How to Monitor

Learning how to monitor water quality is a first step in answering the question “How healthy are our creeks and rivers?” The health of our waterways is affected by the sheer combined impact of so many of us using water.

  • Rivers have a life cycle much like a living organism. They are born from meltwater and they grow physically larger with each tributary stream that joins their flow. They mature as they pass through different landscapes and add chemical "memories" from each place they visit. They finish their life journey at the oceans and give rise to another generation of rivers through the water cycle.
  • Changes in the life and health of a river affect the organisms that live there. Some of these changes occur naturally; some of them are influenced by people. Rivers can be healthy or unhealthy at any stage of their life.
  • At some point in the life of a river, they eventually pass through our communities. We can visit briefly before seeing them off again on their journey to the ocean. These visits provide us with the opportunity to ask, "How are you doing?"

RiverWatch and CreekWatch is about chemical and biological monitoring as a first step in taking care of our water. How are we doing right now and what could we do differently in the future?

Why Monitor?

The health of our waterways is affected by the sheer combined impact of so many of us. Just look at everyone who uses rivers - anglers, boaters, dams, industries, agriculture, towns and cities.

RiverWatch and CreekWatch is about using chemical and biological monitoring as a first step in taking care of rivers.

How can people help care for rivers and creeks?

The First Step
The first step in taking care of rivers and creeks is to become more aware. "How healthy is our river or creek?" How would you know the answer to this question? Students and citizen science volunteers help by collecting science data from their local river.

Real World Science
RiverWatch and CreekWatch is real world science. Students and citizen science volunteers carefully collect data and examine their findings for patterns or changes in water quality. Their findings are presented graphically on this website. There is no correct answer and no one is better suited to conduct the research than caring people.

Long Term Study
The science data collected by RiverWatch and CreekWatch is important. Each day of observations is added to a database, and the data collected by many students and volunteers over many years helps identify trends and changes in water quality. Each new season of students and volunteers contributes to a growing understanding of Alberta waterways.

Personal Action
The science data collected by RiverWatch and CreekWatch is important. Each day of observations is added to a database, and the data collected by many students and volunteers over many years helps identify trends and changes in water quality. Each new season of students and volunteers contributes to a growing understanding of Alberta waterways.

"Anything else you're interested in is not going to happen if you can't breathe the air and drink the water. Don't sit this one out. Do something. You are by accident of fate alive at an absolutely critical moment in the history of our planet." --Carl Sagan

Aquatic Invertebrates

Viewing wildlife is one of the best things about spending time along a river. Even aquatic invertebrates - the "bugs" living at the bottom of a river - are interesting if you take a close look at them!

The kinds of invertebrates found in a river can tell you a lot about the water quality.

Invertebrate Background Information

Viewing wildlife is one of the best things about spending time along a river. Even aquatic invertebrates - the "bugs" living at the bottom of a river - are interesting if you take a close look at them!

The kinds of invertebrates found in a river can tell you a lot about the water quality.

What Are Invertebrates?

Invertebrates are animals without backbones. They may have hard outer shells to protect and support their soft bodies. They are the most numerous and diverse kind of animal on Earth and they play a critical role in the functioning of ecosystems (ie: pollination, nutrient cycling, food webs).

There are several general categories of invertebrates:

Terrestrial invertebrates live on the land.
Marine invertebrates are common along ocean beaches.
Caddisfly Larva
Aquatic invertebrates live at least part of their life in freshwater ponds, lakes, streams or rivers. Some of the adult insects that we see flying around us have spent their early lives feeding underwater.
Macroinvertebrates are species large enough to be seen without using a microscope but they are generally less than 2 cm long
Benthic invertebrates are species that live underwater hiding in between bottom rocks and plants or in the mud.

Insect Life Cycles

Approximately 5% of insects spend all or part of their life cycle in water. The immature stages of these aquatic insects often have streamlined bodies and they breathe with gills.

Functional Feeding Groups

A healthy river has many different invertebrates feeding in many different ways. Diversity is a characteristic of stable, healthy ecosystems. Aquatic invertebrates can be grouped into four functional feeding groups according to how and what they eat:

Aquatic Food Chains

Energy flows from the sun through plants and then through each trophic level of a food chain. Food chains start with solar energy captured by green plants that use photosynthesis to produce simple sugars. Oxygen produced as a by-product is an added bonus for all animals!




plant chlorophyll








Collecting Invertebrates

Collecting aquatic invertebrates is a fun and interesting activity that can reveal useful information about the health of a river. The presence or absence of certain types of invertebrates can indicate the effects of pollution.

Collection Sites
Various invertebrates are adapted for life in areas with different river bottoms and water that may be shallow or deep, fast or slow. Since most observers don't have time to thoroughly sample all these habitats in one trip, a good idea is to focus areas that feature:

  • gravel or rocks
  • shallow water
  • moderate flow velocity

No one likes wading into mud and becoming stuck, and most people avoid wading into fast water that is deeper than their boots. It's obvious from these limitations that the most common choice for sampling sites will not accurately represent all of the habitats found along the length of a river. But, since different habitats have different invertebrates, it is easier to compare results if the same type of habitat is sampled each time. So, good advice would be to sample each time in shallow, moderately flowing water with gravel or rock bottom in order to provide consistency to a monitoring program.

Aquatic invertebrates should be captured by observers wearing rubber boots, hip waders or chest waders, especially if there is a concern over cold water, broken glass or sewage contamination.

Safety should always be the first priority during river monitoring. Observers should wear personal floatation devices (P.F.D.'s) and be under qualified supervision.

Observers collect invertebrates using equipment such as fine-meshed sweep nets, kick nets, Neill cylinders or deepwater artificial samplers (wire cages filled with rocks).

