Waterwatch Australia national technical manual

Module 3 - biological parameters
Waterwatch Australia Steering Committee
Australian Government Department of the Environment and Heritage, 2004
ISBN 0 6425 4856 0

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Using macro-invertebrates to understand the health of the habitat

Understanding the health of the habitat involves following standardised sampling and sorting procedures and identification to the level of order or family. This method produces data of known quality and can be used to assess the condition of sites in the waterway.

The SIGNAL 2 score provides an indication of things that might be affecting waterbugs at a site, such as water quality or habitat. SIGNAL stands for 'Stream Invertebrate Grade Number – Average Level'. Each type of macro-invertebrate has a grade number from 1 to 10, based on its sensitivity to organic pollution. A low-grade number means the waterbug is more tolerant of water pollution. More sensitive waterbugs have high grade numbers. The grade numbers for groups containing phyla, classes and orders can be used but the most accurate SIGNAL scores for a site are obtained by using grade numbers of families.

SIGNAL 2 scores are based on the number of different types of water bugs in the sample. The procedure described here does not use relative abundance but weighting of abundance is possible.

Templates for result sheets required for monitoring macroinvertebrates to understand river health can be found in Appendix 1 of this module (major groups and family level).

Some material in this section has been sourced from SIGNAL 2 Manual, Bruce Chessman, 2003 (www.deh.gov.au/water/rivers/nrhp/signal/index.html).

Overview of procedure

Before rushing out to sample macro-invetebrates, it is important to decide on the objectives of your monitoring program (see Module 2 on how to develop a monitoring plan). It is also a good idea to undertake a site description assessment to document any changes at your site over time to aid you in interpreting your results (a site description record sheet is available in Appendix 1).

  1. Decide whether you will identify waterbugs to family level or major group level (order, class and phylum).
  2. Assemble collection equipment and other supplies.
  3. Follow directions to the first site and find your riffle or edgewater location. It is a good idea to note down or even better draw the location of your site and monitoring location .
  4. Fill in the first page of the Macro-invertebrate Record Sheet(s).
  5. Use the kick sampling or sweep sampling technique to collect macro-invertebrates. Take each sample thoroughly (at least 3 minutes and 10 metres of stream for kick or sweep sampling). Be sure to disturb the stream bed.
  6. Sort your sample on site. Aim to pick at least 100 animals, preferably 150 to 200. Try to find as many different types as possible.
  7. Record the number of macro-invertebrates you found at your site in the Macroinvertebrate result sheet.
  8. Calculate the sum of the individual grade numbers for the water bugs in your sample.
  9. Divide the sum by the number of different groups (families or order class phyla) you collected. This is the SIGNAL 2 score for your site.
  10. Return material to the stream and clean up your site before leaving. Wash your hands to remove parasites when you finish.

Always keep the riffle and edgewater samples separate from one another and in particular only compare samples that have been collected in the same manner. Sampling must not be done when the stream is swollen or turbid due to recent rains. Refer to the notes on safety in Modules 1 and 4.

Equipment

The general equipment you will need for both the kick sampling and sweep sampling techniques includes:

Steps for kick sampling riffles

Kick sampling in riffles is the recommended technique as it is used by professional aquatic ecologists, and riffles contain the greatest diversity of macro-invertebrates.

  1. At your site, select a shallow fast-moving area of broken water (riffle) with a depth of 10–50 centimetres and rocks of tennis ball to soccer ball size.
  2. Approach your riffle from downstream to avoid disrupting the macro-invertebrates before you are ready to collect. You should start at the bottom and work 10 metres upstream.
  3. Position yourself at the downstream end of the riffle. Face downstream and hold the net in front of you with the opening facing upstream so dislodged macro-invertebrates are carried into it by the current. Be sure the net fits tightly against the stream bed.
  4. Disturb the stream bed with your feet. Use your feet to dig well into the stones and turn them over. Continue this process while working upstream over a distance of 10 metres in both the fastest and slowest parts of the riffle. Rub at least two stones by hand to dislodge organisms. If you turn over any large stones, please turn them back again after sampling.
  5. Use a forward scooping motion to lift the net from the water to stop waterbugs escaping. Your net should be free of mud but you may have to flush the net with water to remove mud before sorting.
  6. Gently empty contents of the net into about 2 centimetres of water in a large flat white tray for sorting.
  7. Rinse the net so all the animals and debris are removed before taking another sample.
Figure 7: Kick sampling riffle sites
Figure 7: Kick sampling riffle sites. Source: TVA Clean Water Initiative, 1995

Steps for sweep sampling edgewaters

This technique samples the organisms living in edgewaters of waterways where riffles are unavailable. The best edgewater sites have overhanging or emergent vegetation, undercut banks or root mats that provide suitable living places for macro-invertebrates.

