Appendix 9. Macroinvertebrate Surveys

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Scientific best practice

See England et al. (2021) [1]

1. Introduction to macroinvertebrate surveys

Invertebrates exist in a wide range of aquatic habitats from silted pools to gravel riffles and boulders in fast flowing upland rivers. Invertebrate species are sensitive to the physical, chemical and biological condition of water courses which makes them good indicators of habitat quality and overall ecosystem health. Different species can be particularly sensitive to or tolerant of certain conditions, meaning that their presence or absence can be used to assess the impacts of pressures on water courses.

The two main approaches to macroinvertebrate surveying are unit-time and unit-area surveys. Unit-time surveys are a qualitative (or semi-quantitative) method where macroinvertebrates are collected over a defined length of time, usually with the kick sampling technique. Unit-area surveys are a quantitative method where invertebrates are collected over a standardised area to allow for robust statistical assessments and comparison of samples. The unit-area method is recommended for projects where robust scientific outputs are desired, however these studies are often time intensive and require expertise. The advantage of the unit-time approach is that it can be applied over a large area in less time, and with the use of citizen scientists. This may be more suited to a catchment scale assessment.

2. Unit-time surveys

This involves collecting invertebrate samples for a specific unit of time is a standard approach to sample collection which is applied widely. It is a semi-quantitative approach usually undertaken using a kick-sweep sampling technique.

Standardized timed samples are generally collected using a 3-minute kick/sweep sampling. This technique is utilized within the ARMI citizen science monitoring. The Statutory Agencies apply a 3-minute kick-sample supplemented by a 1-minute hand search to assess ecological status for the WFD and within their wider river assessments. This is known as the RIVPACS monitoring protocol.

Find out more about unit-time surveys

3. Unit-area surveys

To obtain replicated samples and allow robust statistical assessments, a quantitative approach to sampling is recommended using a unit-area method. A variety of quantitative sampling devices are available, all of which enable samples to be taken from a given area and allow results to be calculated for a spatial area. Due to the need to identify and count all invertebrates obtained within a sample this approach is time consuming. It is only applied by professionals or academics in specific studies. When appraising a river restoration scheme, it is important to follow the – BACI principles (Before, After, Control, Impact) (Underwood, 1994).

Find out more about unit-area surveys

4. Sampling benthic invertebrates in deep rivers

Deep rivers aren’t a well-known environment because of the sampling difficulties. This section outlines methods to collect data on the macroinvertebrate community in habitats not wadeable and unsuitable to use the kick-sampling methodology.

Find out more about sampling invertebrates in deep rivers

5. Community involvement

Community involvement through citizen science can play a very useful role in supplementing and complementing the invertebrate monitoring undertaken by professionals. Not only does citizen science increase the amount of environmental data that can be collected but increases public awareness and involvement in local environmental issues. Within the UK the Riverfly Partnership’s Anglers Monitoring Initiative forms the basis of citizen science monitoring of invertebrates.

Find out more about community involvement in macroinvertebrate surveys

6. References

England, J.; Angelopoulos, N.; Cooksley, S.; Dodd, J.; Gill, A.; Gilvear, D.; Johnson, M.; Naura, M.; O’Hare, M.; Tree, A.; et al. (2021)
Best Practices for Monitoring and Assessing the Ecological Response to River Restoration. Water 2021, 13, 3352. https://doi.org/10.3390/w13233352
Hall, N. (2007)
Assessing the Impact of Flow Deflectors on Macroinvertebrate Communities as pat of the STREAM restoration project, Thesis submitted in partial fulfilment of the requirements for the degree of Water Management, Cranfield University, 54pp.
JNCC, (2003)
Monitoring Southern Damselfly, Coenagrion mercuriale. Conserving Natura 2000 Rivers Monitoring Series No. 8, English Nature, Peterborough.
Killeen, I. J., Morrkens, E. A. (2003)
Monitoring Desmoulin‟s Whorl Snail, Vertigo moulinsiana. Conserving Natura 2000 Rivers Monitoring Series No. 6, English Nature, Peterborough.