Biological Water Quality Indicators

There are plenty of good reasons to want to know if the creek around your property or your favorite stream that you kayak on the weekend is being contaminated. Maybe the lake you are fishing on contains pollution that is threatening it. Chances are you’ll see or smell it. What are Biological Water Quality Indicators?

By measuring Biological Indicators using your senses of smell and sight you will be able to get some clues and symptoms of the health of a body of water along with the ecosystem that is supported by it without testing the water. Fish & insect activity on the edge, birdlife, surface color, or sheen.

In most areas all over the country, there are drainage creeks and retention ponds that relieve areas from flooding and groundwater that constantly change the ecosystem and if we’re not aware and know the symptoms, it can degrade them and make them sick.


Water is one of the most vital resources on Earth, sustaining life and supporting ecosystems across the planet. Ensuring the quality of water is essential for the well-being of both humans and the environment. Biological water quality indicators play a crucial role in assessing the health of aquatic ecosystems and monitoring the impacts of human activities on water bodies.

In this article, we will explore the concept of biological water quality indicators, examining the diverse range of organisms and processes that are used to evaluate water quality. By understanding these indicators and their significance, we can gain insights into the overall health and integrity of aquatic environments, as well as identify potential threats and challenges facing our water resources.

From macroinvertebrates to microbial communities, each biological indicator offers unique insights into the complex dynamics of aquatic ecosystems. By examining the presence, abundance, and diversity of these organisms, scientists and water resource managers can assess the impacts of pollution, habitat degradation, and other stressors on water quality.

Throughout this exploration, we will delve into the characteristics of various biological indicators, their ecological significance, and their utility in water quality assessment programs. By recognizing the importance of biological indicators in monitoring and managing water resources, we can work towards safeguarding this precious resource for current and future generations.

Biological Water Quality Indicators

There are 4 main ways of measuring the quality of water:

  • Take samples of the water and measure concentrations of chemicals that suspect that the body of water may contain. If the concentrations are too high and determined to be dangerous, the water is determined to be polluted. Measurements like this are called Chemical Indicators.
  • Another way to measure water quality involves examining fish, insects, and other aquatic life. The whole ecology, which means the area around the body of water that will support all life.  If many different types of creatures are living in and around the body of water, the quality of the water is likely to be very good these are called Biological indicators
  • Indicators that include both fringing (riparian) habitats and instream habitats including the width, continuity, extent of shading, and species composition are called Habitat Indicators. Indicators of instream habitat include measures of the extent of scouring and bank erosion and the presence of woody debris (fallen trees, etc) that provide important habitat for many species.
  • In freshwater, changes to flow are often the main cause of aquatic ecosystem health degradation; the Murray-Darling system is an example of this. Assessing the changes is therefore important. Changes to natural flow caused by humans are varied and include changes to peak flows, base flows, no-flow periods, and seasonality of flows are called Flow Indicators.

Long before Chemical Indicators are used, Biological Indicators give clues to everyone who uses the body of water and who comes in contact with this ecosystem. Water can provide certain indicators that there is a problem. There could be a biological indication that the health of the body of water is struggling. There could be a problem with smaller baitfish, frogs, or minnows that are missing from the environment of the area. There could be color changes on the surface or temperature changes in the water. These are all signs and clues of water contamination in the water. There could be fewer ducks or any bug activity.  Algal blooms that have erupted overnight. All symptoms of a degrading ecosystem.

If a creek is the source of the pollution then that creek can be traced back to the source, without costly analytical equipment that a normal person would not have access to. All you would need is your eyes and nose and the will to do something about it. Most city governments have officials who answer complaints from residents on environmental matters.

To fully grasp the health of our aquatic ecosystems, it is crucial to consider various water quality indicators. These indicators, often measured in levels or properties, give valuable insights into the condition and overall water quality. They serve as benchmarks, letting us understand whether water is fit for human consumption, wildlife habitation, or recreational use. So let’s dive into the essential quality indicators that serve as our water’s report card.

Firstly, the temperature of water is a fundamental water quality indicator. Various species thrive at different temperature levels, so maintaining the right temperature is critical for aquatic life. Secondly, pH, which measures the acidity or alkalinity, is another vital quality indicator for water. Proper pH levels ensure a stable environment for organisms and are therefore closely monitored.

Another significant water quality indicator is dissolved oxygen. This is the lifeblood for aquatic organisms and fluctuating levels can indicate serious changes in waterquality. Moving on, turbidity, which refers to the clarity of water, affects how much sunlight penetrates through the water body and can influence plant growth and wildlife sustainability. Monitoring turbidity levels is thus essential for assessing water quality.

