Association indicates that ideal quality water should not

contain more than 80 mg/L of total hardness as CaCO3. High levels of total hardness are not considered a health concern. On the contrary, calcium is an important component of cell walls of aquatic plants, and of the bones or shells of aquatic organisms. Magnesium is an essential nutrient for plants, and is a component of chlorophyll.

Expected Levels Total hardness in freshwater is usually in the range of 15 to 375 mg/L as CaCO3. Calcium hardness in freshwater is in the range of 10 to 250 mg/L, often double that of magnesium hardness (5 to 125 mg/L). Typical seawater has calcium hardness of 1000 mg/L, magnesium hardness of 5630 mg/L, and total hardness of 6630 mg/L as CaCO3.

5Even though Fe2+, Fe3+, Sr2+, Zn2+, and Mn2+ may contribute to water hardness, their levels are typically much less than Ca2+ and Mg2+. Their levels are not usually included in total hardness measurements.

Hard-Water Cations

• Calcium, Ca2+

• Magnesium, Mg2+

• Others: Fe3+, Sr2+, Zn2+, Mn2+

Total Hardness (mg/L as CaCO3)

• Soft: 0-30

• Moderately soft: 30-60

• Moderately hard: 60-120

• Hard: 120-180

• Very hard: > 180

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Table 1: Ca Hardness, Mg Hardness, and Total Hardness in Selected Sites

Site (fall season) Ca hardness (mg/L as CaCO3)

Mg hardness (mg/L as CaCO3)

Total hardness (mg/L as CaCO3)

Merrimack River, Lowell, NH 15.8 5.0 20.8

Mississippi River, Memphis, TN 120.0 58.3 178.3

Rio Grande River, El Paso, TX 210.0 87.5 297.5

Ohio River, Grand Chain, OH 60.0 26.3 86.3

Willamette River, Portland, OR 16.0 9.2 25.2

Missouri River, Garrison Dam, ND 132.5 83.3 215.8

Sacramento River, Keswick, CA 27.5 18.8 46.3

Hudson River, Poughkeepsie, NY 65.0 19.6 84.6

Platte River, Louisville, NE 180.0 70.8 250.8

Colorado River, Andrade, CA 190.0 104.2 294.2

Slightly Hard Water (1-3.5 g/gallon) Moderately Hard Water (3.5-7 g/gallon) Hard Water (7-10 g/gallon) Very Hard Water (>10 g/gallon)

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Nitrate INTRODUCTION The tests described here are used to measure the concentration of nitrate ions, NO3

–, in a water sample. The concentration of nitrate will be expressed throughout this section in units of mg/L NO3

–-N. The unit, NO3–-N, means simply “nitrogen that is in the form of nitrate.”

Nitrate ions found in freshwater samples result from a variety of natural and manmade sources. Nitrates are an important source of nitrogen necessary for plants and animals to synthesize amino acids and proteins. Most nitrogen on earth is found in the atmosphere in the form of nitrogen gas, N2. Through a process called the nitrogen cycle,6 nitrogen gas is changed into forms that are useable by plants and animals. These conversions include industrial production of fertilizers, as well as natural processes, such as legume-plant nitrogen fixation, plant and animal decomposition, and animal waste.

Legend: (1) Addition of food and nutrients, (2) Production of Urea and Ammonia by Fish, (3) Ammonia is converted to Nitrites by beneficial Nitrosomonas bacteria, (4) Nitrites are converted to Nitrates by beneficial Nitrospira bacteria. Less toxic Nitrates are removed by plants and periodic water changes. (5) Evaporation. (6) Light, (7) Oxygen Cycle, (8) O2 produced by plants, (9) CO2 produced by Fish

Sources of Nitrate Ions

• Agriculture runoff

• Urban runoff

• Animal feedlots and barnyards

• Municipal and industrial wastewater

• Automobile and industrial emissions

• Decomposition of plants and animals

NITROGEN CYCLE IN WATER

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Although nitrate levels in freshwater are usually less than 1 mg/L, manmade sources of nitrate may elevate levels above 3 mg/L. These sources include animal feedlots, runoff from fertilized fields, or treated municipal wastewater being returned to streams. Levels above 10 mg/L in drinking water can cause a potentially fatal disease in infants called methemoglobinemia, or Blue-Baby Syndrome. In this disease, nitrate converts hemoglobin into a form that can no longer transport oxygen.

High nitrate concentrations also contribute to a condition in lakes and ponds called eutrophication, the excessive growth of aquatic plants and algae. Unpleasant odor and taste of water, as well as reduced clarity, often accompany this process. Eventually, dead biomass accumulates in the bottom of the lake, where it decays and compounds the problem by recycling nutrients. If other necessary nutrients are present, algal blooms can occur in a lake with as little as 0.50 mg/L NO3

–-N.