  • Nets have the advantage of being easy to carry, easy to use and inexpensive to build, however, they don't capture all the invertebrates present at a sample site.
  • Neill cylinders are expensive to buy and they capture an overwhelming number of invertebrates that can take many hours to sort and identify with a microscope back in a lab.

Using a Kick Net
Useful invertebrate information can be obtained with a simple kick net, especially if proper procedures are followed.

Identifying Aquatic Invertebrates

Aquatic invertebrates all look the same to the untrained eye - strange and bizarre! Honestly, with some background information, even the most reluctant observer can learn to appreciate and identify these truly amazing life forms hiding at the bottom of a river.

Taking the time to identifying aquatic invertebrates is worthwhile for several reasons:

  • Aquatic invertebrates are interesting and easy to see.
  • Invertebrates are an important part of the food chain.
  • The presence or absence of a particular invertebrate can be an indication of pollution.

Invertebrate Taxonomy

Scientists organize living things into a series of categories. This process is called taxonomy. Taxonomy categories are listed below from largest to smallest along with an example that shows how humans are classified as Homo sapiens.

For quick shoreline and field trip identification, all river organisms can be identified down to the level of phylum, maybe to class, some to orders and only a few to families. Accurate genus and species identification is very complicated and requires the viewing of microscopic features back in a lab.

There are many thousands of species of invertebrates and it helps to know how they are related to each other. Some of the more common river invertebrates are classified below. Special emphasis is placed on the insects that are commonly seen. Click on the highlighted names for more detailed information.

Invertebrate Identification

Shoreline identification and the release of live invertebrates is easily done by merely viewing illustrations.

  • Crustacean
  • Resemble small shrimp
  • Swims on its' side
  • Swims quickly before burrowing into clumps of vegetation
  • Omnivores and scavengers on plant or animal material
  • Requires well-oxygenated water
  • Moderately tolerant of pollution
  • May indicate fair water quality
Blackfly Larvae
  • Insect
  • Complete metamorphosis
  • Blackfly larvae resemble small grubs
  • Head dark coloured
  • Bottom-end swollen and fatter than the head-end
  • Attach to the upper smooth surface of rocks using suckers on the bottom end
  • Heavily populated rocks appear to have a stubble beard
  • Larvae often attach to the bottom of a sorting tray
  • Found in flowing water
  • Omnivores
  • Filtering collectors
  • Pollution tolerant
  • May or may not indicate poor water quality
  • Segmented worm
  • Bristleworms esemble thin, reddish earthworms
  • Bristles on each segment are not visible to the unaided eye
  • Can tolerate low oxygen levels
  • Pollution tolerant
  • Large numbers may indicate poor water quality
  • May indicate organic pollution
Caddisfly Larva
  • Insect
  • Complete metamorphosis
  • Some larvae build tube-like cases to hide in
  • Larvae resemble caterpillars with skinny legs
  • Mostly herbivorous on algae and plants
  • Some are predators that eat nymphs
  • Some are collectors that build nests
  • Larvae and adults are a favourite trout food
  • Larvae are moderately tolerant of pollution and warm water
  • Large numbers may indicate fair water quality
Clams and Mussels
  • Mollusc
  • Found in slow moving, warm rivers
  • Clams are small, round and symmetrical
  • Mussels are larger, oblong and lopsided
  • Filter feeders on plankton and organic debris adrift in the current
  • Can tolerate degraded or polluted environments
  • Moderately pollution tolerant
  • Large numbers may indicate fair water quality
Cranefly Larva
  • Insect
  • Complete metamorphosis
  • Cranefly larvae resemble plump caterpillars with a knobby butt
  • Larvae are found more often in the fall
  • Herbivorous larvae shred leaf material (shredders)
  • Adults do not feed
  • Adults look like "giant mosquitoes" - what a scary thought, but they don't bite
  • Moderately pollution tolerant
  • Large numbers may indicate fair water quality
Damselfly Nymph
  • Insect
  • Incomplete metamorphosis
  • Nymphs have three paddle-shaped tails
  • Extendable lower lip is used to grab prey
  • Predatory on mayfly nymphs and mosquito larvae, worms and anything else small enough to grab
  • Moderately pollution tolerant
  • Large numbers may indicate fair water quality
Diving Beetle
  • Insect
  • Complete metamorphosis
  • Large diving beetles are fun to discover
  • Breaths air from a "scuba tank" air bubble trapped under the wing covers
  • Found in water both as adults and larvae
  • Strong swimmers
  • Carnivorous on larvae and small fish
  • Adults are not useful as an indicator of water quality because they breathe from surface air bubbles
Dragonfly Nymph
  • Insect
  • Incomplete metamorphosis
  • Nymphs are large, ferocious creatures
  • Jet-powered butts squirt water for propulsion
  • Lip is hinged and extendable to capture prey
  • Nymphs express huge attitude with a large lower lip
  • Predatory on larvae, nymphs, tadpoles and small fish
  • Carnivorous - there's something scary about an insect that can eat a fish!
  • Adults don't fold their wings; the wings lay flat and outspread
  • Found in slow moving and still water
  • Moderately pollution tolerant
  • Large numbers may indicate fair water quality
  • Small, pale blobs found in the vegetation or under rocks.
  • Omnivorous on living or dead plants and animals.
  • Old science textbooks are full of drawings that show flatworms growing two heads. What mad scientist would split those heads in half in the first place? Doesn't that hurt, or at least result in a "splitting" headache?
  • Pollution tolerant
  • Large numbers may indicate poor water quality
  • Segmented worm
  • Leeches are fun to watch swimming or inching along the glass of an aquarium.
  • Parasitic on the blood of fish and birds.
  • Pollution tolerant.
  • Large numbers may indicate poor water quality.
Mayfly Nymph
  • Insect
  • Incomplete metamorphosis
  • Three long tails
  • Swims like a dolphin with up and down undulations
  • Feathery gills are located along sides of the abdomen
  • Diverse body types - flat, armoured, short or long and skinny and are adapted for different flow conditions
  • Mainly herbivorous on algae and detritus.
  • Nymphs require clean, oxygenated water.
  • Pollution intolerant.
  • Large numbers likely indicate good water quality and high oxygen levels.
Midge Larva
  • Insect
  • Complete metamorphosis
  • Larvae occur in astronomical numbers and dominate many aquatic samples
  • Some larvae have red blood
  • Larvae resemble a short worm
  • "C-shaped" and swim by flexing rapidly
  • Wiggles back and forth vigorously
  • Appear to have no legs
  • Omnivores feeding on small organisms, decaying matter and algae
  • Pollution tolerant
  • Large numbers may or may not indicate poor water quality and organic enrichment
Damselfly Nymph
  • Mollusc
  • Herbivores that feed on algae scraped from stones and leaves
  • Detritivores that feed on decaying matter
  • Browse by means of a radula - a ribbon-like tongue embedded with thousands of "teeth" - scraped along rocks or leaves
  • Lung-breathing snails have shells coiled like a tuba or spiral shells opening on the left side without a door. (Lung = Left) They obtain air from above the water's surface and therefore are not as sensitive to pollution and are not really good indicators of water quality
  • Gill-breathing snails have spiral shells opening on the right side with a door (operculum). They rely on oxygen dissolved in the water and may be more susceptible to pollution
  • Pollution tolerant
  • Large numbers of lunged snails may indicate poor water quality and organic enrichment
  • Large numbers of gilled snails may indicate good water quality
Stonefly Nymph
  • Insect
  • Incomplete metamorphosis
  • Can be very large
  • Great to find but kind of scary looking with armour and big legs
  • Most are herbivores feeding on decomposing leaves coated in bacteria and fungus
  • Two long tails and antennae
  • Swim like sharks with side-to-side undulations
  • They do push-ups to move water past the "arm-pit" gills
  • Leave their dry, shed skins attached to dry rocks
  • Found in deeper, faster water
  • Very pollution intolerant
  • Indicate good water quality with high oxygen levels
Water Boatman
  • Insect
  • Complete metamorphosis
  • Are water boatman the cutest little bugs, or what?
  • Can fly or swim
  • Adults fly in search of deeper water for breeding and overwintering.
  • Swarms of these swimming insects blacken shallow water in the North Saskatchewan River in Edmonton each fall.
  • Omnivorous and feed on algae, detritus, micro-animals, small midge and mosquito larvae.
  • Found in all types of water, moving or still.
  • Boatman "scuba dive" with an air bubble trapped on their body.
  • Not necessarily useful as indicators of water quality because the adults breathe surface air.

