Evaluate the level of pollution by biological method

Using creature indicator Bioindicators

1. Scientific basis

Black Fly Larvae (Family Simuliidae)

One of the simple measures to assess the quality of flows is to collect and analyze major indicator organisms (aquatic insects and other aquatic organisms). This method is less expensive and not very complicated, but helps us to determine the overall quality of the water bodies. However, in this method, we need to pay attention to the following issues:

Since this measure is designed to be carried out quickly and simply, only major changes in water quality can be detected accurately. Minor changes in the quality of water resources or the determination of pollution sources are not in the field of investigation of this process.

2. Evaluate water quality by macroinvertebrates

Macroinvertebrates are words that indicate invertebrate organisms that can be seen with the naked eye. In fresh water bodies they are often in the form of insects (or their larvae), crustaceans, molluscs, snails, other types of insects and other types. But in most flows, the number of insect larvae is the majority, and these are useful organisms in assessing water quality. Macroinvertebrates are closely related to their habitats.

Therefore, if the quality of a flow changes, it takes a long time to restore the original population structure. Therefore, the identification of the species present in the flow, we can know the quality of that flow at the time of the survey.

Caddisfly Larvae (Order Trichoptera)

3. Interpret the collected data

• When we use the collected data on the macroinvertebrates to interpret the quality of the flow, all the following aspects need to be considered:
• The diversity of these organisms in the collected sample.
• Percentage of each species in the collected sample.
• Number of organisms per unit area
• Variety of samples (including all three aspects above)
• Tolerance levels of organisms in collected samples.

Factors affecting flow quality can be divided into three large groups

Clams (Class Bivalvia (Pelecypoda))

- Theoretical factors: changes in flow, temperature, sediments due to erosion or construction works that affect the shallow beaches of the flow. The effects of change in physical factors can vary from reducing the number of individual organisms to reducing the diversity of the biota in that area.

- Organic pollution and nutrients: due to animal manure and fertilizer. These types of pollution often lead to a reduction in biodiversity in the survey area and an increase in the number of species that can directly eat organic waste. Pollution of organic matter and nutrients also leads to "blooms of algae" (explosion of algae in water bodies) and an increase in the number of individuals of some other aquatic organisms. Some macroinvertebrates may be removed from the water body and replaced with those that survive in low DO (dissolved oxygen).

Crane Fly Larvae (Family Tipulidae)

- Toxic substances: including chemicals such as chlorine, acids, metals, agrochemicals etc. It is difficult to generalize the effects of toxic substances on macroinvertebrates because of their tolerance to each substances vary by species. However, toxins often cause the macroinvertebrates to disappear completely from the water body.

In traditional ways of assessing water quality by indicator organisms, samples must be collected accurately and carefully. Normally, each sample needs an hour to collect and preserve. Analysis of samples requires a few days time with expensive equipment. This process results in high quality and scientific results.

Crayfish (Order Decapoda)

The new Water Watch Biological Monitoring Project's method is simpler and faster. Samples are collected and analyzed on-site using inexpensive devices to detect contamination from moderate to heavy pollution. If the analysis shows that the quality of the flow is low, one will continue to collect additional samples upstream to determine the problem of contamination.

4. Essential tools

• Although there are many different sampling methods, commonly used sampling instruments are the hoop and trawl. Basic tools can be listed as follows:
• A nylon traction net covers 4 square feet
• A saucepan or a plate of paper
• Documentation for macroinvertebrates
• A form to report results.

Damselfly Nymphs (Order Odonata)

When the sample is taken out of the water, it is placed on the surface of the paper plate or pan for easy observation, then divided into groups and collect the data as stated in the interpretation of the collected data. Cross and fill in the report.

If, after analysis, we assess that the water quality is bad (severely polluted - on average), it is necessary to take more samples to determine the source of pollution. The next steps are conducted as follows:

Step 1: Sampling 1 mi from the old sample collection point upstream (1.6 km).

Step 2: If the analytical results show that the pollution level is still ranked at a bad level, repeat step 1. If the pollution level is ranked at a better level (average - good) we move to step 3.

Step 3: Sampling towards the downstream of the sampling point (with more distance) until it detects the beginning of deterioration of the water quality. The source of the pollution will be somewhere close to this point, conducting a survey of waste sources in this area to determine the cause.

Dobsonfly Larvae (Family Corydalidae)

5. Groups of macroinvertebrates used to indicate environmental pollution levels

• Group sensitive to pollution (will disappear or decline in serious numbers when water sources are polluted)
• Intermediaries (appearing in the area where the pollution begins)
• The group suffers from pollution (available in polluted areas).

6. Note that this process is only for non-intensive studies, so it only provides relatively accurate information. The application of this process will achieve the following results:

• Quick assessment, on-site water quality. From there, conducting additional studies upstream to identify problems causing pollution.
• The equipment and the cost of the research process are low, so nonprofit research organizations can cover themselves.
• Amateur researchers can effectively sample and analyze.

7. Group of organisms sensitive to pollution

• Dragonfly Nymphs (Order Odonata)

  Caddisfly Larvae (Order Trichoptera)
•   Dobsonfly Larvae (Family Corydalidae)
• Mayfly Nymphs (Order Ephemeroptera)
• Water Penny Beetle Larvae (Family Psephenidae)
• Riffle Beetles (Family Elmidae)
• Stonefly Nymphs (Order Plecoptera)
• Other Snails (Class Gastropoda)
• Beetle Larvae (Order Coleoptera)
• Damselfly Nymphs (Order Odonata)
• Dragonfly Nymphs (Order Odonata)
• Scuds (Order Amphipoda)
• Crayfish (Order Decapoda)
• Sowbugs (Order Isopoda)

• Scuds (Order Amphipoda)

  Clams (Class Bivalvia (Pelecypoda))
• Crane Fly Larvae (Family Tipulidae)
• Aquatic Worms (Phylum Annelida and others)
• Pouch Snails (Class Gastropoda)
• Black Fly Larvae (Family Simuliidae)
• Leeches (Class Hirudinea)
• Midge Larvae (Family Chironomidae)

Mayfly Nymphs (Order Ephemeroptera)

Other Snails (Class Gastropoda)

Leeches (Class Hirudinea)

Water Penny Beetle Larvae (Family Psephenidae)

Riffle Beetles (Family Elmidae)

Stonefly Nymphs (Order Plecoptera)

Sowbugs (Order Isopoda)

Midge Larvae (Family Chironomidae)

Kentucky Water Watch
Translation: Le Hoang Viet