Nutrients, specifically nitrogen and phosphorus, are also key quality indicators to watch. While they are necessary for ecosystem health, excessive levels can upset the delicate balance, causing issues such as algal blooms. Lastly, the presence of harmful substances, such as heavy metals or pathogens, which compromise water quality, are critical indicators that must be monitored to safeguard both human and ecological health.

Water Flow Quality Indicators in the Ecosystem

Water quality biological indicators are organisms or biological characteristics that can be used to assess the health and condition of water ecosystems. These indicators provide insights into the overall quality of water and can help identify potential pollution or environmental stressors. Here is a list of some common water quality biological indicators:

  1. Macroinvertebrates:
    • Mayfly larvae
    • Stonefly nymphs
    • Caddisfly larvae
    • Aquatic beetles
    • Dragonfly and damselfly nymphs
  2. Algae:
    • Diatoms
    • Green algae
    • Blue-green algae (cyanobacteria)
  3. Fish:
    • Sensitivity and diversity of fish species
    • Presence of indicator species
  4. Benthic Microorganisms:
    • Bacteria
    • Protozoa
  5. Plants:
    • Aquatic macrophytes
    • Presence of sensitive or pollution-tolerant plant species
  6. Biochemical Oxygen Demand (BOD):
    • Measurement of the amount of oxygen consumed by microorganisms during the decomposition of organic matter
  7. Microbial Pathogens:
    • The presence of fecal coliforms and other indicators of microbial contamination
  8. Amphibians and Reptiles:
    • Presence and health of amphibians and reptiles in or near water bodies
  9. Mollusks:
    • Freshwater mussels
    • Snails
  10. Trophic State Index (TSI):
    • Evaluates the nutrient status of a water body based on factors like chlorophyll concentration, total phosphorus, and water clarity.

These indicators are used collectively to assess the ecological integrity and overall health of aquatic ecosystems. The presence, absence, or abundance of these organisms can provide valuable information about the impact of human activities on water quality.

Understanding these water quality parameters enables us to take actionable steps to ensure the safety and purity of our water. Regular testing reveals the properties and levels of these quality indicators, providing a snapshot of water quality at any given moment. Measurements that fall within the acceptable range of these quality indicators mean water quality is generally favorable. Conversely, any deviations prompt further investigation and potential remediation to preserve the water quality.

Monitoring water quality is a complex task, but keeping an eye on these six fundamental properties—temperature, pH, dissolved oxygen, turbidity, nutrients, and harmful substances—provides a manageable framework. As successive tests gauge these levels, we gain a clearer picture of the quality of the water and can act to protect one of our most precious resources.

A person who uses the playground across the street every day after work to chip some golf balls with his 9-iron might also notice that there a strange smells coming from the storm drain by the creek. The same with the Kayaker that uses the river at lower tides for smallmouth bass on the weekends.

Understanding Water Quality Indicators for Ecosystem Health

Water quality indicators for ecosystem health encompass a range of parameters that assess the overall condition of aquatic environments. Biological indicators, including macroinvertebrates and algae, provide insights into the impact of pollutants on living organisms within water bodies.
Additionally, chemical indicators such as dissolved oxygen, nutrient levels, and pH contribute to a comprehensive understanding of water quality.
Physical parameters like temperature and turbidity further influence ecosystem health. By monitoring these indicators, scientists and environmentalists can gauge the resilience and well-being of aquatic ecosystems, aiding in the development of effective conservation and management strategies.
Indicators of Biological Water Pollution

Nearby activities including gas stations, agricultural use of land, an industrial complex, nearby junkyards, or landfills can affect water quality. There could be changes in the structure of land around the body of water, or the source of the water, like a creek that is feeding the system.

Everything is connected to that ecosystem around the body of water. Visually you can map out any changes that may affect the area of the water. You are as much an expert by using the ecosystem as much as you do, and you are more apt to notice a change.

If contaminated water enters a creek from an unknown source the surface of the water may take on a grey or orange color, It may also smell like washing powder or detergent, which is a key sign of ‘misconnected’ household pipes. There is a distinct difference in color and odor for someone like you to see.

Road runoff into a stream or creek can look like suds, cloudy water, or a whitish color that could indicate road salt being washed off the surface. Once in the groundwater, the salt could enter a Well supply and the drinking water and could ruin the Well.

Neighborhood creeks sometimes run through the middle of properties. There could be signs of suds, plastic bags, women’s products, or even toilet paper that will get caught up on the rocks in the creek. That’s an indication of a blocked sewer line or a broken sewer lateral. This kind of thing could be happening for months or even longer without anyone picking up on it. It could cause a lot of damage to the creek in the neighborhood.