Interpreting Invertebrate Data

Aquatic invertebrates are living indicators of pollution levels. The numbers and types of invertebrates in a river change if pollution is present. Invertebrate data can serve as a quick check of water quality.

A survey of invertebrate populations can reveal information about the health of a river. However, the data may have limited value if collected on only one day of one season in one year. Data is more useful if it can reveal trends spanning an entire season, an entire year, several years or along the length of an entire river.

Types of Pollution

Pollution is any substance that has a negative effect on living things. There are several categories of pollution including sediment, toxic chemicals, warm water and organic nutrients.

Sediment Pollution

Particles that wash into a river may originate from street runoff during storms or during spring snowmelt. Sediment can also originate from construction areas, trampled banks or flood events.

  • Sediment pollution does damage when suspended particles gradually settle over the river bottom. The effects of sediment pollution can include:Measuring the turbidity (clarity) of the water can serve as a test for sediment pollution.
  • reduced number of invertebrates and invertebrate types
  • smothering and killing fish eggs, algae and invertebrates
  • murky water that blocks sunlight for photosynthesis
  • rocks and plants covered in silt
Toxic Pollution

Chemicals that are harmful to life can originate from storm sewer outlets, water treatment plants, factories, rail yards, lawns, golf courses and mines. These chemicals can include paint, diesel fuel, chlorine, oil, acid, pesticides, herbicides and heavy metals.

  • The effects of toxic pollution can include:Analysis of invertebrate data can serve as a measure of toxic pollution. Testing for specific toxins is usually beyond the scope of school and public monitoring programs
  • reduction or absence of all types invertebrates
  • water appears clear and clean
Thermal Pollution

Human activities can return warm water to a river. Sources of thermal pollution can include power plants, wastewater treatment plants, fish hatcheries and oil refineries.

  • Recording changes in water temperature can document thermal pollution.

The effects of thermal pollution can include:

  • increased water temperatures
  • increased plant growth
  • slowing of river velocity because of planet growth
  • fewer kinds of invertebrates
  • large numbers of pollution tolerant invertebrates
  • lower dissolved oxygen levels
Organic Nutrient Pollution

Too much of a good thing can be harmful to life. While nutrients are necessary - like nitrogen and phosphorus - too much can result in massive algae and plant growth. Excessive plant growth can be followed by oxygen depletion as dead plant material decomposes and bacteria uses oxygen. Lower oxygen levels can result in fish kills.

Organic nutrients can originate with human and livestock wastes, feedlots, meat packing plants, sewage and fertilizer runoff from yards and farms.

  • Invertebrate data can be used along with testing nitrogen and phosphorus levels to measure of organic nutrient pollution.