Nitrate pollution of surface and groundwater has become a major ecological problem in some agricultural areas. Although fertilizer in runoff is most often blamed, there is evidence that concentration of livestock in feedlots is now the major source of agricultural nitrate pollution. Runoff from fertilized fields is still a significant source of nitrate, although fertilizer use peaked in 1981 and has remained fairly constant since.

Expected Levels The nitrate level in freshwater is usually found in the range of 0.1 to 4 mg/L NO3

–-N. Unpolluted waters generally have nitrate levels below 2 mg/L. The effluent of some sewage treatment plants may have levels in excess of 20 mg/L.

In a study based on 344 USGS sites throughout the United States,7 80% of the sites reported nitrate levels less than 1 mg/L, 16% were in the range of 1 – 3 mg/L, and 4% were greater than 3 mg/L. The percentage of various land types reporting greater than 1 mg/L of nitrate were range land <5%, forested land ~10%, urban areas ~30%, and agricultural land ~40%.

7 U.S. Geological Survey, National Water Summary 1990–91, Hydrologic Events and Stream Water Quality, Water-Supply Paper 2400, United States Government Printing Office, 1993, 122–123.

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pH INTRODUCTION Although not a pollutant, pH plays an important role in the quality of an aquatic ecosystem. What is pH? Water contains hydrogen ions, H+, and hydroxide ions, OH–. The relative concentrations of these two ions determine the pH value.8 Water with a pH of 7 has equal concentrations of these two ions and is considered to be a neutral solution. If a solution is acidic, the concentration of H+ ions exceeds that of the OH– ions. In a basic solution, the concentration of OH– ions exceeds that of the H+ ions. On a pH scale of 0 to 14, a value of 0 is the most acidic, and 14 the most basic. A change from pH 7 to pH 8 in a lake or stream represents a ten-fold increase in the OH– ion concentration.

Organisms that live in aquatic ecosystems are greatly affected by the water’s pH level. pHs of greater than 9.0 or less than 5.0 greatly diminishes the ability aquatic organisms have to complete their life cycle. Rainfall generally has a pH value between 5.6 and 6.5. It is acidic because of dissolved carbon dioxide in the air. Emissions from power plants and car exhausts containing pollutants, such as sulfur dioxide or nitrogen oxides, can react with moisture in the atmosphere to form sulfuric and nitric acids, more commonly known as acid rain. Acid rain has a pH less than 5.6, while normal rain is generally greater than 5.6. The underlying rock and soil type in a watershed determines the general pH in an aquatic system. If the rainwater flows over soil containing hard-water minerals, its pH usually increases. A water body in a drainage system that is largely limestone tends to be more basic. The slightly acid nature of rain causes limestone to weather more

8 The pH value is calculated as the negative log of the hydrogen ion concentration: pH = –log [H+].

Table 1: Effects of pH Levels on Aquatic Life

pH Effect

3.0 – 3.5 Unlikely that fish can survive for more than a few hours in this range, although some plants and invertebrates can be found at pH levels this low.

3.5 – 4.0 Known to be lethal to salmonids.

4.0 – 4.5 All fish, most frogs, insects absent.

4.5 – 5.0 Mayfly and many other insects absent. Most fish eggs will not hatch.

5.0 – 5.5 Bottom-dwelling bacteria (decomposers) begin to die. Leaf litter and detritus begin to accumulate, locking up essential nutrients and interrupting chemical cycling. Plankton begin to disappear. Snails and clams absent. Mats of fungi begin to replace bacteria in the substrate.

Metals (aluminum, lead) normally trapped in sediments are released into the acidified water in forms toxic to aquatic life.

6.0 – 6.5 Freshwater shrimp absent. Unlikely to be directly harmful to fish unless free carbon dioxide is high (in excess of 100 mg/L)

6.5 – 8.2 Optimal for most organisms.

8.2 – 9.0 Unlikely to be directly harmful to fish, but indirect effects occur at this level due to chemical changes in the water.

9.0 – 10.5 Likely to be harmful to salmonids and perch if present for long periods.

10.5 – 11.0 Rapidly lethal to salmonids. Prolonged exposure is lethal to carp, perch.

11.0 – 11.5 Rapidly lethal to all species of fish.

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rapidly than other harder rock types. The weathering of limestone releases bicarbonate ions, HCO3

–. The bicarbonate ions react with the water to produce OH– ions, according to the equation:

HCO3– + H2O → H2CO3 + OH–

As a result, streams and lakes are often basic, with pH values between 7 and 8, sometimes as high as 8.5.

The measure of the pH of a body of water is very important as an indication of water quality, because of the sensitivity of aquatic organisms to the pH of their environment. Small changes in pH can endanger many kinds of plants and animals; for example, trout and various kinds of nymphs can only survive in waters between pH 7 and pH 9. If the pH of the waters in which they live is outside of that range, they may not survive or reproduce. Changes in pH can also be caused by algal blooms (more basic), industrial processes resulting in a release of bases or acids (raising or lowering pH), or the oxidation of sulfide-containing sediments (more acidic).