  1. Use your net to make short upward sweeping movements from about 1 metre out from the bank to the bank edge, disturbing aquatic vegetation if present to dislodge macro-invertebrates.
  2. You should move steadily upstream over a total length of 10 metres.
  3. You will need to stop regularly to flush mud out of your net. The sample should be free of mud before sorting.
  4. Gently empty the contents of the net into about 2 centimetres of water in a white tray for sorting. Keep the sample separate from riffle samples.
  5. Rinse the net so all the animals and debris are removed before taking another sample.

Sorting your samples

Do not mix samples from different habitats, for example, from riffles, edgewaters, or artificial substrates. Each habitat supports a distinct community of macro-invertebrates.

Sort your samples at the site. However, if you have to leave the site before sorting due to lack of time, bad weather or other constraints, take your samples back to your work-base. You can do this by placing your samples into garbage bags with water, loosely tying off the top and placing the bags into large plastic buckets. Remove most of the air from the bags to prevent buffeting during the trip back. If it is a hot day or a long drive, use battery powered aerators to maintain dissolved oxygen levels. Return all organisms to the waterway after noting them on your Record Sheet.

To ensure that an adequate number of macro-invertebrates are collected from the sample, you should aim to transfer around 100 to 200 waterbugs from the sorting tray to ice-cube trays. This generally takes one person between 30 minutes and an hour depending on their experience and the site.

  1. Spread the sample out over the bottom of a white tray. Spend a little time watching the macro-invertebrates. See how they move and look at the different shapes and colours (the colours change when they are preserved).
  2. Add about 1 centimetre of water to the wells in your ice cube tray. Pick through your sample in the sorting tray. Use a pipette, tweezers, spoon or brush to transfer your macroinvertebrates to the wells in the ice cube tray. Place animals belonging to the same group in the same well of your ice cube tray.
  3. For the first 10–20 minutes, transfer any animal that you see from the sorting tray into the ice cube trays. For the last 10–20 minutes, look particularly for animals that are uncommon. Fast moving macro-invertebrates will be obvious but some will only start to move after 10 minutes or so. If after 30 minutes you find an invertebrate you haven’t seen before, sort for another 10 minutes until you find no new taxa.
  4. There are many key guides available to identify your macroinvertebrates, see the following section for a list of further resources. A x10 magnifying glass or low power binocular microscope is useful for looking closely at the animals.
  5. Count the number of each type of animal in each well of the ice cube trays. You can record your results on either the result sheet for SIGNAL 2 for major groups or SIGNAL 2 for families. If you find a macro-invertebrate you cannot identify, record this on your result sheet, giving a brief description of what you found. Consult your Waterwatch Coordinator or macro-invertebrate guides listed in the following section..
  6. When you have finished, return the animals to the water, as close as possible to the collection site.
Figure 8: Sorting your sample
Figure 8: Sorting your sample. Source: Kruger, T and Lubczenko, V, 1994

Identifiying macro-invertebrates – further resources

You can identify macro-invertebrates either by comparing collected specimens with illustrations of the various groups, or by using identification keys.

Identification keys generally consist of a series of paired descriptions of particular bodily features. Each pair, called a couplet, is numbered. You begin with the first couplet and select the description that best fits the specimen you are ‘keying’. The chosen alternative will direct you to another numbered couplet. Continue this process until you have eliminated enough wrong alternatives to positively identify the specimen.

Some Waterwatch manuals contain keys or pictorial guides to macro-invertebrates which are a good start. If you are wanting more detailed information there is a range of books, compact discs and web sites which are very useful (see Further resources for a list).

Setting up a reference collection

It is a very good idea to build a reference collection of aquatic invertebrates. Place up to three or four of each kind in a glass jar or vial. The sample glass jars or vials should be filled with 90 per cent ethanol and sealed to prevent the alcohol from evaporating. You can use methylated spirits if you cannot get ethanol. Add a label that records the type of macro-invertebrate, date and place of collection. You should check these samples every few months and top up the alcohol if necessary. You may need to get permission from your state government agency to sample and preserve macroinvertebrates.

By building a reference collection you will come to know the macro-invertebrates much better and it will make it easier for others to identify their samples. You should get your reference collection checked by an aquatic ecologist. Future Waterwatchers and experts can look at your reference collections and see what kinds of animals lived at your sites in the past.

What are your quality control measures?

Quality control includes the steps you take to make sure your data are accurate and precise. The main quality control challenge is to make sure the sample collected is representative of the macro-invertebrate community living at the site and animals are correctly identified.

Internal quality control checks

The following internal quality control checks are recommended.

External quality control checks

The following external quality control checks are recommended.

SIGNAL stands for ‘Stream Invertebrate Grade Number – Average Level.’ It is a simple scoring system for macroinvertebrate (water bug) samples from Australian rivers.

A SIGNAL score gives an indication of water quality in the river from which the sample was collected. Rivers with high SIGNAL scores are likely to have low levels of salinity, turbidity and nutrients such as nitrogen and phosphorus. They are also likely to be high in dissolved oxygen.

When considered together with macro-invertebrate richness (the number of types of macro-invertebrates), SIGNAL can provide indications of the types of pollution and other physical and chemical factors that are affecting the macro-invertebrate community.

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