The effects of organic pollution can include:

  • fewer kinds of invertebrates
  • large numbers of pollution tolerant invertebrates
  • an increase in collectors and scrapers such as caddisfly larvae or roundworms
  • unpleasant odours
  • rocks covered in algae
  • excessive weed growth
  • high concentrations of nitrogen and phosphorus
  • lower oxygen levels

Invertebrate Pollution Tolerance

Caged canaries were once taken deep inside coal mines to alert the miners of deadly, odourless gases. If a canary died in its cage, it was time for the miners to quickly evacuate to the surface.

In a similar way, benthic (bottom dwelling) invertebrates can indicate the presence of pollution in a river. Some invertebrates are very sensitive to pollution and quickly die off.

Invertebrates are good "bio-indicators" of pollution for several reasons:

  • Invertebrates are basically stationary even though the river is constantly moving past them. The impact of any pollution can be seen in the surviving organisms long after all traces of a chemical have been washed away.
  • Invertebrates have a relatively long life cycle of one to three years. They are available to measure pollution over long periods and at low concentrations.
  • If scrapers or collectors become more common, they may be an indicators of organic nutrient pollution and increased algae growth.
  • If the water quality has been impacted by pollution, it will be home only to those invertebrate species that are tolerant of pollution and these may be present in very great numbers.

It should be noted that surface-breathing invertebrates such as water striders, lunged snails and adult beetles do not depend on dissolved oxygen and therefore have limited use as bio-indicators of pollution. They may be able to live in oxygen poor water by breathing with surface air.

"Chemical measurements are like taking snapshots of the ecosystem, whereas biological measurements are like making a videotape."

- Professor David M. Rosenberg
University of Manitoba

Pollution Tolerance Index

Invertebrates can be assigned to three groups depending on their tolerance to organic nutrient pollution. In this way, the presence or absence of a particular invertebrate is a bio-indicator of water quality.

After collecting, identifying and counting invertebrate samples, the results can be checked against the pollution tolerance index. A majority of invertebrates tending falling into any one category will indicate a certain level of water quality.

Organic Pollution Tolerance Index

For Aquatic Macroinvertebrates

Decreasing Pollution Tolerance --->

Pollution Tolerant


Pollution Intolerant

Increasing Water Quality --->

Presence in great numbers may indicate poor water quality but can be found in any type of water

Presence in great numbers may indicate fair water quality

Presence in great numbers may indicate good water quality

blackfly larvae
midge larvae
round worms
lunged snails

caddisfly larvae
cranefly larvae
dragonfly nymphs
damselfly nymphs
gilled snails

mayfly nymphs
stonefly nymphs

Seasonal Considerations

The numbers and types of invertebrates can change according to the seasons without any relationship to pollution. When analyzing invertebrate data, keep in mind these seasonal considerations:


  • Unusual scouring by high water flows, ice dams or truck loads of snow dumped into rivers may cause a decrease in invertebrate populations.
  • Spring invertebrates tend to be easier to see, easier to count and easier to identify because of their low numbers and large size.


  • Rivers are shallow in the autumn, making it easier for people to wade-in and collect invertebrates.
  • Reproduction over the summer gives rise to higher invertebrate populations.
  • Invertebrate samples collected in the autumn tend to contain higher numbers of organisms.
  • Autumn immature insects are smaller and more difficult to identify.

River Characteristics

The characteristics of a river can change naturally without the influence of human activity or pollution. River characteristics can affect invertebrate populations without necessarily indicating the occurrence of organic pollution. When analyzing invertebrate data, keep in mind the effects of these river characteristics:

  • Rivers tend to age or mature naturally as they flow toward the ocean from cold mountain headwaters and out across the warm prairies.
  • Generally, the downstream sections of a river become warmer, slower, deeper, more nutrient-rich, more turbid and muddier. Some invertebrates prefer warm water.
  • Downstream sections of a river are more likely to support organisms typical of fair or poor water quality.
  • The type of river bottom (substrate) can affect the numbers and types of invertebrates. Rivers with muddy bottoms are more likely to support organisms typical of fair or poor water quality.

So, how do you tell if "older" rivers are polluted? That's a good question! The answer probably lies in evaluating a number of factors such as bacteria and surrounding land-use.

Drawing Conclusions

After collecting, identifying and counting aquatic invertebrate samples, graphing the results will help illustrate differences or changes.

Differences in the graphed invertebrate data may be caused by the time of day, the season, the type of bottom substrate or by pollution. Were the differences natural or the result of human impact?

The following questions may help with the analysis of invertebrate data:

  • How much of the river was affected?
  • Were differences measured on both sides of the river?
  • Were all organisms affected or just specific types?
  • Were the differences related to the seasons?
  • Did each sample site have the same type of substrate and flow rate?
  • Were the invertebrates sampled with the same type of equipment and care?
  • Is there any chemical data corresponding to the invertebrate changes?
  • Were there any unusual smells detected in the area?
  • Did previous sampling, floods or snow dumps disturb the study site?
  • How is the surrounding land being used?


Water is a very good solvent. In fact, pure water is seldom found in nature because it readily dissolves the many chemicals that wash off
the land or pour out of effluent pipes. Most Canadians use surface water from ponds, lakes or rivers for drinking and household use. Clean water is so important to healthy communities. Measuring the concentration of a few key chemicals can help indicate river water quality.

Is your river healthy?

Dissolved Oxygen

Oxygen is an element essential to all living things. Dissolved oxygen is perhaps the most important abiotic or non-living factor affecting aquatic communities such as rivers. Fish and many macroinvertebrates nymphs and larvae are equipped with gills to extract oxygen from the water they live in.

Pre-packaged chemistry test kits are used to measure the concentration of dissolved oxygen. The amount of oxygen dissolving in water is affected by temperature, mixing, decay and pollution. Low levels of dissolved oxygen are harmful to many species and can indicate that pollution has entered the water.

Understanding the basic science of dissolved oxygen will help you interpret the data collected from your local river. Take a deep breath and lick below to learn more about dissolved oxygen!