To gain a full understanding of the relationship between pH and water quality, you need to make measurements of the pH and also determine the stream’s alkalinity (described elsewhere in this manual). Alkalinity is a measurement of the capacity or ability of the body of water to neutralize acids in the water. Acidic rainfall may have very little effect on the pH of a stream or lake if the region is rich in minerals that result in high alkalinity values. Higher concentrations of carbonate, bicarbonate, and hydroxide ions from limestone can provide a natural buffering capacity, capable of neutralizing many of the H+ ions from the acid. Other regions may have low concentrations of alkalinity ions to reduce the effects of acids in the rainfall. In the Northeastern United States and Eastern Canada, fish populations in some lakes have been significantly lowered due to the acidity of the water caused by acidic rainfall. If the water is very acidic, heavy metals may be released into the water and can accumulate on the gills of fish or cause deformities that reduce the likelihood of survival. In some cases, older fish will continue to live, but will be unable to reproduce because of the sensitivity of the reproductive portion of the growth cycle.

Type of Water Buffering Capacity pH

ACIDIC H+ > OH- LOW < 7.0

NEUTRAL H+ = OH- MEDIUM 7.0

BASIC H+ < OH- HIGH > 7.0

Expected Levels The pH value of streams and lakes is usually between pH 7 and 8. pH Levels between 6.5 and 9 are acceptable for most aquatic ecosystems. Areas with higher levels of water hardness (high concentrations of Mg2+, Ca2+, and HCO3

– ) often have water with higher pH values (between 7.5

and 8.5).

Factors that Affect pH Levels

• Acidic rainfall

• Algal blooms

• Level of hard-water minerals

• Releases from industrial processes

• Carbonic acid from respiration or decomposition

• Oxidation of sulfides in sediments

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Phosphates (ortho- and total)

INTRODUCTION Nutrients, primarily nitrogen and phosphorus, are essential for plant growth, though they can become pollutants in certain circumstances. The rate of plant growth is often controlled by a limiting nutrient, typically nitrogen or phosphorus, although it can be any of the essential minerals needed for growth. The limiting nutrient is the one available in quantities smaller than necessary for aquatic plants to reach maximum abundance. When a limiting nutrient is depleted, growth stops even if there is an adequate supply of other nutrients available.

Phosphorus is an essential nutrient for all aquatic plants and algae. Only a very small amount is needed, however, so an excess of phosphorus can easily occur. Water bodies with high levels of nutrients and therefore capable of supporting abundant algae and aquatic plant growth, are referred to as eutrophic. The prefix “eu” means good or sufficient and trophic refers to nutrient requirements. The addition of nutrients into surface waters from human activities is referred to as cultural eutrophication. Major sources of nutrients include fertilizers and manure from agricultural activities, urban runoff containing fertilizer from lawns and golf courses, and domestic and industrial wastewater effluent.

Excess phosphorus is usually considered to be a pollutant because it can lead to eutrophication, leading to increased plant and algal growth. During an algal bloom, the population grows beyond the capacity of the system. During blooms, dissolved oxygen levels during daylight hours can be very high but during the night, when oxygen production ceases and respiration begins, the dissolved oxygen level can drop to lethal levels. The low levels of dissolved oxygen in the water can render the water lethal to many aquatic organisms. Phosphorus is often the limiting factor that determines the level of eutrophication that occurs.

Most phosphorus in surface water is present in the form of phosphates. There are four classifications of phosphates often referred to in environmental literature: • orthophosphates are the inorganic forms of phosphate, such as PO4

3–, HPO42–, and H2PO4

–. These are the forms of phosphates used heavily in fertilizers and are often introduced to surface waters through runoff.

• organically bound phosphates are found in human and animal wastes or in decaying organic matter.

• condensed phosphates (also called polyphosphates), such as P3O105–, are sometimes added to

water supplies and industrial processes to prevent the formation of scaling and to inhibit corrosion. This is the form of phosphate that was commonly found in detergents in the past.

• total phosphates are the sum of all three of the forms described above. This is the most commonly reported form of phosphate concentration.

Sources of Phosphates

• Human and animal wastes

• Industrial wastes

• Agricultural runoff

• Human disturbance of land

Effects of Phosphate Levels

• High levels - eutrophication - increased algal blooms - increased BOD - decreased DO

• Low levels - limiting factor in plant

and algal growth

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Phosphates are added to surface waters by a variety of means. Humans add phosphates to water through industrial and agricultural wastes. Fertilizers contain high levels of phosphates and will enter the water by means of runoff and soil erosion. In areas where land and vegetation have been disturbed, soil erosion will increase. This will lead to even more phosphates being washed out of the soil and into the water. Phosphates can also come from the excrement of animals living in or near the water.

