What are Macroinvertebrates
Macroinvertebrates are used extensively to indicate water quality determination. These are small (most <10mm) animals that lack a backbone and are visible to the naked eye. They include insect larvae/nymphs, crustaceans, worms and snails. They mainly reside among the substrates and vegetation at the bottom of the river or lake. Some reside in the water column or associated with the surface water (pond skater).
Types of Water Sampling:
This sampling will provide an indication of what biota occur within a sampled are. Generates non-numerical data example is a Kick Sampler
This sampling will provide an estimate of the abundance per unit area for the biota sampled. It generates numerical data or information that can be converted into numbers. Surber Sampler and Hess Sampler are examples of Quantitative sampling.
This sampling allows comparison between sites. Getting an approximate of the quantity or amount of a sample /substance between a quantitative and qualitative result.
The advantages and limitations of using macroinvertebrates as indicators of water quality indicators.
Advantages of macroinvertebrates to indicate water quality
- There is a wide diversity of macroinvertebrates species. – In Ireland, there are over 2000 different species. The various species show a range of pollution sensitivity/ tolerance.
- Most species are relatively abundant which means they are sufficiently abundant to be captured
- They are relatively sedentary, so the occurrence of most can be related to conditions at the place of capture
- Most species have a life cycle of 6 months or longer and thus provide an overview of prevailing physical/ chemical conditions.
- Sampling macroinvertebrates is relatively easy and cheap.
- Macroinvertebrates respond to environmental stress so the presence or absence of a particular species can indicate the presence of an environmental stressor such as pollution.
Limitations of macroinvertebrates to indicate water quality
- Lack of response to all types of contaminants, don’t respond to all impacts
- Seasonal changes in distribution – prevent comparison of different seasons
- A large number of samples required
- Difficult to identify to species level.
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