Oily sheens on the water that are rainbow or blueish are signs of contaminants entering the water source from a connection or a path that is not supposed to be there.
Probably the worst sign of organic pollution in a stream is when normal green or brown stream algae become replaced by colorless slimes formed by Sphaerotilus bacteria, commonly known as “sewage fungus”.
This is generally to be considered unexpectable in any stream or river anywhere and should be reported. This bacteria will destroy the receiving water.

Foam forms when surfactants are present in the water. Some surfactants are naturally forming but if the foam is a pure white color with a fragrant smell, this is a sign of pollution. The difference is very clear.

The Role of Bio-indicators in Water Quality Assessment

Bioindicators play a crucial role in water quality assessment by reflecting the health and integrity of aquatic ecosystems. These organisms, such as macroinvertebrates, algae, and certain fish species, respond to changes in water quality, serving as indicators of environmental stressors or pollution.

The abundance, diversity, and behavior of bioindicators help scientists identify and quantify the impact of contaminants on water bodies. Additionally, bioindicators provide a holistic view of ecosystem health, allowing for the early detection of potential issues and informing sustainable management practices.

Their role in water quality assessment supports effective conservation efforts and the development of strategies to protect and restore aquatic environments.

Fish Kills are a clear sign for all to see that something in the water is not right. Fish kills can result from the presence of toxic chemicals, eutrophication lack of dissolved oxygen, or elevated levels of phosphorus or bacteria from agricultural runoff.  Sometimes it’s maybe what you don’t see. The presence of small aquatic life insects, minnows, or frogs will be missing in the picture if the picture is not healthy. If you are in tune with what you used to see and it’s suddenly missing then something may have happened there.

Discolored Water may not stand out but in most cases whatever the contaminant is in the water, if it has color will most likely change the color of the water.

Color is a Standard test for the quality of water in laboratory analysis.

Phosphates and other Nutrients that are in high doses are considered pollutants in receiving rivers and streams.  Wastewater effluents that discharge into a stream can be a troubled spot. Long before testing is done the receiving stream can give hints of contaminants entering the environment.

Although nutrients are needed for healthy biological activity, too much too soon will cause an algal bloom. The receiving stream won’t be able to sustain it, the alga bloom will die and the bacteria that decompose the Algae will rob oxygen out of the water and will kill other aquatic life in the stream. Eventually, the stream becomes dead because of the low Dissolved Oxygen content that is necessary for all healthy biological environments.

Summing Up the Main Indicators Of Water Quality

The main indicators of water quality encompass biological, chemical, and physical parameters. Biological indicators, such as macroinvertebrates and algae, reveal the impact of pollutants on aquatic organisms. Chemical indicators, including dissolved oxygen, nutrient levels, and pH, provide insights into overall water quality and pollution levels.

Physical parameters like temperature and turbidity influence the ecological balance of water ecosystems. The collective assessment of these indicators offers a comprehensive understanding of the health and resilience of aquatic environments, aiding in the development of effective conservation and management strategies to ensure the sustainability of water resources.

All types of smells can indicate pollution concerns. Chemicals can be dumped directly into the stream or through the storm drain that ends up in the stream around the vicinity. A person who regularly visits the area around a stream or a lake will be the one who will notice the effects between one week to the next.

There could be subtle effects or big noticeable changes like an oil spill or the smell of smoke in the woods off the jogging path in the park that shouldn’t be there and is a sign that there is a fire that needs to be reported.

Earthy or musty odors, along with visual evidence of blue-green algae, also known as cyanobacteria, may serve as a warning that harmful cyanotoxins and other contaminants are present in lakes or reservoirs. In a newly published USGS study of cyanobacterial blooms in Midwest lakes, taste-and-odor compounds were found almost every time cyanotoxins were found, indicating odor may serve as a warning that harmful toxins are present.

Some Industrial waste that is draining into a body of water could smell sweet, dairy, or maybe like fuel oil that could be leaking from an underground tank into a creek that’s finding its way into a lake where you use your canoe fishing for largemouth. You may not see the orange waste product coming into the lake. But you can smell the odor. Detergent-like chemicals have odors and are transported along roads that access lakes and creeks. You are using your sense of smell at a place where you have been 100 times before, you’ll know before anyone else does.

The use of pesticides we use in our gardens finds its way into the creeks and streams that surround our properties. A lot of toxic pollution also enters the groundwater from highway runoff where ditches are dug to keep traffic moving.