Background Information

The air that we breathe every second of every day is composed of 21% molecular oxygen gas (O2). This means that about one out of every five molecules in the atmosphere is an oxygen molecule (particle).

Approximately 75% of the atmospheric oxygen is produced by one-celled plants (phytoplankton) floating in the oceans. Oxygen is required by all living things, as well as the processes of combustion (burning) and oxidation (rusting of iron).
What is Dissolved Oxygen?
Dissolved oxygen is merely the oxygen molecules that have mixed in with water molecules. It gets there by diffusing from the air; when trapped by aeration or bubbling; and as a waste product from green plant photosynthesis.

Oxygen gas dissolves in water much like the carbon dioxide responsible for the fizz in a can of soda pop. Carbon dioxide (CO2), however, is 200 times more soluble in water than oxygen.

Oxygen is not very soluble and occurs dissolved in only trace amounts. The tiny amounts of dissolved oxygen are measured in the range of 1-14 milligrams per litre (mg/L). While one out of every five molecules in the atmosphere is oxygen, in water, only 1-14 molecules out of a million are oxygen. Said another way, the concentration of dissolved oxygen is 1-14 parts per million (ppm).

Note: The concentration units of mg/L and ppm are equivalent. (mg/L = ppm)

Aquatic organisms such as fish and macroinvertebrates rely on gills for breathing dissolved oxygen. Bacteria also use oxygen when they decompose dead organisms. So far, however, no one has devised a way for humans to extract oxygen from water during a dive.
What Natural Processes Increase Dissolved Oxygen Levels?
Oxygen is only slightly soluble. Several abiotic (non-living) and biotic (living) processes help to increase the amount of dissolved oxygen.

Abiotic Factors That Increase Dissolved Oxygen

  • Faster moving water holds more oxygen than slow or standing water. Turbulence or splashing whitewater falling over weirs, dams and rocks traps air into the water, increasing dissolved oxygen levels.
  • The mixing of water from top to bottom in a river ensures that oxygen levels are fairly constant no matter what the depth.
  • Water temperature can affect dissolved oxygen levels. Cold water is capable of holding more oxygen than warm water.
  • Increasing barometric pressure can force more oxygen into solution. This effect is also accomplished with decreasing altitude. Water at lower elevations is under greater pressure and contains more dissolved oxygen.

Biotic Factors That Increase Dissolved Oxygen

  • Photosynthesis by aquatic plants and algae adds oxygen into water during daylight. Bubbles of oxygen gas can actually be seen clinging to and rising from submerged leaves under direct sunlight.

During photosynthesis, plants use sunlight in a reaction with carbon dioxide and water. The result is the production of glucose (sugar) and the release of oxygen gas.

6CO2(g) + 6H2O(l) + sunlight --> C6H12O6(s) + 6O2(g)
What Natural Processes Decrease Dissolved Oxygen Levels?
Oxygen is only slightly soluble at the best of times. Compounding this problem are several abiotic (non-living) and biotic (living) processes that actually decrease the amount of dissolved oxygen.

Abiotic Factors That Decrease Dissolved Oxygen

  • Warm water holds less dissolved oxygen than cold water. (This same rule also applies when warm soda pop fizzes out of a can or glass. The carbon dioxide dissolved in the liquid is less soluble at warmer temperatures.)
  • Shallow water holds less dissolved oxygen. River levels tend to drop throughout the summer as mountain snow finishes melting. Shallow water moves more slowly and heats up faster. This often creates a critical time for aquatic organisms as dissolved oxygen levels drop.
  • Turbid or cloudy water may have lower oxygen levels. Less sunlight is able to penetrate the water and less photosynthesis is likely to occur.
  • Decreasing barometric pressure can release oxygen out of a solution. This effect is also accomplished with increasing altitude. Water at higher elevations is under less pressure and contains less dissolved oxygen.

Biotic Factors That Decrease Dissolved Oxygen

  • Levels of dissolved oxygen decrease during the night because photosynthesis stops. A daily graph of oxygen concentrations shows an undulating or wavy pattern with the lowest readings occurring just before dawn on hot summer mornings.
  • With no photosynthesis occurring at night, animal and plant respiration gradually reduces the
remaining dissolved oxygen. During cellular respiration, animals and plants take-in oxygen to "burn" glucose (sugar). This reaction releases carbon dioxide, water and energy.

C6H12O6(s) + 6O2(g) + enzymes --> 6CO2(g) + 6H2O(l) + energy

How is Oxygen Cycled Through the Biosphere?
There are two main processes occurring in all ecosystems - energy flow and material cycling. Oxygen and carbon dioxide are cycled in a symbiotic relationship (mutualism) between plants, animals and bacteria. This carbon-oxygen cycle operates in water in much the same way as it does on land:

  • Green plants use carbon dioxide and release oxygen during photosynthesis.
  • Animals use oxygen and release carbon dioxide during respiration.
  • Bacteria use oxygen and release carbon dioxide during decomposition.

Three natural processes cause the cycling of oxygen and carbon dioxide in aquatic ecosystems:

  • photosynthesis
  • cellular respiration
  • decomposition

The Effects of Low Dissolved Oxygen Levels

High levels of dissolved oxygen are necessary to maintain diversity in aquatic communities. High dissolved oxygen levels can even make drinking water taste better. It's therefore important to understand the human activities that might cause reduced dissolved oxygen levels.