Expected Levels The concentration of phosphates will be expressed throughout this test in units of mg/L PO4-P, meaning phosphorus in the form of phosphates.9 Levels above 0.2 mg/L PO4-P can stimulate plant growth above its natural rate. Water that receives runoff from heavily fertilized areas may have higher levels of phosphates.

A study by the U.S. Geological Survey, based on 410 sites throughout the United States, reports that in 1982, approximately 55% of the sites reported phosphate levels of greater than 0.1 mg/L PO4-P. By 1989, this percentage had dropped to close to 40%. This decline is due in part to the reduction of phosphorus content in detergents and fertilizers.10

It is widely accepted that water suitable for wildlife, human use and recreation should have less than 0.2 mg/L of phosphates. High concentration levels of phosphates usually indicate the presence of fertilizers from runoff, industrial waste, animal waste, cleaning agents, domestic sewage, and excess laundry/soap detergents.

9Note that no charge is given to the PO4 when it is used in reporting phosphate units. Here it is being used as a generic symbol for many forms of phosphates with varying charges, such as PO43– and HPO42–.

10 U.S. Geological Survey, National Water Summary 1990–91, Hydrologic Events and Stream Water Quality, Water-Supply Paper 2400, United States Government Printing Office, 1993, 124–125.

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Stream Flow INTRODUCTION Stream flow or discharge is the volume of water that moves through a specific point in a stream during a given period of time. Discharge is usually measured in units of cubic feet per second (cfs). To determine discharge, a cross-sectional area of the stream or river is measured. Then, the velocity of the stream is measured using a Flow Rate Sensor. The discharge can then be calculated by multiplying the cross-sectional area by the flow velocity.

Stream flow is an important factor in the stream ecosystem and is responsible for many of the physical characteristics of a stream. Stream flow can also modify the chemical and biological aspects of a stream. Aquatic plants and animals depend upon stream flow to bring vital food and nutrients from upstream, or remove wastes downstream.

Stream flow has two components. The first is flow velocity, and the second is the volume of water in the stream.

Flow velocity is influenced by the slope of the surrounding terrain, the depth of the stream, the width of the stream, and the roughness of the substrate or stream bottom. If the surrounding terrain is steep, then rain water and snow melt will have less time to soak into the ground and runoff will be greater. In an area with level terrain, such as farm land, the rain water has plenty of time to soak into the ground and there is less runoff. The flow velocity will also vary as the width or depth of a stream changes. For instance, if you squeeze a water hose with your hand, the flow velocity of the water increases. This is because you have reduced the area that the water must flow through, while the volume of water passing through the hose remained constant. The same thing happens in a stream when the stream channel changes in its width or depth. The substrate of the stream bottom also affects the flow velocity since water moves faster over a smooth surface than a rough surface. Flow velocity is greater when the stream bottom is comprised of sand and clay and lower when it is cobble, rock, and boulders.

The volume of water in the stream is affected by the climate of the region. Areas with more rain and snow will have more water draining into surrounding streams and rivers. Seasonal changes affect stream volume as well. In the summer there will be less water in the stream compared to the winter. The numbers of tributaries that merge with a stream or river contribute more water to the system, increasing the stream volume. Humans are also responsible for altering the volume of water in streams. Water is removed for consumption, industry, and irrigation. Roads and parking lots cover vast areas, preventing rain-water from soaking into the ground. Instead, the water is forced to run off into surrounding streams and rivers. See the graph on the next page.

Factors Influencing Flow Velocity

• Depth of stream channel

• Width of stream channel

• Roughness of stream bottom

• Slope or incline of surrounding terrain

Factors Influencing Stream Volume

• Weather or climate

• Seasonal changes

• Merging tributaries

• Human impact

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Expected Levels Through careful monitoring, the typical discharge of many of our streams and rivers has been determined by using historical stream flow data. Much of this data is available from the USGS in printed form, or over the internet at the USGS website:

http://water.usgs.gov/realtime.html

Table 1: Stream Flow Statistics at Various Locations

Location Min (cfs) Mean (cfs) Max (cfs)

Mississippi River at Thebes, IL 85,500 310,000 725,000

Missouri River at Hermann, MO 28,500 107,000 382,000

Colorado River at Cisco, UT 2,800 18,000 46,900

Hood River at Hood River, OR 593 1,300 3,160

Time

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Temperature, Water INTRODUCTION The temperature of a body of water is a key feature for overall quality. Water temperatures outside the “normal” range for a stream or river can cause harm to the aquatic organisms that live there. It is for this reason that the change in the temperature of the water over a section of a stream is measured, not just the temperature at one location. If the water temperature changes by even a few degrees over a one-mile stretch of the stream, it could indicate a source of thermal pollution.