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Causes of Water Pollution & Water Quality

Certainly, water pollution can arise from various sources and activities. Here is a list of some common causes of water pollution:

  1. Industrial Discharges:
    • Release of pollutants and chemicals from industrial facilities into water bodies.
  2. Agricultural Runoff:
    • Pesticides, fertilizers, and herbicides from agricultural lands enter waterways.
  3. Urban Runoff:
    • Pollutants like oil, heavy metals, and debris washed off from streets and urban areas during rainfall.
  4. Sewage and Wastewater:
    • Disposal of untreated or poorly treated sewage and wastewater into rivers and oceans.
  5. Oil Spills:
    • Accidental or deliberate release of oil into water bodies, causing extensive environmental damage.
  6. Mining Activities:
    • Disposal of mining waste and chemicals into waterways, leading to contamination.
  7. Improper Waste Disposal:
    • Dumping of solid waste, plastics, and hazardous materials into water sources.
  8. Atmospheric Deposition:
    • Airborne pollutants, including heavy metals and toxins, settle into water bodies through precipitation.
  9. Marine Dumping:
    • Discarding waste, including plastics and chemicals, directly into the oceans.
  10. Construction Activities:
    • Sediment runoff and release of construction-related pollutants into nearby waterways.
  11. Aquaculture Practices:
    • Excessive use of antibiotics and chemicals in aquaculture operations leads to water contamination.
  12. Global Warming:
    • Changes in temperature and climate patterns affect water quality and ecosystems.

Addressing these causes is crucial for preventing and mitigating water pollution, and ensuring the sustainable use and preservation of freshwater resources.

Environmental Monitor | Road salt runoff flowing into streams near Cornell approaches ocean-like salinity
Environmental Monitor | Road salt runoff flowing into streams approaches ocean-like salinity

Highways are typically covered with a cocktail of toxic chemicals these come with smells that are familiar from everything from spilled fuel and brake fluids to bits of worn tires (themselves made from chemical additives) and exhaust emissions. When it rains, these chemicals wash into drains and rivers. Oil-based products like paint thinners and solvents used for cleaning medals all end up in our environment somewhere.

It is not unusual for heavy summer rainstorms to wash sewage from treatment overflows or failed septic tanks into neighboring creeks.

Sewage and toxic chemicals that are illegally dumped into rivers in high concentrations can kill large numbers of fish overnight.  If it happens once it probably happens every time it rains hard. The smell from that stuff is pretty easy to figure out. Smells like this are symptoms of water being contaminated. 

Rainstorms wash petroleum used in blacktops, off the highway, and into drainage ditches. It has been estimated that, in one year, the highway runoff from a single large city leaks as much oil into our water environment as a typical tanker spill.

After a hard summer rain, you can see the oil that is coated on a freshly paved road. Your car can slip right off the road after it’s been repaved and a summer thunderstorm washes it down.

A lot of chemicals heavy metals and pesticides are invisible to the eye and can’t be smelled they have no odor they are automatically suspected in Drinking water. A Water Filter and Well water testing is needed to use it. All water is connected and recreational water should be guarded too.  Because recreational water is tomorrow’s Drinking Water.

The average person like us can learn to use Biological Indicators and our senses of smell and sight to evaluate symptoms and the health of our creeks, streams, or lakes in our neighborhoods every time we use them.


The presence, condition, and number of types of fish, insects, algae, plants, and other organisms provide important information about the health of aquatic ecosystems. Studying these factors as a way of evaluating the health of a body of water is called biological assessment. Biological criteria are a way of describing the qualities that must be present to support a desired condition in a water body and serve as the standard against which assessment results are compared.

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EPA-Biological Water Quality Criteria


  • What are biological water quality indicators?  Biological water quality indicators are living organisms used to assess the health of water ecosystems. Common examples include macroinvertebrates, algae, and certain fish species.
  • Why are biological indicators important in water quality assessment?  Biological indicators provide real-time and holistic insights into the impact of pollutants on aquatic life. They reflect the overall health and resilience of water ecosystems.
  • How do scientists use macroinvertebrates as biological indicators?  Scientists analyze the presence, abundance, and diversity of macroinvertebrates to gauge water quality. Certain species are sensitive to pollution, making them valuable indicators.
  • What role do algae play in water quality assessment?  Algae serve as indicators of nutrient levels and can indicate the presence of harmful algal blooms. Changes in algal populations can signal disturbances in the aquatic environment.
  • Can fish be used as reliable biological indicators?  Yes, fish are often used as indicators of water quality. Changes in fish populations, behavior, and species composition can provide valuable information about the health of aquatic ecosystems.
  • How can the information from biological indicators be applied to water management?  Data from biological indicators help formulate effective water management strategies. They aid in identifying pollution sources, assessing the success of conservation efforts, and making informed decisions to protect water quality.

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