What Human Activities Cause Low Levels of Dissolved Oxygen?
Several human activities can affect the oxygen concentrations in a river:

  • Warm water discharged from factories, wastewater treatment plants or power plants reduces dissolved oxygen levels. This is known as thermal pollution.
  • Warm water with low oxygen levels is found in slow, shallow rivers created by withdrawing water for irrigation or the filling of reservoirs. In 2000, there was concern that irrigation water taken from the Little Bow River might leave fish in a desperate situation during late summer.
  • Warm water with low oxygen levels can result when vegetation is removed from stream banks during landscaping, logging or clearing farmland. Less vegetation results in less shade from the sun and higher water temperatures result.
  • Nutrients added to water by fertilizers washing-off fields or added by urban sewage can produce excessive plant or algae growth in rivers. During late summer or winter, decomposing bacteria break down the masses of dying aquatic plants and algae. This decay process consumes large amounts of dissolved oxygen, affecting fish and other pollution sensitive organisms.
  • Animal and plant waste (pulp, manure, vegetable peels, blood, leaves, grass) entering rivers from pulp mills, feedlots, dairies, food-processing plants, meatpacking plants, forests and lawns create eutrophic or organically enriched conditions. This organic loading may result in low oxygen levels as bacteria decompose the material. When populations of microscopic decomposers rapidly increase, a situation of high biological oxygen demand (B.O.D.) is created. Under extreme conditions of high B.O.D., anaerobic bacteria produce hydrogen sulfide gas with a rotten egg smell.
How do low oxygen levels affect aquatic ecosystems?
Dissolved oxygen levels affect the survival of aquatic organisms. Trout and the nymphs of mayflies or stoneflies are found only in water with high oxygen concentrations. If dissolved oxygen levels are low, only organisms such as leeches, snails and roundworms can survive. Fish and stonefly nymphs die while trapped in water with decreased oxygen levels. Low levels of dissolved oxygen can result in significant fish kills, especially in late summer or during the winter.

Dissolved Oxygen (DO) Test Kits

Dissolved oxygen levels can be tested with portable chemistry kits. Using the kits require several steps and careful attention to instructions.
Contents of Dissolved Oxygen Test Kits
WARNING: The chemicals in this kit may be hazardous to the health and safety of the user if inappropriately handled.

  • Read all labels
  • Wear gloves and goggles
  • Collect the waste solution in a plastic Nalgene waste bottle. This solution should be neutralized with sodium thiosulfate before flushing into the sanitary sewer system.
Instructions for Using the Dissolved Oxygen Test Kit

WARNING: The chemicals in this kit may be hazardous to the health and safety of the user if inappropriately handled. Please read all warnings carefully before performing the test and use appropriate safety equipment.

1. Place the kit in a safe, dry place on the ground. Look for a water sample collection site upstream of other classmates in the river.

2. Use the Dissolved Oxygen (DO) Bottle to collect flowing river water. Slowly submerge the tilted bottle with the opening pointing downstream.

3. Fill the DO bottle to 1/2 way up the neck of the bottle. Do not stopper the bottle yet. Stand the bottle back in the test kit.

4. Wear safety goggles and gloves. Open a Dissolved Oxygen #1 Foil Packet and a Dissolved Oxygen #2 Foil Packet. Carefully tap the contents of each packet into the DO bottle. Discard the empty packets into the garbage bag provided. This solution should be rinsed off if skin contact occurs.

5. Place the glass stopper into the DO bottle. Press on the stopper and quickly tip any overflow solution from the top of the DO bottle into the DO Waste Bottle. If an air bubble is trapped under the stopper, ask your guide for help.

6. Grip the bottle and stopper firmly. Invert to mix. A brownish flocculent (floc) precipitate will form. If any powdered reagent is left stuck to the bottom of the bottle it will not affect the test results.

7. Place the DO bottle back in the test kit. Allow the sample to stand until the floc settles to the white line on the bottle. Invert the bottle again and let the floc settle a second time (4 to 5 minutes).

8. Use the clippers to open one Dissolved Oxygen #3 Powder Pillow. Carefully add the acid contents of the pillow to the DO bottle. Restopper the bottle and tip any overflow into the DO Liquid Waste Bottle. At this point, trapped air bubbles are not important. Invert to mix. The floc will dissolve and a yellow colour will appear if oxygen is present.

9. Work over top of the open waste bottle while completely filling the plastic measuring tube with the prepared DO sample. Use the upside down square mixing bottle as a lid, then quickly flip both containers to transfer the contents from the tube into the square mixing bottle.

10. Add Sodium Thiosulfate drop-by-drop into the square mixing bottle until the solution changes from yellow to colourless. Hold the dropper straight up and make sure that drops fall directly into the sample liquid. Swirl to mix after each drop and compare against a white background. Count each drop and record the total number added. Each drop = 1 mg/L dissolved oxygen.

11. Clean-up by pouring the DO bottle solution into the plastic DO Waste Bottle. Next, use the clear solution in the square mixing bottle to rinse the DO bottle and test tube. Add the rinse to the waste bottle. If crystals remain in the DO bottle, rinse with a full square-mixing bottle of river water, swirl and empty into the waste bottle. If crystals still remain, repeat the rinse process.

Chemistry Theory for Dissolved Oxygen Kits

Higher-level science classes will be interested in the balanced chemical equations for each step of the dissolved oxygen test. The reactions for the Modified Winkler Method or Iodometric Method are described below.
Foil Packets #1 and #2

To start the Dissolved Oxygen (DO) Test, the reagents from the two foil packets are added into the river sample. This step combines manganese (II) sulfate from DO Packet #1 with lithium hydroxide base contained in DO Packet #2. Manganese (II) hydroxide is temporarily produced along with lithium sulfate.