The water temperature of a stream is very important because many of the physical, biological and chemical characteristics of a river are directly affected by temperature. Temperature affects: 1. the amount of oxygen that can be dissolved in water; 2. the rate of photosynthesis by algae and larger aquatic plants; 3. the metabolic rates of aquatic organisms, and; 4. the sensitivity of organisms to toxic wastes, parasites and diseases. Remember, cool water can hold more oxygen than warm water because gases (like oxygen and carbon dioxide) are mare easily dissolved in cool water. The normal temperature of a stream varies, depending upon the sources and location of that stream. The average temperature of a Missouri stream is 57°F, although it can be cooler if the stream is spring fed. When stream temperatures become too high, several cold water species have difficulty surviving. See the table to the right.

Thermal pollution caused by human activities is one factor that can affect water temperature. Many industries use river water in their processes. The water is treated before it is returned to the river, but is warmer than it was before. Runoff entering a stream from parking lots and rooftops is often warmer than the stream and will increase its overall temperature.

Shade is very important to the health of a stream because of the warming influences of direct sunlight. Some human activities may remove shade trees from the area, which will allow more sunlight to reach the water, causing the water temperature to rise.

Factors that Affect Water Temperature

• Air temperature

• Amount of shade

• Soil erosion increasing turbidity

• Thermal pollution from human activities

• Confluence of streams

Table 1: Optimal Temperature Ranges

Organism Temperature Range (°C)

Trout 5 – 20

Smallmouth bass 5 – 28

Caddisfly larvae 10 – 25

Mayfly larvae 10 – 25

Stonefly larvae 10 – 25

Water boatmen 10 – 25

Carp 10 – 25

Mosquito 10 – 25

Catfish 20 – 25

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Another factor that may affect water temperature is the temperature of the air above the water. The extent of its influence has a great deal to do with the depth of the water. A shallow stream is more susceptible to changes in temperature than a deep river would be.

While many factors can contribute to the warming of surface water, few cause it to be cooled. One way water can be cooled is by cold air temperatures. Another natural method of cooling a river or lake comes from the introduction of colder water from a tributary or a spring.

One important aspect of water temperature is its effect on the solubility of gases, such as oxygen. More gas can be dissolved in cold water than in warm water. Animals, such as salmon, that require a high level of dissolved oxygen will only thrive in cold water.

Increased water temperature can also cause an increase in the photosynthetic rate of aquatic plants and algae. This can lead to increased plant growth and algal blooms, which can be harmful to the local ecosystem.

A change in water temperature can affect the general health of the aquatic organisms, thus changing the quality of the stream. Table 1 on the previous page lists the optimal temperature ranges of some selected aquatic organisms. When the water temperature becomes too hot or too cold, organisms become stressed, lowering their resistance to pollutants, diseases, and parasites.

Expected Levels Water temperatures can range from 0°C in the winter to above 30°C in the summer. Cooler water in a stream is generally considered healthier than warmer water, but there are no definitive standards. Problems generally occur when changes in water temperature are noted along one stream on the same day. Some sample data are listed in Table 2.

Table 2: Water Temperatures of Selected Rivers

Site Season Temperature (°C)

Season Temperature (°C)

Hudson River, Poughkeepsie, NY Winter 5 Summer 25

Missouri River, Garrison Dam, ND Winter 3 Summer 14

Rio Grande, El Paso, TX Winter 16 Summer 21

Mississippi River, Memphis, TN Winter 7 Summer 29

Willamette River, Portland, OR Winter 9 Summer 22

Effects of Water Temperature

• Solubility of dissolved oxygen

• Rate of plant growth

• Metabolic rate of organisms

• Resistance in organisms

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Total Dissolved Solids INTRODUCTION Solids are found in streams in two forms, suspended and dissolved. Suspended solids include silt, stirred-up bottom sediment, decaying plant matter, or sewage-treatment effluent. Suspended solids will not pass through a filter, whereas dissolved solids will. Dissolved solids in freshwater samples include soluble salts that yield ions such as sodium (Na+), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3

–), sulfate (SO42–

), or chloride (Cl– ). Evaporating a pre-filtered

sample to dryness, and then finding the mass of the dry residue per liter of sample can determine total dissolved solids, or TDS. A second method uses a Vernier Conductivity Probe to determine the ability of the dissolved salts and their resulting ions in an unfiltered sample to conduct an electrical current. The conductivity is then converted to TDS. Either of these methods yields a TDS value in units of mg/L.

The TDS concentration in a body of water is affected by many different factors. A high concentration of dissolved ions is not, by itself, an indication that a stream is polluted or unhealthy. It is normal for streams to dissolve and accumulate fairly high concentrations of ions from the minerals in the rocks and soils over which they flow. If these deposits contain salts (sodium chloride or potassium chloride) or limestone (calcium carbonate), then significant concentrations of Na+, K+, Cl– will result, as well as hard-water ions, such as Ca2+ and HCO3

– from limestone.

