by Sydney Zinner
What can macroinvertebrates tell us about water quality?
Alabama boasts a rich diversity of natural wonders, from lush forests to winding rivers. Among these treasures lies the tiny hidden world of macroinvertebrates beneath the surface of Alabama’s waters —a world teeming with life, often overlooked. What can these tiny critters tell us about water quality?
If you are familiar with Alabama Water Watch, you are likely familiar with our logo, the caddisfly. Read on to learn about how our friend the caddisfly and other creek critters can tell the story of our waters.
What are macroinvertebrates, and why are they used as water quality indicators?
Alabama Water Watch trains citizen scientists to collect benthic macroinvertebrates, which we informally and affectionately refer to as “creek critters.” These critters are:
- Benthic refers to living on the bottom of a waterbody (in the benthos),
- Macro means large enough to see with the naked eye, and
- Invertebrate refers to animals without backbones.
The presence or absence of several types of benthic macroinvertebrates is one of the best ways to assess the level of human disturbance and pollution in streams and rivers (ex. stream health) for several reasons. Each species has unique characteristics regarding habitat requirements, life history, behavior, and pollution tolerance.
Macroinvertebrate sampling (also called stream biomonitoring or bioassessment) serves as a cost-effective and efficient method for long-term monitoring, providing valuable data for informed decision-making and sustainable management practices.
What is stream biomonitoring?
Stream biomonitoring (or bioassessment) is the use of living organisms as water quality indicators to assess a waterbody’s condition and health. Volunteer Monitors assess macroinvertebrate communities in streams (aquatic insects, snails, worms, etc.) as water quality indicators.
Volunteers identify and group critters by pollution tolerance to calculate the biotic index, which is then used to determine if water quality is poor, fair, good, or excellent.
The Biotic Index (BI) of water quality is based on the pollution tolerance of each type of macroinvertebrate found in the sample; therefore, giving more importance to diversity than abundance. The number of any type is not directly used to calculate the index, but knowledge of their abundance (rare, common, or abundant) is important for understanding water quality conditions and trends.
Certain species have specific tolerances to pollution levels, categorizing them into three groups based on their sensitivity:
Group 1: Pollution-Sensitive Organisms
These macroinvertebrates are highly intolerant to pollution and thrive in clean, well-oxygenated waters. Examples include:
- Stoneflies
- Mayflies
- Some Caddisflies
- Some beetle larvae
The presence of these species indicates good water quality, with minimal pollution levels. Their absence or decline may signal deteriorating conditions, prompting further investigation.
Group 2: Moderately Pollution-Tolerant Organisms
These macroinvertebrates can tolerate a moderate pollution level and are often found in slightly degraded environments. Examples include:
- Dragonfly nymphs
- Damselfly nymphs
- Blackfly larvae
- Crustaceans (ex. crayfish and scuds)
- Some Caddisflies (like the Hydrophsyche, which inspired AWW’s logo!)
While the presence of Group 2 organisms suggests some level of disturbance, their abundance may indicate a slight decline in water quality. Monitoring their populations provides valuable insights into changing environmental conditions and potential stressors.
Group 3: Pollution-Tolerant Organisms
These macroinvertebrates exhibit high tolerance to pollution and thrive in degraded or polluted waters. Examples include:
- Midge larvae
- Some snails
- Leeches
- Aquatic worms
The dominance of Group 3 species typically indicates poor water quality, with elevated pollution levels and decreased oxygenation. Their prevalence may signify ongoing pollution sources or environmental stress, warranting immediate attention and remediation efforts.
“Chemical measurements are like taking snapshots of the ecosystem, whereas biological measurements are like making a videotape.” Dr. David Rosenberg
What are examples of common critters in Alabama and how can I identify them?
Macroinvertebrate sampling is a commonly used method because of the relative abundance of them in most any waterbody. Different species will certain habitats and climates, but critters commonly found in Alabama include (but are not limited to!):
Alabama Water Watch, along with many other citizen science groups, identify common critters to the “Order” level of taxonomy.
You can become familiar with identifying critters by Order through online resources such as Macroinvertebrates.org and iNaturalist. Macroinvertebrates.org is a great tool for seeing detailed close-ups of critters as well as lists of identifying features.
iNaturalist allows you to explore observations collected by other citizen scientists, naturalists, and researchers. For example, check out global observations of our friend the Caddisfly.
How can I learn to conduct stream biomonitoring?
GET CERTIFIED BY AWW! Learn how to collect, identify, and categorize macroinvertebrates to calculate a Biotic Index through hands-on field training. Training also covers:
- The Water Environment
- Ecology of Streams, the Stream Continuum, and Microhabitats (riffles, pools, runs, etc.)
- Non-Point Source and Point Source Pollution
- Life Histories and Feeding Groups of Macroinvertebrates
- Principles and Practices of Stream Biomonitoring
- Developing a Monitoring Plan
Check out the AWW Events Calendar for Stream Biomonitoring certification opportunities. Stream Biomonitoring trainings are usually held once or twice per year.
Benefits of becoming a certified Stream Biomonitor through AWW:
- Submit data to the statewide AWW database
- Help with data interpretation
- Borrow monitoring equipment
- Be part of a statewide network of volunteers
MacroBlitz
Even if you are not a certified AWW Stream Biomonitor, you can look for critters and help catalogue biodiversity in your area through MacroBlitz. MacroBlitz is an iNaturalist project established by the South Dakota Discovery Center and funded by the National Geographic Society. The project has an amazing library of resources for interested citizens.
Anyone can participate!
The wonderful thing about citizen science is that ANYONE can participate! Stream biomonitoring is a great educational tool to engage citizens of all ages in stewardship of Alabama’s natural heritage.
Citizen science initiatives empower individuals to participate in data collection, fostering a sense of ownership and responsibility for local ecosystems. By involving communities in monitoring efforts, researchers not only gather valuable data but also cultivate a culture of environmental awareness and activism, ensuring the long-term sustainability of Alabama’s water resources.
Responsible collection of macroinvertebrates
All critters collected during a bioassessment are returned to the waterbody from which they were found. Volunteers do not sample for protected species.