Dissolved oxygen in the river water then reacts immediately with the manganese (II) hydroxide to produce an orange manganese (II) oxide floc that gradually settles to the bottom of the sample bottle.
Sulfamic Acid Pillow #3
The orange manganese (II) oxide floc reacts with the potassium iodide from Reagent #2 and the sulfamic acid now added by Powder Pillow #3. This releases free iodine with a brownish colour. The dissolved oxygen is now "fixed", further air bubbles are not a problem and the final titration step can be delayed up to 8 hours. The focus for remaining procedures is now the iodine, not the oxygen.
Titration Solution
With the final titration step, the focus is on the iodine equivalent rather than on the original molecular oxygen. Each drop of titrant added to the iodine indicates that a greater amount of dissolved oxygen was present in the original river water. The Sodium Thiosulfate Solution is titrated drop-by-drop, reducing the iodine back to its ionic form and changing the colour from yellow-brown to clear.

Interpreting Dissolved Oxygen Test Results

Measuring dissolved oxygen is one of the most important, if not the most important, tests of water quality for aquatic life. High levels of dissolved oxygen can indicate good water quality and a healthy ecosystem; lower levels can be an indication of pollution and environmental stress.
A Guide for Interpreting Dissolved Oxygen Concentrations

Dissolved Oxygen


River Water Quality

River Ecosystem


7 - 11




4 - 7


Borderline Healthy


2 - 4



Very Low

0 - 2

Very Poor

Won't support life

Interpreting Dissolved Oxygen Data

There are many slightly different interpretations of dissolved oxygen (DO) concentrations, but the trend is clear. Within the possible range of 1-14 mg/L...

  • low concentrations indicate poor water quality and unhealthy ecosystems
  • high concentrations indicate good water quality and healthy ecosystems.

Here is a selection of interpretations for dissolved oxygen results:

  • The Global Water Sampling Project in New Jersey states that a dissolved oxygen level of 9-10 mg/L is considered very good; at levels of 4 mg/L or less, some fish and macroinvertebrate populations begin to decline.
  • The Hach Chemical Company suggests that a dissolved oxygen content of 4-5 mg/L is considered borderline for aquatic life over extended periods of time. Sportfish populations require 8-14 mg/L and good fishing waters generally average 9 mg/L. At less than 3.0 mg/L, bottom-feeding fish (suckers) will die. While northern pike require at least 6.0 mg/L in the summer, these fish can get by with as little as 3.1 mg/L in the winter.
  • The 1999 Canadian Water Quality Guidelines (CWQG) for the Protection of Aquatic Life suggest that total oxygen concentrations for freshwater should be 5.5-9.5 mg/L.
  • According to "Stream Analysis and Fish Habitat Design", sportfish have differing requirements for dissolved oxygen at different temperatures:

Fish Species


Minimal Dissolved Oxygen mg/L

Optimal Dissolved Oxygen mg/L

Brown trout

colder than 15
warmer than 15

at least 3
at least 5

more than 7
more than 9


warmer than 15


Rainbow trout


less than 3 is lethal


  • "Save Our Streams" states that trout need at least 6 mg/L at all times to function normally. At less than 3 mg/L, the water is considered oxygen poor.
  • The FEESA "Aquatic Invertebrate Monitoring Program" states that 4-5 mg/L is the minimum value necessary to support aquatic life.

pH Test Kit Instructions

WARNING: The chemicals in this kit may be hazardous to the health and safety of the user if inappropriately handled. Please read all warnings carefully before performing the test and use appropriate safety equipment.

1. Place the test kit on the ground in a safe, dry place.

2. Fill the two glass test tubes up to the 5-ml mark with river water.

3. Wear goggles and gloves. Add four drops of Phenol Red Indicator Solution to one test tube and swirl to mix. This is the prepared sample.

4. Insert the test tube with the prepared sample solution into the inside hole on top of the black colour comparator box.

5. Insert the test tube with the untreated sample water into the outside hole on top of the black colour comparator.

6. Hold the colour comparator up to the sky or sun and look through the two openings in the front. Rotate the colour wheel until a colour match is obtained. Read the number on the colour wheel scale.

7. Have another person try matching the colours and then read the number scale. Agree on the best value. Record the result on the data sheet.

8. Clean-up by pouring the colored prepared solution into the pH Waste Bottle. Use the clear untreated sample water to rinse the prepared test tube and add this to the waste bottle.

A Guide for Interpreting pH Levels



River Water Quality

River Ecosystem


8.5 - 14




6.5 - 8.5




1 - 6.5



The pH is used to measure the relative acidity of solutions such as water.

Solution with a pH greater than 7.0 is considered to be basic or alkaline. The greater the pH, the greater the alkalinity.

Distilled water has a pH of 7.0. This is considered neutral.

Solutions with a pH level less than 7.0 are considered to be acidic. The lower the pH, the more acidic the solution.

A pH range of 6.5 - 8.5 is often considered safe for fish and aquatic invertebrates.

Nitrogen Test Kit Instructions

A Guide for Interpreting Ammonia Levels

Ammonia Nitrogen Concentrations


River Water Quality

River Ecosystem


1.0 or less




1.0 - 3.0


Borderline Healthy


3.0 - 5.0




5.0 or greater


Very Unhealthy

Adapted from "Field Manual for Global Low-Cost Water Quality Monitoring"

The Canadian Water Quality Guidelines (CWQG) for the Protection of Aquatic Life suggest that total ammonia concentrations for freshwater should be no more than 1.3-2.2 mg/L.


Simply put, phosphorus makes life on earth possible. It is an important plant fertilizer and animals require it for:

  • bones
  • teeth
  • blood plasma
  • cell chemistry
  • genetic material

Phosphorus is normally present in rivers at low concentrations. Too much dissolved phosphorus can set off a chain of undesirable events:

  • Extra phosphorus increases the growth of aquatic plants and algae.
  • Bacteria eventually decompose the dead plant material.
  • Decomposition removes dissolved oxygen from the water.
  • Fish die if dissolved oxygen drops to critical levels.