TDS is sometimes used as a “watchdog” environmental test. Any change in the ionic composition between testing sites in a stream can quickly be detected using a Conductivity Probe. TDS values will change when ions are introduced to water from salts, acids, bases, hard-water minerals, or soluble gases that ionize in solution. However, the tests described here will not tell you the specific ion responsible for the increase or decrease in TDS. They simply give a general indication of the level of dissolved solids in the stream or lake. Further tests described in this book can then help to determine the specific ion or ions that contributed to changes in the initial TDS reading.

There are many possible manmade sources of ions that may contribute to elevated TDS readings. Fertilizers from fields and lawns can add a variety of ions to a stream. Increases in TDS can also result from runoff from roads that have been salted in the winter. Organic matter from wastewater treatment plants may contribute higher levels of nitrate or phosphate ions. Treated wastewater may also have higher TDS readings than surrounding streams if urban drinking water has been highly chlorinated. Irrigation water that is returned to a stream will often have higher concentrations of sodium or chloride ions. Acidic rainwater, with dissolved gases like CO2, NO2, or SO2, often yields elevated H+ ion concentrations.

Sources of Total Dissolved Solids

• Hard-Water Ions - Ca2+ - Mg2+ - HCO3

– • Fertilizer in agricultural runoff

- NH4+

- NO3–

- PO43–

- SO42–

• Urban runoff - Na+ - Cl–

• Salinity from tidal mixing, minerals, or returned irrigation water

- Na+ - K+ - Cl–

• Acidic rainfall - H+ - NO3

– - SO3

2–, SO42–

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If TDS levels are high, especially due to dissolved salts, many forms of aquatic life are affected. The salts act to dehydrate the skin of animals. High concentrations of dissolved solids can add a laxative effect to water or cause the water to have an unpleasant mineral taste. It is also possible for dissolved ions to affect the pH of a body of water, which in turn may influence the health of aquatic species. If high TDS readings are due to hard-water ions, then soaps may be less effective, or significant boiler plating may occur in heating pipes.

Expected Levels TDS values in lakes and streams are typically found to be in the range of 50 to 250 mg/L. In areas of especially hard water or high salinity, TDS values may be as high as 500 mg/L. Drinking water will tend to be 25 to 500 mg/L TDS. United States Drinking Water Standards11 include a recommendation that TDS in drinking water should not exceed 500 mg/L TDS. Fresh distilled water, by comparison, will usually have a conductivity of 0.5 to 1.5 mg/L TDS.

Table 1: TDS in Selected Rivers

Site Season TDS (mg/L)

Season TDS (mg/L)

Rio Grande River, El Paso, TX Spring 510 Fall 610

Mississippi River, Memphis, TN Spring 133 Fall 220

Sacramento River, Keswick, CA Spring 71 Fall 60

Ohio River, Benwood, WV Spring 300 Fall 143

Hudson River, Poughkeepsie, NY Spring 90 Fall 119

11 Established by 1986 Amendments to the Safe Drinking Water Act

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Total Solids INTRODUCTION Total solids, TS, is a measure of all the suspended, colloidal, and dissolved solids in a sample of water. This includes dissolved salts such as sodium chloride, NaCl, and solid particles such as silt and plankton. An excess of total solids in rivers and streams is a very common problem. The Environmental Protection Agency’s National Water Quality Inventory12 has concluded that siltation, one of the primary contributors to total solids, is the most common pollutant of streams and rivers they sampled.

Many factors can contribute to the total solids in water. Soil erosion is a large contributor. An increase in water flow or a decrease in stream-bank vegetation can speed up the process of soil erosion and contribute to the levels of suspended particles such as clay and silt. Naturally occurring rocks or minerals in the soil such as halite, NaCl, or limestone, CaCO3, may also dissolve into the water, adding to the total solids.

Total solids can also come from various types of runoff. Agricultural runoff often contains fertilizers and suspended soil particles. Other sources include industrial wastes, effluent from water treatment plants, and urban runoff from parking lots, roads, and rooftops.

Bottom-dwelling aquatic organisms, such as catfish, can contribute to the total solids in the water by stirring up the sediment that has built up on the bottom of the stream. Organic matter such as plankton or decaying plant and animal matter that are suspended in the water will also add to the total solids in a stream.

Dissolved solids often make a significant contribution to the amount of total solids in water. In fact, the mass of the dissolved solids is sometimes higher than the mass of the suspended particles. Dissolved solids in freshwater samples include soluble salts that yield ions such as calcium, chloride, bicarbonate, nitrates, phosphates, and iron.

If the levels of total solids are too high or too low, it can impact the health of the stream and the organisms that live there. High levels of total solids will reduce the clarity of the water. This decreases the amount of sunlight able to penetrate the water, thereby decreasing the photosynthetic rate. Reduced clarity also makes the water less aesthetically pleasing. While this may not be harmful directly, it is certainly undesirable for many water uses. When the water is cloudy, sunlight will warm it more efficiently. This occurs because the suspended particles in the water absorb the sunlight, which, in turn, warm the surrounding water. This leads to other problems associated with increased temperature levels.

12 From the EPA’s Office of Water web site at www.epa.gov/OW/resources.

Sources of Total Solids

• Soil erosion - silt - clay - dissolved minerals

• Agricultural runoff - fertilizers - pesticides - soil erosion

• Urban runoff - road grime - rooftops - parking lots

• Industrial waste - dissolved salts - sewage treatment effluent - particulates

• Organics - microorganisms - decaying plants and animals

- gasoline or oil from roads • Abundant bottom-dwellers

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As previously mentioned, dissolved solids often make a large contribution to total solids. The correct balance of dissolved solids in the water is essential to the health of aquatic organisms for several reasons. One reason is that many of these dissolved materials are essential nutrients for the general health of aquatic organisms. Another reason is that the transport of ions through cellular membranes is dependent on the total ionic strength of the water. Too many dissolved salts in the water can dehydrate aquatic organisms. Too few dissolved salts, however, can limit the growth of aquatic organisms that depend on them as nutrients.

Natural variation. Heavy rains erode soils, and fast-moving water tends to scour a stream or river bottom. The geological characteristics of the watershed can determine the amount of erosion that occurs. This natural variation can also be enhanced by human activities in a watershed. The removal of vegetation along stream banks can result in increased bank erosion. Road construction and clearing land for development, agriculture, and logging are just a few other examples of activities that can enhance the natural erosion potential and increase the turbidity of a stream or river.

Expected Levels Total solids in surface water usually fall within the range of 20 mg/L to 500 mg/L. Values can go much higher especially after heavy rain when the water levels are high. Some sample data from selected rivers are listed in Table 1.

Why are total solids a concern?

• Primary producers (phytoplankton, algae, and other aquatic plants) are less able to produce oxygen by photosynthesis.

• Fish and predators feed less efficiently in turbid waters.

• Suspended sediments settle to the bottom and cover up aquatic habitats. Over a period of time, this reduces the amount of invertebrate food available for fish and other predators.

• If the sediment load is too high, fish gills can become clogged.

• Suspended solids carry plant nutrients and also provide attachment places for other pollutants, such as metals and bacteria.

• The suspended particles can absorb heat from the sun and increase water temperature.

• Water clarity affects the human perception of water quality. Decreased water clarity often causes water to be seen as dirty or polluted.

Table 1: Total Solids in Selected Rivers

Site Season Total Solids (mg/L)

Season Total Solids (mg/L)

Hudson River, Poughkeepsie, NY Spring 134 Fall 259

Colorado River, CO-UT state line Spring 1226 Fall 873

Sacramento River, Keswick, CA Spring 112 Fall 68 Mississippi River, Memphis, TN Spring 222 Fall 371

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Turbidity and Color INTRODUCTION Turbidity refers to the amount of light blocked by water due to the presence of suspended particles. Water with high turbidity is cloudy, while water with low turbidity is clear.

Many factors can contribute to the turbidity of water. An increase in stream flow due to heavy rains or a decrease in stream-bank vegetation can speed up the process of soil erosion. This will add suspended particles, such as clay and silt, to the water.

Runoff of various types contains suspended solids that may add to the turbidity of a stream. Agricultural runoff often contains suspended soil particles. Other types of runoff include industrial wastes, water treatment plant effluent, and urban runoff from parking lots, roads, and rooftops.

Bottom-dwelling aquatic organisms, such as catfish, can contribute to the turbidity of the water by stirring up the sediment that has built up on the bottom of the stream. Organic matter such as plankton or decaying plant and animal matter that is suspended in the water can also increase the turbidity in a stream.

High turbidity will decrease the amount of sunlight able to penetrate the water, thereby decreasing the photosynthetic rate. Reduced clarity also makes the water less aesthetically pleasing. While this may not be harmful directly, it is certainly undesirable for many water uses.

When the water is cloudy, sunlight will warm it more efficiently. This occurs because the

suspended particles in the water absorb the sunlight, warming the surrounding water. This can lead to other problems associated with increased temperature levels.

While highly turbid water can be detrimental to an aquatic ecosystem, it is not correct to assume that clear water is always healthy. Slightly turbid water can be perfectly healthy, while clear water could contain unseen toxins or unhealthy levels of nutrients.

Sources of Turbidity

• Soil erosion - silt - clay

• Urban runoff - road grime - rooftops - parking lots

• Industrial waste - sewage treatment effluent - particulates

• Abundant bottom-dwellers - stirring up sediments

• Organics - microorganisms - decaying plants and animals - gasoline or oil from roads

Effects of Turbidity

• Reduces water clarity

• Aesthetically displeasing

• Decreases photosynthetic rate

• Increases water temperature

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Expected Levels Turbidity is measured in Nephelometric Turbidity Units, NTU. According to the USGS, the turbidity of surface water is usually between 1 NTU and 50 NTU. Turbidity is often higher than this, however, especially after heavy rain when water levels are high. Turbidity can be lower than expected in still water because of the settling of suspended particles that might occur. The turbidity of some selected rivers are shown in Table 1. Water is visibly turbid at levels above 5 NTU. The standard for drinking water is 0.5 NTU to 1.0 NTU. Water that has a turbidity of greater than 20 NTUs over an extended period of time is considered unhealthy.