High levels of dissolved phosphorus are an indicator of pollution. Pre-packaged chemistry kits can be used to measure the concentration of dissolved phosphorus. Excessive phosphorus can enter a river from two major sources:

  • sewage effluent from towns and cities
  • storm water that drains from streets and agricultural land

An understanding of basic phosphorus science can help interpret data collected from local rivers.

Phosphorus Background Information

Phosphorus occurs most commonly bonded with oxygen atoms to form a phosphate. Phosphates are essential chemicals found naturally in all living organisms, soil and water. For example, bones contain calcium phosphate.

Surface water supports the growth of microscopic floating organisms called plankton. One type of plankton is algae. The growth of algae and aquatic plants requires phosphates.

Humans use phosphates in dental cements, water softeners, detergents, rust proofing and processed foods. Phosphoric acid is used in cola soft drinks. Dicalcium phosphate is a food supplement for cattle. Calcium phosphate is an ingredient in plant fertilizers.

What is Phosphorus

Phosphorus is a chemical element identified with the symbol (P). It was discovered in 1669 by the German chemist Henning Brand who prepared it from urine samples.

Phosphorus is the 11th most abundant element in the earth's crust and the second most abundant mineral in the human body. Foods containing high amounts of phosphorus include dairy products, eggs, fish, dried fruit, meat, garlic, nuts and whole grains. North Americans ingest about 1500 milligrams of phosphorus daily, which is almost twice the recommended allowance.

Phosphorus combines readily with oxygen to form oxides, phosphates and a mineral called apatite. The phosphorus required by living things is combined with oxygen and called a phosphate (PO4-3). Phosphates are found dissolved in water (inorganic phosphates) and within living tissue (organic phosphates).

Types of Phosphate

Phosphorus occurs most commonly bonded with oxygen atoms to form a phosphate ion (PO43-). However, there are many other forms of phosphate:

  1. Inorganic Phosphates
    Inorganic phosphates are also called mono, reactive, dissolved, soluble or orthophosphates. Inorganic phosphates are not a part of living tissues and they are not carbon-based.

calcium phosphate Ca3(PO4)2
is an inorganic molecule found in bones

Animals require inorganic phosphorus for bones, teeth, blood plasma and a regular heartbeat. Inorganic phosphorus is absorbed by plants from water or soil.

  1. Organic Phosphates
    Organic phosphates are a part of plants and animals, their wastes or their decomposing remains. Organic phosphates consist of a phosphate ion bonded with a carbon-based molecule.

e.g. adenosine triphosphate (ATP)
is an organic phosphate built on a 5-carbon ribose sugar C5H10O5

Organic phosphates are found in cell membranes, genetic molecules (DNA, RNA) and energy storing molecules (ADP and ATP).

  1. Polyphosphates
    Human-made phosphates are complex inorganic compounds called condensed, meta or polyphosphates. These types of phosphates are used in laundry detergents, commercial cleaners, water treatment and industrial boilers.
e.g. trimetaphosphate P3O74- is a polyphosphate

How Is Phosphorus Cycled Through Ecosystems?

There are two main processes occurring in all ecosystems - energy flow and material cycling. Phosphorus is cycled between living organisms and the earth's crust as energy flows through a food web.

Phosphorus in Living Organisms

In aquatic ecosystems, the short-term cycling of phosphorus is through the food web of living organisms.

  • Plants absorb inorganic phosphates through their roots and convert them into organic phosphates.
  • Animals obtain their phosphorus by eating plants or other animals. Animals excrete inorganic phosphorus in urine.
  • Bacteria decompose dead plants and animals and then release inorganic phosphorus back into the environment to continue the cycle.

Phosphorus in the Earth's Crust

If left undisturbed for millions of years, bottom sediments transform into phosphorus-containing rock.During the long-term cycling of phosphorus in the Earth's crust, phosphorus leaches out of soil and weathers out of rock. This inorganic phosphorus flows downstream and eventually accumulates at the bottom of rivers, lakes and oceans.

"Stored" phosphorus may return again to the surface during the uplifting of mountains, during the mining of potash or when bottom sediments are disturbed.

The phosphorus cycle starts again as water erodes the uplifted phosphorus rock.

The Phosphorus Cycle

Phosphorus moves between plants, animals, bacteria, rock, soil and water. This is called a biogeochemical cycle. Three natural processes contribute to this cycling of phosphorus - food webs, decomposition and the rock cycle.


RiverWatch uses the patented Coliscan Easygel method to test for the presence of coliform bacteria. The growth-medium in the bottles contains inhibitors for non-coliform bacteria and pigment colors that identify coliform bacteria.


  1. At the river, use a sterile pipette to add 1 mL of sample water to an Easygel bottle. Label the bottle and keep cool. Dispose of the pipette and wrapper.


  1. Back at school, pour all of the Easygel bottle contents into the sterile and coated Petri dish.
  2. Seal the Petri dish shut with clear tape. Label the dish.
  3. If necessary, gently tip the Petri dish to spread the solution evenly.
  4. Incubate at the warmest room temperature available.

Counting Colonies

  1. After two days of incubation, count the Coliform bacterial colonies:

pink colonies ...

general coliform bacteria that do not necessarily indicate fecal contamination

purple colonies ...

fecal coliforms (E.coli) indicating fecal contamination

white, etc. colonies ...

non-coliform bacteria

  1. Check the colonies against white and black backgrounds to highlight colors.
  2. Counting the total number of pink and purple colonies indicates the number of Coliform bacteria per 1 ml of river water.
  3. Enter your results on-line at . Click on "River Data & Maps" then "Enter Collected Data from your Trip".


  1. Open the Petri dish and add a capful of bleach to kill the bacteria. Reseal, tape, swirl and allow to sit for five minutes.
  2. Dispose in a plastic garbage bag.