Table 1: Turbidity Levels in Selected Rivers

Site Turbidity (NTU)

Sacramento River, Keswick, CA 4

Hudson River, Poughkeepsie, NY 15

Mississippi River, Memphis, TN 39

Rio Grande, El Paso, TX 80

Colorado River, CO-UT state line 180

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Bibliography

Andrews, William A. and Sandra J. McEwan Investigating Aquatic Ecosystems, Ontario,

Canada, Prentice-Hall Canada, Inc., 1987. De Pew, Jeff, Susanne Reed, and Jennifer Gleason. Stream Ecology: A Journal For Action,

Missouri Botanical Garden, and Education Division, 1993. Johnson, Robyn L., Scott Holman, Dan. D. Holmquist Water Quality with CBL, Portland

Oregon: Vernier Software, 1999. Mitchell, Mark K and William Stapp, Field Manual for Water Quality Monitoring, An

Environmental Education Program for Schools, Michigan, Thomson-Shore, Inc., 1993. White, Kathleen, Ralph Marquez, Larry Soward, and Glenn Shankle, A Guide to Freshwater

Ecology, Austin, Texas: Texas Commission on Environmental Quality, 2005.

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WQI DATA & CALCULATIONS SHEET Stream or lake: _____________________________ Date: _________________________________

Site name: ________________________________ Time of day: ___________________________

Site number: _______________________________

WQI Data Table

A B C D

Test Results Unit Q-Value Weighting Subtotal factor

Temperature, ΔT °C 0.11

pH pH unit 0.11

Turbidity NTU 0.08

Total Solids mg/L 0.07

Dissolved Oxygen % sat. 0.17

5-Day BOD mg/L 0.11

Total Phosphate mg/L PO4-P 0.10

Nitrates mg/L NO3–-N 0.10

Fecal Coliform CFU/100 mL 0.16

Score

WQI Rating Column Procedure:

A. Record the test result for each test. B. Using the weighted graph for each test, record the Q-value. C. Multiply the Q-value in Column B by the weighting factor. D. Record the resulting value of each test. Take the sum of the test subtotals and record the result at

bottom of the table next to Score. Use the score to find the WQI Rating from the graph below.

Water Quality Index Ratings

90 –100 Excellent

70 – 90 Good

50 – 70 Medium

25 – 50 Poor

0 – 25 Very Poor

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Animal Phyla PORIFERA: Sponges CNIDARIA: Hydra, Sea anenomes, Jellyfish, Corals, Man-o-War PLATYHELMINTHES: Flatworms, Planaria, Flukes, Tapeworms NEMATODA: Roundworms, Hookworms, Pinworms, Trichina worms, Horsehair

Worms ANNELIDA: Earthworms, Leeches, Aquatic Segmented Worms, Sandworms, Fan

Worms, Bristle Worms, Tube Worms MOLLUSCA: 3 CLASSES Gastropods: Snails, Slugs, Whelks

Bivalves: Clams, Mussels, Oysters, Scallops

Cephalopods: Squid, Octopus, Chambered Nautilus ARTHROPODA: 5 CLASSES Insects: Bees, Ants, Butterflies, May Flies, Water Penny, Beetles, Black Flies

Crustaceans: Crayfish, Lobsters, Crabs, Pill Bugs, Sow Bugs,

Arachnids: Spiders, Water Mites, Ticks, Scorpians, Tarantulas

Millipedes: Millipede

Centipedes: Centipede ECHINODERMATA: Sea Stars, Brittle Stars, Sea Urchins, Sea Cucumbers, Sand Dollars CHORDATA: 7 CLASSES Jawless Fish: Lamprey Eels, Hagfish

Cartilaginous Fish: Sharks, Skates, Rays

Osteichthyes: Boney Fish, Sculpins, Bleeding Shiners, Catfish, Minnows, Drums, Darters, Bass

Amphibians: Frogs, Tadpoles, Toads, Salamanders, Newts

Reptiles: Turtles, Lizards, Snakes, Crocodiles, Alligators

Birds: Herons, Ducks, Coots, Eagles, Hawks, Vultures, Robins, Cardinals, Sparrows

Mammals: Raccoon, Opossum, Otters, Deer, Mice, Bats, Squirrels, Chipmunks

Documents

John Burroughs School Biotic and Abiotic Stream Factors Manual · Diatoms are a major group of algae and are one of the most common phytoplankton. Diatoms are unicellular but can